Hypoxia-inducible factor-1α activation in HPV-positive head and neck squamous cell carcinoma cell lines

// Jennifer Knuth 1, * , Shachi J. Sharma 1, * , Nora Würdemann 1 , Claudia Holler 1 , Boyan K. Garvalov 2 , Till Acker 2 , Claus Wittekindt 1 , Steffen Wagner 1, # and Jens P. Klussmann 1, # 1 Department of Otorhinolaryngology, Head and Neck Surgery, University of Giessen, Giessen, Germany 2 Institute of Neuropathology, University of Giessen, Giessen, Germany * These authors contributed equally to this work # These authors contributed equally to this work senior authors Correspondence to: Jennifer Knuth, email: jennifer.knuth@hno.med.uni-giessen.de Keywords: human papillomavirus (hpv), head and neck squamous cell carcinoma (hnscc), hypoxia, hypoxia inducible factor-1α (hif-1α), prolyl hydroxylase-domain protein 2 (phd2) Received: November 24, 2016 Accepted: August 21, 2017 Published: September 11, 2017 ABSTRACT Purpose: Human papillomavirus (HPV) is a causative agent for a rising number of head and neck squamous cell carcinomas (HNSCC), which are characterized by distinct tumor biology. Hypoxia inducible-factor (HIF) signaling influences initiation and progression of carcinogenesis and HPV oncoproteins have evolved to highjack cellular pathways for viral reproduction. Therefore, we investigated whether HPV activates HIF-1α expression in HNSCC. Experimental Technique: HPV-positive and -negative HNSCC cells were examined for adaptive responses to hypoxia. Expression of HIF-1α, prolyl hydroxylase-domain protein 2 (PHD2) and E-cadherin was analyzed by Western blotting, immunofluorescence (IF) microscopy and migration/wound healing assays. Results: HPV-positive HNSCC cells showed higher HIF-1α and PHD2 protein levels under normoxia and hypoxia. HIF-1α hydroxylation was reduced in HPV-positive HNSCC cell lines under PHD and proteasomal inhibition. In vitro wound healing assays showed impairment of migration and proliferation by HIF-1α pathway activation in HPV-negative cell lines only. In contrast, migration and proliferation in HPV-positive cell lines was impaired by HIF-1α specific siRNA. Conclusions: HPV-positive HNSCC cells show activation of the HIF pathway and adaptation to HIF-1α upregulation, representing potential therapeutic targets in this emerging tumor entity.