CCL2 and esophageal squamous cell carcinoma: Furthermore, CAF-like cells, which we established by indirect co-culture of human bone marrow-derived mesenchymal stem cells (MSCs, one of the origins of CAFs) with ESCC cell lines, were found to play a tumor-promoting role in the ESCC microenvironment through IL-6 and CCL2 using cytokine array analysis.