Differentiated Cancer Cells Exhibit Increased Potential To Induce Cancer-associated Fibroblasts Than Undifferentiated Cancer Cells In Gastric Cancers

BACKGROUND: Gastric cancer is one of the most common causes of cancerdeath in Southeastern of Asia including Japan and China. Stromal fibroblasts in thetumor microenvironment have recently been implicated in tumor growth, invasion andmetastasis. Cancer-associated fibroblasts (CAFs) have been suggested to be responsiblefor induction of the epithelial-mesenchymal transition (EMT) in cancer cells throughsecretion of Transforming Growth Factor (TGF in undifferentiated scirrhous gastriccancers with vast fibrous stroma. However, which types of gastric cancer cells actuallyprefer inducing CAFs for tumor progression remains unclear. In this study, weinvestigated whether differentiated and/or undifferentiated human gastric cancer cellsinduce CAFs.METHODS: We used one well-differentiated human gastric cancer cell line(MKN-7), two poorly-differentiated human gastric cancer cell lines (MKN-45,NU-GC-2) and one undifferentiated human gastric signet-ring cell carcinoma cell line(KATO-III). Two types of normal human fibroblasts (NHLF, FEF-3) were also used.The conditioned media (CM) from all cancer cells were obtained48hours after serumstarvation. The morphological change and expression of CAF-specific markers (smoothmuscle actin (SMA), fibroblast activation protein (FAP)) in fibroblasts treated withTGF-β (10ng/ml) or CM for48hours were analyzed by microscopy and Western blotanalysis, respectively. Moreover, the effect of CM from activated fibroblasts on themigration of cancer cells were evaluated using in vitro Migration assay.RESULTS: The CM from well-differentiated MKN-7cells induced themorphological change like CAFs more strongly than TGF in two types of normal human fibroblasts, whereas CM from poorly-differentiated MKN-45and NUGC-2cellsor undifferentiated Kato-III cells did not induce. Interestingly, when we separatedmore-differentiated adherent-type MKN-45(MKN-45/AT) cells with increasedE-cadherin expression from parental MKN-45cells, CM from MKN-45/AT cells aswell as MKN-7cells could induce the morphological change in normal fibroblasts.Morphologically changed fibroblasts showed increased SMA expression, whereas FAPexpression was not increased. The CM from morphologically changed fibroblasts, butnot normal fibroblasts, significantly enhanced the migration ability of MKN-45/AT andMKN-7cells.CONCLUSION: These results suggest that differentiated cancer cells have morepotential to induce CAFs compared to undifferentiated cancer cells in the invasionprocess of gastric cancer. CAF-target therapy may be more effective to differentiatedgastric cancers rather than undifferentiated scirrhous gastric cancers with vast fibrousstroma.