DMBA-induced intestinal tumors in the Japanese house musk shrew, Suncus murinus (Insectivora).

Intestinal tumors were induced in the Japanese house musk shrew, Suncus murinus (Family: Soricidae, Order: Insectivora) with 7,12-dimethylbenz(a)anthracene (DMBA). The animals were divided into 10 groups: groups 1-4 received gastric intubation of DMBA, groups 5-8 received intraperitoneal (i.p.) injections of this agent, and groups 9 (female) and 10 (male) were untreated and served as controls. Group 1 (females) and group 2 (males) received 10 mg DMBA at 50 days of age; group 3 (females) and group 4 (males) received 2 x 10 mg doses at 50 and 55 days of age; groups 5 and 6 (females) received weekly i.p. administration of 1.25 mg (group 5) and 2.5 mg (group 6) for 4 weeks; and groups 7 and 8 (females) received weekly i.p. administration of 1.25 mg (group 7) and 2.5 mg (group 8) for 8 weeks from 8 weeks of age. Intestinal tumors developed in 3/8 (38%) animals in group 1, 2/6 (33%) in group 2, 5/11 (45%) in group 3, 5/10 (50%) in group 4, 3/6 (50%) in group 5, 2/4 (50%) in group 6, 5/8 (63%) in group 7, and 5/6 (83%) in group 8, but not in untreated shrews up to 50 weeks of age. The induced tumors, which began to appear by 15 weeks after the initial treatment, were randomly distributed throughout the intestine. Histologically, the lesions were classified as adenocarcinomas similar to those found in humans. BrdU immunohistochemistry indicated an extension of the proliferative zone and labeling of many neoplastic cells. Local invasion was seen but no metastasis was observed.(ABSTRACT TRUNCATED AT 250 WORDS)