Characterization of growth factor(s) produced by chemically transformed hamster dermal fibroblasts

Cell lysates from transformed hamster dermal fibroblasts (HDF cells) induced colony formation of normal HDF cells in soft agar medium and also stimulated proliferation of normal HDF cells in medium supplemented with plasma-derived serum (PDS). The colony forming activities of cell lysates correlated well with their growth stimulating activities in PDS-supplemented medium. The growth factor(s) were shown to be sensitive to trypsin and dithiothreitol (DTT), but heat stable. However, these transformed HDF cell lines did not all produce tumor nodules when injected into hamsters. This was not due to immunological rejection because similar results were obtained in hamsters treated with anti-hamster thymocyte serum (ATS). Thus it was concluded that production of these growth factor(s) by transformed HDF cell lines is not itself sufficient for acquisition of complete malignancy in vivo.