Transforming growth factor-β3 protection of epithelial cells from cycle-selective chemotherapy in vitro

The transforming growth factor-β (TGF-β) family of regulatory growth factors can reversibly arrest cell division in the G₁ phase of the cell cycle. Previously, TGF-β3 was shown to protect epithelial cells and hematopoietic cells from cytotoxic damage in vitro and in vivo, and to reduce the severity and duration of oral mucositis induced by 5-fluorouracil (5-FU) in vivo. In the present study, we tested whether TGF-β3 can protect epithelial cells from a range of chemotherapy drugs with differing mechanisms of action, using the CCL64 cell line as a model system. We report that preincubation of cells with TGF-β3 for 24 hr resulted in enhanced clonogenicity following exposure to vinblastine, vincristine, etoposide, taxol, ara-C, methotrexate, or 5-FU. Protection was measured in colony- forming assays, which demonstrated that the protected cells could re-enter the cell cycle and undergo multiple rounds of cell division. At high cytotoxic drug concentrations, absolute colony counts were increased for the cultures prearrested by TGF-β3, as compared with the proliferating control cultures. The effects of TGF-β1 were reduced for cisplatin and doxorubicin, drugs that are toxic to cells throughout the cell cycle. Thus, TGF-β3 can effectively reduce the cytotoxicity of anticancer drugs that act predominantly in S or M phase of the cell cycle.