Variability in response pattern of DMBA induced mammary tumors of Wistar rats

The incidence and growth pattern of DMBA induced mammary tumors of Wistar rats in altered hormonal conditions induced by endocrine ablation were studied. Elevation of prolactin by pituitary stalk section, removal of primary source of estrogen by bilateral oophorectomy or both were done before administration of DMBA as well as after formation of palpable tumors. The results indicate that while estrogen is essential for the induction of these tumors, elevation of prolactin before administration of DMBA inhibits tumor incidence. From the overall responses (mean tumor volume) in the different groups it is evident that prolactin alone cannot maintain growth of these tumors, estrogen is also essential at least in a large percentage of tumors. The marked intertumor and intratumor differences in the response pattern to altered hormonal situations demonstrate close resemblances of this tumor model to the human breast cancer.