Chimeric antibody targeting unique epitope on onco-mucin16 reduces tumor burden in pancreatic and lung malignancies

Aberrantly expressed onco-mucin 16 (MUC16) and its post-cleavage generated surface tethered carboxy-terminal (MUC16-Cter) domain are strongly associated with poor prognosis and lethality of pancreatic (PC) and non-small cell lung cancer (NSCLC). To date, most anti-MUC16 antibodies are directed towards the extracellular domain of MUC16 (CA125), which is usually cleaved and shed in the circulation hence obscuring antibody accessibility to the cancer cells. Herein, we establish the utility of targeting a post-cleavage generated, surface-tethered oncogenic MUC16 carboxy-terminal (MUC16-Cter) domain by using a novel chimeric antibody in human IgG1 format, ch5E6, whose epitope expression directly correlates with disease severity in both cancers. ch5E6 binds and interferes with MUC16-associated oncogenesis, suppresses the downstream signaling pFAK(Y397)/p-p70S6K(T389)/N-cadherin axis and exert antiproliferative effects in cancer cells, 3D organoids, and tumor xenografts of both PC and NSCLC. The robust clinical correlations observed between MUC16 and N-cadherin in patient tumors and metastatic samples imply ch5E6 potential in targeting a complex and significantly occurring phenomenon of epithelial to mesenchymal transition (EMT) associated with disease aggressiveness. Our study supports evaluating ch5E6 with standard-of-care drugs, to potentially augment treatment outcomes in malignancies inflicted with MUC16-associated poor prognosis.

Abstract 3760: MicroRNA-1 run down the growth and metastasis of small cell lung cancer

Small cell lung cancer (SCLC) is a highly aggressive and metastatic lung cancer subtype with universal relapse and poor prognosis. The lack of potential drug targets limits targeted therapies for SCLC patients. To track down the potential therapeutic molecules in SCLC, we performed micro-RNA sequencing from the serum samples of SCLC patients and compared with the bulk RNA-sequencing data from SCLC tumor tissues. A consistent downregulation of microRNA-1 (miR-1) was observed in the SCLC patient serum samples, cell lines, and tumor tissues compared to their matched normal control. Overexpression of miR-1 in SCLC cell lines decreased cell growth and oncogenic signaling. Metastatic studies using the intracardiac injection model of SCLC cell lines showed that miR-1 overexpression decreases distant organ metastasis. Interestingly, the loss of function studies using miR-1Zip/sponging showed increased tumorigenesis and metastasis in SCLC subcutaneous and intracardiac xenografts. Mechanistic investigations revealed the CXCR4/FOXM1/RRM2 axis as a unique downstream target of miR-1 in SCLC. We found that FOXM1 transcriptionally regulates the RRM2 expression by directly binding to its promoter site, and miR-1 modulates these interactions through CXCR4. The results of the present study provided a strong preclinical rationale that miR-1 has a high potential for developing innovative SCLC therapies.

Citation Format: Parvez Khan, Jawed A. Siddiqui, Shailendra Kumar Maurya, Tamara Mirzapoiazova, Prakash G. Kshirsagar, Ramakanth Chirravuri Venkata, Sanjib Chaudhary, Ranjana Kanchan, Naveenkumar Perumal, Mahek Fatima, Md Arafat Khan, Asad Ur Rehman, Imayavaramban Lakshmanan, Sidharth Mahapatra, Prakash Kulkarni, Apar Kishor Ganti, Maneesh Jain, Ravi Salgia, Surinder Kumar Batra, Mohd Wasim Nasser. MicroRNA-1 run down the growth and metastasis of small cell lung 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 3760.

MUC16 promotes triple-negative breast cancer lung metastasis by modulating RNA-binding protein ELAVL1/HUR

BACKGROUND

Triple-negative breast cancer (TNBC) is highly aggressive with an increased metastatic incidence compared to other breast cancer subtypes. However, due to the absence of clinically reliable biomarkers and targeted therapy in TNBC, outcomes are suboptimal. Hence, there is an urgent need to understand biological mechanisms that lead to identifying novel therapeutic targets for managing metastatic TNBC.

METHODS

The clinical significance of MUC16 and ELAVL1 or Hu antigen R (HuR) was examined using breast cancer TCGA data. Microarray was performed on MUC16 knockdown and scramble TNBC cells and MUC16-associated genes were identified using RNA immunoprecipitation and metastatic cDNA array. Metastatic properties of MUC16 were evaluated using tail vein experiment. MUC16 and HuR downstream pathways were confirmed by ectopic overexpression of MUC16-carboxyl-terminal (MUC16-Cter), HuR and cMyc as well as HuR inhibitors (MS-444 and CMLD-2) in TNBC cells.

RESULTS

MUC16 was highly expressed in TNBC and correlated with its target HuR. Depletion of MUC16 showed decreased invasion, migration, and colony formation abilities of human and mouse TNBC cells. Mice injected with MUC16 depleted cells were less likely to develop lung metastasis (P = 0.001). Notably, MUC16 and HuR were highly expressed in the lung tropic TNBC cells and lung metastases. Mechanistically, we identified cMyc as a HuR target in TNBC using RNA immunoprecipitation and metastatic cDNA array. Furthermore, MUC16 knockdown and pharmacological inhibition of HuR (MS-444 and CMLD-2) in TNBC cells showed a reduction in cMyc expression. MUC16-Cter or HuR overexpression models indicated MUC16/HuR/cMyc axis in TNBC cell migration.

CONCLUSIONS

Our study identified MUC16 as a TNBC lung metastasis promoter that acts through HuR/cMyc axis. This study will form the basis of future studies to evaluate the targeting of both MUC16 and HuR in TNBC patients.

Elevated PAF1-RAD52 axis confers chemoresistance to human cancers

Cisplatin- and gemcitabine-based chemotherapeutics represent a mainstay of cancer therapy for most solid tumors; however, resistance limits their curative potential. Here, we identify RNA polymerase II-associated factor 1 (PAF1) as a common driver of cisplatin and gemcitabine resistance in human cancers (ovarian, lung, and pancreas). Mechanistically, cisplatin- and gemcitabine-resistant cells show enhanced DNA repair, which is inhibited by PAF1 silencing. We demonstrate an increased interaction of PAF1 with RAD52 in resistant cells. Targeting the PAF1 and RAD52 axis combined with cisplatin or gemcitabine strongly diminishes the survival potential of resistant cells. Overall, this study shows clinical evidence that the expression of PAF1 contributes to chemotherapy resistance and worse clinical outcome for lethal cancers.

MUC16 and TP53 family co-regulate tumor-stromal heterogeneity in pancreatic adenocarcinoma

MUC16/CA125 is one of the few oldest cancer biomarkers still used in current clinical practice. As mesothelium is an abundant source of MUC16 and a major contributor to stromal heterogeneity in PDAC, we investigated the regulation of MUC16 in tumor and stromal compartments individually. The trajectories constructed using the single-cell transcriptomes of stromal cells from KPC tumors demonstrated continuity in the trajectory path between MUC16-expressing mesothelial cells and other CAF subsets. Further, the tumor tissues of MUC16 whole-body knockout (KPCM) showed dysregulation in the markers of actomyosin assembly and fibroblast differentiation (iCAF and myCAF), indicating that MUC16 has an extra-tumoral role in controlling CAF differentiation. Although we found mesothelium-derivative stromal cells to be bystanders in normal pancreas, the proportion of these cells was higher in invasive PDAC, particularly in TP53 deficient tumors. Moreover, we also detail the regulation of MUC16, KRAS, and SOX9 by TP53 family members (TP53 and TP63) using multi-omics data from knockout models, PDAC cell lines, and human PDAC tissues.

MicroRNA-1 attenuates the growth and metastasis of small cell lung cancer through CXCR4/FOXM1/RRM2 axis

BACKGROUND

Small cell lung cancer (SCLC) is an aggressive lung cancer subtype that is associated with high recurrence and poor prognosis. Due to lack of potential drug targets, SCLC patients have few therapeutic options. MicroRNAs (miRNAs) provide an interesting repertoire of therapeutic molecules; however, the identification of miRNAs regulating SCLC growth and metastasis and their precise regulatory mechanisms are not well understood.

METHODS

To identify novel miRNAs regulating SCLC, we performed miRNA-sequencing from donor/patient serum samples and analyzed the bulk RNA-sequencing data from the tumors of SCLC patients. Further, we developed a nanotechnology-based, highly sensitive method to detect microRNA-1 (miR-1, identified miRNA) in patient serum samples and SCLC cell lines. To assess the therapeutic potential of miR-1, we developed various in vitro models, including miR-1 sponge (miR-1Zip) and DOX-On-miR-1 (Tet-ON) inducible stable overexpression systems. Mouse models derived from intracardiac injection of SCLC cells (miR-1Zip and DOX-On-miR-1) were established to delineate the role of miR-1 in SCLC metastasis. In situ hybridization and immunohistochemistry were used to analyze the expression of miR-1 and target proteins (mouse and human tumor specimens), respectively. Dual-luciferase assay was used to validate the target of miR-1, and chromatin immunoprecipitation assay was used to investigate the protein-gene interactions.

RESULTS

A consistent downregulation of miR-1 was observed in tumor tissues and serum samples of SCLC patients compared to their matched normal controls, and these results were recapitulated in SCLC cell lines. Gain of function studies of miR-1 in SCLC cell lines showed decreased cell growth and oncogenic signaling, whereas loss of function studies of miR-1 rescued this effect. Intracardiac injection of gain of function of miR-1 SCLC cell lines in the mouse models showed a decrease in distant organ metastasis, whereas loss of function of miR-1 potentiated growth and metastasis. Mechanistic studies revealed that CXCR4 is a direct target of miR-1 in SCLC. Using unbiased transcriptomic analysis, we identified CXCR4/FOXM1/RRM2 as a unique axis that regulates SCLC growth and metastasis. Our results further showed that FOXM1 directly binds to the RRM2 promoter and regulates its activity in SCLC.

CONCLUSIONS

Our findings revealed that miR-1 is a critical regulator for decreasing SCLC growth and metastasis. It targets the CXCR4/FOXM1/RRM2 axis and has a high potential for the development of novel SCLC therapies. MicroRNA-1 (miR-1) downregulation in the tumor tissues and serum samples of SCLC patients is an important hallmark of tumor growth and metastasis. The introduction of miR-1 in SCLC cell lines decreases cell growth and metastasis. Mechanistically, miR-1 directly targets CXCR4, which further prevents FOXM1 binding to the RRM2 promoter and decreases SCLC growth and metastasis.

