Induction of cutaneous mast cell tumors by N-methyl-N'-nitro-N-nitrosoguanidine followed by TPA in female mice of 4 out of 5 strains tested.

Appreciable yields of cutaneous mast cell tumors were induced in a two-stage skin carcinogenesis protocol comprising N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) initiation followed by 12-O-tetradecanoylphorbol-13-acetate (TPA) promotion in 4 of 5 strains of mice. Only female mice of each of the 5 strains were studied. The incidences of benign and/or malignant lesions differed considerably between strains; 27% in DBA/2, 22% in BDF1, 11% in BALB/c, 10% in CDF1 and 0% in C57BL/6 mice and no mast cell tumors were detected in any of the strains when treated with the initiator alone. First found in a DBA/2 mouse at week 50, most tumors were observed after 100 weeks of promotion, and were usually small in size (less than 2 mm in diameter) and predominantly located within the corium, although they occasionally extended into the subcutaneous tissue. Histologically, the benign mast cell tumors were composed of non-encapsulated, well circumscribed densely packed sheets of discrete cuboidal or rhomboid cells. Metachromatic granules were clearly visible in the cytoplasm by Toluidine Blue staining. Two of the tumors induced in DBA/2 mice were diagnosed as malignant mast cell tumors on the twin bases of cellular atypia and deep infiltration into the muscular layer. The cutaneous mast cell tumors were constantly accompanied by subepidermal mast cell aggregations which were also commonly observed in tumor-free skin of mice receiving the initiation-promotion procedure.

Selection and isolation of a new variant of DBA/2 mastocytoma P 815 X 2.

A tumor model was developed in DBA/2 mice for studying the progression of the mastocytoma P 815 X 2 tumor. Tumor cells obtained from ascites were grown in vitro. The number of cells derived from a single clone was increased by in vitro culture. Cells were then injected either i.v. or i.p. into DBA/2 mice. Large volumes of tumor ascites were observed after i.p. but not i.v. injection. The latter led to tumor growth at multiple sites, especially in the liver. Mastocytoma cells were released from liver tissue and then injected i.p. into other recipients. For cloning of liver invading tumor cells, this procedure was repeated for greater than 20 generations of mice. Tumor infiltration of the liver increased strongly during this period, but ascites volume clearly decreased.

Primary liver tumors in beagle dogs exposed by inhalation to aerosols of plutonium-238 dioxide.

Primary liver tumors developed in Beagle dogs exposed by inhalation to aerosols of 238PuO2. Initial deposition of 238PuO2 in the respiratory tract was followed by translocation of a portion of the 238Pu to the liver and skeleton, which resulted in a large dose commitment and tumor risk to all three tissues. In a population of 144 dogs exposed to 238PuO2, 112 dogs died or were killed 4000 days after 238Pu exposure, 100 dogs had osteosarcoma, and 28 dogs had lung cancers. At increasing times after exposure, however, liver lesions have become more pronounced. Ten primary liver tumors in nine animals were diagnosed in the dogs dying before 4000 days after exposure. An additional five primary liver tumors in three dogs occurred in 9 animals killed after 4000 days after exposure. The majority of these tumors have been fibrosarcomas. The liver tumors were usually not the cause of death, and rarely metastasized. The occurrence of liver tumors in this study indicates that 238Pu is an effective hepatic carcinogen. Liver carcinogenesis is assuming an increasing importance in this study at late times after inhalation exposure. These results suggest that the liver may be an important organ at risk for the development of neoplasia in humans at time periods long after inhalation of 238Pu.

Establishment of four mouse mastocytoma cell lines.

Four mastocytoma cell lines were isolated from four different mouse mastocytoma tumors. The tumors had been induced in mice treated with tetramethylpentadecane (pristane) and infected with Abelson murine leukemia virus. The cell lines have been carried in culture for over a year and can induce tumors when injected into the mouse strain in which the tumor originated. The cells contain histamine, have high affinity IgE receptors and release histamine by IgE, immune complex or ionophore A23187-induced reactions. This histamine release reaction requires Ca2+, is optimal at 37 degrees C, and is blocked by a number of metabolic inhibitors. There is no requirement for phosphatidylserine. Cloned sublines have been obtained which will be useful for Fc epsilon R, Fc gamma R; and histamine release studies.

Tumor-producing activity of dithranol (anthralin) and two of its 10-acyl analogs in the dorsal skin of female NMRI mice.

The tumor-producing activity of local applications of dithranol, 10-propionyl dithranol and butantrone was studied in 420 female white NMRI mice. An initiation with 20 micrograms of 7,12-dimethyl-benz(alpha)anthracene (DMBA) was followed 2 weeks later by three applications per week of the test compounds in 50 microliters of acetone for 50 weeks. Several control groups receiving only acetone or DMBA and test compounds without DMBA were included. Dithranol and 10-propionyl dithranol caused transient, although serious, skin irritation during the first 2 weeks of the treatment. Hyperplasia was a common finding in the same groups at the end of the treatment. Dithranol (3.5 mM) induced 11 papillomas in 8 mice (26.7%) without DMBA and 29 papillomas in 17 mice (56.7%) with DMBA. 10-Propionyl dithranol was tumorigenic as well: 3.5 mM caused 15 papillomas in 11 mice (36.6%) without DMBA and 28 papillomas in 17 mice (56.7%) with DMBA and 1.5 mM with DMBA caused 7 papillomas in 6 mice (20%). In the butantrone groups, there was only one single papilloma with the 1.5 mM concentration plus DMBA. It is concluded that, in contrast to dithranol and 10-propionyl dithranol, butantrone (3.5 mM) is not tumorigenic in the dorsal murine skin.

A study of tobacco carcinogenesis XX: mastocytoma induction in mice by cigarette smoke particulates ("cigarette tar").

A significant incidence of cutaneous mastocytomas was observed in female mice of CAF1/J and ARS-HA (ICR) strains upon long-term application of cigarette smoke condensate suspensions ("tar"). The mastocytomas were not detected in control groups treated with acetone, benzo(a)pyrene (BaP), tetradecanoyl phorbol acetate (TPA), nor in mice treated once with an initiator dose of 75 mg 7, 12-dimethylbenz(a)anthracene (DMBA). The skin mastocytomas were constantly accompanied by diffuse dermal mast cell infiltration (DDMI), which was also seen in the tumor-free skin of the "tar"-treated mice. These results indicate that mastocytomas were induced by agents present in the cigarette smoke condensate. DDMI might be a precursor of mastocytomas.

Specific and nonspecific antitumor immunity. III. Specific T lymphocyte-mediated cytolysis of P815 mastocytoma and SL2 lymphoma by draining lymph node cells from syngeneic tumor-bearing DBA/2J mice.

Tumor-specific cytolytic activity, as measured by the 51Cr release assay, has been demonstrated in the draining lymph node cells from DBA/2 mice bearing the syngeneic P815 mastocytoma or SL2 lymphoma. This lytic activity is mediated by cytolytic T lymphocytes (CTL), since cytotoxicity is eliminated by treatment of the effector cells with anti-Thy 1.2 (theta) serum plus complement but is enhanced or unaffected by anti-Thy 1.2 serum alone, antimouse immunoglobulin plus complement, normal or aggregated mouse immunoglobulin, or removal of adherent cells. The time course of the CTL response has been analyzed and is similar for both P815 and SL2, with a peak around Days 10 to 12 after tumor grafting. Detectable CTL activity then wanes despite continued antigenic stimulation from the growing tumor. The ability of the immunotherapeutic agent Corynebacterium parvum to augment such specific CTL responses is documented as one antitumor pathway by which this agent may act.