Guanylate-binding protein 1 modulates proteasomal machinery in ovarian cancer

Guanylate-binding protein 1 (GBP1) is known as an interferon-γ-induced GTPase. Here, we used genetically modified ovarian cancer (OC) cells to study the role of GBP1. The data generated show that GBP1 inhibition constrains the clonogenic potential of cancer cells. In vivo studies revealed that GBP1 overexpression in tumors promotes tumor progression and reduces median survival, whereas GBP1 inhibition delayed tumor progression with longer median survival. We employed proteomics-based thermal stability assay (CETSA) on GBP1 knockdown and overexpressed OC cells to study its molecular functions. CETSA results show that GBP1 interacts with many members of the proteasome. Furthermore, GBP1 inhibition sensitizes OC cells to paclitaxel treatment via accumulated ubiquitinylated proteins where GBP1 inhibition decreases the overall proteasomal activity. In contrast, GBP1-overexpressing cells acquired paclitaxel resistance via boosted cellular proteasomal activity. Overall, these studies expand the role of GBP1 in the activation of proteasomal machinery to acquire chemoresistance.

Abstract 511: A small molecule CET019 inhibits progression of triple negative breast cancer

Triple-negative breast cancer (TNBC) is the most aggressive form of breast cancer, which accounts for 15-20% of total diagnosed breast cancer cases with high rates of metastasis and recurrence. Metastatic breast cancer remains one of the leading causes of cancer related mortality in women. The majority of women with this disease relapse after curative-intent therapy for early breast cancer; while a smaller proportion present with distant metastases at initial diagnosis. Our efforts of developing effective therapies for TNBC have identified CET019, a novel small molecule that effectively inhibits the growth of breast cancer cells. We found that CET019 impedes the clonogenic potential and growth of triple-negative breast cancer cells (MDA-MB-231, MDA-MB-468, SUM159 and 4T1). CET019 treatment induces the G2/M phase cell cycle arrest in TNBC cells. Moreover, the mouse xenograft study with different TNBC models, found that CET019 inhibits growth and progression compared to vehicle control group. Metastatic nodules in the lungs were inhibited by CET019 compared to control group. Collectively, our in vitro and in vivo experiments, provide foundation to further develop CET019 as a potential drug candidate to treat patients with TNBCs.

Citation Format: Arpit Dheeraj, Dhanir Tailor, Fernando Jose Marques, Benedikt Grau, Abel Bermudez, Sharon Pitteri, Sanjay Malhotra. A small molecule CET019 inhibits progression of triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 511.

Abstract 554: The role of Mycobacterium w as a novel treatment for osteosarcoma

Osteosarcoma (OS) is the most common malignant primary tumor of bone and occurs in adolescents and young adults as well as in the elderly. Despite a number of large clinical trial efforts, metastatic sarcoma remains a lethal disease, and there have been no meaningful advances in therapy or improvements in patient outcomes for decades. Mycobacterium w (Mw, also known as Mycobacterium indicus pranii) is a non-pathogenic strain of mycobacterium which has been used as an immunomodulator against leprosy, tuberculosis and several cancers and is approved for treatment of NSCLC along with chemotherapy in India. Mw promotes a Th1 immune response and its administration in tumor bearing animals is associated with an increase in total number of tumor infiltrating immune cells (TIIC) with decrease in FOXP3 and PD-1 expressing TIIC in pancreatic cancer and melanoma. Previous studies in our lab have shown that Mw promotes mature dendritic cell and activated CD8+ T cell accumulation within the tumor microenvironment in a mouse model of pancreatic cancer. We compared the effects Mw with standard of care doxorubicin on OS tumor progression in a subcutaneous K7M2 syngeneic mouse model. Mw treatment was more effective at tumor inhibition than doxorubicin. Immunohistochemistry analyses of OS tumors revealed an increase in macrophages following Mw treatment. We aim to further analyze the tumor immune microenvironment using a panel of 28 antibodies to determine alterations due to Mw treatment. With these results we hope to show that Mw is a promising candidate for further development as a therapy for OS.

Citation Format: Kirsten Stefan, Arpit Dheeraj, Dhanir Tailor, Sushil Kumar, Wenqi Li, Rajiv Modi, Manjul Joshipura, Bakulesh Khamar, Lara E. Davis, Sanjay V. Malhotra. The role of Mycobacterium w as a novel treatment for osteosarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 554.

Abstract 3473: High throughput screening of combination therapies to improve response to checkpoint inhibitors in solid tumors using a myelomonocytic and T cell co-culture assay

Background: Immune checkpoint inhibitors (ICI) targeting the PD-1/PD-L1 pathway are part of the new “standard of care” treatment for a number of advanced cancers. However, for many types of cancer, targeting either PD-1 or PD-L1 is associated with clinical benefit in a minority of patients. Combination strategies are needed to improve clinical benefit rates in ‘immune responsive’ cancers, and to expand treatment options for non-responsive cancers. Preclinical models have revealed that tumor-associated macrophages (TAMs) possess T cell-suppressive activities associated with resistance to PD-1/PD-L1 targeted therapies. To reveal therapeutic targets to relieve this suppression, we developed a robust cell-based high-throughput screening (HTS) assay to identify small molecules that can relieve myelomonocytic cell-dependent T cell-suppression, and that enhance T cell activities when combined with PD-1/PD-L1 ICI.

Methods: Bone marrow-derived myelomonocytic cells and splenic T cells were used to develop the HTS assay. After exposure to libraries of small molecules, co-cultures were evaluated for enhanced T cell activity, followed by in vivo investigations of emerging small molecules in syngeneic murine models of breast cancer to reveal anti-tumor activity.

