Ultraviolet light-induced transformation of human cells to anchorage-independent growth.

We have developed a system for ultraviolet light (UV) transformation of human embryonic cells to anchorage-independent growth. The procedure involves multiple UV irradiations, post irradiation growth, and plating in soft agar. Transformants are obtained at frequencies from 1 to 80 per 10(5) cells at UV exposures to 25 J/sq m. The resulting transformants can be subcultured on solid surfaces. The cells show crisscrossing and piling up; they reach 2- to 5-fold higher saturation densities than the parental cells. Some subcultures show increased plating efficiency in soft agar and increased life span. The susceptibility of the UV transformation process to apparent photoenzymatic reversal implies that purimidine dimers play a role in its induction.