title: ASS1 as a novel tumor suppressor gene in myxofibrosarcomas: aberrant loss via epigenetic DNA methylation confers aggressive phenotypes, negative prognostic impact, and therapeutic relevance.
abstract: OBJECTIVE
  The principal goals were to identify and validate targetable metabolic drivers relevant to myxofibrosarcoma pathogenesis using a published transcriptome.
  
  
  METHODS
  As the most significantly downregulated gene regulating amino acid metabolism, argininosuccinate synthetase (ASS1) was selected for further analysis by methylation-specific PCR, pyrosequencing, and immunohistochemistry of myxofibrosarcoma samples. The roles of ASS1 in tumorigenesis and the therapeutic relevance of the arginine-depriving agent pegylated arginine deiminase (ADI-PEG20) were elucidated in ASS1-deficient myxofibrosarcoma cell lines and xenografts with and without stable ASS1 reexpression.
  
  
  RESULTS
  ASS1 promoter hypermethylation was detected in myxofibrosarcoma samples and cell lines and was strongly linked to ASS1 protein deficiency. The latter correlated with increased tumor grade and stage and independently predicted a worse survival. ASS1-deficient cell lines were auxotrophic for arginine and susceptible to ADI-PEG20 treatment, with dose-dependent reductions in cell viability and tumor growth attributable to cell-cycle arrest in the S-phase. ASS1 expression was restored in 2 of 3 ASS1-deficient myxofibrosarcoma cell lines by 5-aza-2'-deoxycytidine, abrogating the inhibitory effect of ADI-PEG20. Conditioned media following ASS1 reexpression attenuated HUVEC tube-forming capability, which was associated with suppression of MMP-9 and an antiangiogenic effect in corresponding myxofibrosarcoma xenografts. In addition to delayed wound closure and fewer invading cells in a Matrigel assay, ASS1 reexpression reduced tumor cell proliferation, induced G1-phase arrest, and downregulated cyclin E with corresponding growth inhibition in soft agar and xenograft assays.
  
  
  CONCLUSIONS
  Our findings highlight ASS1 as a novel tumor suppressor in myxofibrosarcomas, with loss of expression linked to promoter methylation, clinical aggressiveness, and sensitivity to ADI-PEG20.
authors.affiliation: Department of Pathology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan.
authors.forename: Hsuan-Ying
authors.initials: HY
authors.lastname: Huang
authors.forename: Wen-Ren
authors.initials: WR
authors.lastname: Wu
authors.forename: Yu-Hui
authors.initials: YH
authors.lastname: Wang
authors.forename: Jun-Wen
authors.initials: JW
authors.lastname: Wang
authors.forename: Fu-Min
authors.initials: FM
authors.lastname: Fang
authors.forename: Jen-Wei
authors.initials: JW
authors.lastname: Tsai
authors.forename: Shau-Hsuan
authors.initials: SH
authors.lastname: Li
authors.forename: Hsiao-Chin
authors.initials: HC
authors.lastname: Hung
authors.forename: Shih-Chen
authors.initials: SC
authors.lastname: Yu
authors.forename: Jui
authors.initials: J
authors.lastname: Lan
authors.forename: Yow-Ling
authors.initials: YL
authors.lastname: Shiue
authors.forename: Chung-His
authors.initials: CH
authors.lastname: Hsing
authors.forename: Li-Tzong
authors.initials: LT
authors.lastname: Chen
authors.forename: Chien-Feng
authors.initials: CF
authors.lastname: Li
mesh_terms: D000328:Adult; D000368:Aged; D051046:Amino-Acid N-Acetyltransferase / Q000096:biosynthesis; D000818:Animals; D001124:Argininosuccinate Synthase / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000235:genetics; D049109:Cell Proliferation; D002470:Cell Survival / Q000187:drug effects; D016000:Cluster Analysis; D019175:DNA Methylation; D005260:Female; D005354:Fibrosarcoma / Q000188:drug therapy / Q000235:genetics* / Q000401:mortality / Q000473:pathology; D059585:G1 Phase Cell Cycle Checkpoints / Q000235:genetics; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D055785:Gene Knockdown Techniques; D016147:Genes, Tumor Suppressor; D006801:Humans; D006867:Hydrolases / Q000008:administration & dosage / Q000494:pharmacology; D007890:Leiomyosarcoma / Q000188:drug therapy / Q000235:genetics* / Q000401:mortality / Q000473:pathology; D008297:Male; D051379:Mice; D008875:Middle Aged; D060787:Neoplasm Grading; D009361:Neoplasm Invasiveness; D009367:Neoplasm Staging; D009389:Neovascularization, Pathologic / Q000235:genetics; D010641:Phenotype; D011092:Polyethylene Glycols / Q000008:administration & dosage / Q000494:pharmacology; D011379:Prognosis; D023041:Xenograft Model Antitumor Assays
chemical_list: D011092:Polyethylene Glycols; D051046:Amino-Acid N-Acetyltransferase; D006867:Hydrolases; C512527:ADI PEG20; D001124:Argininosuccinate Synthase