Results: Over 1,400 FDA-approved drugs, used for both cancer or non-cancer indications, were screened in the HTS assay, 66 of which demonstrated activity in the HTS assay. Approximately 50% of these were known anti-inflammatory agents, with the highest density reflecting various COX-2 inhibitors (COX-2i). In vivo, combination therapy of the COX-2i with PD-1/PD-L1 ICI resulted in a significant reduction in tumor growth kinetics in both 4T1 and EMT6 breast cancer models, both of which are resistant to PD-1/PD-L1 inhibitors as monotherapy. In the 4T1 model, slowed tumor kinetics was associated with ICI increased T cell activation as compared to controls or monotherapy anti-PD-1/PD-L1 therapy.

Conclusions: A myelomonocytic cell-dependent T cell-suppression assay can be used to develop a HTS platform for discovering combination therapies showing antitumor responses in preclinical models. COX-2 inhibitors can be repurposed to enhance therapeutic benefits of PD-1/PD-L1 targeting agents in breast cancer patients.

Keywords: Myelomonocytic cells, T-cell, immunotherapy, PD-1, PD-L1, breast cancer

Citation Format: Sushil Kumar, Dhanir Tailor, Arpit Dheeraj, Wenqi Li, Jee Min Lee, Kirsten Stefan, Dylan Nelson, Shivaani Kummar, Lisa M. Coussens, Sanjay V. Malhotra. High throughput screening of combination therapies to improve response to checkpoint inhibitors in solid tumors using a myelomonocytic and T cell co-culture assay [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3473.

Augmenting Vaccine Efficacy against Delta Variant with 'Mycobacterium-w'-Mediated Modulation of NK-ADCC and TLR-MYD88 Pathways

Mycobacterium-w (Mw) was shown to boost adaptive natural killer (ANK) cells and protect against COVID-19 during the first wave of the pandemic. As a follow-up of the trial, 50 healthcare workers (HCW) who had received Mw in September 2020 and subsequently received at least one dose of ChAdOx1 nCoV-19 vaccine (Mw + ChAdOx1 group) were monitored for symptomatic COVID-19 during a major outbreak with the delta variant of SARS-CoV-2 (April-June 2021), along with 201 HCW receiving both doses of the vaccine without Mw (ChAdOx1 group). Despite 48% having received just a single dose of the vaccine in the Mw + ChAdOx1 group, only two had mild COVID-19, compared to 36 infections in the ChAdOx1 group (HR-0.46, p = 0.009). Transcriptomic studies revealed an enhanced adaptive NK cell-dependent ADCC in the Mw + ChAdOx1 group, along with downregulation of the TLR2-MYD88 pathway and concomitant attenuation of downstream inflammatory pathways. This might have resulted in robust protection during the pandemic with the delta variant.

Reengineering Ponatinib to Minimize Cardiovascular Toxicity

Small molecule tyrosine kinase inhibitors (TKI) have revolutionized cancer treatment and greatly improved patient survival. However, life-threatening cardiotoxicity of many TKIs has become a major concern. Ponatinib (ICLUSIG) was developed as an inhibitor of the BCR-ABL oncogene and is among the most cardiotoxic of TKIs. Consequently, use of ponatinib is restricted to the treatment of tumors carrying T315I-mutated BCR-ABL, which occurs in chronic myeloid leukemia (CML) and confers resistance to first- and second-generation inhibitors such as imatinib and nilotinib. Through parallel screening of cardiovascular toxicity and antitumor efficacy assays, we engineered safer analogs of ponatinib that retained potency against T315I BCR-ABL kinase activity and suppressed T315I mutant CML tumor growth. The new compounds were substantially less toxic in human cardiac vasculogenesis and cardiomyocyte contractility assays in vitro. The compounds showed a larger therapeutic window in vivo, leading to regression of human T315I mutant CML xenografts without cardiotoxicity. Comparison of the kinase inhibition profiles of ponatinib and the new compounds suggested that ponatinib cardiotoxicity is mediated by a few kinases, some of which were previously unassociated with cardiovascular disease. Overall, the study develops an approach using complex phenotypic assays to reduce the high risk of cardiovascular toxicity that is prevalent among small molecule oncology therapeutics.

SIGNIFICANCE

Newly developed ponatinib analogs retain antitumor efficacy but elicit significantly decreased cardiotoxicity, representing a therapeutic opportunity for safer CML treatment.

Abstract 4232: TLR2 agonist as a novel therapeutic approach to treat pancreatic adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive malignancy with an overall 5-year survival rate of <10% due to late stage diagnosis and poor clinical outcome with existing therapies. PDAC displays a high degree of tumor heterogeneity and immunosuppressive tumor microenvironment with lower tumor infiltrating lymphocytes (TIL). These factors contribute to resistance against chemotherapies and immunotherapies. Immunotherapies have shown activities across different tumor types including chemotherapy or targeted therapy resistant cancers however these options have little efficacy in the PDAC tumor. Here, in this study we tested the efficacy of gemcitabine in combination with Cadi-05 (TLR2 agonist) against established murine PDAC tumor models (Pan02 in C57/BL6 and 688M in B6129SF1/J). Animals were randomized to receive gemcitabine, Cadi-05, their combination or no treatment when they had tumor size ≈ 50 mm3, 65mm3 and 100 mm3. The weekly treatment of gemcitabine, Cadi-05 and their combination inhibited the tumor progression across all tumor sizes. At the end of study, PBMC and tumors were collected and analyzed for different immune parameters. Results revealed that Cadi-05 treatment alone was associated with increase in CD4+ and CD8+ T cells in PBMC as well as amongst TIL with significant decrease in their expression of immunosuppressive markers like FOXP3 and PD-1. Its combination with gemcitabine synergized the effect of each other. There was further increase in absolute TIL as well as TIL expressing CD4+ and CD8+ markers with decrease in FOXP3 and PD-1 expressing CD4+ and CD8+ TIL. Inhibition of tumor progression was associated with improved effector function of PBMC. Synergy between Cadi-05 and gemcitabine was also evident in effector function. In presence of established tumor, TLR2 agonist Cadi-05 improves effector function, increases CD4+ and CD8+ expressing TIL, decreases immune suppressive TIL and retards tumor growth. Our study suggests that combination of gemcitabine and Cadi-05 inhibits the tumor growth irrespective of its size and it is coupled with increased anti-tumor response and decreased immunosuppressive function

