Identification of differential proteins in nasopharyngeal carcinoma cells with p53 silence by proteome analysis

Although mutation of p53 tumor-suppressor gene is rare in nasopharyngeal carcinoma (NPC), NPC has a high frequency of overexpression of p53 protein. There seem to be complex mechanisms of inactivation and stabilization of p53 in NPC. To detect proteins associated with the function of p53 in high throughout screening, we succeeded in establishing p53 knockdown human NPC CNE2 cell line (CNE2sip53) using stable RNA interference, and compared the proteomic changes between CNE2sip53 and control cell line CNE2/pSUPER using two-dimensional gel electrophoresis. Twenty-two differentially expressed proteins between the two cell lines were identified by both matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and electrospray ionization tandem mass spectrometry, some of which are known to be associated with the p53 function (HSP27, hnRNP K, 14-3-3σ, etc.), and others may be novel proteins associated with p53 function (eIF4B, TPT1, hnRNP H3, SFRS1 etc.). Furthermore, several differential proteins including HSP27, HSP70, GRP75 and GRP78 were verified as p53 interacting proteins in NPC by immunoprecipitation and Western blot analysis, and the suppression of HSP27 expression by HSP27 antisense oligonucleotides could decrease the p53 protein level. Our data suggest that these differential proteins may be associated with the function of p53 in NPC, and provide new clues to elucidate the mechanisms of inactivation and stabilization of p53 in NPC.