Subhash C. Chauhan

MUC13 interaction with receptor tyrosine kinase HER2 drives pancreatic ductal adenocarcinoma progression

Although MUC13, a transmembrane mucin, is aberrantly expressed in pancreatic ductal adenocarcinoma (PDAC) and generally correlates with increased expression of HER2, the underlying mechanism remains poorly understood. Herein, we found that MUC13 co-localizes and interacts with HER2 in PDAC cells (reciprocal co-immunoprecipitation, immunofluorescence, proximity ligation, co-capping assays) and tissues (immunohistofluorescence). The results from this study demonstrate that MUC13 functionally interacts and activates HER2 at p1248 in PDAC cells, leading to stimulation of HER2 signaling cascade, including ERK1/2, FAK, AKT and PAK1 as well as regulation of the growth, cytoskeleton remodeling and motility, invasion of PDAC cells—all collectively contributing to PDAC progression. Interestingly, all of these phenotypic effects of MUC13–HER2 co-localization could be effectively compromised by depleting MUC13 and mediated by the first and second EGF-like domains of MUC13. Further, MUC13–HER2 co-localization also holds true in PDAC tissues with a strong functional correlation with events contributing to increased degree of disorder and cancer aggressiveness. In brief, findings presented here provide compelling evidence of a functional ramification of MUC13–HER2: this interaction could be potentially exploited for targeted therapeutics in a subset of patients harboring an aggressive form of PDAC.

Ormeloxifene suppresses prostate tumor growth and metastatic phenotypes via inhibition of oncogenic β-catenin signaling and EMT progression

Ormeloxifene is a clinically approved selective estrogen receptor modulator, which has also shown excellent anticancer activity, thus it can be an ideal repurposing pharmacophore. Herein, we report therapeutic effects of ormeloxifene on prostate cancer and elucidate a novel molecular mechanism of its anticancer activity. Ormeloxifene treatment inhibited epithelial-to-mesenchymal transition (EMT) process as evident by repression of N-cadherin, Slug, Snail, vimentin, MMPs (MMP2 and MMP3), β-catenin/TCF-4 transcriptional activity, and induced the expression of pGSK3β. In molecular docking analysis, ormeloxifene showed proficient docking with β-catenin and GSK3β. In addition, ormeloxifene induced apoptosis, inhibited growth and metastatic potential of prostate cancer cells and arrested cell cycle in G0–G1 phase via modulation of cell-cycle regulatory proteins (inhibition of Mcl-1, cyclin D1, and CDK4 and induction of p21 and p27). In functional assays, ormeloxifene remarkably reduced tumorigenic, migratory, and invasive potential of prostate cancer cells. In addition, ormeloxifene treatment significantly (P < 0.01) regressed the prostate tumor growth in the xenograft mouse model while administered through intraperitoneal route (250 μg/mouse, three times a week). These molecular effects of ormeloxifene were also observed in excised tumor tissues as shown by immunohistochemistry analysis. Our results, for the first time, demonstrate repurposing potential of ormeloxifene as an anticancer drug for the treatment of advanced stage metastatic prostate cancer through a novel molecular mechanism involving β-catenin and EMT pathway. Mol Cancer Ther; 16(10); 2267–80. ©2017 AACR.

Abstract LB-400: Tannic acid induces prostate cancer cell death via unfolded protein response (UPR) and modulation of CHOP