Citation Format: Arpit Dheeraj, Chandreshwar Shukla, Dhanir Tailor, Nayan K. Jain, Kirsten Stefan, Chintan D. Patel, Rajiv Modi, Bakulesh M. Khamar, Sanjay V. Malhotra. TLR2 agonist as a novel therapeutic approach to treat pancreatic adenocarcinoma [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 4232.

Abstract 3997: Inhibiting ribosomal proteins with a small molecule: Therapeutic strategy for triple negative breast cancer

Aberration in the protein translation can lead to changes in the protein expression that can serve as the drivers of tumor progression. Ribosomes are a molecular machine that acts as a hub for protein synthesis, and dysregulation of ribosome function is causative for cancer formation. Our investigation on the causes of breast cancer progression has identified a small molecule ‘SU056’ that shows efficacy against TNBC models. SU056 treatment inhibits growth and clonogenic potential of TNBC cells (MDA-MB-231, MDA-MB-468, SUM159, 4T1, EMT6 and E0771), by arresting the cell cycle progression through G2/M phase. Proteomics analysis suggested translational process as a target of SU056 in these cells. We found that its treatment modulated expression of several molecules of translational complex such as RPL (RPL9, RPL11, RPL15), RPS (RPSA, RPS9, RPS16, RPS20), and translation initiation factors (eIF6, eIF5, eIF4A, eIF4G), which leads to overall inhibition. This was further confirmed by tumor xenograft study with different TNBC models, which also showed that metastatic nodules in the lungs were inhibited by SU056 compared to control group. The results were further confirmed in a Patient Derived Xenograft (PDX) model SUTI151. Overall, our study has identified a lead candidate SU056, and provides strong foundation to further develop a new therapy for treatment of patients with TNBCs.

Citation Format: Arpit Dheeraj, Dhanir Tailor, Angel Resendez, Fernando Jose Marques, Abel Bermudez, Sharon Pitteri, Sanjay Malhotra. Inhibiting ribosomal proteins with a small molecule: Therapeutic strategy for triple negative breast cancer [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 3997.

Abstract 2645: Targeting mRNA processing pathways in ovarian cancer with a small molecule inhibitor

mRNA processing related pathways, including spliceosome and ribosome are over-expressed and unregulated in cancer cells. To investigate the mRNA processing pathways in patient samples, we performed a comprehensive, tandem mass tag (TMT) labeling-based proteome and phosphoproteome profiling of the normal and ovarian cancerous tissues from patients treated with different chemotherapy revealed that malignant cells have overexpression of mRNA processing pathways compared to normal cells. For this analysis, equal amount of tissues were homogenized, and tissue lysates were collected and processed for the quantitative proteomics and phosphoproteomics analysis. KEGG pathway enrichment analysis revealed that spliceosome, basal transcription factors, mRNA surveillance, ribosome and ribosome biogenesis in eukaryotes pathways are upregulated in cancer cells compared to control. On other hand, pathways associated with metabolism and fatty acid biosynthesis were downregulated in malignant cells. Moreover, kinase Enrichment Analysis shows that CDK2, ATM, ATR, and MAPK associated kinases are upregulated in cancer cells compared to normal. Based on proteome analysis of patient samples, we investigated the pharmacological inhibition of Y-box binding protein 1 (YB-1). This is an RNA binding protein and key regulator of pre-mRNA alternative splicing and processing. We recently showed that a natural product-derived small molecule (SU056) inhibits YB-1 activity. We found that SU056 binds to the YB-1 and blocks the RNA binding pocket. Proteomics results suggest that treatment with this drug strongly inhibits the spliceosome pathway. SU056 treatment arrests the ovarian cancer cells in G1 phase and inhibits the CDK2 and Cyclin E. SU056 inhibits the tumor progression and metastasis in the ID8 mice model and sensitizes the OVCAR8 NSG mice model for paclitaxel treatment. Our study provides a compelling case for YB-1 inhibition using SU056 as a potential therapy for ovarian cancer.

Citation Format: Dhanir Tailor, Chia-Feng Tsai, Alexander Honkala, Wenqi Li, Tao Liu, Tanja Pejovic, Sanjay V. Malhotra. Targeting mRNA processing pathways in ovarian cancer with a small molecule inhibitor [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 2645.

