BTK inhibition potentiates anti-PD-L1 treatment in murine melanoma: potential role for MDSC modulation in immunotherapy

AbstractMyeloid-derived suppressor cells (MDSC) have been linked to loss of immune effector cell function through a variety of mechanisms such as the generation of reactive oxygen and nitrogen species and the production of inhibitory cytokines. Our group has shown that signaling through Bruton ’s tyrosine kinase (BTK) is important for MDSC function. Ibrutinib is an orally administered targeted agent that inhibits BTK activation and is currently used for the treatment of B cell malignancies. Using a syngeneic murine model of melanoma, the effect of BTK inhibition with ibrutinib on the th erapeutic response to systemic PD-L1 blockade was studied. BTK was expressed by murine MDSC and their activation was inhibited by ibrutinib. Ibrutinib was not directly cytotoxic to cancer cells in vitro, but it inhibited BTK activation in MDSC and reduced expression of inducible nitric oxide synthas e (NOS2) and production of nitric oxide. Ibrutinib treatments decreased the levels of circulating MDSC in vivo and increased the therapeutic efficacy of anti-PD-L1 antibody treatment. Gene expression profiling showed that ibrutinib decreasedCybb (NOX2) signaling, and increased IL-17 signaling (upregulating downstream targetsMmp9,Ptgs2, andS100a8). These results suggest that further exploration of MDSC inhibition could enhance the immunotherapy of advanced melanoma.Pr écisInhibition of Bruton ’s tyrosine kinase, a key enzyme in myeloid cellular function, improves therapeutic response to an anti...
Source: Cancer Immunology, Immunotherapy - Category: Cancer & Oncology Source Type: research