Objectives: Endoplasmic reticulum (ER) is an intricate organelle that is crucial for cellular function and survival. Cellular environments that interfere with ER functioning can lead to the accumulation of unfolded proteins, which are sensed by transmembrane sensors that instigate the unfolded protein response (UPR) to reinstate ER proteostasis. When the UPR is perturbed or not sufficient to deal with the stress conditions, apoptotic cell death is ensued. Often, prostate tumor cells (PrCa) are exposed to intrinsic and external factors that alter protein homeostasis producing endoplasmic reticulum (ER) stress. IRE1, PERK, and ATF6 are key signaling stems of the UPR during ER stress. At molecular level, dimerization of PERK kinase phosphorylates eIF2α, resulting in translation attenuation. This selectively enhances translation of the ATF4 transcription factor. Also, activated IRE1 stimulates the nuclear translocation of XBP1. Both ATF4 and XBP1 induces expression of UPR genes. The UPR stimulates and protects tumor cells against stressful conditions within the tumor microenvironment. Therapeutic intervention on this aspect ER Stress mediated apoptosis is much needed. Here, we examined the mechanistic role of tannic acid (TA) through novel targeting inhibition of UPR via modulation of ER stress in PrCa cell death. Methods:In vitro therapeutic perspective of tannic acid was evaluated using clinically relevant human prostate cancer cell line models (C4-2, PC3 and DU145) through cell proliferation and clonogenic assays. The anti-metastatic potential of TA in PrCa cells was determined using invasive and migration studies. The phase arrest and concomitant apoptosis in PrCa cells were examined using Propidium Iodide based flow cytometric studies. TA induced ER stress-mediated UPR cellular apoptotic activity was confirmed using Western blot, real-time studies, and nuclear distortion studies. Results: Protein profiling results have showed yin approach of inhibition ER stress during TA treatments with the inhibition of CHOP protein. Also, we observed TA treated PrCa cells was able to induce ER stress response proteins, such as PERK and IRE1. Its downstream signaling events include the induction of XBP1, EIF2α expression key mediators by alteration of Bcl2/Bax ratio from shifting survival towards apoptosis. With this line we assessed the expression profile of apoptosis-associated markers such as Bid and Bim (upregulated), and Bcl-2 and Bcl-xL which ratifies the induction of apoptosis during treatments. TA exhibited prominent growth arrest at G1 phase and increase of concentration led to elevated sub G1, annotating the increase of apoptotic cells. The expression of P18 and P21 were increased during TA treatments and cyclin D1 expression was inhibited supporting the G1 phase cell arrest. The expression of MMP2 and MMP9 were reduced, signifying the superior anti-metastatic ability of this compound. Cell proliferation studies showed a dose-dependent inhibitory profile of TA. Distinct results of anti-migratory and anti-metastatic effects of TA was observed during treatments. Conclusion: This study suggests that TA can efficiently induce UPR and promote ER stress signaling in cells that renders apoptosis in PrCa cells by the over expression of CHOP. We believe this novel therapeutic paradigm have clinical significance in advanced PrCa. Citation Format: Elham Hatami, Prashanth Kumar Bhusetty Nagesh, Pallabita Chowdhury, Vivek K. Kashyap, Sheema Khan, Bilal Hafeez, Meena Jaggi, Subhash C. Chauhan, Murali M. Yallapu. Tannic acid induces prostate cancer cell death via unfolded protein response (UPR) and modulation of CHOP [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 LB-400.

Abstract 3081: Novel cucurbitacin analogue Cuc D exhibits potent anti-cancer activity in cervical cancer

Background: Cervical cancer is one of the leading cause of mortality among women in US. Naturally occurring dietary compounds have gained increasing attention for their anticancer effects. Cucurbitacins, tetracyclic triterpenoid compound, belong to a family of Cucurbitaceae have shown promising anti-cancer activity. Herein, we investigated the potential anti-cancer effects of a novel analogue of cucurbitacin D (Cuc D) against cervical cancer in in vitro and in a xenograft mouse model. Methods: In our study, we used human cervical cancer cells (CaSki and SiHa). Cells were treated with Cuc D (0.05 to 1μM) for 48 and 72 hrs. MTS and colony formation assays were performed to investigate the effects of Cuc D on cell viability and proliferation. Western Blot analysis was performed to investigate the effects of Cuc D on cell proliferation and apoptotic markers. To determine the therapeutic effects of Cuc D, we used female athymic nude mice and injected CaSki cells (4 × 106) into the cervix to develop orthotopic xenograft tumors. Cuc D (1 mg/kg body weight) was administered through intratumoral injection four weeks post-tumor cell injection. Tumor volume in these mice were recorded bi-weekly. Results: Cuc D inhibited cell viability of cervical cancer cells in a dose-dependent manner. IC50 of Cuc D was observed 400 nM and 250 nM in Caski and SiHa cells, respectively. Cuc D treatment effectively inhibited growth of cervical cancer cells which was determined by decreased cell proliferation and colony formation assays. Cuc D treatment induced apoptosis in cervical cancer cells as measured by enhanced Annexin V staining. Western blot result also illustrated cleavage in PARP protein in Cuc D treated cells which further confirms apoptosis induction. Cuc D treatment also inhibited PI3K and c-Myc protein levels and phosphorylation of STAT3 and Rb proteins. In addition, Cuc D treatment induced the cell cycle inhibitory proteins (p21 and p27) and PTEN and the expression of a tumor suppressor microRNA, miR-145, as determined by qRT-PCR. In an orthotopic tumor xenograft mouse model, Cuc D treatment effectively inhibited tumor growth as compared to vehicle control treated mice. Conclusion: Taken together, our results demonstrate potent anti-cancer efficacy of Cuc D in cervical cancer cells via modulation of key onco/tumor suppressor proteins. Thus, Cuc D could be a useful therapeutic agent for cervical cancer treatment. Citation Format: Mohammed Sikander, Bilal Bin Hafeez, Fathi T. Halaweish, Murali M. Yallapu, Meena Jaggi, Subhash C. Chauhan. Novel cucurbitacin analogue Cuc D exhibits potent anti-cancer activity in cervical cancer. [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 3081.

