Purpose: The precise molecular targets of IFN-α therapy in the context of malignant melanoma are unknown but seem to involve signal transducers and activators of transcription 1 signal transduction within host immune effector cells. We hypothesized that the in vitro transcriptional response of patient peripheral blood mononuclear cells (PBMC) to IFN-α would be similar to the in vivo response to treatment with high-dose IFN-α.

Experimental Design: The gene expression profiles of PBMCs and immune cell subsets treated in vitro with IFN-α were evaluated, as were PBMCs obtained from melanoma patients receiving adjuvant IFN-α.

Results: Twenty-seven genes were up-regulated in PBMCs from normal donors after treatment with IFN-α in vitro for 18 hours (>2-fold, P < 0.001). A subset of these genes (in addition to others) was significantly expressed in IFN-α–treated T cells, natural killer cells, and monocytes. Analysis of gene expression within PBMCs from melanoma patients (n = 13) receiving high-dose IFN-α-2b (20 MU/m² i.v.) revealed significant up-regulation (>2-fold) of 21 genes (P < 0.001). Also, the gene expression profile of in vitro IFN-α–stimulated patient PBMCs was similar to that of PBMCs obtained from the same patient after IFN-α therapy.

Conclusions: This report is the first to describe the transcriptional response of T cells, natural killer cells, and monocytes to IFN-α and characterize the transcriptional profiles of PBMCs from melanoma patients undergoing IFN-α immunotherapy. In addition, it was determined that microarray analysis of patient PBMCs after in vitro stimulation with IFN-α may be a useful predictor of the in vivo response of immune cells to IFN-α immunotherapy.