NOS2 and neoplasm: Furthermore, ibrutinib treatment significantly enhanced iNOS (Fig. 6b) and diminished Arginase1 (Fig. 6c) expression in the tumour, which is perhaps not surprising because ibrutinib is known to induce TH1 selective pressure on T lymphocytes resulting in the production of higher IFN-γ and inducible nitric oxide synthase (iNOS).1 Taken together, these results indicate that ibrutinib enhances T cell proliferation and TH1 effector response.