title: Study on the mechanism of immunopotentiating antitumor effect of 6-MPG, a water-soluble derivative of 6-mercaptopurine.
abstract: We investigated possible mechanisms of the antitumor action of gamma-(9H-purine-6-yl) thiomethyl L-glutamate (6-MPG), a water-soluble derivative of 6-MP. In the double grafted tumor system, BALB/c mice were inoculated intradermally with 10(6) cells of MethA fibrosarcoma at the right inguinal region on day 0 (the primary tumor) and later with 3 x 10(6) cells at the left on day 10 (the secondary tumor). Intraperitoneal administration of 6-MPG at a dose of 100 mg/kg/day from day 3 through 7 completely prevented growth of the secondary tumor. 6-MPG showed no effect on growth of colon 26 adenocarcinoma cells inoculated in place of the secondary MethA cells (antigen specificity). 6-MPG did not inhibit the secondary MethA growth in the BALB/c (nu/nu) mouse. The inhibitory effect of 6-MPG on the secondary tumor growth was diminished by prior treatment of the primed animals with cyclosporin A and anti-Thy antibody. Spleen cells from the tumor-bearing mice treated with 6-MPG showed a tumor-neutralizing activity (Winn assay). Treatment of the spleen cells with anti-CD8 antibody plus complement diminished the tumor-neutralizing effect but that with anti-CD4 antibody plus complement did not, indicating that CD8-positive cells are responsible for potentiation of the tumor immunity. These results suggest that the antitumor effect of 6-MPG against the secondary tumor is elicited by augmenting tumor specific T-cell production.
authors.affiliation: Research Laboratories, Tanabe Seiyaku Co. Ltd., Saitama, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Kashida
authors.forename: N
authors.initials: N
authors.lastname: Narasaki
authors.forename: A
authors.initials: A
authors.lastname: Sakai
authors.forename: K
authors.initials: K
authors.lastname: Tsujihara
authors.forename: K
authors.initials: K
authors.lastname: Tsuzurahara
authors.forename: K
authors.initials: K
authors.lastname: Naito
authors.forename: S
authors.initials: S
authors.lastname: Takeyama
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy; D000276:Adjuvants, Immunologic / Q000494:pharmacology*; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy; D016572:Cyclosporine / Q000494:pharmacology; D004347:Drug Interactions; D005354:Fibrosarcoma / Q000188:drug therapy / Q000276:immunology; D007166:Immunosuppressive Agents / Q000494:pharmacology; D008297:Male; D015122:Mercaptopurine / Q000031:analogs & derivatives* / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D010641:Phenotype; D012995:Solubility; D013154:Spleen / Q000166:cytology / Q000187:drug effects / Q000276:immunology; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology; D014867:Water
chemical_list: C108537:(9H-purin-6-yl)thiomethyl glutamate; D000276:Adjuvants, Immunologic; D000970:Antineoplastic Agents; D007166:Immunosuppressive Agents; D014867:Water; D016572:Cyclosporine; D015122:Mercaptopurine