Muc16 depletion diminishes KRAS-induced tumorigenesis and metastasis by altering tumor microenvironment factors in pancreatic ductal adenocarcinoma

MUC16, membrane-bound mucin, plays an oncogenic role in pancreatic ductal adenocarcinoma (PDAC). However, the pathological role of MUC16 in the PDAC progression, tumor microenvironment, and metastasis in cooperation with KrasG12D and Trp53R172H mutations remains unknown. Deletion of Muc16 with activating mutations KrasG12D/+ and Trp53R172H/+ in mice significantly decreased progression and prolonged overall survival in KrasG12D/+; Trp53R172H/+; Pdx-1-Cre; Muc16-/- (KPCM) and KrasG12D/+; Pdx-1-Cre; Muc16-/- (KCM), as compared to KrasG12D/+; Trp53R172H/+; Pdx-1-Cre (KPC) and KrasG12D/+; Pdx-1-Cre (KC) mice, respectively. Muc16 knockout pancreatic tumor (KPCM) displays decreased tumor microenvironment factors and significantly reduced incidence of liver and lung metastasis compared to KPC. Furthermore, in silico data analysis showed a positive correlation of MUC16 with activated stroma and metastasis-associated genes. KPCM mouse syngeneic cells had significantly lower metastatic and endothelial cell binding abilities than KPC cells. Similarly, KPCM organoids significantly decreased the growth rate compared to KPC organoids. Interestingly, RNA-seq data revealed that the cytoskeletal proteins Actg2, Myh11, and Pdlim3 were downregulated in KPCM tumors. Further knockdown of these genes showed reduced metastatic potential. Overall, our results demonstrate that Muc16 alters the tumor microenvironment factors during pancreatic cancer progression and metastasis by changing the expression of Actg2, Myh11, and Pdlim3 genes.

MUC16 Promotes Liver Metastasis of Pancreatic Ductal Adenocarcinoma by Upregulating NRP2-Associated Cell Adhesion

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal types of cancer, as it commonly metastasizes to the liver resulting in an overall poor prognosis. However, the molecular mechanism involved in liver metastasis remains poorly understood. Here, we aimed to identify the MUC16-mediated molecular mechanism of PDAC-liver metastasis. Previous studies demonstrated that MUC16 and its C-terminal (Cter) domain are involved in the aggressiveness of PDAC. In this study, we observed MUC16 and its Cter expression significantly high in human PDAC tissues, PDAC organoids, and metastatic liver tissues, while no expression was observed in normal pancreatic tissues using IHC and immunofluorescence (IFC) analyses. MUC16 knockdown in SW1990 and CD18/HPAF PDAC cells significantly decreased the colony formation, migration, and endothelial/p-selectin binding. In contrast, MUC16-Cter ectopic overexpression showed significantly increased colony formation and motility in MiaPaCa2 pancreatic cancer cells. Interestingly, MUC16 promoted cell survival and colonization in the liver, mimicking an ex vivo environment. Furthermore, MUC16 enhanced liver metastasis in the in vivo mouse model. Our integrated analyses of RNA-sequencing suggested that MUC16 alters Neuropilin-2 (NRP2) and cell adhesion molecules in pancreatic cancer cells. Furthermore, we identified that MUC16 regulated NRP2 via JAK2/STAT1 signaling in PDAC. NRP2 knockdown in MUC16-overexpressed PDAC cells showed significantly decreased cell adhesion and migration. Overall, the findings indicate that MUC16 regulates NRP2 and induces metastasis in PDAC.

IMPLICATIONS

This study shows that MUC16 plays a critical role in PDAC liver metastasis by mediating NRP2 regulation by JAK2/STAT1 axis, thereby paving the way for future therapy efforts for metastatic PDAC.

Abstract 1489: MicroRNA-1 targets CXCR4/FOXM1/RRM2 axis regulating small cell lung cancer growth and metastasis

Small cell lung cancer (SCLC) is a high-grade neuroendocrine metastatic lung cancer subtype having a universal relapse and poor prognosis. Limited or extensive-stage SCLC patients have limited therapeutic options due to a lack of potential drug targets. In the quest for novel therapeutic molecules, we performed micro-RNA sequencing from the serum samples and also analyzed bulk RNA-sequencing data from tumors of SCLC patients. We found a consistent downregulation of miR-1 in SCLC. These results were recapitulated in SCLC cell lines and tumor tissues compared to their matched normal. To assess the therapeutic potential of miR-1, we overexpressed miR-1 in SCLC cell lines that translated into decreased cell growth and oncogenic signaling. Mechanistic studies revealed that CXCR4 is a direct target for miR-1 in SCLC. Intracardiac injection of SCLC cell lines in the mouse models showed that overexpression of miR-1 decreases the distant organ metastasis, whereas miR-1 sponging potentiates aggressiveness and metastasis. Furthermore, we identified FOXM1-RRM2 as a unique downstream target of the miR-1/CXCR4 axis involved in the growth and metastasis of SCLC. Our results showed that FOXM1 directly binds to the promoter site of RRM2 and regulates its activity. Overexpression of miR-1 decreases the expression and activity of FOXM1-RRM2 through CXCR4 that reduces cell growth and metastasis. Taken together, our results suggest that miR-1 decreases SCLC metastasis by targeting the CXCR4/FOXM1-RRM2 axis and has a high potential for the development of novel SCLC therapies.

Citation Format: Parvez Khan, Jawed A. Siddiqui, Shailendra Kumar Maurya, Tamara Mirzapoiazova, Ranjana Kanchan, Ramakanth Chirravuri Venkata, Pranita Atri, Wemin Tang, NaveenKumar Perumal, Prakash Kshirsagar, Mahek Fatima, Md Arafat Khan, Sanjib Chaudhary, Asad Ur Rehman, Imayavaramban Lakshmanan, Sidharth Mahapatra, Prakash Kulkarni, Apar Kishor Ganti, Maneesh Jain, David Oupicky, Ravi Salgia, Surinder Kumar Batra, Mohd Wasim Nasser. MicroRNA-1 targets CXCR4/FOXM1/RRM2 axis regulating small cell lung cancer growth and metastasis [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 1489.

Pancreatic Tumor Microenvironment Factor Promotes Cancer Stemness via SPP1-CD44 Axis

BACKGROUND & AIMS

Tumor-microenvironment factors and cancer stem cells (CSCs) play a critical role in the aggressiveness of pancreatic cancer (PC). However, the degree to which tumor-microenvironment factors promote stemness remains unexplored. Here, we examined whether cancer-associated fibroblasts (CAFs) promote CSC features in PC.

METHODS

PC cells were treated long-term (30, 60, and 90 days) with conditioned media (CM)-derived from normal human fibroblasts (NFs) and CAFs. The stemness features of tumorsphere formation and stemness populations, along with CSCs markers, were analyzed using 2-dimensional and 3-dimensional sodium alginate bead-based co-culture models. Immunohistochemistry and immunofluorescence staining were performed for CSCs and fibroblast markers in autochthonous KrasG12D/+; Trp53R172H/+; Pdx1-Cre mice and human pancreatic tumors. Polymerase chain reaction array and gene knockdown were performed to identify the mechanism of stemness enrichment.

RESULTS

Long-term treatment of PC cells with CAF-CM enriched stemness, as indicated by significantly higher CD44+, ALDH+, and AF+ populations in PC cells. Increased tumorsphere formation and elevated CSC, self-renewal, and drug-resistance markers in CAF-CM-treated PC cells were observed. In addition, CAFs co-cultured with PC cells in the 3-dimensional model showed a substantial increase in stemness features. CD44 and α-smooth muscle actin were positively correlated and their expressions progressively increased from the early to late stages of KrasG12D/+; Trp53R172H/+; Pdx1-Cre mouse and human pancreatic tumors. Osteopontin/secreted phosphoprotein 1 was identified as the top differentially overexpressed gene in CAF-CM-treated PC cells and knockdown of osteopontin/secreted phosphoprotein 1 significantly reduced stemness characteristics in CAF-CM-treated PC cells.

CONCLUSIONS

Our data uncovered novel insight into the interplay between CAF and enrichment of stemness population through the osteopontin/secreted phosphoprotein 1-CD44 axis in PC.

Dual blockade of EGFR and CDK4/6 delays head and neck squamous cell carcinoma progression by inducing metabolic rewiring

Despite preclinical success, monotherapies targeting EGFR or cyclin D1-CDK4/6 in Head and Neck squamous cell carcinoma (HNSCC) have shown a limited clinical outcome. Here, we aimed to determine the combined effect of palbociclib (CDK4/6) and afatinib (panEGFR) inhibitors as an effective strategy to target HNSCC. Using TCGA-HNSCC co-expression analysis, we found that patients with high EGFR and cyclin D1 expression showed enrichment of gene clusters associated with cell-growth, glycolysis, and epithelial to mesenchymal transition processes. Phosphorylated S6 (p-S6), a downstream effector of EGFR and cyclin D1-CDK4/6 signalling, showed a progressive increase from normal oral tissues to leukoplakia and frank malignancy, and associated with poor outcome of the patients. This increased p-S6 expression was drastically reduced after combination treatment with afatinib and palbociclib in the cell lines and mouse models, suggesting its utiliy as a prognostic marker in HNSCC. Combination treatment also reduced the cell growth and induced cell senescence via increasing reactive oxygen species with concurrent ablation of glycolytic and tricarboxylic acid cycle intermediates. Finally, our findings in sub-cutaneous and genetically engineered mouse model (K14-CreERtam;LSL-KrasG12D/+;Trp53R172H/+) studies showed a significant reduction in the tumor growth and delayed tumor progression after combination treatment. This study collectively demonstrates that dual targeting may be a critical therapeutic strategy in blocking tumor progression via inducing metabolic alteration and warrants clinical evaluation.

