title: SLC25A22 Promotes Proliferation and Survival of Colorectal Cancer Cells With KRAS Mutations and Xenograft Tumor Progression in Mice via Intracellular Synthesis of Aspartate.
abstract: Many colorectal cancer (CRC) cells contain mutations in KRAS. Analyses of CRC cells with mutations in APC or CTNNB1 and KRAS identified SLC25A22, which encodes mitochondrial glutamate transporter, as a synthetic lethal gene. We investigated the functions of SLC25A22 in CRC cells with mutations in KRAS.
  
  
  
  We measured levels of SLC25A22 messenger RNA and protein in paired tumor and nontumor colon tissues collected from 130 patients in Hong Kong and 17 patients in China and compared protein levels with patient survival times. Expression of SLC25A22 was knocked down in KRAS mutant CRC cell lines (DLD1, HCT116, LOVO, SW480, SW620, and SW1116) and CRC cell lines without mutations in KRAS (CACO-2, COLO205, HT29, and SW48); cells were analyzed for colony formation, proliferation, glutaminolysis and aspartate synthesis, and apoptosis in Matrigel and polymerase chain reaction array analyses. DLD1 and HCT116 cells with SLC25A22 knockdown were grown as xenograft tumors in nude mice; tumor growth and metastasis were measured. SLC25A22 was expressed ectopically in HCT116 cells, which were analyzed in vitro and grown as xenograft tumors in nude mice.
  
  
  
  Levels of SLC25A22 messenger RNA and protein were increased in colorectal tumor tissues compared with matched nontumor colon tissues; increased protein levels were associated with shorter survival times of patients (P = .01). Knockdown of SLC25A22 in KRAS mutant CRC cells reduced their proliferation, migration, and invasion in vitro, and tumor formation and metastasis in mice, compared with cells without SLC25A22 knockdown. Knockdown of SLC25A22 reduced aspartate biosynthesis, leading to apoptosis, decreased cell proliferation in KRAS mutant CRC cells. Incubation of KRAS mutant CRC cells with knockdown of SLC25A22 with aspartate increased proliferation and reduced apoptosis, which required GOT1, indicating that oxaloacetate is required for cell survival. Decreased levels of oxaloacetate in cells with knockdown of SLC25A22 reduced regeneration of oxidized nicotinamide adenine dinucleotide and reduced nicotinamide adenine dinucleotide phosphate. Reduced oxidized nicotinamide adenine dinucleotide inhibited glycolysis and decreased levels of adenosine triphosphate, which inactivated mitogen-activated protein kinase kinase and extracellular signal-regulated kinase signaling via activation of AMP-activated protein kinase. An increased ratio of oxidized nicotinamide adenine dinucleotide phosphate to reduced nicotinamide adenine dinucleotide phosphate induced oxidative stress and glutathione oxidation, which suppressed cell proliferation. Asparagine synthetase mediated synthesis of asparagine from aspartate to promote cell migration.
  
  
  
  SLC25A22 promotes proliferation and migration of CRC cells with mutations KRAS, and formation and metastasis of CRC xenograft tumors in mice. Patients with colorectal tumors that express increased levels of SLC25A22 have shorter survival times than patients whose tumors have lower levels. SLC25A22 induces intracellular synthesis of aspartate, activation of mitogen-activated protein kinase kinase and extracellular signal-regulated kinase signaling and reduces oxidative stress.
authors.affiliation: Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong, China. Electronic address: chichunwong@cuhk.edu.hk.
authors.forename: Chi Chun
authors.initials: CC
authors.lastname: Wong
authors.affiliation: Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong, China; Department of Gastroenterology, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Zhejiang, China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Qian
authors.affiliation: State Key Laboratory of Environmental and Biological Analysis, Department of Chemistry, Hong Kong Baptist University, Hong Kong, China.
authors.forename: Xiaona
authors.initials: X
authors.lastname: Li
authors.affiliation: Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Jiaying
authors.initials: J
authors.lastname: Xu
authors.affiliation: Department of Anatomical and Cellular Pathology, State Key Laboratory of Oncology in South China, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Kang
authors.affiliation: Department of Anatomical and Cellular Pathology, State Key Laboratory of Oncology in South China, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Joanna H
authors.initials: JH
authors.lastname: Tong
authors.affiliation: Department of Anatomical and Cellular Pathology, State Key Laboratory of Oncology in South China, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Ka-Fai
authors.initials: KF
authors.lastname: To
authors.affiliation: Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Ye
authors.initials: Y
authors.lastname: Jin
authors.affiliation: Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Weilin
authors.initials: W
authors.lastname: Li
authors.affiliation: Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Huarong
authors.initials: H
authors.lastname: Chen
authors.affiliation: Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Minnie Y Y
authors.initials: MY
authors.lastname: Go
authors.affiliation: State Key Laboratory for Quality Research in Chinese Medicines, Macau University of Science and Technology, Macau, China.
authors.forename: Jian-Lin
authors.initials: JL
authors.lastname: Wu
authors.affiliation: College of Engineering, Peking University, Peking, China.
authors.forename: Ka Wing
authors.initials: KW
authors.lastname: Cheng
authors.affiliation: Department of Surgery, The Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Simon S M
authors.initials: SS
authors.lastname: Ng
authors.affiliation: Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Joseph J Y
authors.initials: JJ
authors.lastname: Sung
authors.affiliation: State Key Laboratory of Environmental and Biological Analysis, Department of Chemistry, Hong Kong Baptist University, Hong Kong, China.
authors.forename: Zongwei
authors.initials: Z
authors.lastname: Cai
authors.affiliation: Institute of Digestive Disease and Department of Medicine and Therapeutics, State Key Laboratory of Digestive Disease, Li Ka Shing Institute of Health Sciences, Shenzhen Research Institute, The Chinese University of Hong Kong, Hong Kong, China. Electronic address: junyu@cuhk.edu.hk.
authors.forename: Jun
authors.initials: J
authors.lastname: Yu
mesh_terms: D000236:Adenoma / Q000378:metabolism* / Q000401:mortality / Q000473:pathology; D000328:Adult; D000368:Aged; D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism*; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism*; D002277:Carcinoma / Q000378:metabolism* / Q000401:mortality / Q000473:pathology; D045744:Cell Line, Tumor; D002465:Cell Movement; D049109:Cell Proliferation; D002470:Cell Survival; D003106:Colon / Q000378:metabolism / Q000473:pathology; D015179:Colorectal Neoplasms / Q000378:metabolism* / Q000401:mortality / Q000473:pathology; D018450:Disease Progression; D005260:Female; D006801:Humans; D008297:Male; D051379:Mice; D008819:Mice, Nude; D008875:Middle Aged; D033681:Mitochondrial Membrane Transport Proteins / Q000172:deficiency / Q000378:metabolism*; D009154:Mutation; D009368:Neoplasm Transplantation; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics*
chemical_list: D014408:Biomarkers, Tumor; C117307:KRAS protein, human; D033681:Mitochondrial Membrane Transport Proteins; C499215:SLC25A22 protein, human; D001224:Aspartic Acid; D016283:Proto-Oncogene Proteins p21(ras)
keywords: Colon Cancer; Glutamic-Oxaloacetic Transaminase 1; Glutaminolysis; Solute Carrier Family 25 Member 22