N,N-DIMETHYLFORMAMIDE-INDUCED ALTERATION OF CELL-CULTURE CHARACTERISTICS AND LOSS OF TUMORIGENICITY IN CULTURED HUMAN COLON-CARCINOMA CELLS

Abstract

Established human colon carcinoma cell lines were treated in vitro with N,N-dimethylformamide. This polar solvent caused morphological changes in the cells and alterations in their growth properties. Untreated cells had cloning efficiencies of up to 77% in soft agar; treatment with N,N-dimethylformamide resulted in a complete loss of clonogenicity in semisolid medium. Growth in the presence of the polar solvent also effected a marked reduction in the tumorigenicity of the cells. All 10 nude mice that received a s.c. inoculum of 1 .times. 106 untreated cells developed tumors histologically similar to colonic adenocarcinomas in 10-14 days. Of 10 nude mice inoculated with 1 .times. 106 treated cells, 9 showed no sign of tumor 3-6 mo. postinjection. Removal of the polar solvent from the culture medium was accompanied by the reappearance of tumorigenicity and the original cell culture characteristics. N,N-dimethylformamide apparently can reversibly effect the reversion of cultured human colon carcinoma cells to less malignant cell types.