MicroRNA-1: Diverse role of a small player in multiple cancers

The process of cancer initiation and development is a dynamic and complex mechanism involving multiple genetic and non-genetic variations. With the development of high throughput techniques like next-generation sequencing, the field of cancer biology extended beyond the protein-coding genes. It brought the functional role of noncoding RNAs into cancer-associated pathways. MicroRNAs (miRNAs) are one such class of noncoding RNAs regulating different cancer development aspects, including progression and metastasis. MicroRNA-1 (miR-1) is a highly conserved miRNA with a functional role in developing skeletal muscle precursor cells and cardiomyocytes and acts as a consistent tumor suppressor gene. In humans, two discrete genes, MIR-1-1 located on 20q13.333 and MIR-1-2 located on 18q11.2 loci encode for a single mature miR-1. Downregulation of miR-1 has been demonstrated in multiple cancers, including lung, breast, liver, prostate, colorectal, pancreatic, medulloblastoma, and gastric cancer. A vast number of studies have shown that miR-1 affects the hallmarks of cancer like proliferation, invasion and metastasis, apoptosis, angiogenesis, chemosensitization, and immune modulation. The potential therapeutic applications of miR-1 in multiple cancer pathways provide a novel platform for developing anticancer therapies. This review focuses on the different antitumorigenic and therapeutic aspects of miR-1, including how it regulates tumor development and associated immunomodulatory functions.

ST6GalNAc-I promotes lung cancer metastasis by altering MUC5AC sialylation

Lung cancer (LC) is the leading cause of cancer-related mortality. However, the molecular mechanisms associated with the development of metastasis are poorly understood. Understanding the biology of LC metastasis is critical to unveil the molecular mechanisms for designing targeted therapies. We developed two genetically engineered LC mouse models Kras^G12D/+ ; Trp53^R172H/+ ; Ad-Cre (KPA) and Kras^G12D/+ ; Ad-Cre (KA). Survival analysis showed significantly (P = 0.0049) shorter survival in KPA tumor-bearing mice as compared to KA, suggesting the aggressiveness of the model. Our transcriptomic data showed high expression of N-acetylgalactosaminide alpha-2, 6-sialyltransferase 1 (St6galnac-I) in KPA compared to KA tumors. ST6GalNAc-I is an O-glycosyltransferase, which catalyzes the addition of sialic acid to the initiating GalNAc residues forming sialyl Tn (STn) on glycoproteins, such as mucins. Ectopic expression of species-specific p53 mutants in the syngeneic mouse and human LC cells led to increased cell migration and high expression of ST6GalNAc-I, STn, and MUC5AC. Immunoprecipitation of MUC5AC in the ectopically expressing p53^R175H cells exhibited higher affinity toward STn. In addition, ST6GalNAc-I knockout (KO) cells also showed decreased migration, possibly due to reduced glycosylation of MUC5AC as observed by low STn on the glycoprotein. Interestingly, ST6GalNAc-I KO cells injected mice developed less liver metastasis (P = 0.01) compared to controls, while colocalization of MUC5AC and STn was observed in the liver metastatic tissues of control mice. Collectively, our findings support the hypothesis that mutant p53^R175H mediates ST6GalNAc-I expression, leading to the sialyation of MUC5AC, and thus contribute to LC liver metastasis.

RNA-based therapies: A cog in the wheel of lung cancer defense

Lung cancer (LC) is a heterogeneous disease consisting mainly of two subtypes, non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC), and remains the leading cause of death worldwide. Despite recent advances in therapies, the overall 5-year survival rate of LC remains less than 20%. The efficacy of current therapeutic approaches is compromised by inherent or acquired drug-resistance and severe off-target effects. Therefore, the identification and development of innovative and effective therapeutic approaches are critically desired for LC. The development of RNA-mediated gene inhibition technologies was a turning point in the field of RNA biology. The critical regulatory role of different RNAs in multiple cancer pathways makes them a rich source of targets and innovative tools for developing anticancer therapies. The identification of antisense sequences, short interfering RNAs (siRNAs), microRNAs (miRNAs or miRs), anti-miRs, and mRNA-based platforms holds great promise in preclinical and early clinical evaluation against LC. In the last decade, RNA-based therapies have substantially expanded and tested in clinical trials for multiple malignancies, including LC. This article describes the current understanding of various aspects of RNA-based therapeutics, including modern platforms, modifications, and combinations with chemo-/immunotherapies that have translational potential for LC therapies.

Epigenetic landscape of small cell lung cancer: small image of a giant recalcitrant disease

Small cell lung cancer (SCLC) is a particular subtype of lung cancer with high mortality. Recent advances in understanding SCLC genomics and breakthroughs of immunotherapy have substantially expanded existing knowledge and treatment modalities. However, challenges associated with SCLC remain enigmatic and elusive. Most of the conventional drug discovery approaches targeting altered signaling pathways in SCLC end up in the 'grave-yard of drug discovery', which mandates exploring novel approaches beyond inhibiting cell signaling pathways. Epigenetic modifications have long been documented as the key contributors to the tumorigenesis of almost all types of cancer, including SCLC. The last decade witnessed an exponential increase in our understanding of epigenetic modifications for SCLC. The present review highlights the central role of epigenetic regulations in acquiring neoplastic phenotype, metastasis, aggressiveness, resistance to chemotherapy, and immunotherapeutic approaches of SCLC. Different types of epigenetic modifications (DNA/histone methylation or acetylation) that can serve as predictive biomarkers for prognostication, treatment stratification, neuroendocrine lineage determination, and development of potential SCLC therapies are also discussed. We also review the utility of epigenetic targets/epidrugs in combination with first-line chemotherapy and immunotherapy that are currently under investigation in preclinical and clinical studies. Altogether, the information presents the inclusive landscape of SCLC epigenetics and epidrugs that will help to improve SCLC outcomes.

Abstract 6072: MUC16-Cter cleavage increases the metastatic potential in pancreatic cancer

Pancreatic cancer (PC) is one of the most lethal malignant tumors. Several membrane-bound mucins are overexpressed in PC, including MUC16. The role and molecular mechanism of MUC16 mucin, particularly carboxyl-terminal domain (MUC16-Cter) in metastasis of pancreatic cancer, are poorly understood. Therefore, we hypothesize that the “MUC16-Cter domain plays a vital role in facilitating metastasis in pancreatic cancer”. Here, we knockout MUC16 in Capan 1 PC cells and overexpressed MUC16-Cter (F114AA) domain in MiaPaCa2 PC cells to study its functional impact in PC. Capan-1 MUC16 knockout cells displayed a significant decrease in colony-forming by in vitro tumorigenicity assay, endothelial binding, and P-selectin binding ability compared to control cells. Whereas, MUC16-Cter domain overexpressed MiaPaCa2 cells showed a significant increase in colony formation as compared to vector control cells. These results suggest that MUC16 plays a role in promoting in vitro tumorigenicity and facilitating intravasation and circulation of PC cell by interacting with endothelial cells during the metastatic spread of PC cells. Interestingly, we observed that chemotherapeutic drug (gemcitabine) induces MUC16-Cter cleavage in PC cells. We generated a genetically engineered mouse model Muc16-/- with KrasG12D, Trp53R172H/+, Pdx1-Cre (KPCM) background to study the role of Muc16 in PC tumorigenesis and metastasis with existing KPC model. KPCM showed decreased the early onset of cancer formation compared to KPC. Further, the Kaplan Meier test showed an increased survival rate in Muc16 -/- with KPC background as compared to KPC mice. EMT markers showed decreased expression in KPCM compared to KPC tumors. KPCM cells showed a significant decreased in migratory potential, endothelial, and P-selectin binding ability KPC PC cells. In conclusion, our in vitro and in vivo findings confirm that MUC16 and its Cter domain might play an essential role during the PC tumorigenesis and metastasis. Therefore, targeting MUC16-Cter might be an ideal therapeutic strategy for inhibiting tumorigenesis and metastasis of PC.

Citation Format: Saravanakumar Marimuthu, Imayavaramban Lakshmanan, Sakthivel Muniyan, Pranita Atri, Maneesh Jain, Moorthy P. Ponnusamy, Surinder K. Batra. MUC16-Cter cleavage increases the metastatic potential in pancreatic cancer [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 6072.

Molecular implications of MUC5AC-CD44 axis in colorectal cancer progression and chemoresistance

BACKGROUND

Differential expression of mucins has been associated with several cancers including colorectal cancer (CRC). In normal physiological conditions, secretory mucin MUC5AC is not expressed in the colonic mucosa, whereas its aberrant expression is observed during development of colon cancer and its precursor lesions. To date, the molecular mechanism of MUC5AC in CRC progression and drug resistance remains obscure.

METHODS

MUC5AC expression was determined in colon tissue microarray by immunohistochemistry. A RNA interference and CRISPR/Cas9-mediated system was used to knockdown/knockout the MUC5AC in CRC cell lines to delineate its role in CRC tumorigenesis using in vitro functional assays and in vivo (sub-cutaneous and colon orthotopic) mouse models. Finally, CRC cell lines and xenograft models were used to identify the mechanism of action of MUC5AC.

RESULTS

Overexpression of MUC5AC is observed in CRC patient tissues and cell lines. MUC5AC expression resulted in enhanced cell invasion and migration, and decreased apoptosis of CRC cells. MUC5AC interacted with CD44 physically, which was accompanied by the activation of Src signaling. Further, the presence of MUC5AC resulted in enhanced tumorigenesis and appearance of metastatic lesions in orthotopic mouse model. Additionally, up-regulation of MUC5AC resulted in resistance to 5-fluorouracil (5-FU) and oxaliplatin, and its knockout increased sensitivity to these drugs. Finally, we observed that up-regulation of MUC5AC conferred resistance to 5-FU through down-regulation of p53 and its target gene p21 and up-regulation of β-catenin and its target genes CD44 and Lgr5.

CONCLUSION

Our findings suggest that differential expression of secretory mucin MUC5AC results in enhanced tumorigenesis and also confers chemoresistance via CD44/β-catenin/p53/p21 signaling.

Reproducibility of CRISPR-Cas9 methods for generation of conditional mouse alleles: a multi-center evaluation

BACKGROUND

CRISPR-Cas9 gene-editing technology has facilitated the generation of knockout mice, providing an alternative to cumbersome and time-consuming traditional embryonic stem cell-based methods. An earlier study reported up to 16% efficiency in generating conditional knockout (cKO or floxed) alleles by microinjection of 2 single guide RNAs (sgRNA) and 2 single-stranded oligonucleotides as donors (referred herein as "two-donor floxing" method).