Abstract 1799: Inhibition of triple negative breast cancer metastasis via Enolase-1 modulation

Triple-negative breast cancer (TNBC) is one of the aggressive forms of breast cancer and frequently relapses and metastases. Currently, very few options are available for TNBC treatment. Cancer cells exploit glycolytic machinery for the Warburg effect and aerobic glycolysis. Enolase 1 (ENO1) is the glycolytic enzyme expressed in the majority of tissues and many cancer cells have its higher expression. Apart from the glycolytic role in the cytosol, ENO1 also plays different roles in cancer cells including function as a surface receptor. We have developed a chemical small molecule (CET12) that strongly binds to ENO1 and restrain its activity and subcellular localization. CET12 treatment arrests the TNBC cells in the mitotic phase and leads the apoptotic cell death via AMPK activation. Global proteome profiling suggested that CET12 pushes the cells toward oxidative phosphorylation. It also inhibits cell migration and invasion in vitro. In vivo studies using 4T1 and EMT6 syngeneic mouse models are also in-line with in vitro results and revealed that SU0212 treatment inhibits tumor progression and metastasis. These results were further supported by tail vain lung metastasis assay and intracardiac injection mouse model. This study provides compelling preclinical data for further development of CET12 for the treatment of TNBC.

Citation Format: Dhanir Tailor, Arpit Dheeraj, Fernando Jose Garcia-Marques, Mallesh Pandrala, Abel Bermudez, Sharon Pitteri, Sanjay V. Malhotra. Inhibition of triple negative breast cancer metastasis via Enolase-1 modulation [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 1799.

Impact of an Immune Modulator Mycobacterium-w on Adaptive Natural Killer Cells and Protection Against COVID-19

The kinetics of NKG2C+ adaptive natural killer (ANK) cells and NKG2A+inhibitory NK (iNK) cells with respect to the incidence of SARS-CoV-2 infection were studied for 6 months in a cohort of healthcare workers following the administration of the heat-killed Mycobacterium w (Mw group) in comparison to a control group. In both groups, corona virus disease 2019 (COVID-19) correlated with lower NKG2C+ANK cells at baseline. There was a significant upregulation of NKG2C expression and IFN-γ release in the Mw group (p=0.0009), particularly in those with a lower baseline NKG2C expression, along with the downregulation of iNK cells (p<0.0001). This translated to a significant reduction in the incidence and severity of COVID-19 in the Mw group (incidence risk ratio-0.15, p=0.0004). RNA-seq analysis at 6 months showed an upregulation of the ANK pathway genes and an enhanced ANK-mediated antibody-dependent cellular cytotoxicity (ADCC) signature. Thus, Mw was observed to have a salutary impact on the ANK cell profile and a long-term upregulation of ANK-ADCC pathways, which could have provided protection against COVID-19 in a non-immune high-risk population.

Synthesis and In Vitro Study of Artemisinin/Synthetic Peroxide Based Hybrid Compounds against SARS‐CoV‐2 and Cancer

The newly emerged severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) cause life‐threatening diseases in millions of people worldwide, in particular, in patients with cancer, and there is an urgent need for antiviral agents against this infection. While in vitro activities of artemisinins against SARS‐CoV‐2 and cancer have recently been demonstrated, no study of artemisinin and/or synthetic peroxide‐based hybrid compounds active against both cancer and SARS‐CoV‐2 has been reported yet. However, the hybrid drug's properties (e. g., activity and/or selectivity) can be improved compared to its parent compounds and effective new agents can be obtained by modification/hybridization of existing drugs or bioactive natural products. In this study, a series of new artesunic acid and synthetic peroxide based new hybrids were synthesized and analyzed in vitro for the first time for their inhibitory activity against SARS‐CoV‐2 and leukemia cell lines. Several artesunic acid‐derived hybrids exerted a similar or stronger potency against K562 leukemia cells (81–83 % inhibition values) than the reference drug doxorubicin (78 % inhibition value) and they were also more efficient than their parent compounds artesunic acid (49.2 % inhibition value) and quinoline derivative (5.5 % inhibition value). Interestingly, the same artesunic acid‐quinoline hybrids also show inhibitory activity against SARS‐CoV‐2 in vitro (EC₅₀ 13–19 μm) and no cytotoxic effects on Vero E6 cells (CC₅₀ up to 110 μM). These results provide a valuable basis for design of further artemisinin‐derived hybrids to treat both cancer and SARS‐CoV‐2 infections.

SU086, an inhibitor of HSP90, impairs glycolysis and represents a treatment strategy for advanced prostate cancer

Among men, prostate cancer is the second leading cause of cancer-associated mortality, with advanced disease remaining a major clinical challenge. We describe a small molecule, SU086, as a therapeutic strategy for advanced prostate cancer. We demonstrate that SU086 inhibits the growth of prostate cancer cells in vitro, cell-line and patient-derived xenografts in vivo, and ex vivo prostate cancer patient specimens. Furthermore, SU086 in combination with standard of care second-generation anti-androgen therapies displays increased impairment of prostate cancer cell and tumor growth in vitro and in vivo. Cellular thermal shift assay reveals that SU086 binds to heat shock protein 90 (HSP90) and leads to a decrease in HSP90 levels. Proteomic profiling demonstrates that SU086 binds to and decreases HSP90. Metabolomic profiling reveals that SU086 leads to perturbation of glycolysis. Our study identifies SU086 as a treatment for advanced prostate cancer as a single agent or when combined with second-generation anti-androgens.

