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Role of Mammary Prolactin in Carcinogenesis

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Final rept. 15 Sep 94-14 Sep 98

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This four year research program focused on the role of prolactin PRL in breast cancer and its interactions with estrogens. The first objective investigated PRL as a local mitogen in carcinogen-induced rat mammary tumors. Both PRL mRNA and immunoreactive PRL were detected in normal mammary glands and in mammary tumors. Addition of PRL antisera suppressed proliferation of mammary tumor cells, suggesting that locally produced PRL stimulates mammary tumor cell proliferation. The second objective examined the effects of xenoestrogens on breast cancer and on PRL release. The results indicated that the in vivo action of such compounds may be amplified by activating multiple targets, i.e., by having a direct effect on the breast and an indirect effect via increased PRL release. The third objective examined the presence of PRL in human breast tissue and the generation of a cleaved fragment of PRL that acts as an angiostatic factor. Immunoreactive PRL, but not mRNA transcripts, were present in normal breast tissue and carcinomas. PRL appears to be cleaved by thrombin, a proteolytic enzyme that is essential for endothelial cell biology. Additional research will undoubtedly uncover the full spectrum of PRL actions.

Subject Categories:

  • Biochemistry
  • Anatomy and Physiology
  • Medicine and Medical Research

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