LAUSR

Objective: Pancreatic cancer (PanCa) is the third leading cause of cancer-related deaths in the U.S. MUC13, mucin, is aberrantly expressed in PanCa and its overexpression leads to tumorigenic and metastatic behavior of cancer cells. Herein, we investigate the role of MUC13 in tumor microenvironment (TME) that favors PanCa progression/metastasis and drug resistance. Methods: MUC13 expressing (Panc-1) and knockdown PanCa cells (HPAF-II) and pancreatic stromal cells (PSCs), derived from freshly collected human pancreatic tissues, were utilized for the study. Using immunoblotting, ELISA, qPCR and RT-PCR techniques, we assessed the MUC13-induced alterations in the expression of important molecules that are involved in promotion of pancreatic tumor stromal interactions and drug resistance. Cytation 3 live cell imaging was performed for 3D tumor-stromal cell co-culture and invasion assays. Xenograft mice tumor tissues generated using ectopically expressing MUC13 and null cells were used for the study. Results: Our results demonstrate that MUC13 activates SHH signaling pathway in PanCa cells via upregulation of SHH and its related important downstream targets such as CXCR-4, Gli-1, SMO, PTCH1/2, NFκB and p-AKT in PanCa cells using immunoblotting and PCR. We also observed increased expression of SHH, Gli-1, CXCR-4 and α-SMA in MUC13-expressing xenograft tumors using Immunohistochemistry. Ectopic MUC13-expressing PanCa cells grown in co-culture with PSCs showed enhanced secretion of IL-6 and CXCL-12 (ELISA), increase in invasion (Matrigel invasion assay) and migratory (Boyden chamber assay) potential of both the cultured PanCa as well as stromal cells. Additionally, ectopically MUC13-expressing cells were resistant to treatment with gemcitabine as depicted by proliferation assay and qPCR results showed enhanced expression of ribonucleoside-diphosphate reductase (RRM1/2) and miR-21, which are known to be involved in gemcitabine resistance. Overall, our results suggest that MUC13 modulates tumor-stromal crosstalk, promoting tumor growth, invasion and drug resistance in TME. Conclusion: Our results suggest that MUC13 expression might influence signaling supportive of interactive TME, leading to increased tumor growth and drug resistance. These findings illustrate mechanisms by which MUC13 promotes tumorigenic TME and contributes to PanCa cell survival, metastasis and drug resistance. Citation Format: Sheema S. Khan, Kyle Doxtater, Sonam Kumari, Saini Setua, Mohammed Sikander, Shabnam Malik, Murali Yallapu, Stephen Behrman, Subhash Chauhan, Meena Jaggi. MUC13 promotes pancreatic tumor-stromal interactions by influencing tumor microenvironment [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 198.