Intrinsic differences in the transplantability and outgrowth potential of DMBA-induced rat mammary tumors.

Only a small proportion of DMBA-induced rat mammary tumors are transplantable in cleared (gland-free) mammary fat pads. To enhance their transplantability, several host factors were modified: age, parity, hormone levels, and tissue integrity of the fat pad. Our 2 important findings were that (1) there were individual differences between the tumors in their transplantability and potential to proliferate normal and hyperplastic outgrowths, and (2) these differences were determined by their inherent potential and not by their environment. These intrinsic differences among the tumors are consistent with the concept that properties of a given type of tumor are independently variable.