Abstract
Beyond cancer-cell intrinsic factors, the immune status of the host has a prognostic impact on patients with cancer and influences the effects of conventional chemotherapies. Metastatic melanoma is intrinsically immunogenic, thereby facilitating the search for immune biomarkers of clinical responses to cytotoxic agents. Here, we show that a multi-tyrosine kinase inhibitor, sorafenib, upregulates interleukin (IL)-15Rα in vitro and in vivo in patients with melanoma, and in conjunction with natural killer (NK) group 2D (NKG2D) ligands, contributes to the Th1 polarization and accumulation of peripheral CD4(+)NKG2D(+) T cells. Hence, the increase of blood CD4(+)NKG2D(+) T cells after two cycles of sorafenib (combined with temozolomide) was associated with prolonged survival in a prospective phase I/II trial enrolling 63 patients with metastatic melanoma who did not receive vemurafenib nor immune checkpoint-blocking antibodies. In contrast, in metastatic melanoma patients treated with classical treatment modalities, this CD4(+)NKG2D(+) subset failed to correlate with prognosis. These findings indicate that sorafenib may be used as an "adjuvant" molecule capable of inducing or restoring IL-15Rα/IL-15 in tumors expressing MHC class I-related chain A/B (MICA/B) and on circulating monocytes of responding patients, hereby contributing to the bioactivity of NKG2D(+) Th1 cells.