title: [Correlation of antitumor effect of recombinant sea snake basic phospholipase A2 to its enzymatic activity].
abstract: OBJECTIVE
  Snake venom phospolipase A2 (PLA(2)), a large family of homologous (14 ku) soluble proteins, exerts diverse pharmacologic activities as well as enzymatic activities. So far, the structure and function of terrestrial snake PLA(2), especially the relationship of its enzymatic and pharmacologic activities have been studied extensively, but the investigation of sea snake PLA(2) are limited. This study was to investigate the in vitro and in vivo antitumor effects of recombinant sea snake basic PLA(2) (rSSBPLA(2)) and its mutants rN48 and rK4 from sea snake Lapemis hardwickii venom, and to explore the influence of 2 residues related with the enzymatic activity on the antitumor effects.
  
  
  METHODS
  Site-directed mutagenesis of the 2 conserved residues related with enzymatic activity (His48 mutated to Asn and Asp49 mutated to Lys) was performed. The inhibitory effects of rSSBPLA(2), rN48 and rK49 on proliferation of human myeloid leukemia cell line HL-60, human neuroblastoma cell line SK-N-SH, human gastric cancer cell line MGC-803, and human liver cancer cell line HepG2 were assessed by MTT assay. Their antitumor effects on sarcoma cell line S180 xenograft and EAC ascites cancer model in mice were detected.
  
  
  RESULTS
  The relative enzymatic activities of rN48 and rK49 were 0 and 5% of that of rSSBPLA(2). The 50% inhibitory concentration (IC(50)) of rSSBPLA(2) for HL60, SK-N-SH, and MGC-803 cells were (45.28+/-0.09) microg/ml, (57.07+/-0.12) microg/ml, and (69.34+/-0.35) microg/ml, respectively, but it had no inhibitory effect on proliferation of HepG2 cells. rSSBPLA(2) obviously inhibited growth of S180 xenograft in miceû the inhibitory rates were 50.8%, 43.2%, 38.2%, and 55.5%, respectively, under the dose of 2 mg/kg (qd x 10), 2 mg/kg (q2d x 5), 4 mg/kg (qd x 1) and 4 mg/kg (q5d x 2). The inhibitory rate of EAC model was 33.5% under the dose of 4 mg/kg (q5d x 2). The inhibitory rates were significantly higher in test groups than in control groups (P<0.01). rN48 and rK49 had no inhibitory effect on proliferation of the 4 tumor cell lines and on growth of the xenograft tumors.
  
  
  CONCLUSIONS
  The antitumor effect of rSSBPLA(2) may be closely related with its enzymatic activity.
authors.affiliation: State Key Laboratory of Oncology in Southern China, Guangzhou, Guangdong 510060, P. R. China.
authors.forename: Yong-Ju
authors.initials: YJ
authors.lastname: Liang
authors.forename: Xiao-Ping
authors.initials: XP
authors.lastname: Yang
authors.forename: Jian-Wen
authors.initials: JW
authors.lastname: Wei
authors.forename: Li-Wu
authors.initials: LW
authors.lastname: Fu
authors.forename: Xiao-Yu
authors.initials: XY
authors.lastname: Jiang
authors.forename: Shang-Wu
authors.initials: SW
authors.lastname: Chen
authors.forename: Wen-Li
authors.initials: WL
authors.lastname: Yang
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000378:metabolism / Q000494:pharmacology; D002286:Carcinoma, Ehrlich Tumor / Q000473:pathology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004546:Elapid Venoms / Q000737:chemistry; D017815:Elapidae; D005260:Female; D018922:HL-60 Cells; D006801:Humans; D008297:Male; D051379:Mice; D016297:Mutagenesis, Site-Directed; D009368:Neoplasm Transplantation; D010741:Phospholipases A / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology*; D054467:Phospholipases A2; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology; D012510:Sarcoma 180 / Q000473:pathology*
chemical_list: D000970:Antineoplastic Agents; D004546:Elapid Venoms; D011994:Recombinant Proteins; D010741:Phospholipases A; D054467:Phospholipases A2