Ras puts the brake on doxorubicin-mediated cell death in p53-expressing cells.

Doxorubicin is one of the most effective molecules used in the treatment of various tumors. Contradictory reports often open windows to understand the role of p53 tumor suppressor in doxorubicin-mediated cell death. In this report, we provide evidences that doxorubicin induced more cell death in p53-negative tumor cells. Several cells, having p53 basal expression, showed increase in p53 DNA binding upon doxorubicin treatment. Doxorubicin induced cell death in p53-positive cells through expression of p53-dependent genes and activation of caspases and caspase-mediated cleavage of cellular proteins. Surprisingly, in p53-negative cells, doxorubicin-mediated cell death was more aggressive (faster and intense). Doxorubicin increased the amount of Fas ligand (FasL) by enhancing activator protein (AP) 1 DNA binding in both p53-positive and p53-negative cells, but the basal expression of Fas was higher in p53-negative cells. Anti-FasL antibody considerably protected doxorubicin-mediated cell death in both types of cells. Activation of caspases was faster in p53-negative cells upon doxorubicin treatment. In contrast, the basal expression of Ras oncoprotein was higher in p53-positive cells, which might increase the basal expression of Fas in these cells. Overexpression of Ras decreased the amount of Fas in p53-negative cells, thereby decreasing doxorubicin-mediated aggressive cell death. Overall, this study will help to understand the much studied chemotherapeutic drug, doxorubicin-mediated cell signaling cascade, that leads to cell death in p53-positive and -negative cells. High basal expression of Fas might be an important determinant in doxorubicin-mediated cell death in p53-negative cells.