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SU086 inhibits prostate cancer growth in preclinical models of prostate cancer

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SU086 targets heat shock protein 90

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SU086 alters prostate cancer glycolysis and decreases intratumoral metabolism

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SU086 in combination with anti-androgens halts prostate cancer growth

Facile synthesis of C6-substituted benz[4,5]imidazo[1,2-a]quinoxaline derivatives and their anticancer evaluation

Cancer remains a leading cause of death worldwide, resulting in continuous efforts to discover and develop highly efficacious anticancer drugs. High-throughput screening of heterocyclic compound libraries is one of the promising approaches that provided several new lead molecules with a novel mechanism of action. On the basis of the promising anticancer potential of imidazoquinoxaline as well as the structurally similar imidazoquinoline-derived scaffold, we prepared a set of C6-substituted benzimidazo[1,2-a]quinoxaline derivatives via two novel synthetic routes using commercially available starting materials, with good to excellent yields and evaluated their anticancer activity against the NCI-60 cancer cell lines. The one-dose (10 µM) anticancer screening of the synthesized compounds in the NCI-60 cell line panel revealed that the substituents have a significant role in the activity. In particular, the indole (7f), imidazole (7g), and benzimidazole (7h) derivatives showed significant activity against the triple-negative breast cancer cell line, MDA-MB-468. The lead compounds also exhibited notable IC₅₀ values against another breast cancer cell line, MCF-7. Furthermore, it was observed that these compounds were relatively nontoxic to normal cell lines: HEK293 (human embryonic kidney cell line) and MCF12A (nontumorigenic human breast epithelial cell line). The IC₅₀ values against healthy cells were at least 5- to 11-fold higher, offering a new class of heterocycles that can be further developed as promising therapeutics for cancer treatment.

Y box binding protein 1 inhibition as a targeted therapy for ovarian cancer

Y box binding protein 1 (YB-1) is a multifunctional protein associated with tumor progression and the emergence of treatment resistance (TR). Here, we report an azopodophyllotoxin small molecule, SU056, that potently inhibits tumor growth and progression via YB-1 inhibition. This YB-1 inhibitor inhibits cell proliferation, resistance to apoptosis in ovarian cancer (OC) cells, and arrests in the G1 phase. Inhibitor treatment leads to enrichment of proteins associated with apoptosis and RNA degradation pathways while downregulating spliceosome pathway. In vivo, SU056 independently restrains OC progression and exerts a synergistic effect with paclitaxel to further reduce disease progression with no observable liver toxicity. Moreover, in vitro mechanistic studies showed delayed disease progression via inhibition of drug efflux and multidrug resistance 1, and significantly lower neurotoxicity as compared with etoposide. These data suggest that YB-1 inhibition may be an effective strategy to reduce OC progression, antagonize TR, and decrease patient mortality.

Novel Aza-podophyllotoxin derivative induces oxidative phosphorylation and cell death via AMPK activation in triple-negative breast cancer

BACKGROUND

To circumvent Warburg effect, several clinical trials for different cancers are utilising a combinatorial approach using metabolic reprogramming and chemotherapeutic agents including metformin. The majority of these metabolic interventions work via indirectly activating AMP-activated protein kinase (AMPK) to alter cellular metabolism in favour of oxidative phosphorylation over aerobic glycolysis. The effect of these drugs is dependent on glycaemic and insulin conditions.  Therefore, development of small molecules, which can activate AMPK, irrespective of the energy state, may be a better approach for triple-negative breast cancer (TNBC) treatment.

METHODS

Therapeutic effect of SU212 on TNBC cells was examined using in vitro and in vivo models.

RESULTS

We developed and characterised the efficacy of novel AMPK activator (SU212) that selectively induces oxidative phosphorylation and decreases glycolysis in TNBC cells, while not affecting these pathways in normal cells.   SU212 accomplished this metabolic reprogramming by activating AMPK independent of energy stress and irrespective of the glycaemic/insulin state. This leads to mitotic phase arrest and apoptosis in TNBC cells. In vivo, SU212 inhibits tumour growth, cancer progression and metastasis.

CONCLUSIONS

SU212 directly activates AMPK in TNBC cells, but does not hamper glucose metabolism in normal cells. Our study provides compelling preclinical data for further development of SU212 for the treatment of TNBC.

Guanylate-Binding Protein 1: An Emerging Target in Inflammation and Cancer

Guanylate-binding protein 1 (GBP1) is a large GTPase of the dynamin superfamily involved in the regulation of membrane, cytoskeleton, and cell cycle progression dynamics. In many cell types, such as endothelial cells and monocytes, GBP1 expression is strongly provoked by interferon γ (IFNγ) and acts to restrain cellular proliferation in inflammatory contexts. In immunity, GBP1 activity is crucial for the maturation of autophagosomes infected by intracellular pathogens and the cellular response to pathogen-associated molecular patterns. In chronic inflammation, GBP1 activity inhibits endothelial cell proliferation even as it protects from IFNγ-induced apoptosis. A similar inhibition of proliferation has also been found in some tumor models, such as colorectal or prostate carcinoma mouse models. However, this activity appears to be context-dependent, as in other cancers, such as oral squamous cell carcinoma and ovarian cancer, GBP1 activity appears to anchor a complex, taxane chemotherapy resistance profile where its expression levels correlate with worsened prognosis in patients. This discrepancy in GBP1 function may be resolved by GBP1's involvement in the induction of a cellular senescence phenotype, wherein anti-proliferative signals coincide with potent resistance to apoptosis and set the stage for dysregulated proliferative mechanisms present in growing cancers to hijack GBP1 as a pro- chemotherapy treatment resistance (TXR) and pro-survival factor even in the face of continued cytotoxic treatment. While the structure of GBP1 has been extensively characterized, its roles in inflammation, TXR, senescence, and other biological functions remain under-investigated, although initial findings suggest that GBP1 is a compelling target for therapeutic intervention in a variety of conditions ranging from chronic inflammatory disorders to cancer.

