CCL2 and cholangiocarcinoma: CCA cell-derived EVs favor the fibroblastic differentiation of bone marrow-derived mesenchymal stem cells (MSCs) and the secretion of pro-inflammatory cytokines and chemokines, including interleukin (IL)-6, chemokine (C-X-C motif) ligand 1 (CLXC1), and chemokine (C-C motif) ligand 2 (CCL2/MCP-1), which ultimately stimulate CCA cell proliferation via IL6/STAT3 signaling pathway (31).