Kensuke Nishi1,2, Hao Luo1, Kazuhiko Nakabayashi3, Keiko Doi1,4, Shuhei Ishikura1,4, Yuri Iwaihara1, Yasuhiro Yoshida1, Kumpei Tanisawa5, Tomio Arai5, Seijiro Mori6, Motoji Sawabe7, Masaaki Muramatsu8, Masashi Tanaka9, Toshifumi Sakata2, Senji Shirasawa1,4, Toshiyuki Tsunoda10,4. 1. Department, of Cell Biology, Faculty of Medicine, Fukuoka University, Fukuoka, Japan. 2. Department, of Otorhinolaryngology, Faculty of Medicine, Fukuoka University, Fukuoka, Japan. 3. Department of Maternal-Fetal Biology, National Research Institute for Child Health and Development, Tokyo, Japan. 4. Central Research Institute for Advanced Molecular Medicine, Fukuoka University, Fukuoka, Japan. 5. Departments of Pathology, Tokyo Metropolitan Geriatric Hospital, Tokyo, Japan. 6. Center for Promotion of Clinical Investigation, Tokyo Metropolitan Geriatric Hospital, Tokyo, Japan. 7. Department of Moleculo-genetic Sciences, Division of Biomedical Laboratory Sciences Molecular Pathophysiology, Graduate School of Health Care Sciences, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan. 8. Department of Molecular Epidemiology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan. 9. Department of Clinical Laboratory, Tokyo Metropolitan Geriatric Hospital, Tokyo, Japan. 10. Department, of Cell Biology, Faculty of Medicine, Fukuoka University, Fukuoka, Japan tsunoda@fukuoka-u.ac.jp.
Abstract
BACKGROUND/AIM: Alpha-kinase 2 (ALPK2), suggested to be a novel tumour-suppressor gene down-regulated by oncogenic KRAS, plays a pivotal role in luminal apoptosis in normal colonic crypts. The aim of this study was to determine the association between ALPK2 germline variants and colorectal cancer. MATERIALS AND METHODS: Missense single nucleotide variants in the exons of the ALPK2 gene in 2,343 consecutive autopsy cases (1,446 cases with cancer and 897 cases without cancer) were screened using HumanExome BeadChip arrays. To address the functional effect of a missense ALPK2 variant, a 3D floating cell culture was performed using HCT116-derived human colorectal cancer cells stably expressing wild-type (wt) ALPK2 (HCT116-wtALPK2) or amino acid-substituted (sub) ALPK2 (HCT116-subALPK2). RESULTS: We identified that one of the ALPK2 germline variants, rs55674018 (p.Q1853E), was significantly associated with the presence of cancer (adjusted odds ratio(OR)=4.39; 95% confidence interval(CI)=1.31-14.78, p=0.001). The p.Q1853E variant was present in the East Asian population and located in the immunoglobulin-like domain. Notably, the basolateral polarity of actin in the surface of HCT116-wtALPK2 spheroids was more attenuated compared to that of HCT116-subALPK2 spheroids. Furthermore, luminal apoptosis and cell aggregation were promoted by wtALPK2, but not by subALPK2 in 3D culture. CONCLUSION: The p.Q1853E variant of ALPK2, which had been accumulating in the Japanese population, induced a metastatic phenotype by disrupting ALPK2 function. Copyright
BACKGROUND/AIM: Alpha-kinase 2 (ALPK2), suggested to be a novel tumour-suppressor gene down-regulated by oncogenic KRAS, plays a pivotal role in luminal apoptosis in normal colonic crypts. The aim of this study was to determine the association between ALPK2 germline variants and colorectal cancer. MATERIALS AND METHODS: Missense single nucleotide variants in the exons of the ALPK2 gene in 2,343 consecutive autopsy cases (1,446 cases with cancer and 897 cases without cancer) were screened using HumanExome BeadChip arrays. To address the functional effect of a missense ALPK2 variant, a 3D floating cell culture was performed using HCT116-derived humancolorectal cancer cells stably expressing wild-type (wt) ALPK2 (HCT116-wtALPK2) or amino acid-substituted (sub) ALPK2 (HCT116-subALPK2). RESULTS: We identified that one of the ALPK2 germline variants, rs55674018 (p.Q1853E), was significantly associated with the presence of cancer (adjusted odds ratio(OR)=4.39; 95% confidence interval(CI)=1.31-14.78, p=0.001). The p.Q1853E variant was present in the East Asian population and located in the immunoglobulin-like domain. Notably, the basolateral polarity of actin in the surface of HCT116-wtALPK2 spheroids was more attenuated compared to that of HCT116-subALPK2 spheroids. Furthermore, luminal apoptosis and cell aggregation were promoted by wtALPK2, but not by subALPK2 in 3D culture. CONCLUSION: The p.Q1853E variant of ALPK2, which had been accumulating in the Japanese population, induced a metastatic phenotype by disrupting ALPK2 function. Copyright