Radiosensitization of Head and Neck Squamous Cell Carcinoma (HNSCC) by a Podophyllotoxin

Surgical resection and radiotherapy are an effective treatment in many head and neck squamous cell carcinomas (HNSCC), but in others, the development of radiotherapy resistance limits treatment efficacy and permits disease progression. We developed a novel multiwell radiation dosing method to increase the throughput of our investigation of the activity of a novel podophyllotoxin SU093 in acting as a radiosensitizer in the HNSCC models FaDu and SCC-25. These in vitro studies showed that combining SU093 with 5 Grays ionizing radiation acted synergistically to increase HNSCC apoptosis and decrease its proliferation via inhibition of Nuclear factor, erythroid 2 like 2 (Nrf2), a key effector of the DNA damage response induced by ionizing radiation. Combined treatment reduced in vitro migration in a simulated wounding model while also promoting cell cycle arrest at the G2/M phase. These findings validate the potential of SU093 as a synergistic radiosensitizing agent for use in combination with localized radiotherapy in treatment resistant HNSCC.

Abstract 3004: Anticancer effects and associated molecular changes of Carica papaya against prostate cancer

Carica papaya (papaya), from the family of Caricaceae, is a perennial plant originating from the Southern part of Mexico. Carica papaya leaf extract (CPE) has been traditionally used to treat various diseases, including infectious diseases and cancer. However, the anticancer effects and molecular mechanism of CPE are elusive. The aim of our study is to examine the anticancer effects of aqueous leaf extract of Carica papaya against prostate cancer (PCa). We investigated the effect of CPE on LNCaP, DU145 and PC-3 PCa cells. CPE treatment (5, 10, 25µl/ml) significantly reduced the cell proliferation and induced cell death in PCa cells. Furthermore, we found that CPE induced G1, S and G1 as well as G2/M phase cell cycle arrest in LNCaP, DU145, and PC-3 cells, respectively. At molecular level, the cell cycle arrest was associated with decreased expression of CDK 4, cyclin D1, cyclin B1, and PCNA. CPE induced cell death was associatedwith depolarization of mitochondrial membrane potential, increase in ratio of Bax/Bcl2, cleavage of caspase-3 and cleaved -Poly(ADP-ribose) polymerase (PARP). CPE treatment also reduced mitochondrial fission and induced mitochondrial fusion by reducing the level of Drp1 protein. Further, we observed that CPE increased the expression of E-cadherin and decreased the expression of N-cadherin and vimentin. We checked the CPE toxicity in C57BL/6 male mice. We found that oral administration of CPE(0.25%, 0.5% and 1% v/v) in drinking water did not show any significant changes in body weight, water consumption and food intake as compared to control group. Collectively, CPE inhibited cell proliferation, induced cell death via apoptosis, mitochondrial fusion, epithelial marker and reduced mesenchymal markers.In vivo toxicity study with CPE treatment via drinking water was found to be non-toxic. These findings suggest that CPE has potential as anticancer therapeutic option for prevention and treatment of prostate cancer.

Citation Format: Surya Pratap Singh, Sivapar V. Mathan, Arpit Dheeraj, Dhanir Tailor, Rana P. Singh, Arbind Acharya. Anticancer effects and associated molecular changes of Carica papaya against prostate cancer [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 3004.

Abstract 5275: Cancer specific caloric restriction using novel small molecule improves the therapeutic regime for triple negative breast cancer

Hyperglycemic and hyper insulin condition are the signature symptoms for type two diabetes which is the most favorable condition for the development of cancer. Women having a type two diabetes has 20-27% high risk to develop breast cancer including triple negative breast cancer (TNBC). Microenvironment including hyperglycemic, hyper insulin condition leads to the therapy resistance. According to ‘Warburg’s effect’ cancer cells consume a high amount of glucose in comparison to normal cells via aerobic glycolysis process. To take care of this condition currently, several clinical studies are going on for the combination therapy of type 2 diabetes and chemotherapy drugs together including erlotinib and metformin. The major drawback of this kind of type 2 diabetes drugs is that they won't affect cancer cells under hyperglycemic and hyper insulin conditions. These drugs including metformin work via AMP-activated protein kinase (AMPK) activation to switch aerobic glycolysis to oxidative phosphorylation. We have developed a novel AMPK activator (SU-18) who selectively induces an oxidative phosphorylation in TNBC cells and glycolysis in normal cells. We found that SU-18 induces G2/M phase arrest, mitochondrial stress and apoptosis in TNBC cells as same as metformin but at 1000 fold less concentration. It selectively reduces the glucose consumption, lactate and ATP production in TNBC cells where normal cells act opposite to this. SU-18 activity is through AMPK activation which got abolished in presence of AMPK inhibitor (Compound c). During mouse xenograft studies, it inhibits the tumor growth and progression. It also improves the blood glucose level in hyperglycemic mice. Comparative studies with metformin suggest that SU-18 works irrespective of hyperglycemia and insulin conditions, whereas metformin, is ineffective in this condition. FDG-PET scan analysis also supported to our in vitro glucose consumption data that treatment with SU-18 reduces the FDG accumulation in tumor cells. This study advocates the clinical candidature of SU-18 for TNBC patients.

Citation Format: Dhanir Tailor, Angel Resendez, Vineet Kumar, Catherine Going, Sharon Pitteri, Sanjay Malhotra. Cancer specific caloric restriction using novel small molecule improves the therapeutic regime for triple negative breast cancer [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 5275.

