Activation of Hedgehog signaling associates with early disease progression in chronic lymphocytic leukemia

Targeted sequencing of 103 leukemia-associated genes in leukemia cells from 841 treatment-naive patients with chronic lymphocytic leukemia (CLL) identified 89 (11%) patients have CLL cells with mutations in genes encoding proteins that putatively are involved in Hedgehog (Hh) signaling. Consistent with this, we found that there was a significant association between the presence of these mutations and the expression of GLI1 (Chi square test P + . Patients with GLI1 + CLL cells had a shorter median treatment free survival (TFS) than patients with CLL cells lacking expression of GLI1 independent of IGHV mutation status. We found that GANT61, a small molecule that can inhibit GLI1, was highly cytotoxic for GLI1 + CLL cells relative to that of CLL cells without GLI1. Collectively, this study shows that a large proportion of patients have CLL cells with activated Hh-signaling, which is associated with early disease progression and enhanced sensitivity to inhibition of GLI1.