The role of collagen triple helix repeat containing 1 (CTHRC1) in cancer development and progression

INTRODUCTION

Collagen triple helix repeat containing 1 (CTHRC1) is a protein that has been implicated in pro-migratory pathways, arterial tissue-repair processes, and inhibition of collagen deposition via the regulation of multiple signaling cascades. Studies have also demonstrated an upregulation of CTHRC1 in multiple cancers where it has been linked to enhanced proliferation, invasion, and metastasis. However, the understanding of the exact role and mechanisms of CTHRC1 in cancer is far from complete.

AREAS COVERED

This review focuses on analyzing the role of CTHRC1 in cancer as well as its associations with clinicopathologies and cancer-related processes and signaling. We have also summarized the available literature information regarding the role of CTHRC1 in tumor microenvironment and immune signaling. Finally, we have discussed the mechanisms associated with CTHRC1 regulations, and opportunities and challenges regarding the development of CTHRC1 as a potential target for cancer management.

EXPERT OPINION

CTHRC1 is a multifaceted protein with critical roles in cancer progression and other pathological conditions. Its association with lower overall survival in various cancers, and impact on the tumor immune microenvironment make it an intriguing target for further research and potential therapeutic interventions in cancer.

Role of PLK1/NUMB/NOTCH in epithelial-mesenchymal transition in human melanoma

Polo-like kinase 1 (PLK1), a serine/threonine kinase, is overexpressed in melanoma and its expression has been associated with poor disease prognosis. PLK1 has been shown to interact with NUMB, a NOTCH antagonist. However, the exact role of PLK1, NUMB, and NOTCH signaling in epithelial-mesenchymal transition (EMT) in melanoma progression is unclear. In this study, Affymetrix microarray analysis was performed to determine differentially expressed genes following shRNA-mediated knockdown of PLK1 in human melanoma cells that showed significant modulations in EMT and metastasis-related genes. Using multiple PLK1-modulated melanoma cell lines, we found that PLK1 is involved in the regulation of cell migration, invasion, and EMT via its kinase activity and NOTCH activation. In vitro kinase assay and mass spectrometry analysis demonstrated a previously unknown PLK1 phosphorylation site (Ser413) on NUMB. Overexpression of non-phosphorylatable (S413A) and phosphomimetic (S413D) mutants of NUMB in melanoma cells implicated the involvement of NUMB-S413 phosphorylation in cell migration and invasion, which was independent of NOTCH activation. To determine the clinical relevance of these findings, immunohistochemistry was performed using melanoma tissue microarray, which indicated a strong positive correlation between PLK1 and N-cadherin, a protein required for successful EMT. These findings were supported by TCGA analysis, where expression of high PLK1 with low NUMB or high NOTCH or N-cadherin showed a significant decrease in survival of melanoma patients. Overall, these results suggest a potential role of PLK1 in EMT, migration, and invasion of melanoma cells. Our findings support the therapeutic targeting of PLK1, NUMB, and NOTCH for melanoma management.

Protective effects of dietary grape against atopic dermatitis-like skin lesions in NC/NgaTndCrlj mice

Atopic dermatitis (AD) is a chronic inflammatory skin disease with significant health/economic burdens. Existing therapies are not fully effective, necessitating development of new approaches for AD management. Here, we report that dietary grape powder (GP) mitigates AD-like symptoms in 2,4-dinitrofluorobenzene (DNFB)-induced AD in NC/NgaTndCrlj mice. Using prevention and intervention protocols, we tested the efficacy of 3% and 5% GP-fortified diet in a 13-weeks study. We found that GP feeding markedly inhibited development and progression of AD-like skin lesions, and caused reduction in i) epidermal thickness, mast cell infiltration, ulceration, excoriation and acanthosis in dorsal skin, ii) spleen weight, extramedullary hematopoiesis and lymph nodes sizes, and iii) ear weight and IgE levels. We also found significant modulations in 15 AD-associated serum cytokines/chemokines. Next, using quantitative global proteomics, we identified 714 proteins. Of these, 68 (normal control) and 21 (5% GP-prevention) were significantly modulated (≥2-fold) vs AD control (DNFB-treated) group, with many GP-modulated proteins reverting to normal levels. Ingenuity pathway analysis of GP-modulated proteins followed by validation using ProteinSimple identified changes in acute phase response signaling (FGA, FGB, FGG, HP, HPX, LRG1). Overall, GP supplementation inhibited DNFB-induced AD in NC/NgaTndCrlj mice in both prevention and intervention trials, and should be explored further.

Abstract 3979: CRISPR/Cas9-mediated knockout of PLK4 results in antiproliferative response in human epidermoid carcinoma cells in vitro and in implanted xenografts

Non-melanoma skin cancers (NMSCs) constitute the largest number of cancers diagnosed in the United States, with an estimated 1 in 5 people affected by the age of 70. The most notable NMSCs are squamous cell carcinomas (SCCs) and basal cell carcinomas (BCCs), which are considered keratinocyte cancers due to their origin. Although the majority of NMSCs can be removed with surgery or curettage, these options are not always available if the tumor occurs in an inoperable location or becomes metastatic. While non-surgical treatment modalities are also currently available, they have not been fully effective in NMSC management. Therefore, novel mechanistic-based therapeutic strategies are needed. The polo-like kinases (PLKs) are a family of serine/threonine kinases that have been found to play multiple roles in regulating the cell cycle. PLK4 is a structurally unique member of this family, which has been shown to be essential for precise centriole duplication. However, PLK4 has been shown to be dysregulated in certain cancers. Though the role of PLK4 in NMSC is not fully understood, we previously showed that PLK4 was significantly overexpressed in NMSC cell lines at both mRNA and protein levels as compared to normal keratinocytes, and its small molecule inhibition resulted in anti-proliferative responses in NMSC cell lines (Cancer Res 2018; 78 [13 Suppl]: Abstract nr 547). Here, we further validated our previous observation by determining the effects of CRISPR/Cas9-mediated knockout (KO) of PLK4 in the A431 human SCC line, both in vitro and in vivo. Our data demonstrated significantly reduced cell growth of multiple A431 PLK4 KO clones compared to wild-type (WT) cells, as measured by RealTime-Glo MT cell viability and trypan blue exclusion assays. In addition, we found significant reduction in clonogenic survival of A431 PLK4 KO cells, as measured by colony formation assays. Using a Human Cancer Pathway Finder RT2 Profiler PCR array, we identified 18 of the 84 genes tested to be greater than 1.6-fold differentially regulated after PLK4 KO in these cells. Employing Ingenuity Pathway Analysis (IPA) software, we identified that the regulation of the epithelial-mesenchymal transition by growth factors was one of the top canonical pathways modulated by PLK4 KO. To determine the in vivo relevance of our in vitro data, we compared the tumorigenicity of the A431 WT and PLK4 KO cells in nu/nu mice. The mice (n=7 per group) were injected subcutaneously with 5 x 105 A431 WT or PLK4 KO cells and tumors were allowed to grow for further analyses. We found a significant reduction in tumor volume in A431 PLK4 KO xenografts as compared to A431 PLK4 WT xenografts. Taken together, these findings support our previous results that suggest PLK4 has pro-proliferative roles in NMSC and should be further studied as a potential novel target for skin cancer management.

Citation Format: Mary A. Ndiaye, Debra R. Garvey, Gagan Chhabra, Chandra K. Singh, Nihal Ahmad. CRISPR/Cas9-mediated knockout of PLK4 results in antiproliferative response in human epidermoid carcinoma cells in vitro and in implanted xenografts [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3979.

PLK4 is upregulated in prostate cancer and its inhibition reduces centrosome amplification and causes senescence

BACKGROUND

Identification of novel molecular target(s) is important for designing newer mechanistically driven approaches for the treatment of prostate cancer (PCa), which is one of the main causes of morbidity and mortality in men. In this study, we determined the role of polo-like kinase 4 (PLK4), which regulates centriole duplication and centrosome amplification (CA), in PCa.

MATERIALS AND METHODS

Employing human PCa tissue microarrays, we assessed the prevalence of CA, correlated with Gleason score, and estimated major causes of CA in PCa (cell doubling vs. centriole overduplication) by staining for mother/mature centrioles. We also assessed PLK4 expression and correlated it with CA in human PCa tissues and cell lines. Further, we determined the effects of PLK4 inhibition in human PCa cells.

RESULTS

Compared to benign prostate, human PCa demonstrated significantly higher CA, which was also positively correlated with the Gleason score. Further, most cases of CA were found to arise by centriole overduplication rather than cell doubling events (e.g., cytokinesis failure) in PCa. In addition, PLK4 was overexpressed in human PCa cell lines and tumors. Moreover, PLK4 inhibitors CFI-400945 and centrinone-B inhibited cell growth, viability, and colony formation of both androgen-responsive and androgen-independent PCa cell lines. PLK4 inhibition also induced cell cycle arrest and senescence in human PCa cells.

CONCLUSIONS

CA is prevalent in PCa and arises predominantly by centriole overduplication as opposed to cell doubling events. Loss of centrioles is cellular stress that can promote senescence and suggests that PLK4 inhibition may be a viable therapeutic strategy in PCa.

Mechanisms of Immunotherapy Resistance in Cutaneous Melanoma: Recognizing a Shapeshifter

Melanoma is one of the seven most common cancers in the United States, and its incidence is still increasing. Since 2011, developments in targeted therapies and immunotherapies have been essential for significantly improving overall survival rates. Prior to the advent of targeted and immunotherapies, metastatic melanoma was considered a death sentence, with less than 5% of patients surviving more than 5 years. With the implementation of immunotherapies, approximately half of patients with metastatic melanoma now survive more than 5 years. Unfortunately, this also means that half of the patients with melanoma do not respond to current therapies and live less than 5 years after diagnosis. One major factor that contributes to lower response in this population is acquired or primary resistance to immunotherapies via tumor immune evasion. To improve the overall survival of melanoma patients new treatment strategies must be designed to minimize the risk of acquired resistance and overcome existing primary resistance. In recent years, many advances have been made in identifying and understanding the pathways that contribute to tumor immune evasion throughout the course of immunotherapy treatment. In addition, results from clinical trials focusing on treating patients with immunotherapy-resistant melanoma have reported some initial findings. In this review, we summarize important mechanisms that drive resistance to immunotherapies in patients with cutaneous melanoma. We have focused on tumor intrinsic characteristics of resistance, altered immune function, and systemic factors that contribute to immunotherapy resistance in melanoma. Exploring these pathways will hopefully yield novel strategies to prevent acquired resistance and overcome existing resistance to immunotherapy treatment in patients with cutaneous melanoma.

PLK1 inhibition-based combination therapies for cancer management

Polo-like kinase I (PLK1), a cell cycle regulating kinase, has been shown to have oncogenic function in several cancers. Although PLK1 inhibitors, such as BI2536, BI6727 (volasertib) and NMS-1286937 (onvansertib) are generally well-tolerated with a favorable pharmacokinetic profile, clinical successes are limited due to partial responses in cancer patients, especially those in advanced stages. Recently, combination therapies targeting multiple pathways are being tested for cancer management. In this review, we first discuss structure and function of PLK1, role of PLK1 in cancers, PLK1 specific inhibitors, and advantages of using combination therapy versus monotherapy followed by a critical account on PLK1-based combination therapies in cancer treatments, especially highlighting recent advancements and challenges. PLK1 inhibitors in combination with chemotherapy drugs and targeted small molecules have shown superior effects against cancer both in vitro and in vivo. PLK1-based combination therapies have shown increased apoptosis, disrupted cell cycle, and potential to overcome resistance in cancer cells/tissues over monotherapies. Further, with successes in preclinical experiments, researchers are validating such approaches in clinical trials. Although PLK1-based combination therapies have achieved initial success in clinical studies, there are examples where they have failed to improve patient survival. Therefore, further research is needed to identify and validate novel biologically informed co-targets for PLK1-based combinatorial therapies. Employing a network-based analysis, we identified potential PLK1 co-targets that could be examined further. In addition, understanding the mechanisms of synergism between PLK1 inhibitors and other agents may lead to a better approach on which agents to pair with PLK1 inhibition for optimum cancer treatment.

