Journal Article

Prolactin confers resistance against cisplatin in breast cancer cells by activating glutathione-<i>S</i>-transferase

Elizabeth W. LaPensee, Sandy J. Schwemberger, Christopher R. LaPensee, El Mustapha Bahassi, Scott E. Afton and Nira Ben-Jonathan

in Carcinogenesis

Volume 30, issue 8, pages 1298-1304
Published in print August 2009 | ISSN: 0143-3334
Published online May 2009 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/bgp120
Prolactin confers resistance against cisplatin in breast cancer cells by activating glutathione-S-transferase

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Resistance to chemotherapy is a major obstacle for successful treatment of breast cancer patients. Given that prolactin (PRL) acts as an anti-apoptotic/survival factor in the breast, we postulated that it antagonizes cytotoxicity by chemotherapeutic drugs. Treatment of breast cancer cells with PRL caused variable resistance to taxol, vinblastine, doxorubicin and cisplatin. PRL prevented cisplatin-induced G2/M cell cycle arrest and apoptosis. In the presence of PRL, significantly less cisplatin was bound to DNA, as determined by mass spectroscopy, and little DNA damage was seen by γ-H2AX staining. PRL dramatically increased the activity of glutathione-S-transferase (GST), which sequesters cisplatin in the cytoplasm; this increase was abrogated by Jak and mitogen-activated protein kinase inhibitors. PRL upregulated the expression of the GSTμ, but not the π, isozyme. A GST inhibitor abrogated antagonism of cisplatin cytotoxicity by PRL. In conclusion, PRL confers resistance against cisplatin by activating a detoxification enzyme, thereby reducing drug entry into the nucleus. These data provide a rational explanation for the ineffectiveness of cisplatin in breast cancer, which is characterized by high expression of both PRL and its receptor. Suppression of PRL production or blockade of its actions should benefit patients undergoing chemotherapy by allowing for lower drug doses and expanded drug options.

Journal Article.  5181 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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