RAB27A and neoplasm: To assess whether reduction in sEVs secretion affects the activation of fibroblasts in the tumor microenvironment, we compared Pan18‐shRab27a/b cells with Pan18‐shLacz cells implanted into the pancreas of C57BL/6J mice because Rab27a and Rab27b are critical for vesicle trafficking (Kosaka et al., 2013) and depletion of Rab27a/b by shRNA reduce their sEVs secretion (Fig. S1D,E).