Phenotypic change and altered protein expression in X‐ray and methylcholanthrene‐transformed C3H10T1/2 fibroblasts

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Abstract
The morphology, growth properties and cellular protein patterns from parent and two transformed C3H10T1/2 cell lines were analyzed to associated the phenotypic and protein differences with cell transformation. Transformed 10T1/2 cells were obtained by colony isolation after exposure of parent 10T1/2 cells to methylcholanthrene (MCA‐1 cell line) or X‐ray irradiation (XR‐III cell line). Compared to parent 10T1/2 and MCA‐1 cells, XR‐III cells were much smaller in size and exhibited the highest growth rate, greatest cell saturation density, increased plating efficiency and greater expression of proliferating cell nuclear antigen. MCA‐1 cells showed intermediate characteristics between parent and XR‐III cells. Among the three cell lines, only XR‐III cells showed anchorage‐independent growth in soft agar. When [35S]methionine‐labeled whole cell lysate proteins were separated by two‐dimensional polyacrylamide gel electrophoresis, computer comparison algorithms revealed a 97% similarity in protein profiles among almost 800 proteins detected from each cell line. However, comparison of proteins patterns of the transformed cell lines to that of parent 10T1/2 cells showed that 30 and 20 proteins were induced or repressed in XR‐III cells and MCA‐1 cells, respectively. Similarly, 81 and 24 proteins showed significant quantitative changes (threefold or greater) in XR‐III and MCA‐1 cells, respectively, as compared with parent 10T1/2 cell proteins. The ahchorage‐independent growth and increased proliferation properties of XR‐III cells suggest a later stage of transformation compared to MCA‐1 cells. Overall, these data suggest that gradational morphologic and phenotypic aberrancy in MCA‐1 and XR‐III cell lines from parent cells is accompanied by an increased diversity in protein expression in a limited set of proteins, some of which may play important roles in the multistep transformation process.