p66Shc deficiency in the Eμ-TCL1 mouse model of chronic lymphocytic leukemia enhances leukemogenesis by altering the chemokine receptor landscape

The Shc family adaptor p66Shc acts as a negative regulator of proliferative and survival signals triggered by the B Cell Receptor and, by enhancing the production of reactive oxygen species, promotes oxidative stress-dependent apoptosis. Additionally, p66Shc controls the expression and function of chemokine receptors that regulate lymphocyte traffic. Chronic lymphocytic leukemia cells have a p66Shc expression defect which contributes to their extended survival and correlates with poor prognosis. We have analyzed the impact of p66Shc ablation on disease severity and progression in the mouse model of chronic lymphocytic leukemia Eμ-TCL1. We show that Eμ-TCL1/p66Shc-/- mice develop an aggressive disease that has an earlier onset, a higher incidence and leads to earlier death compared to Eμ-TCL1 mice. Eμ-TCL1/p66Shc-/- mice display substantial leukemic cell accumulation in both nodal and extranodal sites. The target organ selectivity correlates with an upregulation of chemokine receptors whose ligands are expressed therein. This also applies to chronic lymphocytic leukemia cells, where chemokine receptor expression and extent of organ infiltration were found to inversely correlate with their p66Shc expression levels. p66Shc expression declined with disease progression in Eμ-TCL1 mice and could be restored by treatment with the Bruton tyrosine kinase inhibitor Ibrutinib. Our results highlight p66Shc deficiency as an important factor in chronic lymphocytic leukemia progression and severity and underscore p66Shc expression as a relevant therapeutic target.