Quantitative Proteomic Profiling Reveals Key Pathways in the Anticancer Action of Methoxychalcone Derivatives in Triple Negative Breast Cancer

Triple negative breast cancer is an aggressive, heterogeneous disease with high recurrence and metastasis rates even with modern chemotherapy regimens and thus is in need of new therapeutics. Here, three novel synthetic analogues of chalcones, plant-based molecules that have demonstrated potency against a wide variety of cancers, were investigated as potential therapeutics for triple negative breast cancer. These compounds exhibit IC₅₀ values of ∼5 μM in triple negative breast cancer cell lines and are more potent against triple negative breast cancer cell lines than against nontumor breast cell lines according to viability experiments. Tandem mass tag-based quantitative proteomics followed by gene set enrichment analysis and validation experiments using flow cytometry, apoptosis, and Western blot assays revealed three different anticancer mechanisms for these compounds. First, the chalcone analogues induce the unfolded protein response followed by apoptosis. Second, increases in the abundances of MHC-I pathway proteins occurs, which would likely result in immune stimulation in an organism. And third, treatment with the chalcone analogues causes disruption of the cell cycle by interfering with microtubule structure and by inducing G1 phase arrest. These data demonstrate the potential of these novel chalcone derivatives as treatments for triple negative breast cancer, though further work evaluating their efficacy in vivo is needed.

Abstract 1095: Insulin-like Growth Factor Binding Protein-3 (IGFBP-3) regulates mitochondrial dynamics, EMT and angiogenesis in progression of prostate cancer

Prostate cancer (PCa) is a major epithelial cancer among men and with the second highest incidence rate, worldwide. The high ratio of IGF-1/IGFBP-3 correlates with increased risk of many cancers including prostate cancer. In present study, we have evaluated the role of IGFBP-3 and effect of fisetin, a phytochemical, active constituent of strawberry, apple etc. in the progression of prostate cancer. The exogenous expression of IGFBP-3 moderately decreased the cell growth and it further decreased with addition of fisetin in DU145 and LNCaP cells. The restoration of IGFBP-3 in DU145 cells inhibited the clonogenic potential which is further decreased with fisetin treatment. Increased ROS content was observed in IGFBP-3 overexpression condition, however fisetin treatment reversed the ROS content in DU145, shows antioxidant behaviour. Morphological examination of mitochondria revealed that IGFBP-3 overexpression destabilizes the mitochondrial dynamics by reduction in active DRP1 level which has been reversed by fisetin treatment. We evaluated the effect on mitochondrial mass which was decreased in IGFBP-3 overexpressing DU145 cells which further decreased with addition of fisetin at 12 and 24 h. IGFBP-3 overexpression decreased the migratory potential of DU145 cells under normoxic conditions and under hypoxic condition it increased the migration of DU145 cells. Furthermore, IGFBP-3 overexpression decreased the VEGF expression as compared to vector control which can inhibit the expansion of tumor cells. Under the hypoxic conditions (1% oxygen), cells showed increased levels of IGFBP-3 when compared to normoxic conditions (21% Oxygen) in time dependent manner. The down-regulation of IGFBP-3 in PC3 cells, increased the expression of E-cadherin, a biomarker of epithelial to mesenchymal transition. The wound scratch assay showed the pro-migratory role of IGFBP-3 in PC3 cells and treatment with fisetin inhibited the migration of these cells under the hypoxic condition. The knockdown of IGFBP3 resulted in the decreased invasive potential of PC3 in comparison to cells in hypoxic state. Together with these observation, IGFBP-3 have shown biphasic character depending on normoxic and hypoxic condition in controlling the prostate cancer progression.

Citation Format: Arpit Dheeraj, Dhanir Tailor, Gagan Deep, Rana P. Singh. Insulin-like Growth Factor Binding Protein-3 (IGFBP-3) regulates mitochondrial dynamics, EMT and angiogenesis in progression of 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 1095.

Abstract 4951: Inhibiting guanylate binding protein 1 (GBP1) impedes ovarian cancer progression

Ovarian cancer, the most common gynecologic malignancy, is a leading cause of cancer deaths in women. Seventy percent of patients at diagnosis present with stage III or IV disease, in which the tumor has disseminated beyond the ovaries and pelvic organs to distant sites. Despite resection and and chemotherapy, 80% of patients diagnosed with advanced epithelial ovarian cancer develop recurrent disease and overall prognosis is poor. Resistance to chemotherapeutic agents such as carboplatin and paclitaxel (taxane-based drugs) accounts for the lack of effectiveness of current therapy. Characterization of taxane-resistant tumors has shown that Class III β-tubulin (βTUB3) is significantly overexpressed in ovarian cancer as well as other cancers. Also, molecular characterization of the causes of treatment resistance revealed that βTUB3 plays a prominent role in the incorporation of guanylate binding protein 1, a conditionally expressed GTPase normally involved in the inflammatory response, as one of the critical effectors of taxane and radiotherapy resistance in ovarian cancer. Once in the cytoskeleton, GBP1 binds to pro-survival kinases such as serine/threonine-protein kinase pim-1 (PIM1) and initiates a signaling cascade that induces treatment resistance. We hypothesize that inhibiting the activity of GBP1 will restore sensitivity to taxane therapy. This is now well supported by our preliminary proof-of-concept studies. We have demonstrated that natural product-derived small molecule SU093 stabilizes GBP1 in a nonbinding conformation, resulting in the inhibition of GBP1:PIM1 interaction. The mechanistic studies using confocal microscopy showed that SU093 inhibits GBP1 by blocking its nuclear translocation and disrupts the tubulin dynamics. Cell cycle analysis showed that SU093 leads to G1 phase arrest followed by apoptotic cell death. SU093 treatment also induced pro-apoptotic protein Bax and reduced anti-apoptotic protein Bcl2. Overall, our in vitro and in vivo investigations provide a compelling foundation to develop a novel therapy to treat ovarian cancer by inhibition of GBP1.

