GZMB and neoplasm: Interestingly, previous studies on Tax, which is another oncoprotein of HTLV-1, showed that transgenic mice expressing Tax under control of the granzyme B promoter developed LGL leukemia, and knocking out of IFN-γ in this strain enhanced the tumor formation [46, 47], suggesting that IFN-γ has the opposite effect on Tax-mediated oncogenesis that it has on HBZ-mediated oncogenesis.