Effect Of Pericytes On Epithelial-To-Mesenchymal Transition In Melanoma

84 Background: Melanoma-associated stroma cells play an important role in supporting cancer cell proliferation, invasion, and dissemination. Increased invasiveness has been observed in cancer cells undergoing epithelial-to-mesenchymal transition (EMT); however, it is unknown whether EMT is facilitated by stroma cells. We showed that pericytes constitute a predominant stroma subpopulation that promotes melanoma growth by interacting with cancer cells. This study investigates the mechanism by which pericytes facilitate melanoma development.GFP(+) pericytes isolated from tumors and adipose tissue were co-cultured in vitro with B16 melanoma cells at a 3:1 ratio. After 4 days, proliferation of B16 cells and pericytes was assessed. Also, co-cultures were labeled for several markers and analyzed by flow cytometry (FC). Tumorigenicity was investigated by isolating B16 cells from co-cultures by FACS sorting and then injected into SCID mice to measure tumor growth.B16 cells induced pericyte differentiation into FAP(+) myofibroblasts. However, no change in the pericyte proliferation rate was observed. B16 cells co-cultured with pericytes, and later separated by FACS sorting, displayed faster proliferation rates in vitro, and induced increased tumor growth rates when injected into SCID mice, compared with naive B16 cells. Pericytes increased B16 cell proliferation rate and induced a change in cell morphology, from cobblestone to fibroblast-like colonies. Interaction between B16 cells and pericytes in co-culture increased pericyte production of TGF-β and increased the expression of the stem cell markers SSEA-1, OCT3/4 and CD271 in B16 cells. In addition, cadherin switching, demonstrated by loss of E-cadherin expression and an up-regulation of the mesenchymal markers N-cadherin and vimentin was observed in B16 cells.Pericyte production of TGF-β promotes B16 cell development of EMT, as shown by loss of E-cadherin expression and up-regulation of the mesenchymal markers N-cadherin and vimentin, resulting in an increase in melanoma cell tumorigenicity. These results suggest that therapies targeting stromal pericytes may be a promising approach for melanoma treatment.