Human prolactin and its antagonist, hPRL-G129R, regulate bax and bcl-2 gene expression in human breast cancer cells and transgenic mice.
To gain insight into the molecular mechanisms involved in human prolactin receptor antagonist (hPRL-G129R)-induced apoptosis, we used real-time reverse transcription-polymerase chain reaction to measure bax and bcl-2 gene expression in 11 human breast cancer cell lines following treatment with hPRL and hPRL-G129R. We also measured bax and bcl-2 gene expression in the mammary glands of transgenic mice expressing hPRL or hPRL-G129R. A time-course study of hPRL and antagonist treatment in T-47D cells indicated changing bax/bcl-2 mRNA ratios beginning at 24 h. We found that bax/bcl-2 mRNA ratios were significantly elevated in seven of the 11 hPRL-G129R-treated cell lines, as well as in the hPRL-G129R transgenic mice. To confirm these results, Bax and Bcl-2 proteins were analysed by Western blot methods in mammary gland tissue homogenates of transgenic mice. Bax/Bcl-2 ratios were highest in the 6-month group of hPRL-G129R transgenics, and lowest in the 6-month group of hPRL transgenics. We expanded our findings by examining the release of a downstream Bax-induced protein, cytochrome c, a hallmark protein of apoptosis, in transgenic mice. Again, cytochrome c levels were highest in the 6-month hPRL-G129R transgenic group. Thus, hPRL-G129R-induced breast cancer cell and/or mammary gland apoptosis is mediated, at least in part, through the regulation of Bax and Bcl-2 gene expression.
Peirce
Susan K
SK
Department of Genetics and Biochemistry, Clemson University, Clemson, SC 29630, USA.
Chen
Wen Y
WY
D000818:Animals; D017209:Apoptosis; D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D008321:Mammary Glands, Animal / Q000166:cytology; D051379:Mice; D008822:Mice, Transgenic; D016297:Mutagenesis, Site-Directed; D011388:Prolactin / Q000235:genetics* / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics*; D011994:Recombinant Proteins / Q000378:metabolism; D014407:Tumor Cells, Cultured; D051028:bcl-2-Associated X Protein
C494826:BAX protein, human; C494827:Bax protein, mouse; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011994:Recombinant Proteins; D051028:bcl-2-Associated X Protein; D011388:Prolactin