Chinmay Gundewar

Pancreatic Cancer: The Role of Pancreatic Stellate Cells in Tumor Progression

Pancreatic ductal adenocarcinoma is an aggressive and highly lethal disease frequently characterized by a dense stromal or desmoplastic response. Accumulating evidence exists that tumor desmoplasia plays a central role in disease progression and that e.g. activated pancreatic stellate cells (PSCs) are responsible for the excess matrix production. The mechanisms underlying the tumor versus stroma interplay are complex. Pancreatic cancer cells release mitogenic and fibrogenic stimulants, such as transforming growth factor β1, platelet-derived growth factor (PDGF), sonic hedgehog, galectin 3, endothelin 1 and serine protease inhibitor nexin 2, all of which may promote the activated PSC phenotype. Stellate cells in turn secrete various factors, including PDGF, stromal-derived factor 1, epidermal growth factor, insulin-like growth factor 1, fibroblast growth factor, secreted protein acidic and rich in cysteine, matrix metalloproteinases, small leucine-rich proteoglycans, periostin and collagen type I that mediate effects on tumor growth, invasion, metastasis and resistance to chemotherapy. This review intends to shed light on the mechanisms by which PSCs in the stroma influence pancreatic cancer development. The increased understanding of this interaction will be of potential value in designing new modalities of targeted therapy.

The role of SPARC expression in pancreatic cancer progression and patient survival.

Abstract Background. Secreted protein acidic and rich in cysteine (SPARC) is a matricellular glycoprotein that has been implicated in tumor–stroma interactions in pancreatic cancer. Here we evaluated the expression of SPARC during the progression of pancreatic cancer and its correlation with survival following curative intent surgery. Methods. The expression profile of SPARC was investigated in normal pancreas, invasive adenocarcinoma, and lymph node metastasis by immunohistochemistry. Kaplan–Meier and multivariate Cox regression were used to assess for mortality risk. Results. None (0%) of 10 normal pancreata, 68 (77%) of 88 primary tumors, and 28 (67%) of 42 lymph node metastases were labeled with the SPARC antibody used in this study. SPARC was expressed exclusively in stromal cells. The survival of patients with high stromal SPARC expression was significantly worse than that of the patients with low stromal SPARC expression (11.5 vs 25.3 months; p = 0.020). Multivariate analysis showed that stromal SPARC expression (hazard ratio (HR) 2.12; p = 0.012), tumor location (body/tail) (HR 2.95; p = 0.003), and adjuvant chemotherapy (HR 0.55; p = 0.018) were significant independent risk factors. Conclusion. This study describes the pattern of SPARC expression in pancreatic neoplastic progression and supports the role of stromal SPARC expression as a prognostic factor and target for directed therapy.

Conditionally immortalized human pancreatic stellate cell lines demonstrate enhanced proliferation and migration in response to IGF-I.

Pancreatic stellate cells (PSCs) play a key role in the dense desmoplastic stroma associated with pancreatic ductal adenocarcinoma. Studies on human PSCs have been minimal due to difficulty in maintaining primary PSC in culture. We have generated the first conditionally immortalized human non-tumor (NPSC) and tumor-derived (TPSC) pancreatic stellate cells via transformation with the temperature-sensitive SV40 large T antigen and human telomerase (hTERT). These cells proliferate at 33°C. After transfer to 37°C, the SV40LT is switched off and the cells regain their primary PSC phenotype and growth characteristics. NPSC contained cytoplasmic vitamin A-storing lipid droplets, while both NPSC and TPSC expressed the characteristic markers αSMA, vimentin, desmin and GFAP. Proteome array analysis revealed that of the 55 evaluated proteins, 27 (49%) were upregulated ≥3-fold in TPSC compared to NPSC, including uPA, pentraxin-3, endoglin and endothelin-1. Two insulin-like growth factor binding proteins (IGFBPs) were inversely expressed. Although discordant IGFBP-2 and IGFBP-3 levels, IGF-I was found to stimulate proliferation of both NPSC and TPSC. Both basal and IGF-I stimulated motility was significantly enhanced in TPSC compared to NPSC. In conclusion, these cells provide a unique resource that will facilitate further study of the active stroma compartment associated with pancreatic cancer.

Comparison of MUC4 expression in primary pancreatic cancer and paired lymph node metastases

Abstract Objective. Mucin 4 (MUC4) is a transmembrane glycoprotein that is expressed in pancreatic ductal adenocarcinoma (PDAC), but not in normal pancreatic tissue. MUC4 has a proposed role in pancreatic tumor progression and metastasis. The purpose of this pilot study was to investigate MUC4 expression during PDAC metastasis by comparing the expression in the primary tumor and paired lymph node metastases from the same patient. Material and methods. Surgical specimens from 17 cases of primary PDAC and paired lymph node metastases were immunohistochemically analyzed for MUC4 expression. The modified histochemical score (H-score) was used for staining assessment. Results. Positive staining for MUC4 was detected in most primary and metastatic PDAC tumors (15/17 vs. 14/17). The concordance for MUC4 expression in primary tumors and corresponding lymph node metastases was 82%. In two cases, the primary tumor was MUC4-positive and the lymph node metastases were negative, while in one patient with a MUC4-negative primary tumor, the lymph node metastasis was positive. The distribution of H-score for expression of MUC4 significantly correlated (r = 0.615; p = 0.009) between primary tumors and paired metastatic lesions. Conclusions: MUC4 was observed in both primary and matched metastatic tumors with a high level of concordance, suggesting that MUC4 expression is retained following PDAC metastasis.

Abstract LB-226: Celecoxib synergizes human pancreatic ductal adenocarcinoma cells to sorafenib-induced growth inhibition involving p21 suppression

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Purpose : The aim of this study was to evaluate the potential for combining the multikinase inhibitor sorafenib and the specific cyclo-oxygenase 2 (COX-2) inhibitor celecoxib as therapy in pancreatic adenocarcinoma cells and to test the hypothesis that a synergistic or additive effect on the Ras/MAPK/ERK and related pathways might be obtained. Experimental design : COX-2 positive (BxPC-1) and low/negative (MIAPaCa-2, PANC-1 and AsPC-1) human pancreatic adenocarcinoma cells were exposed to sorafenib and celecoxib combined treatment in vitro , after which cell viability and various growth promoting and survival signaling pathways were monitored by MTT, flow cytometry and Western blotting. Results : Combined treatment with sorafenib and celecoxib resulted in synergistic inhibition of pancreatic adenocarcinoma cell proliferation through COX-2 independent mechanisms. This regimen produced combination index (CI) values between 0.67 and 0.92 for the various cell lines, suggesting significant synergistic interactions between sorafenib and celecoxib, which also markedly inhibited the migratory capacity. The growth inhibition was associated with a reduction of basal ERK1/2 activity, accumulation of cells in the G/G1 phase of the cell cycle, induction of apoptosis and poly(ADP-ribose) polymerase cleavage. These changes were accompanied by a significant reduction of p21WAF1/Cip1 levels, where celecoxib sensitized the cells to sorafenib-mediated p21WAF1/Cip1 suppression. Conclusion : p21WAF1/Cip1 levels are elevated frequently in human pancreatic adenocarcinoma and increases with disease progression. In this study we demonstrate that combined treatment with sorafenib and celecoxib synergistically induce growth inhibition and apoptosis through a process involving phospho-ERK1/2 and p21WAF1/Cip1 suppression. These data suggest the combined treatment of sorafenib and celecoxib as potential therapy for clinical testing in patients with pancreatic adenocarcinoma. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-226. doi:10.1158/1538-7445.AM2011-LB-226