RESULTS

We re-evaluate the two-donor method from a consortium of 20 laboratories across the world. The dataset constitutes 56 genetic loci, 17,887 zygotes, and 1718 live-born mice, of which only 15 (0.87%) mice contain cKO alleles. We subject the dataset to statistical analyses and a machine learning algorithm, which reveals that none of the factors analyzed was predictive for the success of this method. We test some of the newer methods that use one-donor DNA on 18 loci for which the two-donor approach failed to produce cKO alleles. We find that the one-donor methods are 10- to 20-fold more efficient than the two-donor approach.

CONCLUSION

We propose that the two-donor method lacks efficiency because it relies on two simultaneous recombination events in cis, an outcome that is dwarfed by pervasive accompanying undesired editing events. The methods that use one-donor DNA are fairly efficient as they rely on only one recombination event, and the probability of correct insertion of the donor cassette without unanticipated mutational events is much higher. Therefore, one-donor methods offer higher efficiencies for the routine generation of cKO animal models.

Cigarette Smoke Induces Stem Cell Features of Pancreatic Cancer Cells via PAF1

BACKGROUND & AIMS

Cigarette smoking is a major risk factor for pancreatic cancer. Aggressive pancreatic tumors contain cancer cells with stem cell features. We investigated whether cigarette smoke induces stem cell features in pancreatic cancer cells.

METHODS

Kras^G12D; Pdx1-Cre mice were exposed to cigarette smoke or clean air (controls) for up to 20 weeks; pancreata were collected and analyzed by histology, quantitative reverse transcription polymerase chain reaction, and confocal immunofluorescence microscopy. HPNE and Capan1 cells were exposed to cigarette smoke extract (CSE), nicotine and nicotine-derived carcinogens (NNN or NNK), or clean air (controls) for 80 days and evaluated for stem cell markers and features using flow cytometry-based autofluorescence, sphere formation, and immunoblot assays. Proteins were knocked down in cells with small interfering RNAs. We performed RNA sequencing analyses of CSE-exposed cells. We used chromatin immunoprecipitation assays to confirm the binding of FOS-like 1, AP-1 transcription factor subunit (FOSL1) to RNA polymerase II-associated factor (PAF1) promoter. We obtained pancreatic ductal adenocarcinoma (PDAC) and matched nontumor tissues (n = 15) and performed immunohistochemical analyses.

RESULTS

Chronic exposure of HPNE and Capan1 cells to CSE caused them to increase markers of stem cells, including autofluorescence and sphere formation, compared with control cells. These cells increased expression of ABCG2, SOX9, and PAF1, via cholinergic receptor nicotinic alpha 7 subunit (CHRNA7) signaling to mitogen-activated protein kinase 1 and FOSL1. CSE-exposed pancreatic cells with knockdown of PAF1 did not show stem cell features. Exposure of cells to NNN and NNK led to increased expression of CHRNA7, FOSL1, and PAF1 along with stem cell features. Pancreata from Kras^G12D; Pdx1-Cre mice exposed to cigarette smoke had increased levels of PAF1 mRNA and protein, compared with control mice, as well as increased expression of SOX9. Levels of PAF1 and FOSL1 were increased in PDAC tissues, especially those from smokers, compared with nontumor pancreatic tissue. CSE exposure increased expression of PHD-finger protein 5A, a pluripotent transcription factor and its interaction with PAF1.

CONCLUSIONS

Exposure to cigarette smoke activates stem cell features of pancreatic cells, via CHRNA7 signaling and FOSL1 activation of PAF1 expression. Levels of PAF1 are increased in pancreatic tumors of humans and mice with chronic cigarette smoke exposure.

MUC16 as a novel target for cancer therapy

INTRODUCTION

MUC16 is overexpressed in multiple cancers and plays an important role in tumorigenicity and acquired resistance to therapy. Area covered: In this review, we describe the role of MUC16 under normal physiological conditions and during tumorigenesis. First, we provide a summary of research on MUC16 from its discovery as CA125 to present anti-MUC16 therapy trials that are currently in the initial phases of clinical testing. Finally, we discuss the reasons for the limited effectiveness of these therapies and discuss the direction and focus of future research. Expert opinion: Apart from its protective role in normal physiology, MUC16 contributes to disease progression and metastasis in several malignancies. Due to its aberrant overexpression, it is a promising target for diagnosis and therapy. Cleavage and shedding of its extracellular domain is the major barrier for efficient targeting of MUC16-expressing cancers. Concerted efforts should be undertaken to target the noncleaved cell surface retained portion of MUC16. Such efforts should be accompanied by basic research to understand MUC16 cleavage and decipher the functioning of MUC16 cytoplasmic tail. While previous efforts to activate anti-MUC16 immune response using anti-CA125 idiotype antibodies have met with limited success, ideification of neo-antigenic epitopes in MUC16 that correlate with improved survival have raised raised hopes for developing MUC16-targeted immunotherapy.

Development and characterization of carboxy-terminus specific monoclonal antibodies for understanding MUC16 cleavage in human ovarian cancer

MUC16 is overexpressed in ovarian cancer and plays important roles in invasion and metastasis. Previously described monoclonal antibodies against cell surface expressed MUC16 recognize the N-terminal tandemly repeated epitopes present in cancer antigen 125 (CA125). MUC16 is cleaved at a specific location, thus, releasing CA125 into the extracellular space. Recent reports have indicated that the retained carboxy-terminal (CT) fragment of MUC16 might play an important role in tumorigenicity in diverse types of cancers. However, limited data is available on the fate and existence of CT fragment on the surface of the cancer cell. Herein, we characterize two monoclonal antibodies (mAbs) showing specificity to the retained juxtamembrane region of MUC16. For the first time, we demonstrate that MUC16 is cleaved in ovarian cancer cells (NIH:OVCAR-3 [OVCAR-3]) and that the cleaved MUC16 subunits remain associated with each other. Immunohistochemical analyses on different grades of ovarian tumor tissues indicated differential reactivity of CA125 and MUC16 CT mAbs. The CA125 (M11) mAb detected 32/40 (80%), while the CT mAb (5E6) detected 33/40 (82.5%) of total ovarian cancer cases. For serous and serous papillary cases, the CA125 (M11) mAb stained 27/31 cases (87%), while CT mAb (5E6) stained 29/31 cases (93.5%). The CT mAb(s) accurately predict expression of MUC16 since their epitopes are not tandemly repeated and their reactivity may not be dependent on O-linked glycosylation. These antibodies can serve as valuable reagents for understanding MUC16 cleavage and may also serve as potential therapeutic agents for treatment of ovarian cancer.

hPaf1/PD2 interacts with OCT3/4 to promote self-renewal of ovarian cancer stem cells

Cancer stem cells (CSCs), which mediate drug resistance and disease recurrence in several cancers, are therapeutically relevant to ovarian cancer (OC), wherein approximately 80% of patients manifest with tumor recurrence. While there are several markers for ovarian CSCs (OCSCs), the mechanism for their self-renewal maintenance by unique driver/markers is poorly understood. Here, we evaluated the role of hPaf1/PD2, a core component of RNA Polymerase II-Associated Factor (PAF) complex, in self-renewal of OCSCs through marker and functional analyses, including CRISPR/Cas9-silencing of hPaf1/PD2 in OCSCs and provided a possible mechanism for maintenance of OCSCs. Expression of hPaf1/PD2 showed moderate to intense staining in 32.4% of human OC tissues, whereas 67.6% demonstrated basal expression by immunohistochemistry analysis, implying that the minor proportion of cells overexpressing hPaf1/PD2 could be putative OCSCs. Isolated OCSCs showed higher expression of hPaf1/PD2 along with established CSC and self-renewal markers. Knockdown of hPaf1/PD2 in OCSCs resulted in a significant downregulation of CSC and self-renewal markers, and impairment of in vitro tumor sphere (P < 0.05) and colony formation (P = 0.013). Co-immunoprecipitation revealed that OCT3/4 specifically interacts with hPaf1/PD2, and not with other PAF components (Ctr9, Leo1, Parafibromin) in OCSCs, suggesting a complex-independent role for hPaf1/PD2 in OCSC maintenance. Moreover, there was a significant overexpression and co-localization of hPaf1/PD2 with OCT3/4 in OC tissues compared to normal ovary tissues. Our results indicate that hPaf1/PD2 is overexpressed in OCSCs and maintains the self-renewal of OCSCs through its interaction with OCT3/4; thus, hPaf1/PD2 may be a potential therapeutic target to overcome tumor relapse in OC.

MUC16 Regulates TSPYL5 for Lung Cancer Cell Growth and Chemoresistance by Suppressing p53

Purpose: MUC16, a tumor biomarker and cell surface-associated mucin, is overexpressed in various cancers; however, its role in lung cancer pathogenesis is unknown. Here, we have explored the mechanistic role of MUC16 in lung cancer.Experimental Design: To identify the functional role of MUC16, stable knockdown was carried in lung cancer cells with two different shRNAs. Clinical significance of MUC16 was evaluated in lung cancer patient tissues using IHC. We have generated genetically engineered mouse model (Kras^G12D; AdCre) to evaluate the preclinical significance of MUC16.Results: MUC16 was overexpressed (P = 0.03) in lung cancer as compared with normal tissues. MUC16 knockdown (KD) in lung cancer cell lines decreased the in vitro growth rate (P < 0.05), migration (P < 0.001), and in vivo tumor growth (P = 0.007), whereas overexpression of MUC16-carboxyl terminal (MUC16-Cter) resulted in increased growth rate (P < 0.001). Transcriptome analysis of MUC16 KD showed a downregulation (P = 0.005) of TSPYL5 gene, which encodes for a testis-specific Y-like protein. Rescue studies via overexpression of MUC16-Cter in MUC16 KD cells showed activation of signaling proteins, such as JAK2 (Y1007/1008), STAT3 (Y705), and glucocorticoid receptor (GR), which constitutes an important axis for the regulation of TSPYL5 for oncogenic process. Further, inhibition of STAT3 (Y705) led to decreased GR and TSPYL5, suggesting that MUC16 regulates TSPYL5 through the JAK2/STAT3/GR axis. Also, MUC16 overexpression induced cisplatin and gemcitabine resistance by downregulation of p53.Conclusions: Our findings indicate a significant role of MUC16 in tumorigenesis and metastasis of lung cancer cells possibly via regulation of TSPYL5 through the JAK2/STAT3/GR axis. Clin Cancer Res; 23(14); 3906-17. ©2017 AACR.

