Proliferation, apoptotic, and senescence markers in mammary tumors from PyMT/Fet−/− and PyMT/Fet+/+ animals. Mammary tumors (120 days old) from fetuin-A null and qjwild-type PyMT animals were sectioned and processed for immunohistochemical analysis as described in Materials and Methods. The slides were stained for PCNA (proliferation) (A) and cleaved caspase-3 (cas-3, apoptosis) (B). C: The slides were also stained for β-galactosidase activity that was quantified as number of cells positive for β-galactosidase (β-gal) activity per field (*P < 0.004). Original magnification, ×40. +ve, positive.