Anti-melanoma effects of concomitant inhibition of SIRT1 and SIRT3 in BrafV600E/PtenNULL mice

Novel therapeutic strategies are required for the effective and lasting treatment of metastatic melanoma, one of the deadliest skin malignancies. In this study, we determined the anti-melanoma efficacy of 4'-bromo-resveratrol (4'-BR), which is a small molecule dual inhibitor of SIRT1 and SIRT3 in a Braf^V600E/Pten^NULL mouse model that recapitulates human disease, including metastases. Tumors were induced by topical application of 4-hydroxy-tamoxifen on shaved backs of 10-week-old mice, and the effects of 4'-BR (5-30 mg/kg b.wt.; intraperitoneally; 3d/week for 5 weeks) were assessed on melanoma development and progression. We found that 4'-BR at a dose of 30 mg/kg significantly reduced size and volume of primary melanoma tumors, as well as lung metastasis, with no adverse effects. Further, mechanistic studies on tumors showed significant modulation in markers of proliferation, survival and melanoma progression. As SIRT1 and SIRT3 are linked to immunomodulation, we performed differential gene expression analysis via NanoString PanCancer Immune Profiling panel (770 genes). Our data demonstrated that 4'-BR significantly downregulated genes related to metastasis-promotion, chemokine/cytokine-regulation, and innate/adaptive immune functions. Overall, inhibition of SIRT1 and SIRT3 by 4'-BR is a promising anti-melanoma therapy with anti-metastatic and immunomodulatory activities warranting further detailed studies, including clinical investigations.

Abstract 2157: Potential correlations between PLK1, BRAF and MITF in melanoma

Melanoma is one of the most aggressive types of cancer and extremely difficult to treat after metastasis. BRAFV600E-activating mutations give rise to ∼80% of melanocytic nevi, yet only one-third of melanocytic nevi result in melanoma, suggesting the involvement of other factors. Polo-like kinase 1 (PLK1), an important regulator of cell cycle progression, is overexpressed in melanoma and its expression has been shown to correlate with patient prognosis. Microphthalmia-associated transcription factor (MITF) is a melanocytic lineage-specific transcription factor that regulates a variety of genes critical for melanin synthesis as well as melanoma progression. The goal of this study was to define potential interactions between PLK1, BRAFV600E, and MITF in human melanoma. First, we employed a commercially available human tissue microarray (TMA) coupled with high-throughput, multispectral Vectra scanning and inForm analysis to study a number of clinical tissue cores (nevus, malignant and metastatic melanoma). The TMA was simultaneously immunostained for PLK1, BRAFV600E, MITF, proliferation marker Ki67, melanoma biomarker S100 and DAPI, and was subjected to Vectra scanning and inForm analyses. Using Simple Linear Regression analyses, we found significant correlations among each pair of the selected four proteins (PLK1, BRAFV600E, MITF and Ki67) with correlation co-efficient ranging 0.24-0.84. To analyze if PLK1, and BRAFV600E are contributing to cell proliferation (Ki67 expression) or affecting MITF expression, we employed a Multiple Linear Regression analysis. Our data suggested that high expressions of both BRAFV600E and PLK1 are correlated positively with the expression of Ki67. However, when fitting both PLK1 and BRAFV600E versus MITF, only high PLK1 had significant positive correlation with MITF, while BRAFV600E did not show correlation with MITF. These results suggest that PLK1 and MITF could contribute to melanoma progression independent to BRAFV600E. To further validate our findings, we analyzed The Cancer Genome Atlas (TCGA) database containing a large melanoma cohort of 432 melanoma patients with information on overall survival (OS). To visualize the survival plots, the expression level of PLK1 and MITF was sorted and equally separated to two groups using the median value as a cutoff. Kaplan-Meier analyses showed that high mRNA expression of both PLK1 and MITF were individually associated with significant reductions in OS. Interestingly, when we sorted the data for both high PLK1 and high MITF in the same patient, the OS was shorter than that of patients with low PLK1 and low MITF. Overall, our study suggests an association between PLK1 and MITF pathways during melanoma progression, which may affect overall survival in melanoma patients. Thus, concomitant targeting of PLK1 and MITF could provide an advantage over monotherapy towards melanoma management. However, in-depth studies are required to validate our findings.

Citation Format: Gagan Chhabra, Shengqin Su, Chandra K. Singh, Mary A. Ndiaye, Nihal Ahmad. Potential correlations between PLK1, BRAF and MITF in melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2157.

Dietary Phytochemicals in Zinc Homeostasis: A Strategy for Prostate Cancer Management

Studies have suggested an important role of the trace element zinc (Zn) in prostate biology and functions. Zn has been shown to exist in very high concentrations in the healthy prostate and is important for several prostatic functions. In prostate cancer (PCa), Zn levels are significantly decreased and inversely correlated with disease progression. Ideally, restoration of adequate Zn levels in premalignant/malignant prostate cells could abort prostate malignancy. However, studies have shown that Zn supplementation is not an efficient way to significantly increase Zn concentrations in PCa. Based on a limited number of investigations, the reason for the lower levels of Zn in PCa is believed to be the dysregulation of Zn transporters (especially ZIP and ZnT family of proteins), metallothioneins (for storing and releasing Zn), and their regulators (e.g., Zn finger transcription factor RREB1). Interestingly, the level of Zn in cells has been shown to be modulated by naturally occurring dietary phytochemicals. In this review, we discussed the effect of selected phytochemicals (quercetin, resveratrol, epigallocatechin-3-gallate and curcumin) on Zn functioning and proposes that Zn in combination with specific dietary phytochemicals may lead to enhanced Zn bioaccumulation in the prostate, and therefore, may inhibit PCa.

Genetic Manipulation of Sirtuin 3 Causes Alterations of Key Metabolic Regulators in Melanoma

The mitochondrial sirtuin SIRT3 plays key roles in cellular metabolism and energy production, which makes it an obvious target for the management of cancer, including melanoma. Previously, we have demonstrated that SIRT3 was constitutively upregulated in human melanoma and its inhibition resulted in anti-proliferative effects in vitro in human melanoma cells and in vivo in human melanoma xenografts. In this study, we expanded our data employing knockdown and overexpression strategies in cell culture and mouse xenografts to further validate and establish the pro-proliferative function of SIRT3 in melanocytic cells, and its associated potential mechanisms, especially focusing on the metabolic regulation. We found that short-hairpin RNA (shRNA) mediated SIRT3 knockdown in G361 melanoma cells showed diminished tumorigenesis in immunodeficient Nu/Nu mice. Conversely, SIRT3 overexpressing Hs294T melanoma cells showed increased tumor growth. These effects were consistent with changes in markers of proliferation (PCNA), survival (Survivin) and angiogenesis (VEGF) in xenografted tissues. Further, in in vitro culture system, we determined the effect of SIRT3 knockdown on glucose metabolism in SK-MEL-2 cells, using a PCR array. SIRT3 knockdown caused alterations in a total of 37 genes involved in the regulation and enzymatic pathways of glucose (32 genes) and glycogen (5 genes) metabolism. Functions annotation of these identified genes, using the ingenuity pathway analysis (IPA), predicted cumulative actions of decreased cell viability/proliferation, tumor growth and reactive oxygen species (ROS), and increased apoptosis in response to SIRT3 knockdown. Further, IPA gene network analysis of SIRT3 modulated genes revealed the interactions among these genes in addition to several melanoma-associated genes. Sirtuin pathway was identified as one of the top canonical pathways showing the interaction of SIRT3 with metabolic regulatory genes along with other sirtuins. IPA analysis also predicted the inhibition of HIF1α, PKM, KDM8, PPARGC1A, mTOR, and activation of P53 and CLPP; the genes involved in major cancer/melanoma-associated signaling events. Collectively, these results suggest that SIRT3 inhibition affects cellular metabolism, to impart an anti-proliferative response against melanoma.

PLK1 and NOTCH Positively Correlate in Melanoma and Their Combined Inhibition Results in Synergistic Modulations of Key Melanoma Pathways

Melanoma is one of the most serious forms of skin cancer, and its increasing incidence coupled with nonlasting therapeutic options for metastatic disease highlights the need for additional novel approaches for its management. In this study, we determined the potential interactions between polo-like kinase 1 (PLK1, a serine/threonine kinase involved in mitotic regulation) and NOTCH1 (a type I transmembrane protein deciding cell fate during development) in melanoma. Employing an in-house human melanoma tissue microarray (TMA) containing multiple cases of melanomas and benign nevi, coupled with high-throughput, multispectral quantitative fluorescence imaging analysis, we found a positive correlation between PLK1 and NOTCH1 in melanoma. Furthermore, The Cancer Genome Atlas database analysis of patients with melanoma showed an association of higher mRNA levels of PLK1 and NOTCH1 with poor overall, as well as disease-free, survival. Next, utilizing small-molecule inhibitors of PLK1 and NOTCH (BI 6727 and MK-0752, respectively), we found a synergistic antiproliferative response of combined treatment in multiple human melanoma cells. To determine the molecular targets of the overall and synergistic responses of combined PLK1 and NOTCH inhibition, we conducted RNA-sequencing analysis employing a unique regression model with interaction terms. We identified the modulations of several key genes relevant to melanoma progression/metastasis, including MAPK, PI3K, and RAS, as well as some new genes such as Apobec3G, BTK, and FCER1G, which have not been well studied in melanoma. In conclusion, our study demonstrated a synergistic antiproliferative response of concomitant targeting of PLK1 and NOTCH in melanoma, unraveling a potential novel therapeutic approach for detailed preclinical/clinical evaluation.

Abstract 4052: Effects of CRISPR/Cas9-mediated knockout of SIRT6 in human melanoma cells, in vitro and in vivo

Melanoma is one of the most aggressive and fatal forms of skin cancer, with dismal 5-year survival if not diagnosed early. Although recent advances have led to better targeted- and immuno- therapeutic approaches, many patients develop resistance and recurrence. Therefore, it is crucial to develop newer druggable molecular targets that could be exploited towards the management of this deleterious neoplasm. Earlier studies from our laboratory have shown that SIRT6, a member of the sirtuin family of class III histone deacetylases, possesses a potential pro-proliferative role in melanoma. Extending on these novel findings, the objective of this study was to determine the effects of CRISPR/Cas9-mediated knockout (KO) of SIRT6 in melanoma cells, both in vitro and in vivo. First, we evaluated the effects of SIRT6 KO on growth, viability, and clonogenic survival in the A375 human melanoma cell line. We found that KO of SIRT6 resulted in a significant anti-proliferative response in melanoma cells, as measured by trypan blue and RealTime-Glo assays. Further, SIRT6 KO also resulted in a significant decrease in the long-term clonogenic survival of melanoma cells, as measured by a colony formation assay. Additionally, we used DNA cell cycle analysis by flow cytometry to assess the effect of SIRT6 KO on cell cycle perturbation in melanoma cells. Our data demonstrated that SIRT6 KO induced a G1-phase arrest in the A375 melanoma cells. Furthermore, we employed a PCR array (RT2 Profiler Cancer Pathway Array; with 84 genes) to understand the molecular mechanisms associated with the observed anti-proliferative response of SIRT6 KO. We found that SIRT6 KO caused statistically significant alteration in genes involved in important cellular pathways, including angiogenesis (CCL2, KDR, SERPINF1, and FLT1), hypoxia signaling (ADM and CA9), cellular senescence (IGFBP5 and TBX2), apoptosis (CFLAR), epithelial-to-mesenchymal transition (EMT) (SNAI2), and telomere maintenance (TEP1). Finally, to validate the in vitro findings to in vivo situation, we determined the growth of SIRT6 KO A375 human melanoma cells-implanted tumors in immunocompromised mice. We observed a significant slow growth of SIRT6 KO tumors compared to wild-type A375 tumors, suggesting that SIRT6 reduction decreases cell survival in melanoma both in vitro and in vivo. Overall, our results re-emphasize the tumor promoter role of SIRT6 in melanoma. Further detailed studies are required to determine the potential of SIRT6 inhibition as a novel treatment regimen against melanoma.

Citation Format: Liz M. Garcia-Peterson, Mary A. Ndiaye, Glorimar Guzman-Perez, Chandra K. Singh, Gagan Chhabra, Nihal Ahmad. Effects of CRISPR/Cas9-mediated knockout of SIRT6 in human melanoma cells, in vitro and in vivo [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4052.

