p53 but not cyclin e acts in a negative regulatory loop to control her-2 expression in mcf-7 breast carcinoma cell line.

cyclin e, her-2 and p53, are considered as major prognostic markers in breast cancer. as they are related in patho-clinical level, we aimed to check if they have any direct interaction on expression of each other. to study the effect of cyclin e on her-2 expression, cell lines stably overexpressing cyclin e or its low molecular weight (lmw) isoforms were generated. to understand the results of p53 silencing either alone or in combination with cyclin e overexpression, we created three different p53 stably knocked down cell lines. protein expression was analyzed by western blot, her-2 expression in the established cell lines were determined using sybr green real time pcr and data analyzed by rest software. results indicate that her-2 expression is only downregulated following p53 silencing and none of cyclin e isoforms can alter its expression. the presence of cyclin e isoforms in p53 silenced clones also does not altered her-2 expression. given the fact that p53 degradation is increased by her-2 overexpression, these data can draw a regulatory loop in which a non-mutated functional p53 and her-2 can bidirectionally regulate the expression of these two genes. this study improves our understandings of these pathways and these proteins can be introduced either as a marker or as a target in cancer treatment.