Journal Article

Stat5 in breast cancer: potential oncogenic activity coincides with positive prognosis for the disease

Itamar Barash

in Carcinogenesis

Volume 33, issue 12, pages 2320-2325
Published in print December 2012 | ISSN: 0143-3334
Published online December 2012 | e-ISSN: 1460-2180 | DOI:
Stat5 in breast cancer: potential oncogenic activity coincides with positive prognosis for the disease

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  • Clinical Cytogenetics and Molecular Genetics


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Nuclear localization of signal transducer and activator of transcription (Stat) 5 marks good prognosis in estrogen receptor/progesterone receptor-positive breast tumors. This positive characteristic is counteracted by studies in laboratory animals demonstrating that deregulated Stat5 activity may convert proper mammary development into a latent oncogenic process. Tumorigenesis is initiated during the parity cycles, most probably during pregnancy, when the activated Stat5 antagonizes or manipulates parity’s protective mechanisms. For example, it can alter the differentiation/proliferation balance, induce growth hormone signaling, cause specific alteration in chromatin structure, inhibit tumor-suppressor activity and induce DNA damage that counteracts the enhanced DNA-damage response exerted by parity. Palpable tumors develop after a latent period from individual cells. This happens in the estropausal period in transgenic mice maintaining deregulated Stat5 activity in the mammary gland, or during involution, months after transplantation of transfected cells with constitutively active Stat5. Candidate vulnerable cells are those which maintain high nuclear Stat5 activity. Due to the hazardous outcome of deregulated Stat5 activity in these cells, such as induced DNA damage or high cyclin D1 activity, the gland is prone to transformation. The developing tumors are mostly adenocarcinomas or their subtypes. They are estrogen receptor–positive and maintain a specific Stat5 gene signature that allows tracking their inducer. From a clinical point of view, deregulated Stat5 activity represents a genuine risk factor for breast cancer. Monitoring Stat5 activity during vulnerable periods and developing specific tools for its suppression in breast epithelial cells could potentially limit new incidence of the disease.

Journal Article.  5731 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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