Spontaneous gastric neoplasia in mice of the Br-S strain; incidence and genetic linkage tests.

INTRODUCTION Several differing strains of mice have been pro duced from the NHO stock (7) as a result of sib inbreeding associated with repeated subcutaneous injections of methylcholanthrene. One of these strains, Br-S, is characterized by a high incidence of gastric adenomas or adenocarcinomas. The cvi dence for a hereditary basis of the abnormality is extensive (7—10). However, the etiology is not clear; studies of the gastric pathology (@—4, 6 11) in this strain indicate considerable variability, and the term “lesion― has often been used instead of tumor. Andervont (1) also uses the term “lesion― for the adenomatous condition characteristic of the I strain. The latter is not the same as that of the Br-S strain in two respects : (a) position of origin—at the forestomach junction in strain I mice, but near the pylorus in Br-S; and (b) in heritance—outcross F1 hybrids have the lesion in the case of Br-S, but not in the case of I. The two strains have not yet been crossed with one another. It is the purpose of the present paper to give data on the incidence of gastric neoplasia in an un treated sub-line of the Br-S and a further study of the genetic basis of the condition in an outcross. The term “tumor― will be used, without patho logical certainty, but simply in preference to the more ambiguous “lesion.― Other kinds of tumors (e.g., lung tumors) and pathologicalconditions will be omitted from consideration, since they were infrequent and seem to bear little if any relationship to the main problem.