TRANSFECTION AND EXPRESSION OF MUTANT P53 PROTEIN DOES NOT ALTER THE IN-VIVO OR IN-VITRO GROWTH-CHARACTERISTICS OF THE AA C1 HUMAN ADENOMA DERIVED CELL-LINE, INCLUDING SENSITIVITY TO TRANSFORMING GROWTH-FACTOR-BETA-1/

Mutation of the p53 gene is thought to be a late event in human colore ctal carcinogenesis, involved in the malignant conversion of the adeno ma to the carcinoma. One of the questions that we hoped to address was whether, in vivo, a single mutational event in one p53 gene is suffic ient to confer a significant growth advantage on a colonic epithelial cell. Such a growth advantage could result either from an increase in growth rate and/or loss of response to inhibitory growth signals natur ally present in the colonic crypt. We therefore introduced the pC53-SC X3 143 (Val-Ala) p53 mutation into a non tumorigenic adenoma derived c ell line, AA/C1, which contained a truncating APC mutation, activating K-ras mutation but was wild-type for the p53 protein. High levels of mutant p53 protein were detected in the pC53-SCX3 transfected AA/C1 ce ll lines but was found not to affect either the in vitro (colony formi ng efficiency, anchorage independence) or in vivo (tumorigenicity in n ude mice) growth, when compared to vector control or the parental AA/C 1 cell line. In addition, to test whether the cells become less sensit ive to inhibitory growth factors, the response of the cell lines to th e naturally occurring growth inhibitor TGF beta was also investigated. Even though TGF beta had previously been implicated in the control of growth of intestinal epithelium, expression of the mutant p53 protein did not affect the sensitivity of the parental AA/C1 cell line to TGF beta. Under the experimental conditions tested expression of the 143 (Val-Ala) p53 protein was unable to affect the in vitro or in vivo gro wth characteristics of the adenoma derived AA/C1 cell line. When compa red to other studies, these results suggest that the genetic backgroun d of the individual recipient cell may greatly influence the effect of expression of a particular p53 mutation.