Apoptosis in Mammary Gland Involution: Isolation and Characterization of Apoptosis-Specific Genes
The massive cell death of secretory epithelium in the mammary gland following each cycle of pregnancy/lactation offers an especially convenient model for studies on the biochemistry of programmed cell death. Programmed cell death in the mammary gland takes the form of an apoptosis (Walker et al., 1989; Strange et al., 1992). Few examples of in vivo apoptosis occur so synchronously, involve such a large cell mass, or are so approachable for study. At the same time apoptosis in the mammary gland is important not merely for academic reasons. Nullparity is a positive risk factor for women, while pregnancy and lactation correlate with a lowered probability of developing mammary carcinoma (Yoo et al., 1992; Yang et al,1993). One can speculate that in the course of the mammary involution which follows on pregnancy/lactation, the apoptotic death of premalignant cells, cells bearing initial mutations conferring an elevated potential for neoplasia, is a desirable, but unspecific side-effect of the massive restructuring of the gland. The suggestion that genes like bcl-2 which interfere with apoptotic cell death can act as oncogenes because they tilt the balance normally existing between cell proliferation and death (Raff, 1992), lends credence to this speculation. Furthermore, when tumors develop and the oncologist resorts to DNA damaging radiation or chemotherapy, again it is the death of tumor cells by apoptosis which can free the patient of disease.
KeywordsMammary Gland Programme Cell Death Ventral Prostate Secretory Epithelium Leucine Zipper Protein
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