PRF1 and chronic myelogenous leukemia, BCR-ABL1 positive: Given that N-BPs stimulate γδT proliferation and IFN-γ production through enhancement of IPP release [8, 10–12], we next explored whether TKIs-treated CML cells could induce expression of cytotoxic cytokines, namely TNF-α and IFN-γ, and release of perforin by γδT cells.