E6致癌蛋白活化人體端粒酶反轉錄酶在人類乳突病毒 16/18型感染的肺腫瘤化角色

Abstract

Our recent report indicates that HPV16/18 E6 oncoprotein is expressed in lung tumors and is related to p53 inactivation. We further explored whether hTERT transcription could be upregulated by E6 and contributes to lung tumor development. In the present study, HPV16 E6 oncoprotein of 135 lung tumors was detected by immunohistochemistry (IHC), and hTERT mRNA was evaluated by real-time RT-PCR and in situ hybridization, respectively. Our data indicated that hTERT mRNA levels in E6 -positive tumors, which were prevalent in female nonsmokers and adenocarcinomas, were significantly higher than in E6 -negative tumors. In addition, hTERT mRNA levels in early tumors (stage I) were greater than levels in advanced tumors (stage II and III). CHIP assay showed that Sp1 cooperated with c-Myc to activate hTERT transcription in TL-1 cells which was similar to the SiHa cells. The telomerase activity of the TL-1 cells decreased concomitantly with the transfection of various doses of E6 or hTERT-RNAi. The telomerase activity and oncogenic potential of TL-1 with or without E6 or hTERT-RNAi was determined by real-time quantitative TRAP ASSAYanalysis and soft agar assay, respectively. A soft agar assay showed that the oncogenic potential of TL-1 cells was significantly reduced after being transfected with E6 RNAi. Moreover, the oncogenic potential of TL-1 cells was almost diminished after being transfected with hTERT RNAi. Collectively, transcriptional activation of hTERT by E6 is required for HPV16/18-infected lung tumorigenesis. To verify whether hTERT mRNA and telomerase activity could predict the clinical outcome of lung cancer, 56 lung tumors were enrolled to determine hTERT mRNA and telomerase activity by RT-PCR and TRAP ASSAYassay, respectively. Kaplain-Meier analysis showed that patients without telomerase activity had favorable survival than those with telomerase activity； however, the prognostic significance was not observed in hTERT mRNA. Therefore； reactivated telomerase activity may be a poor prognostic factor in non-small cell lung cancer.