Angiogenic responses elicited from chorioallantoic membrane vessels by neoplastic, preneoplastic, and normal mammary tissues from GR mice

Neoplastic tumors are able to elicit the ingrowth of new capillaries, a process known as angiogenesis. The chorioallantoic membrane (CAM) of chicken embryos was used in an assay for this response, and normal mammary glands and various mammary growths from GR mice, including plaques, hyperplasic alveolar nodules, and hormone-dependent and hormone-independent tumors were tested. Fifteen percent of the male mammary glands tested were positive, as were 28% of the resting female mammary glands. Fifty percent of the plaques and 63% of the hyperplastic alveolar nodules tested induced neovascularization. Eighty percent of the hormone-dependent tumors and 97% of the hormone-independent tumors tested elicited angiogenesis. A fine-structural study revealed that capillaries invaded to within less than 0.5 microns of the tumor cells, but no penetration of tumor cells through the basal lamina was observed. Positive responses were directly correlated with the neoplastic potential of the tissues tested, indicating that angiogenesis can predict mammary gland growths most likely to become malignant.