Abstract 2495: hPaf1/PD2 interacts with OCT3/4 in maintenance of the self-renewal process of ovarian cancer stem cells

Background: Ovarian cancer (OC) is the most lethal gynecological malignancy among women with more than 85% of the patients manifesting tumor recurrence. Emerging evidence suggests that a small population of cells within the tumor - the ‘cancer stem cells (CSCs)’ is capable to giving rise to the entire histopathology of the tumor and is responsible for mediating drug resistance, recurrence, and disease aggressiveness. Previously, hPaf1(human RNA polymerase II associated factor1)/PD2 (Pancreatic Differentiation2) - a core component of RNA polymerase II associated factor (PAF) complex, was shown to be overexpressed in pancreatic CSCs and involved in the maintenance of mouse ESCs. Hence, we hypothesized that hPaf1 is involved in the maintenance of self-renewal property of ovarian CSCs (OCSCs). In this study, we investigated the functional role of hPaf1 in OCSCs which has not been explored before.

Methods: Expression of hPaf1, cancer stem cell marker ESA, and self-renewal protein OCT3/4 was analyzed using confocal microscopy on OC tissue array. Side population (SP) was isolated from two OC cell lines OVCAR3 and A2780 by Hoechst staining using flow-cytometer, and characterized using tumor sphere assay. Immunoblotting was performed on characterized SP and NSP (non-SP) for OCSC and self-renewal markers. Transient knockdown of hPaf1 in SP was performed to understand how hPaf1 affects the CSC phenotype through immunoblotting, confocal microscopy, colony formation assay, and tumor sphere formation assay. To determine the interaction between hPaf1 and OCT 3/4, reciprocal co-immunoprecipitation was performed in SP/OCSCs.

Results: There was a significant overexpression and considerable co-localization of hPaf1/PD2 with ESA and OCT3/4 in OC tissues compared to normal ovary tissues. SP from OVCAR3 formed larger and greater number of tumor spheres compared to NSP cells. Moreover, SP isolated from OVCAR3 and A2780 showed higher expression of hPaf1 along with CSC markers (CD44, CD133, ESA, CD24), and self- renewal proteins (β-CATENIN, SOX2, OCT3/4, SHH, and HER2). Transient knockdown of hPaf1 resulted in a significant decrease in expression of CSC markers and self-renewal proteins. In addition, functional characteristics of CSCs such as in vitro tumor formation capacity in non-adherent media and colony formation ability were impaired upon knockdown of hPaf1 suggesting that hPaf1 is involved in maintenance of the CSC phenotype. We also observed that hPaf1 physically interacts with OCT3/4 in OVCAR3 SP cells which provides a mechanism for the maintenance of OCSCs by hPaf1.

Conclusion: Altogether, hPaf1/PD2 is overexpressed in OCSCs and its knockdown resulted in loss of OCSC phenotype. Moreover, hPaf1 is responsible for the maintenance of OCSCs through its interaction with OCT3/4. Hence, therapies that are able to abrogate hPaf1 mediated self-renewal of OCSCs represent potential therapeutic avenues to overcome tumor relapse in OC.

Citation Format: Saswati Karmakar, Parthasarathy Seshacharyulu, Arokia Priyanka Vaz, Imayavaramban Lakshmanan, Moorthy Palanimuthu Ponnusamy, Surinder Kumar Batra. hPaf1/PD2 interacts with OCT3/4 in maintenance of the self-renewal process of ovarian cancer stem cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2495.

Abstract 2490: Smoking enriches cancer stem cell population and activates Sox9 through NF-kB signaling in pancreatic ductal adenocarcinoma

Introduction: Recent studies have demonstrated a clear association between smoking and the incidence of pancreatic ductal adenocarcinoma (PDAC); however, the effect of cigarette smoke in the activation of stem cell (SC) or cancer stem cell (CSC) genes and their involvement in the initiation and progression of PDAC have not yet been studied. It is well known that CSCs are responsible for the drug resistance and aggressiveness of the disease including PDAC. In this study, we investigated the effects of smoking on enrichment of SC/CSCs in pancreatic normal and ductal adenocarcinoma cells, and we also examined whether smoking can activate NF-kB signaling, which is in part leads to enrichment of CSC and induction of CSC markers in PDAC.

Methods: Cigarette smoke extract (CSE) was prepared, and HPNE (Human pancreatic nestin positive cells) and Capan-1 pancreatic cancer (PC) cells were treated with CSE for up to ∼15 weeks. Side population (SP) were analyzed by Hoechst staining using Flow-cytomer, and various CSC markers such as PD2 (a stem cell maintenance marker), CD44, ALDH-1, SOX-9 (a multipotent SC marker) and Oct-3/4 (a pluripotent marker), and NF-kB signaling molecules were analyzed by western blotting. ALDH1+ cells, CD44+CD24+ CSCs and G0/G1 phase low cycling quiescent cells were analyzed by flow cytometer. An in-vitro sphere culture was also performed to further confirm the smoke induced CSC properties. Smoke exposed pancreatic tissues excised from unfloxed littermate control (LSL-K-Ras G12D) pancreatic tissue sections were immunostained for SOX-9 using immunohistochemistry (IHC), and for SOX9 and CD44 using immunofluorescence.

Results: Our results showed increased SC/CSCs and more number of spheres by CSE treated cells as compared to their untreated controls and displayed elevated protein expressions of SC/CSC markers. We also observed an elevated CD44+CD24+ CSCs, increased ALDH1+ cells and increased G0/G1 low cycling quiescent cell population in CSE treated cells as compared to untreated controls. In addition, increased immunohistochemical staining for SOX9 and increased immunofluorescent signal for SOX-9 and CD44 were observed in smoke exposed animal tissues indicating that smoking may transform SOX-9+ multipotent SCs into SOX9+CD44+ CSCs. We also analyzed the expression levels of NF-kB signaling molecules in CSE treated HPNE and Capan-1 cells. As compared to their untreated controls, CSE treated cells showed elevated protein expression levels of phospho AKT, phospho RelA (SOX-9 promoter binding subunit of NF-kB complex) and phospho IKKα (a kinase that phosphorylates IKBα, an inhibitor of RelA) suggesting that smoking activates NF-kB signaling.

Conclusion: Our results illustrate that smoking enriches SC/CSCs populations in normal pancreatic cells as well as in pancreatic cancer cells, and activates SOX9 through NF-kB signaling in PDAC.

Citation Format: Ramakrishna Nimmakayala, Parthasarathy Seshacharyulu, Seema Chugh, Imayavaramban Lakshmanan, Satyanarayana Rachagani, Surinder K Batra, Moorthy P Ponnusamy. Smoking enriches cancer stem cell population and activates Sox9 through NF-kB signaling in pancreatic ductal adenocarcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2490.

Abstract 1629: Novel interaction of MUC16 with FAK activate EMT process and metastasis of pancreatic ductal adenocarcinoma

Introduction: MUC16 is a heavily glycosylated, type I transmembrane mucin, which is over expressed in different cancers. We have previously shown that significant overexpression of MUC16 in human PDAC tissues with disease progression compared to normal pancreas. However, the functional consequences of MUC16 and their role in PDAC is poorly understood. Based on this our hypothesis is that MUC16 can drive pancreatic cancer metastasis through FAK-mediated Akt and ERK/MAPK signaling activation and altering EMT markers.

Methods: We have developed MUC16 knockdown Capan1 and Colo-357 PDAC cells to study the functional impacts. Congenic cell survival, soft-agar colony formation, and trans-well chamber assays were performed to determine the in vitro tumorigenicity. Orthotopic implantation was carried out using capan-1 and colo-357 PDAC cells to determine the oncogenic and metastatic potential of MUC16. Binding assay was performed to determine the cell adhesion property of MUC16 in colo-357 cells. The physical interaction between MUC16 and mesothelin, galectin-3 and FAK were evaluated by confocal and immunoprecipitation analysis. Immunoblot analyses were performed to determine the downstream signaling in MUC16 knockdown cells.

Results: MUC16 knockdown in capan-1 and colo-357 PDAC cell lines resulted in significantly decreased cell proliferation (P&lt;0.05), colony formation (P&lt;0.01), and migration (P&lt;0.01) in vitro. Further, MUC16 knockdown capan-1 and colo-357 cells significantly decreases the tumor formation (P&lt;0.05) and metastasis (liver P&lt;0.05, spleen P&lt;0.001, intestinal wall P&lt;0.01, diaphragm P&lt;0.01 and peritoneum P&lt;0.001) in orthotopic xenograft mouse model. Adhesion assay displays decreased cell attachment of MUC16 knockdown cells with recombinant galectin-1 and galectin-3 proteins. Immunoprecipitation and immunofluorescence studies confirmed that MUC16 interaction with mesothelin and galectin-3 in PDAC cells. Co-immunoprecipitation revealed a novel interaction between MUC16 and FAK in PDAC cells. Interestingly, we observed decreased expression of mesenchymal markers (N-cadherin and Zeb1) and increased expression of epithelial markers (E-cadherin and CK18) in MUC16 silenced PDAC cells, correlating with the decrease in metastasis. Moreover, MUC16 knockdown show decreased FAK-mediated Akt and ERK/MAPK activation in PDAC cells.

Conclusion: Overall our study concludes that MUC16 interacts with FAK leads to the activation of EMT markers for enhancing pancreatic cancer metastasis.

Citation Format: Sakthivel Muniyan, Dhanya Haridas, Satyanarayana Rachagani, Imayavaramban Lakshmanan, Suprit Gupta, Seema Chugh, Parthasarathy Seshacharyulu, Moorthy P. Ponnusamy, Surinder K. Batra. Novel interaction of MUC16 with FAK activate EMT process and metastasis of pancreatic ductal adenocarcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1629.

