Investigation of constitutive and cytokine-induced expression of pSTAT 1, 3, and 5 in PBL of breast cancer patients

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3042 Background: Although cytokines mediate their effects by latent transcription factors, STATs, their dysregulation has not been much investigated in peripheral blood lymphocytes (PBL) of breast cancer patients. As alterations in the JAK-STAT pathway contribute to immunosuppression in cancer patients in this study, aside from baseline-level, we investigated the level and cytokine-mediated activation of STAT1, 3, and 5 in healthy controls and breast cancer patients. Methods: PBL (5x106/ml) of breast cancer patients in all four clinical stages, as well as healthy controls, were treated in vitro with culture medium (CM) alone, IFNα (250 IU/ml CM) and IL-2 (500 IU/ml) for 24h at 37°C. Induction of phosphorylated STAT proteins was assessed in cellular lysates by Western blotting using monoclonal anti-STAT1, 3, and 5 antibodies. Treated PBL were also analyzed for IFNγ using an intracellular flow cytometry assay. Results: Our results indicate that untreated PBL of breast cancer patients, compared to healthy controls, express a significantly lower baseline level of pSTAT1, 3, and 5. The induction of pSTAT1 expression by IFNα, similar to the induction of pSTAT3 and pSTAT5 by IL-2, is significant for healthy controls and breast cancer patients, although the effect in patients is significantly below that for healthy controls. Moreover, the induction of pSTAT5 by IL-2 is of a higher magnitude than pSTAT3. PBL of breast cancer patients, compared to healthy controls, have a lower level of IFNγ. The production of IFNγ in PBL is enhanced by IFNα, as well as IL-2, although in breast cancer patients to a much lower level than in healthy controls. Conclusions: These results provide evidence that evaluation of STAT expression in PBL of breast cancer patients could be of diagnostic and therapeutic significance for cytokine-based therapy. No significant financial relationships to disclose.