Tobacco smoke activates human papillomavirus 16 p97 promoter and cooperates with high-risk E6/E7 for oxidative DNA damage in lung cells.

Nelson Peña,Jonás Chnaiderman,Juan P Muñoz,Oscar León,Alejandro H Corvalán,Maria L Tornesello,Diego Carrillo,Ricardo Soto-Rifo,Francisco Aguayo,Ulises Urzúa

doi:10.1371/journal.pone.0123029

Abstract

We have previously shown a functional interaction between human papillomavirus type 16 (HPV-16) E6 and E7 oncoproteins and cigarette smoke condensate (CSC) in lung cells suggesting cooperation during carcinogenesis. The molecular mechanisms of such interaction, however, remain to be elucidated. Here we first present evidence showing that cigarette smoke condensate (CSC) has the ability to activate the HPV-16 p97 promoter by acting on the long control region (LCR) in lung epithelial cells. Interestingly, we observed that CSC-induced p97 promoter activation occurs in a dose-dependent manner in both tumor A-549 (lung adenocarcinoma), H-2170 (bronchial carcinoma), SiHa or Hela (cervical carcinoma) cells but not in non-tumor BEAS-2B (bronchial) or NL-20 (alveolar) lung cells unless they ectopically expressed the HPV-16 E6 and E7 oncogenes. In addition, we also observed a significant increase of primary DNA damage in tumor and non-tumor CSC-treated lung cells expressing HPV-16 E6 and E7 oncogenes suggesting a cooperative effect in this process, even though the contribution of E7 was significantly higher. Taken together, our results strongly suggest that tobacco smoke is able to induce the activation of the HPV-16 p97 promoter in cooperation with HPV-16 E6 and E7 oncogenes that, in turn, sensitize lung cells to tobacco smoke-induced DNA damage.

Highlights

Lung cancer is a leading cause of cancer-related death in the world [1]
We showed that tobacco smoke was able to activate the human papillomavirus type 16 (HPV-16) p97 promoter in a dose dependent-manner in tumor lung cells when it is under the control of its cognate long control region (LCR)
In order to confirm that p97 activation by cigarette smoke condensate (CSC) leads to an increase in the level of the E6E7 transcript, we exposed Human papillomavirus (HPV)-16 positive SiHa cells to 10 μg/mL CSC and quantified the E7 transcript by reverse transcriptase quantitative PCR (RT-qPCR)

Summary

Introduction

Tobacco Smoke and HPV Cooperation in Lung Epithelial Cells towards its development [2]. An international pooled analysis reported that among the HPV positive lung carcinomas, 71% belong to smoking or former smoking groups [9]. The potential involvement of HPV in lung cancer associated with tobacco smoke is a concern that warrants further investigations. We have previously reported that HPV-16 E6 and E7 oncoproteins and cigarette smoke condensate (CSC) cooperate increasing the proliferative and tumor properties of lung epithelial cells [10]. The mechanism by which tobacco smoke and HPV are able to interact in lung cells is unknown, it is widely accepted that constitutive high-risk (HR)HPV E6 and E7 expression is necessary for cell immortalization and for the maintenance of the tumor phenotype [11]. HPV-immortalized cells are not tumorigenic in animal models suggesting that additional molecular alterations are necessary for complete HPV-induced tumoral transformation [11]

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Results

Conclusion