Abstract: The MSU - 1 lineage of human fibroblast including 3 immortalized cell strains with wrowth advantage to varying extents , was generated by t ransfection of normal human fibroblasts with a v - myc oncogene and their gaining additional genetic alteration ( s) spontaneously. Those derived cell variant s may represent different premalignant stages in the progression from normal cells to malignant cells. To establish in vit ro model of human cell carcinogenesis , the 3 cell types were characterized for their responses to induction of malignant t ransformation by different carcinogens. The result s shwoed that cell st rains MSU - 1. 1 and MSU - 1. 2 were malignantly transformed after exposure to BPDE , ICR - 191 and 60 Coγ- ray , respectively , followed by selection for focus forming ability or anchorage independent growth. The parental cell of the lineage MSU - 1. 0 was not found to be malignantly tranformed. Studies using this in vit ro model with carcinogens revealed that different phenotypic properties of the resulted malignant cells were acquired by a step - wise progressive process.

Key words: Human Fibroblast, Chemical Carcinogen, Radiation, Malignant Transformation