Abstract 2918: Concomitant inhibition of SIRT1 and SIRT3 reduces melanoma growth and metastasis in BRAFV600E/PTENNULL transgenic mice

Metastatic melanoma, one of the most aggressive types of skin cancer, is extremely difficult to treat, with a median overall survival of less than one year. Despite recent advances in targeted- and immune- therapies, the treatment options have either failed to achieve >25% response or the responses have been short-lived with the emergence of resistance. Therefore, newer approaches are needed for the management of this deadly neoplasm. 4′-bromo-resveratrol [5-(2-(4-hydroxyphenyl)vinyl)-1,3-benzenediol; 4′-BR], an analog of resveratrol, is a dual small molecule inhibitor of sirtuins 1 and 3 (SIRTs 1 & 3), which have pro-proliferative functions in melanoma. In a recently published study, we demonstrated that 4′-BR induced apoptosis and caused metabolic reprogramming in human melanoma cells, leading to reduced proliferation and growth of melanoma cells in vitro. In order to validate our in vitro findings to in vivo situations, in this study, we evaluated the therapeutic efficacy of 4′-BR on melanoma growth and metastasis in a genetically engineered transgenic (BRAFV600E/PTENNull) mouse model of melanoma. This mouse model shows melanoma's cardinal features and is an excellent model to test drug efficacy in pre-clinical settings. To induce melanoma tumors, 4-hydroxytamoxifen was applied on shaved backs of 10-week-old mice topically once per day for 3 consecutive days. Highly pigmented tumors appeared 10 days after tamoxifen application. At this point, treatment with 4′-BR (0, 5, 10, 20 and 30 mg/kg b.wt.; intraperitoneal; 3d/week; n=6 mice/group) was started. Body weight, tumor size and volume were measured weekly. At the termination of the study (~17 weeks of age), we observed significant reduction in tumor volume and tumor weight in mice treated with 30 mg/kg 4'-BR with no noticeable adverse effects. Further, we analyzed markers for cell proliferation and survival (Ki67, PCNA, and Survivin), metastasis (Vimentin), oxidative stress (Nrf2 and Keap1) and growth factor signaling (IGF1 and IGFBP5) using immunohistochemistry (IHC) or real-time quantitative PCR (RT-qPCR) in tumors. IHC analysis revealed that 4′-BR treatment markedly decreased Ki67 positive tumor cells. RT-qPCR analysis showed that 4'-BR treatments significantly decreased expression of PCNA, Survivin, and IGF1 (a melanoma promoting growth factor), as well as significantly increased expression of IGFBP5, a tumor suppressor gene. Furthermore, we observed that 4'-BR treatment significantly decreased the ratio of Nrf2/Keap1. In addition, our data demonstrated a significant decrease in lung metastasis and the levels of metastasis marker Vimentin in 4'-BR treatment group. Overall, these data show the ability of 4′-BR to exert anti-proliferative, anti-tumorigenic, and anti-metastatic effects in a human-relevant melanoma mouse model, thus warranting further pre-clinical and clinical investigations in this direction.

Citation Format: Gagan Chhabra, Chandra K. Singh, Mary A. Ndiaye, Kenneth A. Iczkowski, Nihal Ahmad. Concomitant inhibition of SIRT1 and SIRT3 reduces melanoma growth and metastasis in BRAFV600E/PTENNULL transgenic mice [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2918.

Abstract 222: RNA-seq analysis of differential gene expression in melanoma cells after combined inhibition of Plk1 and Notch

Melanoma is one of the most brutal forms of skin cancer, and its increasing incidence coupled with non-lasting therapeutic options for metastatic tumor highlight the need for additional strategies for the management of this neoplasm. Using tissue microarray analysis, we previously found that the expression of polo-like kinase 1 (Plk1, a serine/threonine kinase involved in mitotic regulation) and Notch1 (a type I transmembrane protein deciding cell fate during development) were positively correlated in melanoma (Cancer Res 2018; 78 [13 Suppl]: Abstract nr 2530), and their combined inhibition resulted in a synergistic anti-proliferative response in human melanoma cells (Cancer Res 2019; 79 [13 Suppl]: Abstract nr 302). In this study, to determine the possible mechanisms behind this observed synergism, we used RNA-seq technology to obtain the differential gene expression following treatment of SK-MEL-2 human metastatic melanoma cells with Plk1 inhibitor volasertib (BI6727, 20 nM) and Notch1 inhibitor MK-0752 (100 μM) for 48 h. After data pre-processing by RSEM algorithm, the DESeq2 package was implemented to identify differentially expressed genes (DEGs, |log2-fold change| >= 1, false positive rate ⇐ 0.05) when comparing the individual and combined treatments to vehicle (DMSO), as well as the interaction between volasertib:MK-0752. As a result, we identified 909 DEGs from volasertib treatment, 675 DEGs from MK-0752 treatment, 2142 genes from the combined treatment of volasertib and MK-0752, as well as 304 DEGs from the interaction of volasertib and MK-0752. In addition, employing GOstats and KEGGprofile packages in R programming, we conducted Gene Ontology (GO) and KEGG pathway analysis of the various DEGs. In GO analysis (counts >= 2, p ⇐ 10−5), we identified 202 downregulated GO terms affected by the combined inhibition of Plk1 and Notch1, including metabolism, cell proliferation, and migration. In KEGG pathway analysis, the combined inhibition of Plk1 and Notch1 was found to be associated with downregulation of several pathways shared with single drug treatments, such as PI3K-Akt, extracellular matrix receptor interaction, and protein digestion and absorption, as well as some novel pathways that were only affected by combined treatment, such as MAPK, Ras, and Rap1 pathways. Interestingly, our analysis predicted that the combined inhibition of Plk1 and Notch may make the melanoma cells more sensitive to immune responses. Overall, our data demonstrated that not only does targeting both Plk1 and Notch1 signaling pathways alters multiple melanoma progression pathways, but it may also potentially result in an increased sensitivity to other therapeutic targets, such as immune checkpoint blockade. However, these mechanistic findings need to be validated further in other relevant in vitro and in vivo models.

Citation Format: Shengqin Su, Gagan Chhabra, Mary A. Ndiaye, Chandra K. Singh, Colin N. Dewey, Nihal Ahmad. RNA-seq analysis of differential gene expression in melanoma cells after combined inhibition of Plk1 and Notch [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 222.

Quercetin-Resveratrol Combination for Prostate Cancer Management in TRAMP Mice

Prostate Cancer (PCa) is a leading cause of cancer-related morbidity and mortality in men. Therefore, novel mechanistically-driven approaches are needed for PCa management. Here, we determined the effects of grape antioxidants quercetin and/or resveratrol (60 and 600 mg/kg, respectively, in diet) against PCa in Transgenic Adenocarcinoma of Mouse Prostate (TRAMP)-model in prevention and intervention settings. We found resveratrol alone and in combination significantly inhibited prostate tumorigenesis in prevention setting, while the same was seen only in combination after intervention. The observed effects were associated with marked inhibition in proliferation, oxidative stress, and tumor survival markers, and induced apoptosis markers. Utilizing PCa PCR array analysis with prevention tumor tissues, we identified that quercetin-resveratrol modulates genes involved in promoter methylation, cell cycle, apoptosis, fatty acid metabolism, transcription factors, androgen response, PI3K/AKT and PTEN signaling. Ingenuity Pathway Analysis (IPA) identified IGF1 and BCL2 as central players in two gene networks. Functional annotation predicted increased apoptosis and inhibited cell viability/proliferation, hyperplasia, vasculogenesis, and angiogenesis with dual treatment. Furthermore, IPA predicted upstream inhibition of major PCa signaling VEGF, Ca2+, PI3K, CSF2, PTH). Based on PCR array, we identified decreased levels of EGFR, EGR3, and IL6, and increased levels of IGFBP7 and NKX3.1, overall supporting anti-PCa effects of quercetin-resveratrol.

CRISPR/Cas9-mediated Knockout of SIRT6 Imparts Remarkable Antiproliferative Response in Human Melanoma Cells in vitro and in vivo

Melanoma is one of the most aggressive, potentially fatal forms of skin cancer and has been shown to be associated with solar ultraviolet radiation-dependent initiation and progression. Despite remarkable recent advances with targeted and immune therapeutics, lasting and recurrence-free survival remain significant concerns. Therefore, additional novel mechanism-based approaches are needed for effective melanoma management. The sirtuin SIRT6 appears to have a pro-proliferative function in melanocytic cells. In this study, we determined the effects of genetic manipulation of SIRT6 in human melanoma cells, in vitro and in vivo. Our data demonstrated that CRISPR/Cas9-mediated knockout (KO) of SIRT6 in A375 melanoma cells resulted in a significant (1) decrease in growth, viability and clonogenic survival and (2) induction of G1-phase cell cycle arrest. Further, employing a RT² Profiler PCR array containing 84 key transformation and tumorigenesis genes, we found that SIRT6 KO resulted in modulation of genes involved in angiogenesis, apoptosis, cellular senescence, epithelial-to-mesenchymal transition, hypoxia signaling and telomere maintenance. Finally, we found significantly decreased tumorigenicity of SIRT6 KO A375 cells in athymic nude mice. Our data provide strong evidence that SIRT6 promotes melanoma cell survival, both in vitro and in vivo, and could be exploited as a target for melanoma management.

Protective Effects of Dietary Grape on UVB-Mediated Cutaneous Damages and Skin Tumorigenesis in SKH-1 Mice

Non-melanoma skin cancers (NMSCs) are the most diagnosed cancers in the US and occur more frequently in males. We previously demonstrated chemoprotective effects of dietary grape powder (GP) against UVB-mediated skin tumorigenesis in female SKH-1 mice. To expand on this, here, we determined the effects of GP in a short-term UVB exposure protocol (0 or 5% GP, followed by UVB every other day for 2 weeks) in male and female SKH-1 mice, as well as explored any sex-related differences in UVB carcinogenesis via male SKH-1 mice (0, 3, or 5% GP; UVB twice weekly for 28 weeks). In the short-term study, we found that GP protects against early-stage epithelial hyperplasia and mast cell infiltration in both sexes. In the long term, GP markedly reduced tumor counts and malignant conversion, along with significant decreases in mast cell infiltration, serum IgE and Eotaxin. We also found inhibition of P38 phosphorylation and reduced PCNA, Ki67 and BCL2 levels, suggesting that the anti-inflammatory effects of GP inhibits P38, acting as an upstream regulator to inhibit proliferation and reduce tumor cell survival. Together, GP appears to protect against UVB-mediated skin damage and carcinogenesis in SKH-1 mice and should be explored further as a supplement for NMSC prevention.

Mitochondrial Sirtuins in Skin and Skin Cancers

Mammalian sirtuins (SIRTs 1-7) are a family of NAD+-dependent deacetylases with distinct subcellular localization and biological functions that regulate various important cellular processes. Among these, SIRTs -3, -4 and -5 are located in the mitochondria and have been implicated in caloric restriction, oxidative stress, aging and various human diseases. Emerging evidence has found dysregulation of mitochondrial sirtuins in multiple dermatological conditions, including responses to ultraviolet radiation (UVR), suggesting their importance in maintaining skin health. In this review, we discuss the roles and implications of mitochondrial sirtuins in cutaneous cellular processes, and their emerging potential as a target for the management of skin diseases, including skin cancer. Among mitochondrial sirtuins, SIRT3 is the most studied and linked to multiple skin conditions and diseases (keratinocyte differentiation, wound healing, chronological aging, UVR and ozone response, systemic sclerosis, melanoma, basal cell carcinoma (BCC) and squamous cell carcinoma (SCC)). SIRT4 has been connected to keratinocyte differentiation, chronological aging, UVR response, alopecia, BCC and SCC. Further, SIRT5 has been associated with keratinocyte differentiation, melanoma, BCC and SCC. Overall, while there is compelling evidence for the involvement of mitochondrial sirtuins in skin, additional detailed studies are needed to understand their exact roles in skin and skin cancers.

Whole Fruit Phytochemicals Combating Skin Damage and Carcinogenesis

Skin is arguably the largest organ of the body and is continuously subjected to intrinsic, extrinsic, and environmental stresses. Therefore, skin developed elaborate mechanisms to maintain homeostasis, including antioxidant, antiinflammatory, and DNA damage repair capabilities. However, repeated and excessive stresses can overwhelm these systems, causing serious cutaneous damages, including skin carcinogenesis. Phytonutrients present in the diet possess a myriad of health-promoting effects by protecting skin from damaging free radicals as well as by other mechanisms. Although many chemoprotective phytonutrients have been shown to be efficacious individually, a combination of multiple agents could have synergistic response in curtailing or preventing cutaneous damages. Here, we discuss the benefits of natural amalgamation of phytonutrients in select fruits against skin damage including carcinogenesis. However, a majority of these studies have been done in preclinical models. Therefore, clinical studies are needed to determine the human relevance of the available preclinical data, especially in the human population who are at higher risk for skin cancers (e.g., organ transplant patients). In addition, detailed well-structured preclinical animal studies in the models of high-risk skin carcinogenesis could also be useful toward informing the design for human trials.