Novel HER3/MUC4 oncogenic signaling aggravates the tumorigenic phenotypes of pancreatic cancer cells

Several studies have demonstrated that MUC4 is involved in progression and metastasis of pancreatic cancer (PC). Here, we report that HER3/MUC4 interaction in HER2 low cells is critical in driving pancreatic tumorigenesis. Upon HER2 knockdown, we observed elevated expression of HER3 and MUC4 and their interactions, which was confirmed by immunoprecipitation and bioinformatics analyses. In paired human PC tissues, higher percentage of HER3 positivity (10/33, 30.3%; p = 0.001) was observed than HER2 (5/33, 15.1%; p = 0.031), which was further confirmed in spontaneous mice (KPC; Kras^G12D; Trp53^R172H/+; Pdx-Cre) tumors of different weeks. Mechanistically, increased phosphorylation of ERK and expression of PI3K and c-Myc were observed in HER2 knockdown cells, suggesting a positive role for HER3/MUC4 in HER2 low cells. Further, HER2 knockdown resulted in increased proliferation, motility and tumorigenicity of PC cells. Consistently, transient knockdown of HER3 by siRNA in HER2 knockdown cells led to decreased proliferation. These observations led us to conclude that HER3 interacts with MUC4 to promote proliferation in HER2 low PC cells. Further, deficiency of both HER2 and HER3 leads to decreased proliferation of PC cells. Hence targeting these newly identified HER3/MUC4 signals would improve the PC patients survival by intercepting MUC4 mediated oncogenic signaling.

RAC1 GTPase promotes the survival of breast cancer cells in response to hyper-fractionated radiation treatment

Radiation therapy is a staple approach for cancer treatment, whereas radioresistance of cancer cells remains a substantial clinical problem. In response to ionizing radiation (IR) induced DNA-damage, cancer cells can sustain/activate pro-survival signaling pathways, leading to apoptotic resistance and induction of cell cycle checkpoint/DNA repair. Previous studies show that Rac1 GTPase is overexpressed/hyperactivated in breast cancer cells and is associated with poor prognosis. Studies from our laboratory reveal that Rac1 activity is necessary for G2/M checkpoint activation and cell survival in response to IR exposure of breast and pancreatic cancer cells. In the present study, we investigated the effect of Rac1 on the survival of breast cancer cells treated with hyper-fractionated radiation (HFR), which is used clinically for cancer treatment. Results in this report indicate that Rac1 protein expression is increased in the breast cancer cells that survived HFR compared to parental cells. Furthermore, this increase of Rac1 is associated with enhanced activities of ERK1/2 and NF-κB signaling pathways and increased levels of anti-apoptotic protein Bcl-xL and Mcl-1, which are downstream targets of ERK1/2 and NF-κB signaling pathways. Using Rac1 specific inhibitor and dominant negative mutant N17Rac1, here we demonstrate that Rac1 inhibition decreases the phosphorylation of ERK1/2 and IκBα, as well as the levels of Bcl-xL and Mcl-1 protein in the HFR-selected breast cancer cells. Moreover, inhibition of Rac1 using either small molecule inhibitor or dominant negative N17Rac1 abrogates clonogenic survival of HFR-selected breast cancer cells and decreases the level of intact PARP, which is indicative of apoptosis induction. Collectively, results in this report suggest that Rac1 signaling is essential for the survival of breast cancer cells subjected to HFR and implicate Rac1 in radioresistance of breast cancer cells. These studies also provide the basis to explore Rac1 as a therapeutic target for radioresistant breast cancer cells.

Carboxyl-terminal domain of MUC16 imparts tumorigenic and metastatic functions through nuclear translocation of JAK2 to pancreatic cancer cells

MUC16 (CA125) is a type-I transmembrane glycoprotein that is up-regulated in multiple cancers including pancreatic cancer (PC). However, the existence and role of carboxyl-terminal MUC16 generated following its cleavage in PC is unknown. Our previous study using a systematic dual-epitope tagged domain deletion approach of carboxyl-terminal MUC16 has demonstrated the generation of a 17-kDa cleaved MUC16 (MUC16-Cter). Here, we demonstrate the functional significance of MUC16-Cter in PC using the dual-epitope tagged version (N-terminal FLAG- and C-terminal HA-tag) of 114 carboxyl-terminal residues of MUC16 (F114HA). In vitro analyses using F114HA transfected MiaPaCa-2 and T3M4 cells showed enhanced proliferation, motility and increased accumulation of cells in the G2/M phase with apoptosis resistance, a feature associated with cancer stem cells (CSCs). This was supported by enrichment of ALDH⁺ CSCs along with enhanced drug-resistance. Mechanistically, we demonstrate a novel function of MUC16-Cter that promotes nuclear translocation of JAK2 resulting in phosphorylation of Histone-3 up-regulating stemness-specific genes LMO2 and NANOG. Jak2 dependence was demonstrated using Jak2^+/+ and Jak2^−/− cells. Using eGFP-Luciferase labeled cells, we demonstrate enhanced tumorigenic and metastatic potential of MUC16-Cter in vivo. Taken together, we demonstrate that MUC16-Cter mediated enrichment of CSCs is partly responsible for tumorigenic, metastatic and drug-resistant properties of PC cells.

Overexpression of PD2 leads to increased tumorigenicity and metastasis in pancreatic ductal adenocarcinoma

Pancreatic differentiation 2 (PD2), an important subunit of the human PAF complex, was identified after differential screening analysis of 19q13 amplicon, and its overexpression induces oncogenic transformation of NIH3T3 cells, hence raising the possibility of a role for PD2 in tumorigenesis and metastasis. To test this hypothesis, we analyzed here the functional role and clinical significance of PD2 in pancreatic ductal adenocarcinoma (PDAC) and its pathogenesis. Using immunohistochemical analysis, we found that PD2 is detected in the acini but not in the ducts in the normal pancreas. In human PDAC specimens, PD2 was instead primarily detected in the ducts (12/48 patients 25%; p-value < 0.0001), thereby showing that PDAC correlates with increased ductal expression of PD2. Consistently, PD2 expression was increased in telomerase-immortalized human pancreatic ductal cells (HPNE cells) modified to express the HPV16 E6 and E7 proteins, whose respective functions are to block p53 and RB. In addition, ectopic expression of PD2 in PDAC cells (Capan-1 and SW1990) led to increased clonogenicity and migration in vitro, and tumor growth and metastasis in vivo. Interestingly, PD2 overexpression also resulted in enrichment of cancer stem cells (CSCs) and upregulation of oncogenes such as c-Myc and cell cycle progression marker, cyclin D1. Taken together, our results support that PD2 is overexpressed in the ducts of PDAC tissues, and results in tumorigenesis and metastasis via upregulation of oncogenes such as c-Myc and cyclin hence D1 implicating PD2 upregulation in pancreatic oncogenesis with targeted therapeutic potential.

Targeting EGF-receptor(s) - STAT1 axis attenuates tumor growth and metastasis through downregulation of MUC4 mucin in human pancreatic cancer

Transmembrane proteins MUC4, EGFR and HER2 are shown to be critical in invasion and metastasis of pancreatic cancer. Besides, we and others have demonstrated de novo expression of MUC4 in ~70-90% of pancreatic cancer patients and its stabilizing effects on HER2 downstream signaling in pancreatic cancer. Here, we found that use of canertinib or afatinib resulted in reduction of MUC4 and abrogation of in vitro and in vivo oncogenic functions of MUC4 in pancreatic cancer cells. Notably, silencing of EGFR family member in pancreatic cancer cells decreased MUC4 expression through reduced phospho-STAT1. Furthermore, canertinib and afatinib treatment also inhibited proliferation, migration and survival of pancreatic cancer cells by attenuation of signaling events including pERK1/2 (T202/Y204), cyclin D1, cyclin A, pFAK (Y925) and pAKT (Ser473). Using in vivo bioluminescent imaging, we demonstrated that canertinib treatment significantly reduced tumor burden (P=0.0164) and metastasis to various organs. Further, reduced expression of MUC4 and EGFR family members were confirmed in xenografts. Our results for the first time demonstrated the targeting of EGFR family members along with MUC4 by using pan-EGFR inhibitors. In conclusion, our studies will enhance the translational acquaintance of pan-EGFR inhibitors for combinational therapies to combat against lethal pancreatic cancer.

MUC5AC interactions with integrin β4 enhances the migration of lung cancer cells through FAK signaling

MUC5AC is a secretory mucin aberrantly expressed in various cancers. In lung cancer, MUC5AC is overexpressed in both primary and metastatic lesions; however, its functional role is not well understood. The present study was aimed at evaluating mechanistic role of MUC5AC on metastasis of lung cancer cells. Clinically, the overexpression of MUC5AC was observed in lung cancer patient tissues and was associated with poor survival. In addition, the overexpression of Muc5ac was also observed in genetically engineered mouse lung adenocarcinoma tissues (Kras(G12D); Trp53(R172H/+); AdCre) in comparison with normal lung tissues. Our functional studies showed that MUC5AC knockdown resulted in significantly decreased migration in two lung cancer cell lines (A549 and H1437) as compared with scramble cells. Expression of integrins (α5, β1, β3, β4 and β5) was decreased in MUC5AC knockdown cells. As both integrins and MUC5AC have a von Willebrand factor domain, we assessed for possible interaction of MUC5AC and integrins in lung cancer cells. MUC5AC strongly interacted only with integrin β4. The co-localization of MUC5AC and integrin β4 was observed both in A549 lung cancer cells as well as genetically engineered mouse adenocarcinoma tissues. Activated integrins recruit focal adhesion kinase (FAK) that mediates metastatic downstream signaling pathways. Phosphorylation of FAK (Y397) was decreased in MUC5AC knockdown cells. MUC5AC/integrin β4/FAK-mediated lung cancer cell migration was confirmed through experiments utilizing a phosphorylation (Y397)-specific FAK inhibitor. In conclusion, overexpression of MUC5AC is a poor prognostic marker in lung cancer. MUC5AC interacts with integrin β4 that mediates phosphorylation of FAK at Y397 leading to lung cancer cell migration.

Mucins in lung cancer: diagnostic, prognostic, and therapeutic implications

Aberrant expression of mucins is associated with cancer development and metastasis. An overexpression of few mucins contributes to oncogenesis by enhancing cancer cell growth and providing constitutive survival signals. This review focuses on the importance of mucins both in the normal bronchial epithelial cells and the malignant tumors of the lung and their contribution in the diagnosis and prognosis of lung cancer patients. During lung cancer progression, mucins either alone or through their interaction with many receptor tyrosine kinases mediate cell signals for growth and survival of cancer cells. Also, stage-specific expression of certain mucins, like MUC1, is associated with poor prognosis from lung cancer. Thus, mucins are emerging as attractive targets for developing novel therapeutic approaches for lung cancer. Several strategies targeting mucin expression and function are currently being investigated to control lung cancer progression.