Abstract 4468: Anticancer activity of novel cucurbitacin analogue in pancreatic cancer

Background: Human pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer-related deaths in the United States. Accumulating studies have witnessed the malfunction of many chemotherapeutic regimens and the current standard-of-care therapy, gemcitabine (GEM), enhances patient survival by only few months. Cucurbitacins, naturally occurring dietary tetracyclic triterpenoid compounds, have shown promising anti-cancer activities. Herein, we investigated the potency and anti-cancer efficacy of a novel analogue of cucurbitacin (Cuc D) in pancreatic cancer cell lines and in a xenograft mouse model. Additionally, we determined efficacy of this analogue on MicroRNAs (miRNAs) which are important regulators of genes that have crucial roles in pancreatic tumorigenesis. Methods: The effect of Cuc D on the growth of pancreatic cancer cells was determined by cell proliferation assay using six pancreatic cancer (MiaPaCa-2, CaPan-1, HPAF-II, Panc-1, BxPC-3 and AsPc-1) cells. Cell growth kinetic assay was carried out at 24, 48, 72 and 96 h. The clonogenic potential of cancer cells was also studied using the colony formation assay. Tumor suppressor miR-145, which is downregulated in pancreatic cancer, directly target MUC13. Thus the effect of Cuc D was also investigated on the expression of miR-145 through qPCR analysis. Immunoblotting techniques were performed to study the known direct targets of miRNA-145 and its associated proteins. The anti-cancer potential of Cuc D in pancreatic cancer was also evaluated in vivo using a xenograft mouse model. Results: Our results demonstrate potent anticancer effects of Cuc D on pancreatic cancer cells. Cuc D induces dose and time dependent inhibition of cell proliferation in a panel of gemcitabine sensitive/resistant pancreatic cancer cell line models at nanomolar concentrations (100-500 nM). It also inhibits colony formation and invasiveness of pancreatic cancer cells. Furthermore, Cuc D blocks the cell cycle progression in G2/M phase and decreases the mitochondrial membrane potential in pancreatic cancer cells. Notably, Cuc D significantly increases the expression of tumor suppressor miR-145 in HPAF-II cells as observed by qPCR. Furthermore, Cuc D decreases the expression of MUC13 and its associated proteins including pAKT and HER2. In addition, it restores the expression of p53 level as studied by immunofluorescence technique. The expression of key oncogenic proteins including NF-κB, STAT3 (Tyr-705) and Mcl-1 were also downregulated. The levels of PTEN and p27 (Kip1) tumor suppressor genes were increased after Cuc D treatment. Additionally, in vivo administration of Cuc D effectively inhibited pancreatic tumor growth in xenograft mouse model. Conclusion: Overall, this study suggests that Cuc D modulates the expression of key oncogenes and tumor suppressors, thus it can be a promising therapeutic modality for pancreatic cancer prevention and treatment. Citation Format: Mohammed Sikander, Sheema Khan, Neeraj Chauhan, Mohd Saif Zaman, Murali Mohan Yallapu, Fathi T. Halaweish, Bhavin Chauhan, Shabnam Malik, Meena Jaggi, Subhash C. Chauhan. Anticancer activity of novel cucurbitacin analogue in pancreatic cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4468. doi:10.1158/1538-7445.AM2015-4468