Detection and Characterization of cry1Ac Transgene Construct in Bt Cotton: Multiple Polymerase Chain Reaction Approach

To comply with international labeling regulations for genetically modified (GM) crops and food, and to enable proper identification of GM organisms (GMOs), effective methodologies and reliable approaches are needed. The spurious and unapproved GM planting has contributed to crop failures and commercial losses. To ensure effective and genuine GM cultivation, a methodology is needed to detect and identify the trait of interest and concurrently evaluate the structural and functional stability of the transgene insert. A multiple polymerase chain reaction (PCR) approach was developed for detection, identification, and gene stability confirmation of cry1Ac transgene construct in Bt cotton. As many as 9 samples of Bt cotton hybrid seeds comprising 3 approved Bt hybrids, MECH-12Bt, MECH-162Bt, MECH-184Bt, and a batch of 6 nonapproved Bt hybrids were tested. Initially, single standard PCR assays were run to amplify predominant GM DNA sequences (CaMV 35S promoter, nos terminator, and npt-II marker gene); a housekeeping gene, Gossypium hirsutum fiber-specific acyl carrier protein gene (acp1); a trait-specific transgene (cry1Ac); and a sequence of 7S 3 transcription terminator which specifically borders with 3 region of cry1Ac transgene cassette. The concurrent amplification of all sequences of the entire cassette was performed by 3 assays, duplex, triplex, and quadruplex multiplex PCR assays, under common assay conditions. The identity of amplicons was reconfirmed by restriction endonuclease digestion profile. The 2 distinct transgene cassettes, cry1Ac and npt-II, of the Bt cotton were amplified using the respective forward primer of promoter and reverse primer of terminator. The resultant amplicons were excised, eluted, and purified. The purified amplicons served as template for nested PCR assays. The nested PCR runs confirmed the transgene construct orientation and identity. The limit of detection as established by our assay for GM trait (cry1Ac) was 0.1. This approach can be adopted as a standard procedure for complete molecular characterization of Bt cotton. These assays will be of interest and use to importers, breeders, research laboratories, safety regulators, and food processors for detection of cry1Ac bearing GMOs.

Identification of Molecular Targets of Dietary Grape-Mediated Chemoprevention of Ultraviolet B Skin Carcinogenesis: A Comparative Quantitative Proteomics Analysis

We recently showed that dietary grape powder (GP) imparts considerable protection against ultraviolet B (UVB)-mediated skin carcinogenesis in SKH-1 mice. To determine molecular mechanisms of this response, we employed tandem mass tag (TMT) quantitative global proteomics approach on skin tumors from mice exposed to 180 mJ/cm² UVB twice per week and fed control or 5% GP diet. We found 2629 proteins modulated by GP feeding, with 34 identified using stringent cutoffs (false discovery rate (FDR) q-value ≤ 0.1, fold change ≥ 1.2, p-value ≤ 0.05, ≥ 3 unique peptides). Ingenuity Pathway Analysis helped identify seven proteins involved in protein ubiquitination, including the deubiquitinase UCHL5 and 6 subunits of the 20S proteasome (PSMA1,3,4,6 and PSMB4,7). A second data set without the FDR q-value identified 239 modulated proteins, seven of which are involved in protein ubiquitination. Further, 14 proteins involved in acute phase response signaling were modulated >1.5-fold, including acute phase proteins APCS, FGA, FGB, HP, HPX, and RBP1. Evaluation of upstream regulators found inhibition of ERK1/2 phosphorylation and NF-κB p65, and an increase in IκBα in GP-treated tumors. Overall, our data suggested that GP consumption may mitigate tumorigenesis by enhancing protein ubiquitination and degradation caused by oxidative stress, and manipulates an otherwise tumor-promoting anti-inflammatory environment.

4'-Bromo-resveratrol, a dual Sirtuin-1 and Sirtuin-3 inhibitor, inhibits melanoma cell growth through mitochondrial metabolic reprogramming

Sirtuin-1 and -3 (SIRT1 and SIRT3) are important nicotinamide adenine dinucleotide (NAD⁺ )-dependent deacetylases known to regulate a variety of cellular functions. Studies have shown that SIRT1 and SIRT3 were overexpressed in human melanoma cells and tissues and their inhibition resulted in a significant antiproliferative response in human melanoma cells and antitumor response in a mouse xenograft model of melanoma. In this study, we determined the antiproliferative efficacy of a newly identified dual small molecule inhibitor of SIRT1 and SIRT3, 4'-bromo-resveratrol (4'-BR), in human melanoma cell lines (G361, SK-MEL-28, and SK-MEL-2). Our data demonstrate that 4'-BR treatment of melanoma cells resulted in (a) decrease in proliferation and clonogenic survival; (b) induction of apoptosis accompanied by a decrease in procaspase-3, procaspase-8, and increase in the cleavage of caspase-3 and poly (ADP-ribose) polymerase (PARP); (c) marked downregulation of proliferating cell nuclear antigen (PCNA); and (d) inhibition of melanoma cell migration. Further, 4'-BR caused a G0/G1 phase arrest of melanoma cells that was accompanied by an increase in WAF-1/P21 and decrease in Cyclin D1/Cyclin-dependent kinase 6 protein levels. Furthermore, we found that 4'-BR causes a decrease in lactate production, glucose uptake, and NAD⁺ /NADH ratio. These responses were accompanied by downregulation in lactate dehydrogenase A and glucose transporter 1 in melanoma cells. Collectively, our data suggest that dual inhibition of SIRT1 and SIRT3 using 4'-BR imparted antiproliferative effects in melanoma cells through a metabolic reprogramming and affecting the cell cycle and apoptosis signaling. Therefore, concomitant pharmacological inhibition of SIRT1 and SIRT3 needs further investigation for melanoma management.

Abstract 5085: Molecular analysis of chemopreventive effects of grape antioxidants resveratrol and quercetin in transgenic adenocarcinoma of the mouse prostate

Prostate cancer (PCa) is one of the most frequently diagnosed cancers of the male population and current treatments are insufficient to fully manage this neoplasm. Therefore, identification of novel mechanism-based approaches are needed for PCa management. Earlier, we demonstrated that a combination of the grape antioxidants resveratrol and quercetin impart superior anti-proliferative responses in multiple human PCa cell lines, as well as a significant anti-tumor response in transgenic adenocarcinoma of the mouse prostate (TRAMP) (Cancer Res 75(15 Suppl):2801). The rationale of the study was based on the fact that i) both resveratrol and quercetin are naturally present in several plants ii) quercetin improves bioavailability of resveratrol by inhibiting its sulfation, and iii) separately, both agents have shown potential for management of PCa in previously published studies. This study extended our previous work and determined the mechanisms of chemopreventive effects of resveratrol-quercetin combination employing a mouse PCa RT² Profiler PCR array that profiles 84 key PCa-related genes. For this, we employed tumor tissues generated in a chemoprevention protocol where TRAMP mice were given AIN76A diet supplemented with resveratrol (600 mg/kg), quercetin (60 mg/kg), or a combination of both. PCR array analysis found significant modulation (≥2-fold) in 14, 15, and 10 genes in the quercetin, resveratrol, and combination groups, respectively. To explore the involved gene networks using Ingenuity Pathway Analysis (IPA), we selected total 22 genes with ≥2-fold change in any one group and ≥1.5-fold change in other group(s). IPA analysis identified that resveratrol-quercetin modulated genes supported the cumulative actions of increased apoptosis, as well as inhibition of cell viability/proliferation, hyperplasia, vasculogenesis, and angiogenesis. Further, IPA predicted inhibition of major PCa promoting upstream signaling molecules viz. Pi3k, Vegf, Csf2, Ca2+, and Pth. This PCR array also identified decreased levels of Igf1, Egfr, Egr3, and Il6, which are known to support PCa progression, as well as found increased levels of Nkx3-1, which is a tumor suppressor in PCa. Furthermore, IPA exploration identified a gene network where decreased Igf1 emerged as a central regulatory player, interacting with most of the resveratrol-quercetin modulated genes. Additionally, employing IHC, immunoblot, and RT-qPCR analyses, we found marked decrease in the levels of cell proliferation markers Ki67 and PCNA, oxidative stress biomarker 4-HNE, EMT marker vimentin, and prosurvival marker Bcl2. These results suggest that this natural combination of grape polyphenols may be useful as a chemopreventive regimen for PCa. Further detailed studies including clinical trials are needed to determine the translational significance of our findings.

Citation Format: Chandra K. Singh, Mary A. Ndiaye, Gagan Chhabra, Charlotte A. Mintie, Nihal Ahmad. Molecular analysis of chemopreventive effects of grape antioxidants resveratrol and quercetin in transgenic adenocarcinoma of the mouse prostate [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5085.

Abstract 1875: Polo-like kinase 1 positively correlates with N-cadherin and promotes epithelial-mesenchymal transition in melanoma

Polo-like kinase 1 (PLK1), a serine/threonine kinase and important cell cycle regulator, is overexpressed in melanoma and has been linked with enhanced cell proliferation. Recent studies have shown involvement of PLK1 in epithelial-mesenchymal transition (EMT) in certain cancer types. However, the role of PLK1 in EMT in melanoma is not well understood. EMT has been shown to promote metastasis, and is associated with an upregulation of the mesenchymal marker N-cadherin (CDH2), downregulation of the epithelial marker E-cadherin (CDH1), and increased cell migration and invasion ability. Earlier, we demonstrated that PLK1 is involved in EMT and its kinase activity is important for EMT-related modulations in A375 melanoma cells (Cancer Res 2018; 78 (13 Suppl): Abstract #2016). In this study, we employed a human tissue microarray (TMA) co-immunostained for PLK1, N-cadherin, E-cadherin and the melanoma biomarker S100 to determine the association between PLK1 and EMT effectors. This TMA, coupled with high-throughput, multispectral Vectra scanning and inForm analysis, allowed us to objectively analyze and quantify protein levels in 57 clinical tissue specimens of nevus (n=15), primary (n=22) and metastatic melanoma (n=20). We observed an increase in PLK1 expression in primary and metastatic melanoma as compared to benign nevi, with a significant increase in metastatic tumors compared to primary tumors (p=0.004). Similarly, N-cadherin expression was markedly higher in metastatic melanoma (fold-change=2.31; p=0.001) and primary melanoma (fold-change=1.8; p=0.03) when compared to benign nevi. Further, we observed a significant decrease in E-cadherin expression in metastatic tumors compared to primary melanoma (fold-change=2.53; p=0.02). Moreover, using single linear regression analyses between expression of two proteins, we found a significant strong positive correlation between PLK1 and mesenchymal marker N-cadherin (correlation co-efficient R=0.75; p<0.01). We also found a weak but negative correlation between PLK1 and epithelial marker E-cadherin (correlation co-efficient R=-0.25). To further confirm the role of PLK1 in EMT, using shRNA-mediated PLK1 knockdown in SK-MEL-2 cells (a human melanoma line that possesses high metastatic potential), we performed cell migration and invasion assays, as well as immunofluorescence staining for expression of N-cadherin and E-cadherin. Interestingly, we found a decrease in expression of mesenchymal marker N-cadherin and an increase in expression of epithelial marker E-cadherin after PLK1 knockdown. These were accompanied by decreased cell migration and invasion, suggesting that inhibition of PLK1 in these human melanoma cells leads to inhibition of EMT. Overall, these results suggest that PLK1 is an important regulator of EMT in melanoma, and therefore can be exploited as a therapeutic target to inhibit melanoma metastasis.

Citation Format: Gagan Chhabra, Mary A. Ndiaye, Shengqin Su, Chandra K. Singh, Nihal Ahmad. Polo-like kinase 1 positively correlates with N-cadherin and promotes epithelial-mesenchymal transition in melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1875.

