methylnitronitrosoguanidine and Neoplasm-Regression--Spontaneous

The experiments reported here describe the derivation of an immunogenic melanoma cell line from B16 melanoma by sequential in vitro mutagenization with two chemical mutagens: n-methyl n-nitro n-nitrosoguanine (MNNG) and ethane methyl sulfonate (EMS). Following in vivo screening of over 100 mutant melanoma clones, a single clone was selected for further study. When transplanted to the anterior segment of the mouse eye, the mutant melanoma (D5.1G4) underwent spontaneous resolution in 20% of the immunologically intact hosts. Tumor rejection involved extensive necrosis and culminated in phthisis of the tumor-containing eye. Histologic analysis revealed a prominent mononuclear cellular infiltrate in contrast to the parental progressor B16 melanoma. Immunologic analysis of tumor-bearing hosts showed variable cytotoxic T lymphocyte (CTL) responses but potent delayed-type hypersensitivity (DTH) responses directed against the melanoma cells. Fluorescent activated cell sorter (FACS) analysis of tumor-infiltrating cells from ocular tumors revealed a cellular response consisting mainly of CD8+ CTLs and macrophages. Cultured D5.1G4 melanoma cells demonstrated: 1) enhanced expression of class I major histocompatibility complex (MHC) antigens; 2) increased susceptibility to CTL-mediated killing; and 3) increased susceptibility to tumor necrosis factor (TNF)-mediated cytolysis. Therefore, the intraocular D5.1G4 mutant melanoma model provides important insights into the immunology and immunopathology of intraocular tumor rejection. More intensive analysis of this intraocular melanoma may yield strategies for directing the immune response toward tumor rejection while minimizing damage to normal ocular components.

Topics: Animals; Anterior Eye Segment; Cell Separation; Disease Models, Animal; Eye Neoplasms; Female; Flow Cytometry; Histocompatibility Antigens Class I; Hypersensitivity, Delayed; Killer Cells, Natural; Melanoma, Experimental; Mesylates; Methylnitronitrosoguanidine; Mice; Mice, Inbred C57BL; Mutation; Neoplasm Regression, Spontaneous; Neoplasm Transplantation; T-Lymphocytes, Cytotoxic; T-Lymphocytes, Regulatory; Tumor Cells, Cultured

Polyploid carcinoma in the gastric antrum of a Beagle dog induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was sequentially studied by endoscopy and biopsy. Ulcer appeared on the angulus of the stomach at the 28th week and resulted in ulcer scar at the 42nd week. A new depression with atypical glands arose on the ulcer scar at the 69th week, developed elevated border at the 77th week, and progressed to a polyploid lesion at the 90th week. Well-differentiated adenocarcinoma in situ was found in the polyploid lesion at the 97th week. It gradually grew with nodular change of its surface. However, the carcinoma was ulcerated at the 126th week, became an elevated lesion with central depression at the 138th week, and finally regressed at the 154th week. At necropsy on the 202nd week, no carcinoma was found in the stomach.

Topics: Adenocarcinoma; Animals; Carcinoma in Situ; Dogs; Male; Methylnitronitrosoguanidine; Neoplasm Regression, Spontaneous; Neoplasms, Experimental; Polyps; Stomach Neoplasms