Journal of cellular biochemistry
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Lactoferrin inhibits cell proliferation and suppresses tumor growth in vivo. However, the molecular mechanisms underlying these effects remain unknown. In this in vitro study, we demonstrate that treatment of breast carcinoma cells MDA-MB-231 with human lactoferrin induces growth arrest at the G1 to S transition of the cell cycle. ⋯ Additional experiments with synchronized cells by serum depletion confirm the anti-proliferative activity of human lactoferrin. These effects of lactoferrin occur through a p53-independent mechanism both in MDA-MB-231 cells and other epithelial cell lines such as HBL-100, MCF-7, and HT-29. These findings demonstrate that lactoferrin induces growth arrest by modulating the expression and the activity of key G1 regulatory proteins.
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Using the combination of a cDNA library prepared from membrane glucocorticoid (mGR)-enriched S-49 cells and a mouse leukocyte genomic library, we have cloned a 7.3 kb full-length glucocorticoid receptor 1A cDNA. Primer extension, 5'RACE, and long distance PCR identified the transcription start site as being located at 1026 bp from the ATG codon. The first 1,013 nucleotides (nts) of the full length sequence constitute 5' UTR sequence (exon 1), the next 2349 bp, the coding region, and the last 3,907 bp, the 3'UTR. ⋯ Western blot analysis compared the molecular weight of in vitro translation products from the cloned 1A cDNA with partially purified cellular mGR. Both preparations contained the novel 150 KD and the 94 KD classical GR peptides, suggesting that transcript 1A encodes both receptor forms. Transfection of mGR-less and glucocorticoid lysis-resistant AtT-20 and HL-60 cells with full-length GR 1A cDNA imparted both mGR expression and glucocorticoid lysis-sensitivity to these cells.