¹Department of Experimental Oncology, Regina Elena Cancer Institute, Rome, Italy

Correspondence: Professor A Sacchi or Dr G Bossi, Regina Elena Cancer Institute, Molecular Oncogenesis Laboratory, Department of Experimental Oncology, Via delle Messi d'Oro 156, 00158 Rome, Italy. E-mail: sacchi@ifo.it; bossi@ifo.it

Received 10 March 2005; Revised 21 July 2005; Accepted 21 July 2005; Published online 19 September 2005.

Abstract

Mutations in the TP53 tumor suppressor gene are the most frequent genetic alteration in human cancers. These alterations are mostly missense point mutations that cluster in the DNA binding domain. There is growing evidence that many of these mutations generate mutant p53 proteins that have acquired new biochemical and biological properties. Through this gain of function activity, mutant p53 is believed to contribute to tumor malignancy. The purpose of our study was to explore mutant p53 as a target for novel anticancer treatments. To this aim, we inhibited mutant p53 expression by RNA interference in three different cancer cell lines endogenously expressing mutant p53 proteins, and evaluated the effects on the biological activities through which mutant p53 exerts gain of function. We found that depletion of mutant p53 reduces cell proliferation, in vitro and in vivo tumorigenicity, and resistance to anticancer drugs. Our results demonstrate that mutant p53 knocking down weakens the aggressiveness of human cancer cells, and provides further insight into the comprehension of mutant p53 gain of function activity in human tumor.