Epigenetic Control of Tumor Cell Morphology

XC cell line derived from a single rat cell transformed by the Prague strain of Rons sarcoma virus produced morphologically different colonies. Among them, two distinct cell types consisting of thick, fusiform cells (L‐type), and of flat, polygonal cells (R‐type) were apparent. By repeated subclonings, pure cultures, L1 and R1, respectively, were obtained. These clones underwent morphological conversion during prolonged culture; L‐type colonies appeared in the R‐type clone and vice versa. The kinetic curve suggested that the conversion was multi‐stepped. When inoculated into nude mice, L‐type cells produced much larger tumors at a higher frequency than R‐type cells, and the tumors induced by these two clones were histologically different. The expression of v‐src gene was higher in L‐type than in R‐type cells at both mRNA and protein levels.