Gastroenterology. 2022 Feb 24. pii: S0016-5085(22)00198-6. [Epub ahead of print]
BACKGROUND: Secreted mucin 5AC (MUC5AC) promotes pancreatic cancer (PC) progression and chemoresistance, suggesting its clinical association with poor prognosis. RNA sequencing analysis from the autochthonous pancreatic tumors showed a significant stromal alteration upon genetic ablation of Muc5ac. Previously, depletion or targeting the stromal fibroblasts showed an ambiguous effect on PC pathogenesis. Hence, identifying the molecular players and mechanisms driving fibroblast heterogeneity is critical for improved clinical outcomes.
METHODS: Autochthonous murine models of PC [KrasG12D, Pdx1-Cre (KC); KrasG12D, Pdx1-Cre, Muc5ac-/- (KCM)] and co-implanted allografts of murine PC cell lines (Muc5ac-WT and CRISPR/Cas-KO) with adipose-derived mesenchymal stem cells (AD-MSCs) were used to assess the role of Muc5ac in stromal heterogeneity. Proliferation, migration, surface expression of cell-adhesion markers on AD-MSCs were measured using live-cell imaging and flow cytometry. MUC5AC-interactome was investigated using mass-spectrometry and ELISA.
RESULTS: The KCM tumors showed a significant decrease in the expression of α-smooth muscle actin and fibronectin compared to histology-matched KC tumors. Our study showed that MUC5AC, carrying tumor secretome, gets enriched in the adipose tissues of tumor-bearing mice and PC patients, promoting CD44/CD29 (integrin-β1) clustering that leads to Rac1 activation and migration of AD-MSCs. Further, treatment with KC-derived serum enhanced proliferation and migration of AD-MSCs, which was abolished upon Muc5ac-depletion or pharmacological inhibition of CXCR2 and Rac1, respectively. The AD-MSCs significantly contribute towards α-SMA-positive CAFs population in Muc5ac-dependent manner, as suggested by autochthonous tumors, co-implantation xenografts, and patient tumors.
CONCLUSION: MUC5AC, secreted during PC progression, enriches in adipose and enhances the mobilization of AD-MSCs. Upon recruitment to pancreatic tumors, AD-MSCs proliferate and contribute towards stromal heterogeneity.
Keywords: MUC5AC; Mesenchymal stem cells; Pancreatic Cancer; Stroma; cancer-associated fibroblast; chemokines