TGF-β promotes colorectal cancer cell growth in vitro and in vivo.

TGF-β has dual functions as a tumor promoter or a tumor suppressor. Recent studies suggest the roles of TGF-β might change from a tumor suppressor to a tumor promoter, when lacking SMAD4 expression in CRC (colorectal cancer). However, the precise role of TGF-β as tumor promoter in CRC is still unclear.We evaluated the role of TGF-β in SMAD4-null CRC SW620 cells. In vitro, we measured cell growth and cell cycle distribution by flow cytometry. In vivo, we implanted SW620 cells into mice and measured tumor weight after TGF-β treatment. We also determined cell proliferation ability in tumor by immunohistochemistry of proliferating cell nuclear antigen (PCNA).Cell growth and DNA synthesis in S phase was remarkably enhanced by TGF-β in vitro. Besides, TGF-β-activated ERK1/2 MAPK signal was also observed. In vivo, TGF-β enhanced tumor growth and cell proliferation in tumor.TGF-β serves as a tumor promoter, which promotes CRC cell growth in vitro and in vivo. These suggest that TGF-β might be developed as an effective therapeutic target for CRC patients.