Abstract 302: The combined inhibition of Plk1 and Notch1 results in a synergistic anti-proliferative response in human melanoma cells

Melanoma is the most aggressive form of skin cancer, and its incidence and mortality have been increasing over the past thirty years. Therefore, additional therapeutic strategies are needed for an effective management of this neoplasm. We previously demonstrated that polo-like kinase 1 (Plk1, a serine/threonine kinase involved in mitotic regulation) and Notch1 (a type I transmembrane protein deciding cell fate during development) are strongly correlated in melanoma (Cancer Res 2018; 78 (13 Suppl): Abstract nr 2530). In addition, a number of studies from our lab and elsewhere have suggested the important functions of Plk1- as well as Notch- signaling in melanoma progression. Based on these observations, in this study, we determined the potential efficacy of a combined inhibition of Plk1 and Notch1 against melanoma cells. Employing Plk1 inhibitor volasertib (BI6727) and Notch1 inhibitor MK-0752, we determined the effects of concomitant targeting of these pathways in A375 (wild type TP53) and SK-MEL-2 (mutant TP53) human melanoma cell lines. Employing RealTime-Glo and trypan blue exclusion assays, we found that volasertib (10 and 20 nM) and MK-0752 (50 and 100 μM) resulted in a significant decrease (60-80%) in viability and growth of human melanoma cells A375 and SK-MEL-2. The Combination Index (CI), as calculated using the Chou-Talalay theorem, was less than 1 when volasertib at 10 nM was given with MK-0752 at 50 and 100 μM, indicating a synergism between these two drugs. As a result of the synergism, the melanoma cells treated with combined drugs showed decreased colony formation ability compared to individual drugs. In addition, the combined treatment also resulted in enhanced apoptosis of melanoma cells. Interestingly, cell cycle analysis by flow cytometry showed that combined inhibition of Plk1 and Notch1 caused a G2-M phase arrest of melanoma cells. Furthermore, our data demonstrated that volasertib and MK-0752 combination caused a marked increase of cleaved PARP (poly ADP ribose polymerase) and cleaved caspase-3 in both melanoma cell lines, as well as increased expression of tumor suppressor protein TP53 and its target p21 (CDKN1A) in A375 melanoma cells. Taken together, our data demonstrated that a combined targeting of Plk1- and Notch1- signaling pathways imparts a synergistic anti-proliferative response against melanoma. However, additional experiments are needed i) to validate our in vitro data to in vivo situations in human relevant melanoma models, and ii) to define the interactive mechanism(s) of the observed synergistic response.

Citation Format: Shengqin Su, Gagan Chhabra, Chandra K. Singh, Mary A. Ndiaye, Nihal Ahmad. The combined inhibition of Plk1 and Notch1 results in a synergistic anti-proliferative response in human melanoma cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 302.

Molecular approach for ante-mortem diagnosis of rabies in dogs

Background & objectives:

The ante-mortem diagnosis of rabies is of great significance in establishing the status of infection in dogs, especially since they are involved in exposure to human beings. The present study was, therefore, undertaken to elucidate the most appropriate secretion/tissue for reliable diagnosis of rabies in 26 living dogs suspected to be rabid.

Methods:

In the present study 26 dogs suspected to have rabies were included for ante-mortem diagnosis of rabies in clinical samples of skin and saliva by molecular approach viz. heminested reverse-transcriptase polymerase chain reaction (HnRT-PCR). Skin and saliva samples were collected from 13 dogs each.

Results:

Of the 13 clinically suspected dogs, fluorescent antibody technique (FAT) confirmed rabies in nine cases of dogs. Of these nine true-positive dogs, eight cases could be confirmed by HnRT-PCR from skin. Of the other 13 dogs clinically suspected for rabies, FAT confirmed rabies in 10 cases. Of these 10 true-positive dogs, rabies was detected ante-mortem by HnRT-PCR from the saliva in seven dogs. Thus, rabies was detected from skin with 90 per cent sensitivity, 100 per cent specificity and 92.85 per cent accuracy. With saliva, rabies was detected with a sensitivity of 76.92 per cent, specificity of 100 per cent and accuracy of 62.50 per cent. The positive predictive values were 100 per cent for both skin and saliva samples while negative predictive values were 80 and 50 per cent, respectively.

Interpretation & conclusions:

Skin biopsy may be more appropriate clinical sample as compared to saliva for ante-mortem diagnosis of rabies in dogs. HnRT-PCR can be employed for molecular diagnosis of rabies from skin in live dogs.

Chemoprotective Effects of Dietary Grape Powder on UVB Radiation-Mediated Skin Carcinogenesis in SKH-1 Hairless Mice

Skin cancer is the most frequently diagnosed cancer in the United States, and solar UVR is an established causative factor for approximately 90% of these cases. Despite efforts aimed at UV protection, including use of sunscreen and clothing, annual cases of skin cancer continue to rise. Here, we report that dietary grape powder mitigates UVB-mediated skin carcinogenesis in an SKH-1 hairless mouse model. Using a UVB initiation-promotion protocol, whereby mice were exposed to 180 mJ/cm² UVB two times per week for 28 weeks, we determined the effects of a grape powder-fortified diet (3% or 5%) on skin carcinogenesis. Grape powder consumption at both doses resulted in marked inhibition in tumor incidence, as well as a delay in onset of tumorigenesis. Molecular analyses of skin and tumor tissue showed that grape powder-mediated protective response against UVB-induced skin cancer was accompanied by enhanced DNA damage repair, reduced proliferation, increased apoptosis, and modulations in several oxidative stress markers specifically related to inhibition of oxidative stress and increased reactive oxygen species metabolism. NRF2, an activator of cellular antioxidant response, was decreased by grape powder feeding, suggesting a supportive role in tumor cell survival. Overall, our study suggested that dietary grape, containing several antioxidants in natural amalgamation, may protect against UVB-mediated skin carcinogenesis.

Effects and Mechanism of Nicotinamide Against UVA- and/or UVB-mediated DNA Damages in Normal Melanocytes

Melanoma incidences are increasing rapidly, and ultraviolet (UV) radiation from the sun is believed to be its major contributing factor. UV exposure causes DNA damage in skin which may initiate cutaneous skin cancers including melanoma. Melanoma arises from melanocytes, the melanin-producing skin cells, following genetic dysregulations resulting into hyperproliferative phenotype and neoplastic transformation. Both UVA and UVB exposures to the skin are believed to trigger melanocytic hyperplasia and melanomagenesis. Melanocytes by themselves are deficient in repair of oxidative DNA damage and UV-induced photoproducts. Nicotinamide, an active form of vitamin B3 and a critical component of the human body's defense system has been shown to prevent certain cancers including nonmelanoma skin cancers. However, the mechanism of nicotinamide's protective effects is not well understood. Here, we investigated potential protective effects and mechanism of nicotinamide against UVA- and/or UVB- induced damage in normal human epidermal melanocytes. Our data demonstrated an appreciable protective effect of nicotinamide against UVA- and/or UVB- induced DNA damage in melanocytes by decreasing both cyclobutane pyrimidine dimers and 8-hydroxy-2'-deoxyguanosine levels. We found that the photoprotective response of nicotinamide was associated with the activation of nucleotide excision repair genes and NRF2 signaling. Further studies are needed to validate our findings in in vivo models.

Abstract 547: The potential role of polo-like kinase 4 in non-melanoma skin cancers

Nonmelanoma skin cancers (NMSC), including basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), are the most common malignancies in the United States, with over 5.4 million cases treated in more than 3.3 million people each year. The existing preventive and therapeutic strategies have not been fully effective in NMSC management. Therefore, an enhanced knowledge of the molecular mechanisms of NMSC may provide novel targets for prevention and treatment of these cancers. This study was undertaken to determine the potential role of the serine/threonine kinase, polo-like kinase 4 (PLK4) in NMSC. PLK4 plays an important role in cell division by regulating centriole duplication during the cell cycle. Essentially, PLK4 is a low abundance suicidal kinase capable of auto-phosphorylating itself to cause its own destruction to limit centriole duplication once per cell cycle phase. Since centrosome aberrations are frequently seen in cancer, the central role of PLK4 in centriole duplication suggests its significance as a potential target for cancer management. In this study, employing in vitro and ex vivo approaches, we tested the hypothesis that PLK4 is differentially expressed in NMSC and may be used as a potential new target for the management of these neoplasms. Employing real time quantitative polymerase chain reaction as well as immunoblot analyses, we found that compared to normal human epidermal keratinocytes (NHEKs), PLK4 was significantly overexpressed in human epidermoid carcinoma A431 cells and basal cell carcinoma UW-BCC1 cell lines at both mRNA and protein levels. Further, we determined the expression profile of PLK4 in NMSC using immunohistochemical analysis of multiple tissue microarrays containing cores of normal skin, BCC and SCC. Our data demonstrated a marked overexpression of PLK4 in cancerous tissues, compared to normal skin. To further assess the role of PLK4 overexpression in NMSC, we determined the effects of small molecule inhibitors of PLK4, centrinone-B and CFI-400945 in vitro. We found that treatment with centrinone-B or CFI-400945 resulted in dose- as well as time-dependent decreases in the growth and viability. Further, centrinone-B and CFI-400945 treatments also resulted in a marked reduction in the clonogenic survival of skin cancer cells. Taken together, our study suggests that PLK4 has a pro-proliferative function in NMSC. Additional detailed studies are ongoing in our laboratory to determine the functional significance of PLK4 in NMSC. Based on our data, we suggest that PLK4 should be further evaluated as a potential target and prognostic biomarker for the management of NMSC.

Citation Format: Debra R. Garvey, Mary A. Ndiaye, Chandra K. Singh, Ambria Noll, Nihal Ahmad. The potential role of polo-like kinase 4 in non-melanoma skin cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 547.

Abstract 5830: Combination of volasertib (BI6727) and abemaciclib (LY2835219) for melanoma management: Concomitant targeting of multiple cell cycle phases

Melanoma is one of the most lethal forms of skin cancer that kills an average of around one person every hour in the United States alone. Melanoma can be surgically removed if diagnosed early, however, undiagnosed or untreated melanomas can rapidly metastasize to become lethal. Significant progress has been made in the treatment of metastatic melanoma over the past decade, especially with novel targeted therapeutic approaches (such as BRAF- and MEK- inhibitors or immunotherapies). However, even with these newer therapies, melanoma can acquire resistance and become untreatable, with fatal consequences. Therefore, novel therapeutic approaches are required for the management of this neoplasm. It is commonly accepted that mechanism-based combination therapeutics could be better for an efficient and complete elimination of cancer cells, thereby limiting the chances of recurrence and resistance. Based on this rationale, we reasoned that a simultaneous targeting of G2/M and G1 phases of the cell cycle could provide a more efficacious response against melanoma. Studies in our laboratory have suggested that polo-like kinase 1 (PLK1), which is a mitotic regulator acting in the G2/M phase of the cell cycle, is overexpressed in melanoma and is a potentially druggable target for melanoma management. We demonstrated that BI6727, a small-molecule PLK1 inhibitor, resulted in delay and regression of melanoma xenografts. Similarly, dysregulation of the p16-cyclin D1-CDK4/6-Rb pathway has been shown to frequently occur in melanoma, and CDK4/6 inhibition is being extensively investigated in the management of several cancers, including melanoma. In this study, we evaluated the anti-proliferative efficacy of a combination of G2/M-phase targeting by BI6727 and G1-phase targeting by the CDK4/6 inhibitor LY2835219 in human melanoma cells. We determined the effect of BI6727 and/or LY2835219 on growth and viability of human melanoma cells using the RealTime-Glo Cell Viability- and Trypan Blue exclusion- assays. We found that the combination of BI6727 and LY2835219 resulted in a better anti-proliferative response, when compared to either of the agents alone. Further, the combination treatment was found to result in a marked decrease in the clonogenic survival of melanoma cells, as assessed by colony formation assay. Cell cycle analysis showed a G2/M-phase arrest in BI6727 treated cells and G1-phase arrest in LY2835219 treated cells. Interestingly, the combination was found to cause G2/M as well as G1- phase arrest of melanoma cells. Overall, our data suggests that a concomitant inhibition of PLK1 with CDK4/6 provides a superior anti-proliferative response, suggesting that dual inhibition should be further evaluated in detailed in vitro and in vivo experiments. Additional studies to determine the mechanisms of this combination are currently underway in our laboratory.

Citation Format: Sanghamitra Nethramurthy, Mary A. Ndiaye, Chandra K. Singh, Nihal Ahmad. Combination of volasertib (BI6727) and abemaciclib (LY2835219) for melanoma management: Concomitant targeting of multiple cell cycle phases [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5830.