The canonical Wnt pathway regulates the metastasis-promoting mucin MUC4 in pancreatic ductal adenocarcinoma

Aberrant Wnt signaling frequently occurs in pancreatic cancer (PC) and contributes to disease progression/metastases. Likewise, the transmembrane-mucin MUC4 is expressed de novo in early pancreatic intraepithelial neoplasia (PanINs) and incrementally increases with PC progression, contributing to metastasis. To determine the mechanism of MUC4 upregulation in PC, we examined factors deregulated in early PC progression, such as Wnt/β-catenin signaling. MUC4 promoter analysis revealed the presence of three putative TCF/LEF-binding sites, leading us to hypothesize that MUC4 can be regulated by β-catenin. Immunohistochemical (IHC) analysis of rapid autopsy PC tissues showed a correlation between MUC4 and cytosolic/nuclear β-catenin expression. Knock down (KD) of β-catenin in CD18/HPAF and T3M4 cell lines resulted in decreased MUC4 transcript and protein. Three MUC4 promoter luciferase constructs, p3778, p3000, and p2700, were generated. The construct p3778, encompassing the entire MUC4 promoter, elicited increased luciferase activity in the presence of stabilized β-catenin. Mutation of the TCF/LEF site closest to the transcription start site (i.e., -2629/-2612) and furthest from the start site (i.e., -3425/-3408) reduced MUC4 promoter luciferase activity. Transfection with dominant negative TCF4 decreased MUC4 transcript and protein levels. Chromatin immunoprecipitation confirmed enrichment of β-catenin on -2629/-2612 and -3425/-3408 of the MUC4 promoter in CD18/HPAF. Functionally, CD18/HPAF and T3M4 β-catenin KD cells showed decreased migration and decreased Vimentin, N-cadherin, and pERK1/2 expression. Tumorigenicity studies in athymic nude mice showed CD18/HPAF β-catenin KD cells significantly reduced primary tumor sizes and metastases compared to scrambled control cells. We show for the first time that β-catenin directly governs MUC4 in PC.

Emerging role of mucins in epithelial to mesenchymal transition

Epithelial to mesenchymal transition (EMT) is an important and complex phenomenon that determines the aggressiveness of cancer cells. The morphological transformation of cancerous cells is accompanied by various cellular processes such as alterations in cell-cell adhesion, cell matrix degradation, down regulation of epithelial marker Ecadherin and upregulation of mesenchymal markers N-cadherin and Vimentin. Besides these markers several other important tumor antigens/mucins are also involved in the EMT process. Mainly high molecular weight glycoproteins such as mucin molecules (MUC1, MUC4 and MUC16) play a major role in the cellular transformation and signaling alteration in EMT process. In addition to these factors, EMT may be an essential process triggering the emergence or expansion of the CSC population, which slowly results in the initiation of tumor at metastatic sites. Furthermore, mucins have been demonstrated to be involved in the EMT process and also in the enrichment of cancer stem cell population. Mucin mediated EMT is very complex since the key components of tumor microenvironment are also regulating mucin molecules. In this review, we have discussed all the aforementioned factors and their mechanistic involvement for EMT process.

Abstract 1760: MUC16 upregulates TSPYL5 gene and mediates Lung cancer cell proliferation by suppressing p53 activity

Background: Lung cancer is the most common cause of cancer related death in the world. The 5-year survival of lung cancer patients is a dismal 15%. MUC16 is a very high molecular weight glycoprotein with 22,152 amino acid residues in its protein sequence. According to Oncomine data, MUC16 is highly overexpressed in lung cancer particularly Non Small Cell Lung Cancer cell [NSCLC]. MUC16 is a well-established tumor marker in ovarian cancer but its functional and mechanistic role is not well understood. The Testis Specific Y-Like Protein (TSPYL5), which is also overexpressed in lung carcinoma (68%) and it has been suggested that overexpression of TSPYL5 induces cancer cell growth by suppressing p53 activity in terms. We evaluated the interplay between MUC16 and TSPYL5 in lung carcinogenesis.

Materials and Methods: Endogenously expressed MUC16 was stably knocked down using a MUC16 shRNA construct (pSUPER-Retro-MUC16-sh) in H292 and H827 lung cancer cells by stable transfection method. The cells were treated with cisplatin to investigate the role of MUC16 and TSPYL5 on chemoresistance in lung cancer cells and its role in p53 degradation.

Results: MUC16 is overexpressed in lung cancer while it is absent in normal lung tissues by immunohistochemistry analysis. Specifically MUC16 is highly observed in Stage III of lung carcinoma than other stages and metastatic sites as well. Significant expression of MUC16 was observed in NSCLC derived cell lines (H292 and H827) that express p53 (wild type). On knocking down MUC16 in H292 cells, a decrease in proliferation and an increase in the percentage of apoptotic cells were observed in comparison to vector control cells (by FACs). MUC16 knockdown in H292 cell lines decreased the motility and invasion compared to the MUC16 expressing control cells. Our microarray data suggest that multiple cancer-related genes including TSPYL5, CXCL1, CXCL2, CCL20, and IL8 are down-regulated in MUC16 knockdown cells. TSPYL5 suppresses p53 activity and thereby mediates cancer cell proliferation. Cisplatin treatment in H292 and H827 cells resulted in decreased expression of MUC16 and TSPYL5, and increased expression of p53. This indicates that MUC16 overexpression upregulates TSPYL5, which may suppresses the p53 activity thereby inducing lung cancer cell proliferation and making the cells insensitive to various cytotoxic agents.

Conclusion: MUC16 may play a significant role in lung cancer cell proliferation through the upregulation of TSPYL5 which in turn control p53 activity.

Citation Format: Imayavaramban Lakshmanan, Prabin D. Majhi, Moorthy P. Ponnusamy, Srustidhar Das, Parthasarathy Seshacharyulu, Dhanya Haridas, Surinder K. Batra, Apar Ganti. MUC16 upregulates TSPYL5 gene and mediates Lung cancer cell proliferation by suppressing p53 activity. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1760. doi:10.1158/1538-7445.AM2013-1760

Abstract 5113: Carboxyl terminal region of MUC16 is critical for tumor cell invasion and drug resistance

MUC16, also known as CA125, is routinely used to monitor the progression (as a biomarker) and response to therapeutics (as a prognostic marker) for epithelial ovarian cancer (EOC), but the deregulated expression is not restricted only to EOC. Recent studies from our lab have shown that normal breast and pancreas (ducts) do not express MUC16; however its expression progressively increases in primary and metastatic breast and pancreatic cancers. In addition, we have observed the involvement of MUC16 in enhancing the tumorigenic potential by shRNA studies. In the present study, to understand the mechanistic involvement of MUC16, we have focused on its C-terminal region. MUC16 is a type-I membrane-bound mucin with a heavily glycosylated N-terminal domain, a transmembrane region (TM) and a 32-residue cytoplasmic tail (CT) domain. Though it has been predicted that MUC16 undergoes cleavage/shedding in the extracellular SEA domain(s) by proteases such as MMP7 and neutrophil elastase, the exact nature and site of cleavage and the fate of the membrane bound portion (C-terminal) after release of extracellular portion is not entirely understood. The post cleavage C-ter region is interesting due to presence of (a) stretch of polybasic aminoacids, the site of interaction for cytoskeletal proteins like Ezrin/Radixin/Moesin, (b) potential nuclear localization signal (bioinformatics prediction) which might facilitate its nuclear localization with associated transcription factors modulating the transcription of various target genes and (c) several potential serine, threonine and tyrosine phosphorylation sites facilitating its interaction(s) with proteins influencing oncogenic signaling pathways. Therefore, we hypothesized that the oncogenic potential of MUC16 is in part, mediated by the potential involvement of C-terminal domain of MUC16. Thusly, we have made several truncated versions of MUC16 from the C-terminal end with N-terminal FLAG tag and C-terminal HA-tag and are in the process of characterization. To understand the functional significance of this C-terminal region, we have stably transfected MCF7 (breast cancer), MiaPaCa and T3M4 (pancreatic cancer) cells with an empty vector, FLAG-MUC16-114AA-HA and FLAG-MUC16-114AA-dCT (32 AA in the CT is deleted). Our results from in vitro functional assays indicate that C-terminal region of MUC16 is responsible for enhancing the invasive potential of cancer cells and confers resistance to chemotherapeutic agents such as Cisplatin and Gemcitabine. Moreover, we see that the function of the carboxyl terminal MUC16 is dependent on the stability of the protein, which is a function of N-glycosylation and ubiquitylation. Overall, our studies indicate that C-terminal region of MUC16 is an important mediator of cancer cell invasion and drug resistance. (This work is supported from the Department of Defense BC101014).

Citation Format: Srustidhar Das, Maria P. Torres-Gonzalez, Prabin D. Majhi, Imayavaramban Lakshmanan, Moorthy P. Ponnusamy, Satyanarayana Rachagani, Eric Cruz, Dhanya Haridas, Surinder K. Batra. Carboxyl terminal region of MUC16 is critical for tumor cell invasion and drug resistance. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5113. doi:10.1158/1538-7445.AM2013-5113

Abstract 1745: Role and mechanism of MUC16 in the pathogenesis of pancreatic cancer

Background: MUC16/ CA125 is a high-molecular weight O-glycosylated protein that has been shown to be dysregulated and aberrantly expressed during the progression of several malignant conditions including pancreatic cancer (PC). MUC16 is the gold standard tumor marker used in clinics for detecting ovarian cancer. CA125 levels have been shown to be elevated in PC but its functional significance in PC remains elusive. Hence we hypothesize that MUC16 plays an important role in the proliferation and metastasis of PC.

Materials and methods: MUC16 expression was analyzed in 14 human PC cell lines and stable knockdown clones of MUC16 were established in Capan1 and Colo357 PC cell lines by retroviral transfection using the shRNA construct (pSUPER-Retro-MUC16-sh). Growth kinetics, motility and tumorogenicity assays were done on both MUC16 knocked down cells and scramble cells. In addition we also analyzed the expression of Muc16 during PC progression using the spontaneous mouse model (KrasG12D;Pdx1-Cre and KrasG12D;Pdx1-Cre; Trp53R172H) to identify the role of Muc16 in facilitating PC progression.

