Effects of High-Dose IFNα2b on Regional Lymph Node Metastases of Human Melanoma: Modulation of STAT5, FOXP3, and IL-17

Purpose: Signal transducer and activator of transcription 5 (STAT5) and STAT3 oppose one another in regulation of the reciprocal development of CD4(+)CD25(+)FOXP3(+) regulatory T cells (Treg) and T helper 17 (Th17). A reduction in STAT3 is associated with up-regulation of Treg, and STAT5 activation promotes T-reg differentiation or function while constraining Th17 generation. The effects of IFN alpha on STAT signaling in relation to tumor tissue T-reg and Th17 have not been documented in humans beyond the observations that IFN alpha 2b down-regulates STAT3. Experimental Design: Following diagnostic biopsy and before definitive surgery, 20 doses of high-dose IFN alpha 2b (HDI) were administered to patients with stage IIIB melanoma who gave written informed consent. Lymph node biopsies, in which both total STAT3 and phosphorylated STAT3 were down-regulated by HDI, were probed with STAT5, FOXP3, CD4, and interleukin 17 (IL-17) with immunohistochemistry and/or immunofluorescence techniques. Results: The percentage of FOXP3(+) lymphocytes determined by immunohistochemistry was up-regulated from 3.06 +/- 0.65% to 9.86 +/- 1.27% (n = 13, P = 0.0002), and this observation was confirmed by immunofluorescence evaluation of CD4(+)FOXP3(+) Tregs. HDI induced STAT5 up-regulation (five cases observed) in melanoma cells and lymphocytes but did not induce the generation of IL-17-expressing lymphocytes. Increased STAT5 expression was associated with increased FOXP3 expression among lymphocytes, and STAT5 was constitutively activated among both melanoma cells and lymphocytes. Conclusion: IFN alpha 2b up-regulates STAT5 and down-regulates STAT3, in conjunction with up-regulation of T-reg and inhibition of IL-17-expressing lymphocytes in melanoma tissues. These findings suggest that the effects of IFN alpha may be potentiated through interference with the response of Tregs and/or STAT5.