The Raf Kinase Inhibitor Sorafenib Inhibits JAK-STAT Signal Transduction in Human Immune Cells.

Sorafenib is an oral multikinase inhibitor that was originally developed as a Raf kinase inhibitor. We hypothesized that sorafenib would also have inhibitory effects on cytokine signaling pathways in immune cells. PBMCs from normal donors were treated with varying concentrations of sorafenib and stimulated with IFN-α or IL-2. Phosphorylation of STAT1 and STAT5 was measured by flow cytometry and confirmed by immunoblot analysis. Changes in IFN-α- and IL-2-stimulated gene expression were measured by quantitative PCR, and changes in cytokine production were evaluated by ELISA. Cryopreserved PBMCs were obtained from cancer patients before and after receiving 400 mg sorafenib twice daily. Patient PBMCs were thawed, stimulated with IL-2 or IFN-α, and evaluated for phosphorylation of STAT1 and STAT5. Pretreatment of PBMCs with 10 µM sorafenib decreased STAT1 and STAT5 phosphorylation after treatment with IFN-α or IL-2. This inhibitory effect was observed in PBMCs from healthy donors over a range of concentrations of sorafenib (5-20 µM), IL-2 (2-24 nM), and IFN-α (10(1)-10(6) U/ml). This effect was observed in immune cell subsets, including T cells, B cells, NK cells, regulatory T cells, and myeloid-derived suppressor cells. Pretreatment with sorafenib also inhibited PBMC expression of IFN-α- and IL-2-regulated genes and inhibited NK cell production of IFN-γ, RANTES, MIP1-α, and MIG in response to IFN-α stimulation. PBMCs from patients receiving sorafenib therapy showed decreased responsiveness to IL-2 and IFN-α treatment. Sorafenib is a Raf kinase inhibitor that could have off-target effects on cytokine-induced signal transduction in immune effector cells.

Patients with pancreatic adenocarcinoma exhibit elevated levels of myeloid-derived suppressor cells upon progression of disease.

Elevated levels of myeloid-derived suppressor cells (MDSCs) induced by tumor-derived factors are associated with inhibition of immune responses in patients with gastrointestinal malignancies. We hypothesized that pro-MDSC cytokines and levels of MDSC in the peripheral blood would be elevated in pancreatic adenocarcinoma patients with progressive disease. Peripheral blood mononuclear cells (PBMCs) were isolated from 16 pancreatic cancer patients undergoing chemotherapy and phenotyped for MDSC using a five antigen panel (CD33, HLA-DR, CD11b, CD14, CD15). Patients with stable disease had significantly lower MDSC levels in the peripheral blood than those with progressive disease (1.41 ± 1.12 vs. 5.14 ± 4.58 %, p = 0.013, Wilcoxon test). A cutoff of 2.5 % MDSC identified patients with progressive disease. Patients with ECOG performance status ≥2 had a weaker association with increased levels of MDSC. Plasma was obtained from 15 chemonaive patients, 13 patients undergoing chemotherapy and 9 normal donors. Increases in the levels of pro-MDSC cytokines were observed for pancreatic cancer patients versus controls, and the pro-MDSC cytokine IL-6 was increased in those patients undergoing chemotherapy. This study suggests that MDSC in peripheral blood may be a predictive biomarker of chemotherapy failure in pancreatic cancer patients.

A phase I trial of bortezomib and interferon-α-2b in metastatic melanoma.

The possibility that cytokine administration could enhance the antitumor effects of proteasome inhibition was explored. It was found that coadministration of bortezomib and interferon-α (IFN-α) induced synergistic apoptosis in human melanoma cell lines and prolonged survival in a murine model of melanoma. A phase I study was conducted to determine the tolerability and the maximum tolerated dose of bortezomib when administered in combination with IFN-α-2b to patients with metastatic melanoma. Patients were treated on a 5-week cycle. In week 1 of cycle 1, patients received 5 million U/m(2) IFN-α subcutaneously thrice weekly. During weeks 2-4 of cycle 1, bortezomib was administered intravenously weekly along with IFN-α thrice weekly. There was a treatment break during week 5. After cycle 1, bortezomib was administered in combination with IFN-α. Bortezomib was administered in escalating doses (1.0, 1.3, or 1.6 mg/m) to cohorts of 3 patients. Sixteen patients were treated (8 women, 8 men; median age 59 y). Common grade 3 toxicities included fatigue (5), vomiting (3), and diarrhea (3). Grade 4 toxicities included fatigue (3) and lymphopenia (1). The maximum tolerated dose for bortezomib was 1.3 mg/m(2). One patient had a partial response, and 7 had stable disease. Progression-free survival was 2.5 months, and overall survival was 10.3 months. Bortezomib administration did not augment the ability of IFN-α to induce phosphorylation of STAT1 in circulating immune cells; however, it did lead to reduced plasma levels of proangiogenic cytokines. The combination of bortezomib and IFN-α can be safely administered to melanoma patients.