Prolactin-inducible proteins in human breast cancer cells

Published on Tuesday, 06 March 2018


The mechanism of action of prolactin in target cells and the role of prolactin in human breast cancer are poorly understood phenomena.

The present study examines the effect of human prolactin (hPRL) on the synthesis of unique proteins by a human breast cancer cell line, T-47D, in serum-free medium containing bovine serum albumin.

[35S]Methionine-labeled proteins were analysed by sodium dodecyl sulfate-polyacrylamide slab gel electrophoresis and fluorography.

Treatment of cells with hPRL (1-1000 ng/ml) and hydrocortisone (1 microgram/ml) for 36 h or longer resulted in the synthesis and secretion of three proteins having molecular weights of 11,000, 14,000, and 16,000. Neither hPRL nor hydrocortisone alone induced these proteins.

Of several other peptide hormones tested, only human growth hormone, a hormone structurally and functionally similar to hPRL, could replace hPRL in causing protein induction. These three proteins were, therefore, referred to as prolactin-inducible proteins (PIP).

Each of the three PIPs was purified to homogeneity by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and specific antibodies were generated to them in rabbits.

By immunoprecipitation and immunoblotting (Western blot) of proteins secreted by T-47D cells, it was demonstrated that the three PIPs were immunologically identical to one another. In addition, the 16-kDa and 14-kDa proteins (PIP-16 and PIP-14), and not the 11-kDa protein (PIP-11), incorporated [3H]glycosamine. Furthermore, 2-deoxyglucose (2 mM) and tunicamycin (0.5 micrograms/ml), two compounds known to inhibit glycosylation, blocked the production of PIP-16 and PIP-14, with a concomitant increase in the accumulation of PIP-11.

These results indicate PIP-16 and PIP-14 are glycosylated variants of PIP-11.

Finally, in vitro translation of poly(A)+ messenger RNA followed by immunoprecipitation revealed a 12.5-kDa protein, possibly the precursor form of PIPs.

In addition, T-47D cells treated with hPRL plus hydrocortisone contained 10-fold more mRNA for PIPs than control cells, suggesting that the hormones' action is at the level of gene expression.

Our finding represents a first demonstration of prolactin regulation of gene expression in human target cells.

The human breast cancer cells, T-47D, appear to be an excellent model to afford future studies on the molecular action of prolactin and on the possible role of prolactin in human breast cancer.


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See also:

- The Di Bella Method (A Fixed Part - Bromocriptine/Cabergoline);

- Somatostatin in oncology, the overlooked evidences in the "Some additional publications about hGH/GH-GHRH/GHRF/GRF" section.

- The Di Bella Method (A Fixed Part - Somatostatin, Octreotide, LAR analogues and/or derivatives);

- Complete objective response, stable for 5 years, with the Di Bella Method, of multiple-metastatic carcinoma of the breast;

- Evaluation of the safety and efficacy of the first-line treatment with somatostatin combined with melatonin, retinoids, vitamin D3, and low doses of cyclophosphamide in 20 cases of breast cancer: a preliminary report;

- The Di Bella Method (DBM) improved survival, objective response and performance status in a retrospective observational clinical study on 122 cases of breast cancer;

- Complete objective response to biological therapy of plurifocal breast carcinoma.