Results: MUC16 is not expressed in the normal pancreatic ducts or acini; however, a strong expression is observed in PC tissues. Further a similar observation was obtained in the spontaneous mouse model wherein expression of Muc16 increased in tandem with PC progression. PC cells with stably silenced MUC16 exhibited significantly decreased proliferation, motility (in vitro), tumorigenicity and metastasis (in vivo) when compared to scrambled RNA transfected cells. In addition, MUC16 knockdown cells accumulated in the G1/S phase of the cell cycle indicating that MUC16 might play a role in cell cycle regulation. Western blot analysis of MUC16 knockdown cells with Cyclin E, p21 and p27 showed a decrease in their expression indicating that MUC16 could be playing an important role during PC cell cycle progression.

Conclusion: Our results show that MUC16 expression is aberrantly upregulated in PC tissues and plays a key role in the proliferation and metastasis of PC cells as inferred from the various in vitro and in vivo assays. Further MUC16 may be play a significant in facilitating cell cycle progression as Cyclin E, p21 and p27 levels were altered when MUC16 was knocked down. In conclusion, our results reveal that MUC16 is differentially expressed in PC and could be a potential player facilitating distant metastasis in PC. Further studies need to be done to determine the specific role of MUC16 in the metastasis of PC.

Citation Format: Dhanya Haridas, Imayavaramban Lakshmanan, Moorthy P. Ponnusamy, Satyanarayana Rachagani, Srustidhar Das, Sushil Kumar, Surinder K. Batra. Role and mechanism of MUC16 in the pathogenesis of pancreatic cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1745. doi:10.1158/1538-7445.AM2013-1745

MUC4 overexpression augments cell migration and metastasis through EGFR family proteins in triple negative breast cancer cells

INTRODUCTION

Current studies indicate that triple negative breast cancer (TNBC), an aggressive breast cancer subtype, is associated with poor prognosis and an early pattern of metastasis. Emerging evidence suggests that MUC4 mucin is associated with metastasis of various cancers, including breast cancer. However, the functional role of MUC4 remains unclear in breast cancers, especially in TNBCs.

METHOD

In the present study, we investigated the functional and mechanistic roles of MUC4 in potentiating pathogenic signals including EGFR family proteins to promote TNBC aggressiveness using in vitro and in vivo studies. Further, we studied the expression of MUC4 in invasive TNBC tissue and normal breast tissue by immunostaining.

RESULTS

MUC4 promotes proliferation, anchorage-dependent and-independent growth of TNBC cells, augments TNBC cell migratory and invasive potential in vitro, and enhances tumorigenicity and metastasis in vivo. In addition, our studies demonstrated that MUC4 up-regulates the EGFR family of proteins, and augments downstream Erk1/2, PKC-γ, and FAK mediated oncogenic signaling. Moreover, our studies also showed that knockdown of MUC4 in TNBC cells induced molecular changes suggestive of mesenchymal to epithelial transition. We also demonstrated in this study, for the first time, that knockdown of MUC4 was associated with reduced expression of EGFR and ErbB3 (EGFR family proteins) in TNBC cells, suggesting that MUC4 uses an alternative to ErbB2 mechanism to promote aggressiveness. We further demonstrate that MUC4 is differentially over-expressed in invasive TNBC tissues compared to normal breast tissue.

CONCLUSIONS

MUC4 mucin expression is associated with TNBC pathobiology, and its knockdown reduced aggressiveness in vitro, and tumorigenesis and metastasis in vivo. Overall, our findings suggest that MUC4 mucin promotes invasive activities of TNBC cells by altering the expression of EGFR, ErbB2, and ErbB3 molecules and their downstream signaling.

Protocol for Apoptosis Assay by Flow Cytometry Using Annexin V Staining Method

This assay is used to count the number of cells that have undergone apoptosis. Apoptosis will be detected by initially staining the cells with Annexin V and propidium Iodide solution followed by flow cytometry analysis. It is based on the principle that normal cells are hydrophobic in nature as they express phosphatidyl serine in the inner membrane (side facing the cytoplasm) and when the cells undergo apoptosis, the inner membrane flips to become the outer membrane, thus exposing phosphatidyl serine. The exposed phosphatidyl serine is detected by Annexin V, and propidium iodide stains the necrotic cells, which have leaky DNA content that help to differentiate the apoptotic and necrotic cells.

Pathobiological implications of MUC16 expression in pancreatic cancer

MUC16 (CA125) belongs to a family of high-molecular weight O-glycosylated proteins known as mucins. While MUC16 is well known as a biomarker in ovarian cancer, its expression pattern in pancreatic cancer (PC), the fourth leading cause of cancer related deaths in the United States, remains unknown. The aim of our study was to analyze the expression of MUC16 during the initiation, progression and metastasis of PC for possible implication in PC diagnosis, prognosis and therapy. In this study, a microarray containing tissues from healthy and PC patients was used to investigate the differential protein expression of MUC16 in PC. MUC16 mRNA levels were also measured by RT-PCR in the normal human pancreatic, pancreatitis, and PC tissues. To investigate its expression pattern during PC metastasis, tissue samples from the primary pancreatic tumor and metastases (from the same patient) in the lymph nodes, liver, lung and omentum from Stage IV PC patients were analyzed. To determine its association in the initiation of PC, tissues from PC patients containing pre-neoplastic lesions of varying grades were stained for MUC16. Finally, MUC16 expression was analyzed in 18 human PC cell lines. MUC16 is not expressed in the normal pancreatic ducts and is strongly upregulated in PC and detected in pancreatitis tissue. It is first detected in the high-grade pre-neoplastic lesions preceding invasive adenocarcinoma, suggesting that its upregulation is a late event during the initiation of this disease. MUC16 expression appears to be stronger in metastatic lesions when compared to the primary tumor, suggesting a role in PC metastasis. We have also identified PC cell lines that express MUC16, which can be used in future studies to elucidate its functional role in PC. Altogether, our results reveal that MUC16 expression is significantly increased in PC and could play a potential role in the progression of this disease.

Mucins in the pathogenesis of breast cancer: implications in diagnosis, prognosis and therapy

Mucins are high molecular weight, multifunctional glycoproteins comprised of two structural classes-the large transmembrane mucins and the gel-forming or secreted mucins. The primary function of mucins is to protect and lubricate the luminal surfaces of epithelium-lined ducts in the human body. Recent studies have identified a differential expression of both membrane bound (MUC1, MUC4 and MUC16) and secreted mucins (MUC2, MUC5AC, MUC5B and MUC6) in breast cancer tissues when compared with the non-neoplastic breast tissues. Functional studies have also uncovered many unique roles of mucins during the progression of breast cancer, which include modulation in proliferative, invasive and metastatic potential of tumor cells. Mucins function through many unique domains that can form complex association with various signaling molecules including growth factor receptors and intercellular adhesion molecules. While there is growing information about mucins in various malignancies including breast cancer, no focused review is there on the expression and functional roles of mucins in breast cancer. In this present review, we have discussed the differential expression and functional roles of mucins in breast cancer. The potential of mucins as diagnostic and prognostic markers and as therapeutic targets in breast cancer have also been discussed.

Abstract 5180: MUC4 mucin upregulates N-cadherin: A novel mechanism for human ovarian tumor metastasis

The human MUC4 protein is a high molecular weight transmembrane glycoprotein which is over-expressed in ovarian tumors and plays a role in increasing the cellular motility of the ovarian cancer cells. Previous reports have indicated that gain of expression of N-cadherin in tumor cells is associated with increased motility and metastasis. We hypothesize that MUC4 upregulates N-cadherin and plays a major role in metastasis of ovarian cancer. The aim of the present study was to analyze the mechanism of MUC4 induced cellular motility, invasion and metastasis in ovarian cancer cells. For this we have used a MUC4 gene construct (entire coding sequence along with 10% of the central tandem repeat region) for ectopic expression to determine the metastatic function of MUC4 in human ovarian cancer cells (SKOV3). Interestingly, we observed that N-cadherin was up-regulated in MUC4 overexpressing ovarian cancer cells (SKOV3-MUC4) compared to control (vector transfected) cells. We further discovered that N-cadherin upstream pathways such as FAK, MKK7, JNK and c-Jun are activated in the MUC4 expressing SKOV3 cells. Additionally, inhibition of pFAK led to the downregulation of N-cadherin by inhibiting the activation of MKK7, JNK and c-Jun in MUC4 overexpressing SKOV3 cells. On other hand, knockdown of N-cadherin decreased the activation of ERK, AKT and MMP9 in the MUC4 expressing SKOV3 cells. Inhibition of pFAK, pJNK and knockdown of N-cadherin in the MUC4 overexpressing cells further led to a significant decrease in cellular motility. Upon tumorigenisis and metastasis analysis with NOD-SCID mice, the SKOV3-MUC4 cells produced significantly larger tumors and demonstrated a higher incidence of metastasis to distant organs (peritoneal wall, colon, intestine, stomach, lymph nodes, liver and diaphragm) than the SKOV3-vector cells. Taken together, our result suggests that MUC4 mediated upregulation of N-cadherin plays a major role in promoting the metastatic property of ovarian cancer cells.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5180.

Immunopathogenesis of ovarian cancer

Ovarian cancer, the most aggressive gynecologic cancer, is the foremost cause of death from gynecologic malignancies in the developed world. Over 90% of ovarian cancers arise from the surface epithelium, which are classified as epithelial ovarian cancer (EOC). EOCs can be categorized as serous, mucinous, endometrioid, clear cell, and transitional cell types. The molecular pathology of ovarian carcinomas is heterogeneous and involves various putative precursor lesions and multiple pathways of development. Furthermore, in another aspect, immune deficiencies that are present in the ovarian tumor environment enhance the progression of the tumor in the host. The presence of regulatory T cells, the inhibition of natural killer cytotoxic responses, the accumulation of myeloid suppressor cells in the tumor, deficiencies on interferon signaling, the secretion of cytokines that enhance tumor growth (i.e., IL-6, IL-10, CSF-1, TGF-b, TNF), and the expression of surface molecules (i.e., HLA-G, B7-H1, B7-H4, CD40, CD80) that have a role on immune suppression, are discussed in detail. The aim of this review is to provide insight of the evidence that supports the role of immunodeficiency in the progression of ovarian cancer and future directions for ovarian cancer therapies. It also discusses the genetic alterations in the subtypes of ovarian cancers.