Single-cell profiling of pediatric T-cell acute lymphoblastic leukemia: Impact of PTEN exon 7 mutation on PI3K/Akt and JAK–STAT signaling pathways

Background: The PI3K/Akt/mTOR (PI3K) signaling pathway has a crucial role in T-cell acute lymphoblastic leukemias (T-ALLs). Although loss-of-function of phosphatase and tensin homolog (PTEN) is a common event in pediatric T-ALLs, the exact role of this tumor suppressor in T-ALL development has yet to be defined. Methods: Here, we report an optimized cytometric method for accurate proteomic profiling of T-ALL leukemic blasts at single-cell level. We determined the expression of PI3K and JAK–STAT signaling components in both primary and immortalized T-ALL cells as well as in normal T cells. Results: We observed that PTEN exon 7 mutated T-ALL cells retain a distinct PI3K activation; in particular, these cells show higher pAkt levels and a lower pS6 expression. Interestingly, we demonstrated for the first time that PTEN exon 7 mutated T-ALL are nonresponsive to IL7 in vitro as assessed by lack of pSTAT5 activation, although they do express IL7R. Conclusions: Phosphoflow analysis represents a fast, reliable, and accurate method to study the signaling profile of T-ALL. PTEN exon 7 mutated T-ALL cells are nonresponsive to IL7 in vitro suggesting that they may activate other mechanisms to support their viability and proliferation such as a higher constitutive PI3K/Akt signaling. Further investigations are necessary to elucidate the significance of this peculiar signaling behavior. Our observations should be taken into account in future studies aiming at molecular targeting of PI3K and/or JAK/STAT pathways for pharmacological intervention in T-ALL.