Figure 3.

Mammary tumorigenesis enhanced by carcinogen exposures in Apc^min mice. (A) Increased mammary tumor incidence in Apc^min mice. Carcinogen-naive Apc^min mice typically remained mammary tumor free and only rarely developed solitary mammary tumors after a long latency (3 of 13 mice; 23%). By contrast, all DMBA-exposed (n = 8) and ENU-exposed (n = 6) Apc^min mice developed mammary tumors within 10 weeks of carcinogen exposure. Arrowhead indicates the time of mutagen exposure. (B) Increased tumor multiplicity following carcinogen exposure. Each carcinogen exposure resulted in approximately a 40-fold increase in mammary tumor multiplicity. Error bars represent standard error of the mean. *Denotes P < 0.0001, t-test. (C) Uniform Apc^min mammary tumor histopathology in the presence and absence of carcinogen exposure. All tumors showed hallmark features of adenocarcinoma interspersed with areas of squamous differentiation and keratin pearls. Scale bar, 50 µm.