Inhibition of transplanted carcinomas in mice by retinoids but not by vitamin C.

A squamous cell carcinoma (ASB XIII) and a large cell carcinoma (ASB XIV) induced from mouse lung cells by chrysotile asbestos were established in serial transplant in BALB/c mice. New hosts were treated with retinoids by ip injection at 10 mg/kg 5 days/week. Growth inhibition of ASB XIII was 58%-64% (P less than 0.005) after treatments with all-trans retinoic acid, 52% after trimethylmethoxyphenyl analog, ethyl ester, 26% (not significant) after 13-cis retinoic acid. Growth inhibition of ASB XIV was 39% (P less than 0.02) after injections of all-trans retinoic acid, and 33% (P greater than 0.05) after trimethylmethoxyphenyl analog, ethyl ester. After daily oral administration of 10 mg/kg of all-trans retinoic acid in feed, there was 61%-81% inhibition (P less than 0.005) of ASB XIII. Growth of ASB XIII was not significantly inhibited by daily im injections of 200 mg/kg of vitamin C.

Chemotherapeutic trials with hamster mesothelioma 10-24: responses to azacitidine, aziridinylbenzoquinone, cisplatin, and PCNU.

Asbestos-induced peritoneal mesothelioma 10-24 serially transplanted in Syrian golden hamsters was used to test responses to seven drugs as single agents. Compared to saline-treated controls, the average survival time increased 51%-85% with azactitidine, 42%-60% with aziridinylbenzoquinone, 43% with cisplatin, and 35%-45% with PCNU. No cures were achieved. Therapeutic responses were not observed with dactinomycin, dianhydroxyanthracenedione, or DTIC.

An experimental model for treatment of mesothelioma.

A peritoneal mesothelioma was induced by asbestos in a hamster, and was established in serial transfer to new hosts by injection of peritoneal effusion containing tumor cells. Biologically and histopathologically, this tumor is similar to its human counterpart. Three drugs were tested for efficacy using this model. Survival time was used as the only parameter of response and was compared with survival time of controls. Survival time increased 25 to 50% after short regimens of doxorubicin or 5-fluorouracil. Survival time increased up to 308% after long-continued treatments with cyclophosphamide. No cures were achieved.

Health of experimental animals drinking water with and without amosite asbestos and other mineral particles.

In view of diseases associated with inhalation of asbestos fibers, interest attaches to the question of whether risks are presented by ingestion of asbestos or mineralogically related fibrous-shaped particles reported in drinking water supplies. Experimental animals (hamsters) were maintained on filtered drinking water with and without addition of mineral particles. A peritoneal mesothelioma, pulmonary carcinoma and two early squamous cell carcinomas of the forestomach were found in hamsters so exposed to a preparation of amosite asbestos. These tumors could not be specifically attributed to amosite, but they show that hamsters of the strain used were capable of developing tumors of particular interest in this experiment. No deleterious health effects and no tumors related to treatment were found in hamsters exposed to milled taconite ore containing fibrous-shaped particles of cummingtonite/grunerite, mineralogically related to amosite but in shorter lengths more comparable in size to fibers associated with drinking water supplies.

Dimensions of fibres in relation to biological activity.

Intrathoracic tumours were induced in Syrian golden hamsters given intrapleural injections of chrysotile, tremolite or glass fibres; but the carcinogenicity of these materials was reduced or disappeared with reductions in fibre size. After lifetime administration of UICC amosite in drinking-water, a peritoneal mesothelioma, a pulmonary carcinoma and two early squamous-cell carcinomas of the forestomach were found in 4 of 180 hamsters. No tumours related to treatment were found in animals exposed to fibre-shaped particles of cummingtonite/grunerite, mineralogically related to amosite but of shorter length.