Proteomic and transcriptomic investigation of the mechanisms and consequences of p53 gain of function mutation in laryngeal squamous cell carcinoma

• Main Author: Behrendt, Anna
• Published: University of Liverpool 2011
• Subjects: 616.99477
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.569205

Loss of p53 function is a critical event in tumour development. It has been well documented that p53 mutation can lead to an oncogenic gain of function (GOF) associated with poorer prognosis and therapeutic response. Such mutants exert their gain-of-function properties by modifying cells through altered transcriptional activity as well as novel protein-protein interactions, but the molecular details of the mechanisms involved are still not entirely understood. Recent reports indicate that mutant p53 increases TGFβ-dependent metastatic potential of cancer cells via inhibition of p63 function and also promotes invasion through increased integrin (aSpl) and EGFR recycling, which is also linked with suppression of transcriptionally active p63 in normal epithelial cells, lung cancer cells and invasive breast cancer cells. The aim of this study was to investigate the mechanism of mutant p53 GOF in squamous cell carcinoma of the head and neck (SCCHN) cells. To avoid the potentially confounding impact of studying cells from biologically distinct anatomical sub-sites, the studies described here focused upon the most common sub-type of SCCHN -laryngeal squamous cell carcinoma (LSCC). Two hot-spot p53 mutants representing two distinct mutational classes have been chosen for these studies: R17SH (structural mutation) and R273H (contact mutation), both of which have been previously demonstrated to have GOF properties and have been documented to occur in laryngeal cancer. The mechanism of mutant p53 GOF was investigated by identifying protein interactions of mutant p53 and by studying gene expression changes in LSCC cells expressing these p53 mutants. In addition, the functional consequences of mutant p53 expression in LSCC cells were investigated in terms of response to radiation (a primary treatment modality for LSCC) and motility/invasiveness (key determinants of metastatic potential). A number of proteins have been identified in the mutant p53 containing protein complexes in LSCC cells and one of these, HSP70, has been confirmed by immunoprecipitation to selectively interact with the p53-175H mutant. p53-273H-expressing cells and to a smaller extent p53-175H-expressing cells display increased motility. A stable knock-down of the mutant p53 has been shown to reduce the motility of cells suggesting that p53-273H contributes to increased