Abstract 548: The effects of Sirtuin 6 inhibition on autophagy-related pathways in melanoma

Melanoma is an aggressive skin cancer that can rapidly metastasize to become fatal, if not diagnosed early. Despite therapeutic advances, clinical management of melanoma remains challenging. The existing chemotherapeutic drugs either fail to achieve greater than 25% response or ultimately develop resistance to therapy. Therefore, novel molecular targets and treatments are required for an effective management of melanoma. In order to design novel and more effective approaches for lasting cure of melanoma, a deeper understanding of the mechanisms involved in melanomagenesis are needed. In our laboratory, we are assessing the role and functional and therapeutic significance of sirtuin proteins in melanoma. We have previously demonstrated that Sirtuin 6 (SIRT6) is significantly overexpressed in human melanoma cells and clinical tissues, and its genetic knockdown resulted in a marked anti-proliferative response in human melanoma cells (Genes & Cancer; In Press). A limited number of studies have implicated SIRT6 in autophagy regulation. Autophagy forms part of a basic cellular process that copes with cellular stress and is considered to be an important metabolic mechanistic essential for degradation and recycling of unnecessary intracellular components. In melanoma autophagy is believed to be a tumor suppressing process in early stages of cancer, but tumor-promoting in established tumors. This study was designed to determine the connection between SIRT6 and autophagy in melanoma. Employing lentiviral short hairpin RNA-mediated knockdown of SIRT6 in A375 melanoma cells, we determined the modulation in autophagy related pathways. We employed a PCR array containing 84 genes that are involved in the regulation of autophagy. Our data demonstrated that 17 of the 84 genes were significantly modulated (two-fold or more) upon SIRT6 knockdown. Of these 17 genes, 2 were upregulated (ATG10 and GAA) and 15 were downregulated (AKT1, ATG12, ATG3, ATG7, BAK1, BCL2L1, CLN3, CTSB, CTSS, DRAM2, HSP90AA1, IRGM, NPC1, SQSTM1, and TNF). Modulated genes were analyzed using Ingenuity Pathway Analysis (IPA) for predicted gene-gene interactions and functional networks. Many of the network genes were found to have definitive links to cancer. These genes were found to be associated with cell transformation and tumor invasion. Further validation at mRNA and protein levels, confirmed the significant modulations in autophagy markers BECN1, SQSTM1, ATG3, ATG7, ATG10 and GAA, upon SIRT6 knockdown. Moreover, SIRT6 knockdown was found to cause a marked decrease in the LC3 II protein level, which is a central protein in the autophagy pathway. Taken together, our data suggest that SIRT6 knockdown significantly alters pathways related to autophagy in melanoma cells. Future studies are required to carefully study the role of SIRT6 and autophagy in early versus late melanomas.

Citation Format: Liz M. Garcia-Peterson, Mary A. Ndiaye, Chandra K. Singh, Gagan Chhabra, Nihal Ahmad. The effects of Sirtuin 6 inhibition on autophagy-related pathways in melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 548.

Abstract 1260: Mechanism of skin cancer chemoprevention by dietary grape: A global proteomics approach

Non-melanoma skin cancer (NMSC), composed mainly of squamous cell carcinomas (SCC) and basal cell carcinomas (BCC), is the most commonly diagnosed form of cancer in the United States, with more than 5 million cases diagnosed each year. Ultraviolet (UV) radiation, a major component of sunlight, is the primary contributing factor in the development of NMSCs. Based on research in the past few decades, the naturally occurring dietary antioxidants have shown considerable promise towards preventing or delaying the process of carcinogenesis. We have previously demonstrated that dietary grape powder (GP) imparts considerable chemopreventive effects against UVB exposure-mediated skin carcinogenesis in SKH-1 hairless mice (AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5263). Here, we extended our study to determine the molecular mechanisms associated with the observed chemopreventive response of grapes. We employed a quantitative proteomics approach to identify the mechanism of observed protective effects of GP against UVB exposure-mediated skin carcinogenesis. The trypsin-digested protein extracts from UVB exposure-mediated skin tumors excised from control and 5% GP-fed mice were labeled using TMT10plex isobaric mass tagging reagents, fractionated, and analyzed by high-resolution Orbitrap LC-MS/MS. Post-acquisition analysis was performed using MaxQuant and Perseus computational software. We found that approximately 2600 total proteins were modulated by GP consumption. In our first set of data reduction, we used cut-off parameters of a p-value less than 0.05, 3 unique peptides, and greater than 1.2 fold change. A low fold change threshold was selected due to ratio compression, a known phenomenon in isobaric mass tagging which leads to underestimation of quantitative ratios. The resulting subset of 239 proteins were then subjected to Ingenuity Pathway Analysis (IPA), which identified Acute Phase Response (APR), a systemic response to trauma which is linked to poor cancer prognosis when prolonged, as a pathway affected by GP. We observed modulations in nine APR proteins (APCS, HP, RBP1, FGB, FGA, CRABP2, C1S, HPX, IL36G, AMBP). Application of a more stringent data filter (permutation FDR q-value less than 0.07) exposed a subset of 20 proteins. When analyzed by IPA, the results suggested that GP affects signaling proteins associated with the 20s proteasome (PSMA6, PSMA3, and PSMB7) and 19s proteasome (UCHL5), both components of the 26s proteasome signaling, which plays an important role in cancer. Further studies are underway to validate our proteomics data.

Citation Format: Charlotte A. Mintie, Chandra K. Singh, Mary A. Ndiaye, Gregory A. Barrett-Wilt, Nihal Ahmad. Mechanism of skin cancer chemoprevention by dietary grape: A global proteomics approach [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1260.

Abstract 539: Pro-proliferative function of the histone deacetylase SIRT3 in prostate cancer

Worldwide, prostate cancer (PCa) is the second most frequently diagnosed cancer and fifth leading cause of cancer death in males. The existing treatments, as well as surgical approaches, have not been fully effective either for prevention or treatment of PCa. This necessitates a need to intensify our efforts towards the understanding of genetics and mechanism(s) of PCa. This may lead to the identification of the novel molecular target(s) and mechanism-based approaches for the management of this neoplasm. Sirtuin-3 (SIRT3) is a nicotinamide adenine dinucleotide (NAD)-dependent deacetylase primarily located in the mitochondria and known to play important roles in the regulation of a variety of cellular processes, including transcription and programmed cell death. The fact that SIRT3 can regulate several cellular processes those are critical in cancer cell proliferation, makes it a potential therapeutic target for cancer management. Moreover, SIRT3 is a central regulator of mitochondrial adaptive responses that relate to metabolic reprogramming of cancer cells. However, the role of SIRT3 in cancer, including PCa, is not well understood and it has been shown to act both as a tumor suppressor as well as a tumor promoter. In this study, we determined the role of SIRT3 in PCa, employing in vitro and ex vivo approaches. The first step in our efforts to understand the role of SIRT3 in PCa was to check the expression profile of SIRT3 in a panel of human PCa cell line (DU145, 22Rν1, PC3, LNCaP, C4-2, MDA PCa 2b, E006AA-Par and E006AA-hT) by RT-qPCR and immunoblot analyses. Compared to normal human prostate epithelial cells (NrPEC), PCa cells showed higher expression of SIRT3, both at mRNA and protein levels. Further, we determined the expression profile of SIRT3 by immunostaining of a tissue microarray (TMA) containing paraffin-embedded sections of 40 cases of prostate adenocarcinoma and 8 normal prostate tissues. Our data demonstrated a significant upregulation of SIRT3 in cancerous prostatic tissues compared to the normal tissues. We next determined the effect of chemical inhibition of SIRT3 using a recently described SIRT3 inhibitor viz. 4'-Bromo-Resveratrol (4BR), in human PCa cells (DU145 and 22Rν1). 4BR treatment at 10, 20 and 40 μM concentrations for 48 and 72 h resulted in a dose- and time-dependent decrease in cell growth and proliferation. Further, 4BR treatment resulted in a marked decrease in clonogenic survival of DU145 and 22Rν1 PCa cells. Furthermore, 4BR treatment resulted in a marked cleavage of PARP, an indicator of apoptosis induction; and a decrease in the level of PCNA, a marker of cellular proliferation, in human PCa cells. Overall, our data suggest a possible pro-proliferative function of SIRT3 in PCa. Further studies are underway to unravel the role and functional significance of SIRT3 during PCa development and progression.

Citation Format: Chandra K. Singh, Gagan Chhabra, Minakshi Nihal, Kenneth A. Iczkowski, Nihal Ahmad. Pro-proliferative function of the histone deacetylase SIRT3 in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 539.

Abstract 2530: An analysis of correlative interactions between Plk1, Notch1 and FoxM1 in melanoma

Melanoma is one of the most aggressive forms of skin cancer, and existing therapies have not been effective in managing this neoplasm. Therefore, a deeper understanding of the mechanisms of melanoma development/progression is required. The goal of this study was to define the potential interactions between several key melanoma-linked proteins, namely Polo-like kinase 1 (Plk1; a cell cycle regulator involved in G2/M transition), Notch (Notch1; a type I transmembrane protein that decides cell fate during development), and forkhead box M1 (FoxM1; a transcription factor regulating S and G2/M phases of cell cycle) in human melanoma. Previously, we have shown that Plk1 is overexpressed in melanoma, and its inhibition results in G2/M phase arrest and apoptosis in multiple melanoma cells. Recent studies have shown that both Notch1 and FoxM1 may be involved in the pathogenesis of certain cancers, including melanoma. In this study, employing an in-house human tissue microarray (TMA) coupled with high-throughput, multispectral Vectra scanning and inForm analysis, we analyzed 126 clinical tissue specimens of normal skin and localized cutaneous melanoma. The TMA was co-immunostained for Plk1, Notch1, FoxM1, and the melanoma biomarker S100, followed by Vectra scanning and analyses with inForm software. Using this system, we determined the levels of Plk1, Notch1, and FoxM1 in both the nucleus and cytoplasm of melanoma cells which were positive for S100 staining. By applying statistical tools of Wilcoxon Signed-Rank Test and Pearson's Correlation Coefficient in R programming, we found that while all the proteins are detected in both nucleus and cytoplasm, FoxM1 and Notch1 are enriched in the nucleus, and Plk1 is enriched in the cytoplasm. Visualization of the correlation coefficients on a heat-map showed that all 3 sets of proteins (Plk1:Notch1, Plk1:FoxM1, and Notch1:FoxM1) are positively correlated, with Plk1:Notch1 having the strongest correlation, and FoxM1 having a weaker correlation with the other two proteins. The associative relationship between Plk1 and Notch1 leads to the hypothesis that Plk1 and Notch1 may be positively correlated in melanoma. We further studied how Breslow thickness, a measure of melanoma aggressiveness, is related to Plk1, Notch1 and FoxM1. By analyzing the TMA cores with available clinical data, we found a positive correlation between Breslow thickness and Notch1, as well as Plk1. Interestingly, although Breslow thickness was significantly correlated with FoxM1 in the nucleus, no correlation was found in the cytoplasm, suggesting that FoxM1 levels may be independent of Plk1 and Notch1. Overall, our study found novel correlative interactions between Plk1 and Notch1 in melanoma, which may have relevance to melanoma progression. Additional studies are needed to validate our findings and dissect the possible interaction between Plk1 and Notch1 during melanoma development and progression.

Citation Format: Shengqin Su, Chandra K. Singh, Mary A. Ndiaye, Vijayasaradhi Setaluri, Nihal Ahmad. An analysis of correlative interactions between Plk1, Notch1 and FoxM1 in melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2530.

