Effects of high-dose IFNα.2b on regional lymph node metastases of human melanoma: modulation of STAT5, FOXP3, and IL-17

Abstract

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 Tcells (Treg) and T helper 17 (Th17). Areduction in STAT3 is associated with up-regulation ofTreg, and STAT5 activation promotes T reg differentiation or function while constraining Th17 generation. The effects of IFNα on STAT signaling in relation to tumor tissueT reg and Th17 have not been documented in humans beyond the observations that IFNα2b down-regulates STAT3. Experimental Design: Following diagnostic biopsy and before definitive surgery, 20 doses of high-dose IFNα2b (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: IFNα2b 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 IFNα may be potentiated through interference with the response of Tregs and/or STAT5. © 2008 American Association for Cancer Research.