[The skin allograft reduces the incidence of mammary cancer in Co60-irradiated female mice]. / O aloenxerto de pele diminui a frequência do cancro da mama em ratinhos femeas irradiadas com Co60.

Skin allografts were performed in 51 BALB/c female mice by means of an easy technique devised by the authors. The skin for the allografts was taken from C57BL/6 male mice. All the mice were homozygotic. One month after the graft, the female mice were irradiated with 400 cGy of Co60. A control group of 148 female mice belonging to the same strain and with the same age were irradiated in equal conditions. All the animals were observed daily and all the occurrences registered. Dead animals were identified and their necropsies performed. Results were analysed bearing in mind the incidence of malignancy. It was observed that mammary carcinoma was the most frequent solid tumour and that the statistical difference between mice with skin allografts and those of the control group was significant (p = 0.009). In the two groups studied the difference between dead animals without tumour pathology was also statistically significant (p = 0.0011). With regard to other neoplastic pathologies, the results were not statistically different between the two groups of animals. According to the literature, skin allografts have not been used in oncogenic protection. However, in this work, irradiated mice proved to be protected against oncogenic effects of Co60 radiation, when they had previously received a skin graft. In conclusion, the authors emphasize the protection of skin allograft in BALB/c female mice against the oncogenic effect of Co60 radiation in the mice studied, with special significance for mammary carcinoma.

Active immunization against spontaneous tumors in mice.

The incidence of spontaneous tumors was studied in a group of 136 female mice and in another group of 138 females after a sublethal dose of total body irradiation. Of the nonirradiated mice 10.2% developed mammary tumors, and 8% developed lung tumors. Of the irradiated mice 19.5% developed mammary tumors, 21.7% ovary tumors, 24.5% lung tumors, and 7.9% tumors in other organs. A vaccine was prepared for only mammary and ovary tumors through an original technique. The results showed a signficantly lower incidence of tumors in another two groups of mice that were immunized: in 80 nonirradiated vaccinated femal mice, mammary tumors decreased from 10.2% to 2.5%, and in 78 irradiated and vaccinated female mice, mammary tumors decreased from 19.5% to 8.9% and ovary tumors from 21.7% to 3.8%. Lung tumors also decreased in the latter group, suggesting a common factor protecting the immunized mice.

Evidence of oncogenic cofactors in radiation-induced tumors in mice.

Five groups of 587 inbred female mice (WHC) were studied to determine the incidence of tumors as affected by irradiation of different areas. A dose of 400 rad of 60Co was given to all the groups. One group of 166 mice was total body irradiated, another group of 90 mice was irradiated in the upper-third portion of the body, another group of 93 mice was irradiated in the lower two-thirds of the body, and another group of 90 mice was half body irradiated on the right side. As control, a group of 148 nonirradiated mice was followed. The results showed a different incidence of cancer in mice, depending not only on the irradiated areas but also on the shielded ones. This suggested that other factors besides irradiation affect carcinogenesis.