Abstract 2016: Potential role of polo-like kinase 1 in epithelial-mesenchymal transition in melanoma

Mammalian polo-like kinase 1 (Plk1), an important serine/threonine kinase, has been shown to be a critical regulator of mitosis and cytokinesis. A number of studies, including those from our laboratory, have shown that Plk1 is significantly overexpressed in several cancers, including melanoma. Plk1 has also been linked with poor disease prognosis in cancer patients. A limited number of recent studies have suggested that Plk1 may be involved in epithelial-mesenchymal transition (EMT) in different cancers. However, the role of Plk1 in EMT process in melanoma has not been studied. Indeed, EMT plays a driving role in the acquisition of cancer metastasis and an important hallmark of EMT is downregulation of epithelial marker E-cadherin, and upregulation of mesenchymal marker, N-cadherin. In this study, we investigated whether the kinase activity of Plk1 plays a role in EMT process by modulating EMT markers in melanoma cells. To determine this, we performed western blots, RT-qPCR, cell migration and cell invasion assays using A375 melanoma cells stably transfected with plasmids for wild-type (WT) Plk1 overexpression, constitutively active Plk1 (T210D) and kinase-inactive (K82R) Plk1, as well as shRNA-mediated Plk1 knockdown. We observed that overexpression of WT Plk1 upregulated the mesenchymal markers N-cadherin, Vimentin, and Fibronectin, and downregulated the epithelial marker E-cadherin. We also found that the modulation in EMT markers by Plk1 in melanoma cells was associated with the upregulation of transcription factors Snail and Zeb1. Interestingly, downregulation of endogenous Plk1 by specific shRNA resulted in a downregulation of N-cadherin, Vimentin, Fibronectin, Snail and Zeb1. Further, when we assessed the EMT-related molecular changes in A375 melanoma cells containing constitutively active and kinase-inactive Plk1, the cells containing constitutively active Plk1 showed a significant decrease in epithelial marker as well as marked increases in mesenchymal markers. However, the cells containing kinase-inactive Plk1 showed the opposite trend. Moreover, A375 melanoma cells containing constitutively active Plk1 showed higher migration and invasion potential, whereas cells containing kinase-inactive Plk1 showed limited cell migration and invasion. Overall, these results suggest that Plk1 is involved in the EMT process and its kinase activity is important for EMT-related changes in melanoma cells. Further studies are in progress to determine the cause-and-effect molecular mechanisms of Plk1 mediated EMT regulation.

Citation Format: Gagan Chhabra, Chandra K. Singh, Mary A. Ndiaye, Nihal Ahmad. Potential role of polo-like kinase 1 in epithelial-mesenchymal transition in melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2016.

The Role of Sirtuins in Antioxidant and Redox Signaling

SIGNIFICANCE

Antioxidant and redox signaling (ARS) events are regulated by critical molecules that modulate antioxidants, reactive oxygen species (ROS) or reactive nitrogen species (RNS), and/or oxidative stress within the cell. Imbalances in these molecules can disturb cellular functions to become pathogenic. Sirtuins serve as important regulators of ARS in cells. Recent Advances: Sirtuins (SIRTs 1-7) are a family of nicotinamide adenine dinucleotide (NAD)-dependent histone deacetylases with the ability to deacetylate histone and nonhistone targets. Recent studies show that sirtuins modulate the regulation of a variety of cellular processes associated with ARS. SIRT1, SIRT3, and SIRT5 protect the cell from ROS, and SIRT2, SIRT6, and SIRT7 modulate key oxidative stress genes and mechanisms. Interestingly, SIRT4 has been shown to induce ROS production and has antioxidative roles as well.

CRITICAL ISSUES

A complete understanding of the roles of sirtuins in redox homeostasis of the cell is very important to understand the normal functioning as well as pathological manifestations. In this review, we have provided a critical discussion on the role of sirtuins in the regulation of ARS. We have also discussed mechanistic interactions among different sirtuins. Indeed, a complete understanding of sirtuin biology could be critical at multiple fronts.

FUTURE DIRECTIONS

Sirtuins are emerging to be important in normal mammalian physiology and in a variety of oxidative stress-mediated pathological situations. Studies are needed to dissect the mechanisms of sirtuins in maintaining redox homeostasis. Efforts are also required to assess the targetability of sirtuins in the management of redox-regulated diseases. Antioxid. Redox Signal. 28, 643-661.

Prostate cancer chemoprevention by natural agents: Clinical evidence and potential implications

Prostate cancer (PCa) is the most common non-skin cancer and the second leading cause of cancer-related deaths in American men. Due to its long latency period, PCa is considered as an ideal cancer type for chemopreventive interventions. Chemopreventive agents include various natural or synthetic agents that prevent or delay cancer development, progression and/or recurrence. Pre-clinical studies suggest that many natural products and dietary agents have chemopreventive properties. However, a limited number of these agents have been tested in clinical trials, with varying success. In this review, we have discussed the available clinical studies regarding the efficacy of natural chemopreventive agents against PCa, including tea polyphenols, selenium, soy proteins, vitamins and resveratrol. We have also provided a discussion on the clinical challenges and opportunities for the potential use of chemopreventive agents against PCa. Based on available literature, it appears that the variable outcomes of the chemopreventive clinical studies necessitate a need for additional studies with more rigorous designs and methodical interpretations in order to measure the potential of the natural agents against PCa.

Centriole Overduplication is the Predominant Mechanism Leading to Centrosome Amplification in Melanoma

Centrosome amplification (CA) is common in cancer and can arise by centriole overduplication or by cell doubling events, including the failure of cell division and cell-cell fusion. To assess the relative contributions of these two mechanisms, the number of centrosomes with mature/mother centrioles was examined by immunofluorescence in a tissue microarray of human melanomas and benign nevi (n = 79 and 17, respectively). The centrosomal protein 170 (CEP170) was used to identify centrosomes with mature centrioles; this is expected to be present in most centrosomes with cell doubling, but on fewer centrosomes with overduplication. Using this method, it was determined that the majority of CA in melanoma can be attributed to centriole overduplication rather than cell doubling events. As Polo-like kinase 4 (PLK4) is the master regulator of centriole duplication, the hypothesis that PLK4 overexpression contributes to centriole overduplication was evaluated. PLK4 is significantly overexpressed in melanoma compared with benign nevi and in a panel of human melanoma cell lines (A375, Hs294T, G361, WM35, WM115, 451Lu, and SK-MEL-28) compared with normal human melanocytes. Interestingly, although PLK4 expression did not correlate with CA in most cases, treatment of melanoma cells with a selective small-molecule PLK4 inhibitor (centrinone B) significantly decreased cell proliferation. The antiproliferative effects of centrinone B were also accompanied by induction of apoptosis.Implications: This study demonstrates that centriole overduplication is the predominant mechanism leading to centrosome amplification in melanoma and that PLK4 should be further evaluated as a potential therapeutic target for melanoma treatment. Mol Cancer Res; 16(3); 517-27. ©2018 AACR.

Exploring animal rabies endemicity to inform control programmes in Punjab, India

Previous studies estimate that one-third of the annual global burden of rabies (~20,000 cases) occurs in India. Elimination of canine rabies is essential to reduce this burden. Surveillance of animal cases can assess both the risk to humans and the efficacy of control strategies. The objective of this study was to describe the spatial and temporal occurrence of reported confirmed cases of rabies in animals in Punjab, India, from 2004 to 2014. We analysed passive surveillance data on 556 samples submitted from 2004 to 2014 to GADVASU, Ludhiana, Punjab, India. Regression and time series analyses were conducted to understand seasonal and long-term variation of cases and identify cross-correlation of monthly cases between species. Spatio-temporal analyses assessed spatial autocorrelation of date of reporting, mean geographic centres of disease occurrence and clustering of cases using Kulldorff's space-time permutation statistic. The annual number of submissions and proportion of confirmed cases were consistent throughout 2004-2014. Most submissions (320; 57.6%) were confirmed rabies cases, including dogs (40.6%), buffalo (29.7%) and cattle (23.1%). Regression analysis of monthly cases in dogs showed seasonal variation with significant increases in cases in March and August. Monthly case numbers in buffalo decreased over time. Long-term temporal trend was not detected in dog and cattle cases. Time-series models identified significant cross-correlation between dog and buffalo cases, suggesting that buffalo cases were spillover events from dogs. Significant spatio-temporal variation or clusters of cases were not detected. These results indicate that rabies cases in animals-and therefore, the potential for exposure to humans-were temporally and spatially stable during 2004-2014 in Punjab, India. The endemic nature of rabies transmission in this region demands a coordinated, sustained control programme. This study provides baseline information for assessing the efficacy of rabies control measures and developing seasonally targeted dog vaccination and rabies awareness strategies.

Abstract 4139: Role of zinc transporters in prostate cancer and a potential association with racial disparity

Optimal intracellular zinc concentration is essential for many cellular functions as it serves as a catalytic and/or structural cofactor for a variety of proteins. Although, a number of proteins are tangled in regulating cellular zinc homeostasis, the most important are two protein families of zinc transporters, 14 members of solute carrier family 39 (SLC39A) and 10 members of solute carrier family 30 (SLC30A). These two families are known to transport zinc into- and out of- the cytoplasm, respectively. Prostate cells accumulate a high amount of zinc to sustain a metabolic condition unique to the prostate which is characterized by a truncation of the Krebs cycle and production of high amounts of citrate. Zinc depletion has frequently been noted in the progression of prostate cancer (PCa). Whether zinc transporters are a steering cause of zinc depletion in PCa development and progression and/or are key determinants in the racial disparity in PCa is not well studied. In this study, we determined the connection of zinc transporters (SLC39A 1-14 and SLC30A 1-10) in PCa, in the perspective of racial health disparity in human PCa samples taken from African-American (AA) and European-American (EA) patients and compared them with respective adjacent benign samples. We also assessed the mRNA level of zinc transporters in normal prostate epithelial cells (NrPEC and RWPE1) and among PCa cells derived from AA (MDA PCa 2b, E006AA-PAR, E006AA-HT) and EA patients (DU145, PC3, 22Rν1, LNCaP, C4-2B). In addition, we performed a dataset analysis of the Oncomine database for differential expression profile of zinc transporters in PCa versus normal prostate. We found that SLC39As mRNA levels were differentially expressed in PCa with a significant downregulation of SLC39A1, SLC39A10, SLC39A11, SLC39A13 and SLC39A14, and upregulation of SLC39A3, SLC39A5, SLC39A6 and SLC39A8. Further, SLC30As showed a significant downregulation of SLC30A5 and SLC30A6 and upregulation of SLC30A1, SLC30A9 and SLC30A10, in PCa. Further, compared to EA samples, the AA PCa showed an increasing trend of SLC39A5, SLC39A6 and SLC30A9. In addition, compared to AA samples, the EA PCa showed a trend of increasing SLC30A1 and SLC30A9 and decreasing SLC39A10. These data provide evidence that the zinc transporters may be linked to racial disparity of PCa in AA versus EA. Moreover, Ingenuity Pathway Analysis revealed regulatory interactions between zinc transporters and tumor suppressor/promoter genes proven to be modulated in PCa. These genes are HOXB13, ELAVL1, DIRAS3, ALPP, CSF2, CCL4, INSR, AKT, IL6, TGFBP1, CHI3L1, EGFR and HNF4A. Overall, our study provides interesting data about the expression profiles of zinc transporters and their interaction with tumor suppressor and promoter genes in PCa, which may offer novel strategies for the management of PCa by pharmacologically modulating zinc transporters.

Citation Format: Chandra K. Singh, Kareem M. Malas, Caitlin Tydrick, Kenneth A. Iczkowski, Nihal Ahmad. Role of zinc transporters in prostate cancer and a potential association with racial disparity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4139. doi:10.1158/1538-7445.AM2017-4139

Abstract 5263: Chemopreventive effects of dietary grapes on skin cancer

Non-melanoma skin cancer (NMSC) is the most commonly diagnosed malignancy in the United States, affecting more than 3 million Americans each year. Ultraviolet (UV) radiation from the sun, particularly its UVB component (290-320 nm), is an established causative factor for ~90% of skin cancers. The two most common forms of skin cancer, basal- and squamous- cell carcinomas, are treatable if detected early. However, they can be difficult to treat and potentially fatal if left until late stages. Further, epidemiological studies have suggested an amplified risk of other deadly cancers in individuals with a history of skin cancer. Therefore, it is important to design novel approaches, especially focusing on prevention, for the management of skin cancers. Studies from our laboratory and by others have shown that topical application of the grape antioxidant resveratrol possesses promise in the prevention of skin cancer. However, ideally cancer preventive agents need to be orally administrable for ease of use and broader human acceptability. With this in mind, in this study, we determined the efficacy of dietary grape powder (containing resveratrol in natural amalgamation with catechins, anthocyanins, polyphenols and flavonols) against UVB-mediated skin tumorigenesis in the SKH-1 hairless mouse model, which is regarded to have relevance to human NMSC. We employed a UVB initiation-promotion protocol in which the mice were subjected to chronic UVB exposure (180 mJ/cm2; twice weekly, for 28 weeks). The animals received either AIN-76A or grape powder (GP) fortified diet (3% and 5% GP, obtained from the California Table Grape Commission), all of which were sugar-matched to the highest GP content. Our data demonstrated that the consumption of GP at both 3% and 5% resulted in a significant inhibition in skin tumor incidence and delay in the onset of tumorigenesis. The average consumption of feed per mouse was 3.5 g/day, corresponding to 105 and 174 mg GP/day in the 3% and 5% GP treatment groups. This dosing regimen seems to be easily achievable for human consumption, as it corresponds to 25.5 and 42.4 g/day, which are equivalent to 1.1 and 1.8 serving of fresh grapes, respectively. Our data also demonstrated that the observed skin cancer chemopreventive effects of grape powder were accompanied by significant i) decreases in cellular proliferation markers Ki67 and PCNA, ii) decreases in the oxidative stress marker 4-HNE, and iii) increases in the levels of cleaved caspase 7 and poly (ADP-ribose) polymerase (PARP). Interestingly, NRF2, an activator of cellular antioxidant response, was found to be downregulated in GP treated tumors, compared to UVB alone groups, suggesting a potential protective role of NRF2 in the survival of tumor cells. Overall, our study suggests a strong chemopreventive effect of dietary grape and provides a basis for future human studies.

