Abstract A49: Carcinoma-associated fibroblasts in the tumor microenvironment affect growth, invasiveness, and drug response of human pancreatic cancer cells

Pancreatic cancer is one of the most aggressive malignancies, with a 5-year overall survival of less than 5%. Tumor drug resistance to conventional chemotherapy, such as gemcitabine, is often a significant contributor to poor overall survival. One of the common mechanisms of gemcitabine resistance is activation of cell signaling via increased phosphorylation of Mitogen-Activated kinase (MAP) kinases, leading to increased tumor survival and reduced sensitivity to chemotherapeutic agents. A growing body of evidence suggests that the CXCL12/CXCR4 signal transduction axis in the tumor microenvironment is an important mediator of tumor migration, growth, and drug resistance. We hypothesized that carcinoma-associated fibroblasts (CAFs), an important cellular component of the TME, play a contributory role in the growth, invasiveness, and drug response of pancreatic cancer cells (PCCs) by activating CXCL12/CXCR4-mediated signal transduction. To test this, we used an in vitro model system to study the growth, invasion, and drug response of human PCCs in the presence or absence of in vitro-generated CAFs. Functional studies demonstrated that co-culture of PCCs with CAFs led to significant increase in tumor cell invasion, which was abrogated by blockade of CXCR4 by AMD3100-plerixafor (AMD3100), a CXCR4 antagonist, and by siRNA-mediated knockdown of CXCR4 in CAFs. Increased invasion of PCCs after co-culture with orthotopically derived CAFs was also abrogated by CXCR4 blockade, demonstrating a critical role for this receptor in regulating the tumor-promoting abilities of CAFs. Additionally, we investigated the effect of CAFs on the MAPK Signaling pathway (MEK1/2, p-MEK1/2, ERK1/2, p-ERK1/2, Akt, and p-Akt) via Western blot assays. Further, we examined the effect of AMD3100 on the chemo-resistance of PCCs to gemcitabine. Our results indicated that AMD3100 reversed gemcitabine-mediated chemo-resistance of PCCs cells in the presence of CAFs or CAF-conditioned media. In co-culture with pancreatic cancer cells, CAFs induced activation of MAPK signaling pathways and enhanced transcription of Mn-SOD, G6PD, and catalase, genes involved in reactive oxygen species (ROS) pathways. Using phloretin, a ROS inhibitor, we observed attenuation of MAPK signaling, SOD activity, and reversal of drug resistance in CAF-exposed pancreatic cancer cells. These findings implicate CXCL12/CXCR4-dependent MAPK signaling and ROS pathways in CAF-mediated modulation of the growth, migration, and drug resistance of PCCs. Citation Format: Ahlim Al. Sanani, Brijsh Patel, Alix Duarte, Nitu Bansal, Tushar Bhagat, Yanique Rattigan, Anirban Maitra, Amit Verma, Debabrata Banerjee. Carcinoma-associated fibroblasts in the tumor microenvironment affect growth, invasiveness, and drug response of human pancreatic cancer cells. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Innovations in Research and Treatment; May 18-21, 2014; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2015;75(13 Suppl):Abstract nr A49.