Citation Format: Dhanir Tailor, Vineet Kumar, Mallesh Pandrala, Angel Resendez, Sanjay V. Malhotra. Inhibiting guanylate binding protein 1 (GBP1) impedes ovarian cancer progression [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 4951.

Inhibition of mitochondrial fusion is an early and critical event in breast cancer cell apoptosis by dietary chemopreventative benzyl isothiocyanate

Benzyl isothiocyanate (BITC) is a highly promising phytochemical abundant in cruciferous vegetables with preclinical evidence of in vivo efficacy against breast cancer in xenograft and transgenic mouse models. Mammary cancer chemoprevention by BITC is associated with apoptotic cell death but the underlying mechanism is not fully understood. Herein, we demonstrate for the first time that altered mitochondrial dynamics is an early and critical event in BITC-induced apoptosis in breast cancer cells. Exposure of MCF-7 and MDA-MB-231 cells to plasma achievable doses of BITC resulted in rapid collapse of mitochondrial filamentous network. BITC treatment also inhibited polyethyleneglycol-induced mitochondrial fusion. In contrast, a normal human mammary epithelial cell line (MCF-10A) that was derived from fibrocystic breast disease, was resistant to BITC-mediated alterations in mitochondrial dynamics as well as apoptosis. Transient or sustained decrease in levels of proteins engaged in regulation of mitochondrial fission and fusion was clearly evident after BITC treatment in both cancer cell lines. A trend for a decrease in the levels of mitochondrial fission- and fusion-related proteins was also observed in vivo in tumors of BITC-treated mice compared with control. Immortalized mouse embryonic fibroblasts from Drp1 knockout mice were resistant to BITC-induced apoptosis when compared with those from wild-type mice. Upon treatment with BITC, Bak dissociated from mitofusin 2 in both MCF-7 and MDA-MB-231 cells suggesting a crucial role for interaction of Bak and mitofusins in BITC-mediated inhibition of fusion and morphological dynamics. In conclusion, the present study provides novel insights into the molecular complexity of BITC-induced cell death.

Sodium butyrate induces DRP1-mediated mitochondrial fusion and apoptosis in human colorectal cancer cells

Sodium butyrate (NaBt) is the byproduct of anaerobic microbial fermentation inside the gastro-intestinal tract that could reach up to 20mM, and has been shown to inhibit the growth of various cancers. Herein, we evaluated its effect on mitochondrial fusion and associated induction of apoptosis in colorectal cancer cells (CRC). NaBt treatment at physiological (1-5mM) concentrations for 12 and 24h decreased the cell viability and induced G2-M phase cell cycle arrest in HCT116 (12h) and SW480 human CRC cells. This cell cycle arrest was associated with mitochondria-mediated apoptosis accompanied by a decrease in survivin and Bcl-2 expression, and generation of reactive oxygen species (ROS). Furthermore, NaBt treatment resulted in a significant decrease in the mitochondrial mass which is an indicator of mitochondrial fusion. Level of dynamin-related protein 1 (DRP1), a key regulator of mitochondrial fission and fusion where its up-regulation correlates with fission, was found to be decreased in CRC cells. Further, at early treatment time, DRP1 down-regulation was noticed in mitochondria which later became drastically reduced in both mitochondria as well as cytosol. DRP1 is activated by cyclin B1-CDK1 complex by its ser616 phosphorylation in which both cyclin B1-CDK1 complex and phospho-DRP1 (ser616) were strongly reduced by NaBt treatment. DRP1 was observed to be regulated by apoptosis as pan-caspase inhibitor showing rescue from NaBt-induced apoptosis also caused the reversal of DRP1 to the normal level as in control proliferating cells. Together, these findings suggest that NaBt can modulate mitochondrial fission and fusion by regulating the level of DRP1 and induce cell cycle arrest and apoptosis in human CRC cells.

Acacetin inhibits in vitro and in vivo angiogenesis and downregulates Stat signaling and VEGF expression

Angiogenesis is an effective target in cancer control. The antiangiogenic efficacy and associated mechanisms of acacetin, a plant flavone, are poorly known. In the present study, acacetin inhibited growth and survival (up to 92%; P < 0.001), and capillary-like tube formation on Matrigel (up to 98%; P < 0.001) by human umbilical vein endothelial cells (HUVEC) in regular condition, as well as VEGF-induced and tumor cells conditioned medium-stimulated growth conditions. It caused retraction and disintegration of preformed capillary networks (up to 91%; P < 0.001). HUVEC migration and invasion were suppressed by 68% to 100% (P < 0.001). Acacetin inhibited Stat-1 (Tyr701) and Stat-3 (Tyr705) phosphorylation, and downregulated proangiogenic factors including VEGF, endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS), matrix metalloproteinase-2 (MMP-2), and basic fibroblast growth factor (bFGF) in HUVEC. It also suppressed nuclear localization of pStat-3 (Tyr705). Acacetin strongly inhibited capillary sprouting and networking from rat aortic rings and fertilized chicken egg chorioallantoic membrane (CAM; ∼71%; P < 0.001). Furthermore, it suppressed angiogenesis in Matrigel plugs implanted in Swiss albino mice. Acacetin also inhibited tyrosine phosphorylation of Stat-1 and -3, and expression of VEGF in cancer cells. Overall, acacetin inhibits Stat signaling and suppresses angiogenesis in vitro, ex vivo, and in vivo, and therefore, it could be a potential agent to inhibit tumor angiogenesis and growth.