Identification of novel mutant p53 target genes in triple negative breast cancer

DI BENEDETTO CAROLINA; BORINI ETICHETTI CARLA; GIRARDINI JAVIER E; ROSSI CAROLINA

Varadero

Workshop; Emerging Targeted Therapies in Cancer & Autoimmunity; 2016

Center of Genetic Engineering and Biotechnology (CIGB)

Most human cancers inactivate the tumor suppressor p53 through missense mutations, leading to the abundant expression of full-length point mutant proteins. p53 mutants not only lose the tumor suppressor function of the wild type protein but may also acquire novel activities that actively promote tumor progression. Despite a large body of evidences showing that mutant p53 enhances tumor aggressiveness, the mechanisms underlying this activity are still poorly understood. Even if the mutation abrogates the ability to bind p53 responsive elements on DNA, point mutants alter gene expression through mechanisms that are not well characterized. Previous data from microarray analysis on MDA-MB-231 Triple Negative Breast Cancer cells suggested that mutant p53 may cooperate with tumor progression by modifying gene expression. We confirmed by qPCR that the expression of a group of genes is altered by mutant p53 indicating that they may be novel targets for transcriptional regulation. We hypothesized that some genes in this group may promote oncogenic mechanisms. To explore this hypothesis we studied particularly their effect on tumor cell behavior. We focused on ICMT (isoprenylcysteine carboxylmethyltransferase), which is involved in a complex post-translational modification process that allows correct localization of proteins with a C-terminal CaaX motif, including members of the RAS and RHO families. In order to characterize the effect of the p53 family members on transcription we generated reporters containing the promoter of ICMT and performed luciferase assays.