Evolutionary selected Tibetan variants of HIF pathway and risk of lung cancer

// Lucie Lanikova 1, 2, * , N. Scott Reading 1, 3, 4, * , Hao Hu 5 , Tsewang Tashi 1 , Tatiana Burjanivova 6 , Anna Shestakova 1, 4 , Bhola Siwakoti 7 , Binay Kumar Thakur 7 , Chin Bahadur Pun 7 , Amir Sapkota 8 , Sarah Abdelaziz 9 , Bing-Jian Feng 10 , Chad D. Huff 5 , Mia Hashibe 9 , Josef T. Prchal 1, 11 1 Division of Hematology, University of Utah School of Medicine, Salt Lake City, Utah, USA 2 Institute of Molecular Genetics, Academy of Sciences, Prague, Czech Republic 3 Institute for Clinical and Experimental Pathology, ARUP Laboratories, Salt Lake City, Utah, USA 4 Department of Pathology, University of Utah School of Medicine, Salt Lake City, Utah, USA 5 University of Texas, MD Anderson Cancer Center, Houston, Texas, USA 6 Department of Molecular Biology, Comenius University in Bratislava, Jessenius Faculty of Medicine in Martin, Slovak Republic 7 B.P. Koirala Memorial Cancer Hospital, Bharatpur, Chitwan, Nepal 8 Maryland Institute for Applied Environmental Health, and University of Maryland College Park School of Public Health, Maryland, USA 9 Division of Public Health, Department of Family & Preventive Medicine and Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, Utah, USA 10 Department of Dermatology, University of Utah School of Medicine, Salt Lake City, Utah, USA 11 Department of Pathophysiology and 1st Department of Medicine, 1st Faculty of Medicine, Charles University in Prague, Czech Republic * These authors have contributed equally to this work Correspondence to: Josef T. Prchal, email: josef.prchal@hsc.utah.edu Mia Hashibe, email: mia.hashibe@utah.edu Keywords: hypoxia, ENGL1/PHD2, EPAS1/HIF-2α, high-altitude adaptation, lung cancer Received: June 15, 2016     Accepted: December 16, 2016     Published: December 28, 2016 ABSTRACT Tibetans existed in high altitude for ~25 thousand years and have evolutionary selected unique haplotypes assumed to be beneficial to hypoxic adaptation. EGLN1 /PHD2 and EPAS1 /HIF-2α, both crucial components of hypoxia sensing, are the two best-established loci contributing to high altitude adaptation. The co-adapted Tibetan-specific haplotype encoding for PHD2:p.[D4E/C127S] promotes increased HIF degradation under hypoxic conditions. The Tibetan-specific 200 kb EPAS1 haplotype introgressed from an archaic human population related to Denisovans which underwent evolutionary decay; however, the functional variant(s) responsible for high-altitude adaptation at EPAS1 /HIF-2α have not yet been identified. Since HIF modulates the behavior of cancer cells, we hypothesized that these Tibetan selected genomic variants may modify cancer risk predisposition. Here, we ascertained the frequencies of EGLN1 D4E/C127S and EGLN1 C127S variants and ten EPAS1 /HIF-2α variants in lung cancer patients and controls in Nepal, whose population consists of people with Indo-Aryan origin and Tibetan-related Mongoloid origin. We observed a significant association between the selected Tibetan EGLN 1/PHD2 haplotype and lung cancer (p=0.0012 for D4E, p=0.0002 for C127S), corresponding to a two-fold increase in lung cancer risk. We also observed a two-fold or greater increased risk for two of the ten EPAS1 /HIF-2α variants, although the association was not significant after correcting for multiple comparisons (p=0.12). Although these data cannot address the role of these genetic variants on lung cancer initiation or progression, we conclude that some selected Tibetan variants are strongly associated with a modified risk of lung cancer.