title: CMTM4 is frequently downregulated and functions as a tumour suppressor in clear cell renal cell carcinoma.
abstract: BACKGROUND
  Chemokine-like factor (CKLF)-like MARVEL transmembrane domain-containing family (CMTM) is a gene family involved in multiple malignancies. CMTM4 is a member of this family and is located at chromosome 16q22.1, a locus that harbours a number of tumour suppressor genes. It has been defined as a regulator of cell cycle and division in HeLa cells; however, its roles in tumourigenesis remain poorly studied.
  
  
  METHODS
  An integrated bioinformatics analysis based on the array data from the GEO database was conducted to view the differential expression of CMTM4 across multiple cancers and their corresponding control tissues. Primary clear cell renal cell carcinoma (ccRCC) and the paired adjacent non-tumour tissues were then collected to examine the expression of CMTM4 by western blotting, immunohistochemistry, and quantitative RT-PCR. The ccRCC cell lines A498 and 786-O and the normal renal tubular epithelial cell line HK-2 were also tested for CMTM4 expression by western blotting. Cell Counting Kit-8 (CCK-8) and viable cell counting assays were used to delineate the growth curves of 786-O cells after CMTM4 overexpression or knockdown. Wound healing and transwell assays were performed to assess the cells' ability to migrate. The effects of CMTM4 on cellular apoptosis and cell cycle progression were analysed by flow cytometry, and cell cycle hallmarks were detected by western blotting and RT-PCR. The xenograft model in nude mice was used to elucidate the function of CMTM4 in tumourigenesis ex vivo.
  
  
  RESULTS
  By omic data analysis, we found a substantial downregulation of CMTM4 in ccRCC. Western blotting then confirmed that CMTM4 was dramatically reduced in 86.9 % (53/61) of ccRCC tissues compared with the paired adjacent non-tumour tissues, as well as in the 786-O and A498 ccRCC cell lines. Restoration of CMTM4 significantly suppressed 786-O cell growth by inducing G2/M cell cycle arrest and p21 upregulation, and cell migration was also inhibited. However, knockdown of CMTM4 led to a completely opposite effect on these cell behaviours. Overexpression of CMTM4 also markedly inhibited the tumour xenograft growth in nude mice.
  
  
  CONCLUSIONS
  CMTM4 is downregulated and exhibits tumour-suppressor activities in ccRCC, and could be exploited as a target for ccRCC treatment.
authors.affiliation: Peking University Center for Human Disease Genomics, Department of Immunology, Key Laboratory of Medical Immunology, Ministry of Health, School of Basic Medical Sciences, Peking University Center for Human Disease Genomics, Peking University Health Science Center, 38 Xueyuan Road, Beijing, 100191, China. tingfanta@163.com.
authors.forename: Ting
authors.initials: T
authors.lastname: Li
authors.affiliation: Peking University Center for Human Disease Genomics, Department of Immunology, Key Laboratory of Medical Immunology, Ministry of Health, School of Basic Medical Sciences, Peking University Center for Human Disease Genomics, Peking University Health Science Center, 38 Xueyuan Road, Beijing, 100191, China. chengyingying1987@163.com.
authors.forename: Yingying
authors.initials: Y
authors.lastname: Cheng
authors.affiliation: Peking University Center for Human Disease Genomics, Department of Immunology, Key Laboratory of Medical Immunology, Ministry of Health, School of Basic Medical Sciences, Peking University Center for Human Disease Genomics, Peking University Health Science Center, 38 Xueyuan Road, Beijing, 100191, China. wangpzh@bjmu.edu.cn.
authors.forename: Pingzhang
authors.initials: P
authors.lastname: Wang
authors.affiliation: Peking University Center for Human Disease Genomics, Department of Immunology, Key Laboratory of Medical Immunology, Ministry of Health, School of Basic Medical Sciences, Peking University Center for Human Disease Genomics, Peking University Health Science Center, 38 Xueyuan Road, Beijing, 100191, China. wywang@bjmu.edu.cn.
authors.forename: Wenyan
authors.initials: W
authors.lastname: Wang
authors.affiliation: Department of Urology, Peking University People's Hospital, 11 Xi-Zhi-Men South Street, Beijing, 100044, China. guyue0910@163.com.
authors.forename: Fengzhan
authors.initials: F
authors.lastname: Hu
authors.affiliation: Peking University Center for Human Disease Genomics, Department of Immunology, Key Laboratory of Medical Immunology, Ministry of Health, School of Basic Medical Sciences, Peking University Center for Human Disease Genomics, Peking University Health Science Center, 38 Xueyuan Road, Beijing, 100191, China. moxiaoning@bjmu.edu.cn.
authors.forename: Xiaoning
authors.initials: X
authors.lastname: Mo
authors.affiliation: Peking University Center for Human Disease Genomics, Department of Immunology, Key Laboratory of Medical Immunology, Ministry of Health, School of Basic Medical Sciences, Peking University Center for Human Disease Genomics, Peking University Health Science Center, 38 Xueyuan Road, Beijing, 100191, China. lvhongxia@yshbio.com.
authors.forename: Hongxia
authors.initials: H
authors.lastname: Lv
authors.affiliation: Department of Urology, Peking University People's Hospital, 11 Xi-Zhi-Men South Street, Beijing, 100044, China. xutao@medmail.com.cn.
authors.forename: Tao
authors.initials: T
authors.lastname: Xu
authors.affiliation: Peking University Center for Human Disease Genomics, Department of Immunology, Key Laboratory of Medical Immunology, Ministry of Health, School of Basic Medical Sciences, Peking University Center for Human Disease Genomics, Peking University Health Science Center, 38 Xueyuan Road, Beijing, 100191, China. hanwl@bjmu.edu.cn.
authors.forename: Wenling
authors.initials: W
authors.lastname: Han
mesh_terms: D000328:Adult; D000368:Aged; D000818:Animals; D017209:Apoptosis / Q000235:genetics; D002292:Carcinoma, Renal Cell / Q000235:genetics* / Q000473:pathology; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000235:genetics; D049109:Cell Proliferation / Q000235:genetics; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000096:biosynthesis; D015536:Down-Regulation; D005260:Female; D059565:G2 Phase Cell Cycle Checkpoints / Q000235:genetics; D016147:Genes, Tumor Suppressor; D006801:Humans; D007680:Kidney Neoplasms / Q000235:genetics* / Q000473:pathology; D062792:MARVEL Domain-Containing Proteins / Q000096:biosynthesis / Q000235:genetics*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D008875:Middle Aged; D009368:Neoplasm Transplantation; D034622:RNA Interference; D034741:RNA, Small Interfering; D014183:Transplantation, Heterologous; D025521:Tumor Suppressor Proteins / Q000235:genetics*; D055815:Young Adult
chemical_list: C551726:CMTM4 protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D062792:MARVEL Domain-Containing Proteins; D034741:RNA, Small Interfering; D025521:Tumor Suppressor Proteins