Functional RNAi screen targeting cytokine and growth factor receptors reveals oncorequisite role for interleukin-2 gamma receptor in JAK3-mutation-positive leukemia

To understand the role of cytokine and growth factor receptor-mediated signaling in leukemia pathogenesis, we designed a functional RNA interference (RNAi) screen targeting 188 cytokine and growth factor receptors that we found highly expressed in primary leukemia specimens. Using this screen, we identified interleukin-2 gamma receptor (IL2R gamma) as a critical growth determinant for a JAK3A572V mutation-positive acute myeloid leukemia cell line. We observed that knockdown of IL2R. abrogates phosphorylation of JAK3 and downstream signaling molecules, JAK1, STAT5, MAPK and pS6 ribosomal protein. Overexpression of IL2R gamma in murine cells increased the transforming potential of activating JAK3 mutations, whereas absence of IL2R. completely abrogated the clonogenic potential of JAK3A572V, as well as the transforming potential of additional JAK3-activating mutations such as JAK3M511I. In addition, mutation at the IL2R gamma interaction site in the FERM domain of JAK3 (Y100C) completely abrogated JAK3mediated leukemic transformation. Mechanistically, we found IL2R gamma contributes to constitutive JAK3 mutant signaling by increasing JAK3 expression and phosphorylation. Conversely, we found that mutant, but not wild-type JAK3, increased the expression of IL2R gamma, indicating IL2R gamma and JAK3 contribute to constitutive JAK/STAT signaling through their reciprocal regulation. Overall, we demonstrate a novel role for IL2R gamma in potentiating oncogenesis in the setting of JAK3-mutation-positive leukemia. In addition, our study highlights an RNAi-based functional assay that can be used to facilitate the identification of non-kinase cytokine and growth factor receptor targets for inhibiting leukemic cell growth.