Citation Format: Chandra K. Singh, Mary A. Ndiaye, Charlotte A. Mintie, Gagan Chhabra, Nihal Ahmad. Chemopreventive effects of dietary grapes on skin cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5263. doi:10.1158/1538-7445.AM2017-5263

Abstract 5415: Targeted depletion of polo-like kinase 1 alters metabolic regulation in melanoma

Polo-like kinase 1 (PLK1), a critical regulator of mitosis, is shown to be overexpressed in a variety of cancers. PLK1 overexpression has also been linked to poor disease prognosis and a lessened survival in cancer patients. Previously, we have shown that PLK1 is overexpressed in human melanoma and its inhibition causes significant anti-proliferative response in vitro (in multiple melanoma cells) as well as in vivo (in human melanoma xenografts). Further, in another study we demonstrated, based on a large-scale label-free comparative proteomics analysis, that PLK1 inhibition via the small-molecule inhibitor BI 6727 (Volasertib) in human melanoma cells resulted in an alteration of certain metabolism-associated proteins with an associated decrease in cellular metabolism. In this study, to further explore the association between PLK1 and cellular metabolism, we utilized a doxycycline-inducible PLK1 knockdown approach in A375 melanoma cells coupled with a Human Glucose Metabolism PCR array that covers 84 key genes involved in the regulation and enzymatic pathways of glucose and glycogen metabolism. We found that PLK1 knockdown resulted in a significant downregulation of 29 genes and upregulation of 3 genes (more than 2 fold change) associated with cellular metabolism. IDH1, PDP2 and PCK1 were >3-fold downregulated while FBP1 was >7-fold upregulated. Through Ingenuity Pathway Analysis (IPA), we identified glycolysis and the pentose phosphate pathway as major canonical pathways altered by PLK1 inhibition. Further, IPA identified that PLK1 inhibition-modulated genes were largely associated with the proliferation of cells, where FBP1 appeared as a key regulatory player. PCK1 was found to be highly downregulated in our array, and IPA identified it as part of a monosaccharide regulation network. We further validated our data in vivo and found that BI 6727 treatment resulted in a decrease in PCK1 and increase in FBP1 in A375 melanoma cell implanted xenografts. In addition, we observed a strong inverse correlation between PLK1 and FBP1 in multiple melanoma cell lines, with FBP1 expression significantly downregulated in a panel of melanoma cells compared to normal melanocytes. Moreover, BI 6727 treatment resulted in an upregulation in FBP1 in A375, Hs 294T and G361 melanoma cells. Interestingly, in recent studies, FBP1 (fructose-bisphosphatase) that is a rate-limiting enzyme in gluconeogenesis, has been shown to function as a tumor suppressor in certain cancers. Overall, our study support the hypothesis that PLK1 is a regulator of metabolism maintenance that affects the melanoma cell growth.

Citation Format: Rosie E. Gutteridge, Chandra K. Singh, Mary A. Ndiaye, Nihal Ahmad. Targeted depletion of polo-like kinase 1 alters metabolic regulation in melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5415. doi:10.1158/1538-7445.AM2017-5415

Abstract 820: Potential pro-proliferative role of SIRT6 in melanoma

Melanoma is one of the deadliest form of skin cancer that can rapidly metastasize to become lethal, if not diagnosed early or left untreated. In 2016, approximately 76,380 new melanoma cases and 10,130 melanoma-related deaths are predicted in the United States. Current preventive and therapeutic strategies have not been sufficiently effective in the management of melanoma. Therefore, novel molecular targets and treatments are required for an effective management of this neoplasm. In our laboratory, we are assessing the role and functional and therapeutic significance of sirtuin family of proteins in melanoma. Sirtuins (SIRTs) have been conserved through evolution from prokaryotic to eukaryotic cells. SIRTs are nicotinamide adenine dinucleotide (NAD+) dependent protein deacetylases and belong to class III of the histone deacetylase (HDAC) family. Seven members of the mammalian SIRT family are known to date, and despite structural similarities, each SIRT has their own biological niche, performing unique functions via regulating critical mechanisms in the cell. The role of SIRTs in cancer is somewhat controversial, as they have exhibited conflicting functions (tumor promoter vs. tumor suppressor) depending on cell and tissue contexts. The sirtuin SIRT6, a predominantly nuclear protein, has been shown to conduct ADP-ribosyl transferase and histone deacetylase activities. SIRT6 plays key roles in DNA repair, inflammation and metabolic diseases such as cancer. Currently, the role of SIRT6 in melanoma is not known. The objective of this study was to determine the role of SIRT6 in melanoma. Using a panel of human melanoma cell lines (A375, Hs 294T, G361, SK-MEL-2, SK-MEL-28, SK-MEL-31, WM115 and WM35) differing in genetic complexity and disease progression stage, and normal human epidermal melanocytes (NHEMs), we determined the endogenous expression levels of SIRT6. We found that compared to NHEMs, SIRT6 is significantly upregulated in melanoma cell lines, at mRNA as well as protein levels, as shown by quantitative Real-Time PCR and western blot analyses. Further, employing a human tissue microarray (TMA) coupled with quantitative Vectra™ analysis, we determined the expression profile of SIRT6 protein in human melanoma and melanocytic nevus tissues. Our data demonstrated that SIRT6 is significantly overexpressed in human melanoma tissues when compared to nevi. Furthermore, lentiviral short hairpin RNA-mediated knockdown of SIRT6 in human melanoma cells was found to result in a marked anti-proliferative response in melanoma cells. Taken together, our data suggest that SIRT6 overexpression could potentially be a contributing factor in melanoma progression. Further detailed studies are underway to understand the functional significance of SIRT6 in melanoma development and progression.

Citation Format: Liz Garcia-Peterson, Mary A. Ndiaye, Chandra K. Singh, Wei Huang, Nihal Ahmad. Potential pro-proliferative role of SIRT6 in melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 820. doi:10.1158/1538-7445.AM2017-820

Targeted knockdown of polo-like kinase 1 alters metabolic regulation in melanoma

A limited number of studies have indicated an association of the mitotic kinase polo-like kinase 1 (PLK1) and cellular metabolism. Here, employing an inducible RNA interference approach in A375 melanoma cells coupled with a PCR array and multiple validation approaches, we demonstrated that PLK1 alters a number of genes associated with cellular metabolism. PLK1 knockdown resulted in a significant downregulation of IDH1, PDP2 and PCK1 and upregulation of FBP1. Ingenuity Pathway Analysis (IPA) identified that 1) glycolysis and the pentose phosphate pathway are major canonical pathways associated with PLK1, and 2) PLK1 inhibition-modulated genes were largely associated with cellular proliferation, with FBP1 being the key modulator. Further, BI 6727-mediated inhibition of PLK1 caused a decrease in PCK1 and increase in FBP1 in A375 melanoma cell implanted xenografts in vivo. Furthermore, an inverse correlation between PLK1 and FBP1 was found in melanoma cells, with FBP1 expression significantly downregulated in a panel of melanoma cells. In addition, BI 6727 treatment resulted in an upregulation in FBP1 in A375, Hs294T and G361 melanoma cells. Overall, our study suggests that PLK1 may be an important regulator of metabolism maintenance in melanoma cells.

Folic Acid Modulates Matrix Metalloproteinase-2 Expression, Alleviates Neuropathic Pain, and Improves Functional Recovery in Spinal Cord-Injured Rats

BACKGROUND

The molecular underpinnings of spinal cord injury (SCI) associated with neuropathic pain (NP) are unknown. Recent studies have demonstrated that matrix metalloproteinases (MMPs) such as MMP2 play a critical role in inducing NP following SCI. Promoter methylation of MMPs is known to suppress their transcription and reduce NP. In this context, it has been shown in rodents that folic acid (FA), an FDA approved dietary supplement and key methyl donor in the central nervous system (CNS), increases axonal regeneration and repair of injured CNS in part via methylation.

PURPOSE

Based on above observations, in this study, we test whether FA could decrease MMP2 expression and thereby decrease SCI-induced NP.

METHODS

Sprague-Dawley male rats weighing 250-270 g received contusion spinal cord injuries (cSCIs) with a custom spinal cord impactor device that drops a 10 g weight from a height of 12.5 mm. The injured rats received either i.p. injections of FA (80 µg/kg) or water (control) 3 days prior and 17 days post-cSCI (mid phase) or for 3 days pre-cSCI and 14 days post-cSCI ending on the 42nd day of cSCI (late phase). The functional neurological deficits due to cSCI were then assessed by Basso, Beattie, and Bresnahan (BBB) scores either on post-impaction days 0 through 18 post-cSCI (mid phase) or on days 0, 2, 7, 14, 21, 28, 35, and 42 (late phase). Baseline measurements were taken the day before starting treatments. Thermal hyperalgesia (TH) testing for pain was performed on 4 days pre-cSCI (baseline data) and on days 18, 21, 28, 35, and 42 post-cSCI. Following TH testing, animals were euthanized and spinal cords harvested for MMP-2 expression analysis.

RESULT

The FA-treated groups showed higher BBB scores during mid phase (day 18) and in late phase (day 42) of injury compared to controls, suggesting enhanced functional recovery. There is a transient decline in TH in animals from the FA-treated group compared to controls when tested on days 18, 21, 28, and 35, indicative of a decrease in NP. However, when tested 25 days after stopping FA administration on day 42 of cSCI, no significant difference in TH was observed between FA-treated and control animals. Western blot analysis of the injured spinal cord from FA-treated animals showed significant decline in MMP2 expression compared to spinal cord samples from water-treated controls.

CONCLUSION

Together, these data suggest that FA could alleviate NP and improve functional recovery post-SCI, possibly by reducing the expression of MMP2. Further studies will open up a novel and easy natural therapy, ideal for clinical translation with minimal side effects, for managing SCI-induced NP. Such studies might also throw light on a possible epigenetic mechanism in FA-induced recovery after SCI.

Targeted nanoparticles encapsulating (-)-epigallocatechin-3-gallate for prostate cancer prevention and therapy

Earlier we introduced the concept of ‘nanochemoprevention’ i.e. the use of nanotechnology to improve the outcome of cancer chemoprevention. Here, we extended our work and developed polymeric EGCG-encapsulated nanoparticles (NPs) targeted with small molecular entities, able to bind to prostate specific membrane antigen (PSMA), a transmembrane protein that is overexpressed in prostate cancer (PCa), and evaluated their efficacy in preclinical studies. First, we performed a molecular recognition of DCL- and AG-PEGylation on ligand binding on PSMA active site. Next, the biocompatible polymers PLGA-PEG-A were synthesized and used as base to conjugate DCL or AG to obtain the respective copolymers, needed for the preparation of targeted NPs. The resulting EGCG encapsulating NPs led to an enhanced anti-proliferative activity in PCa cell lines compared to the free EGCG. The behavior of EGCG encapsulated in NPs in modulating apoptosis and cell-cycle, was also determined. Then, in vivo experiments, in mouse xenograft model of prostatic tumor, using EGCG-loaded NPs, with a model of targeted nanosystems, were conducted. The obtained data supported our hypothesis of target-specific enhanced bioavailability and limited unwanted toxicity, thus leading to a significant potential for probable clinical outcome.