CRLF2 and acute lymphoblastic leukemia: In xenograft studies with CRLF2-rearragned B-ALL, JQ1 suppressed MYC expression and STAT5 phosphorylation, prolonging survival [32]. Da Costa et al. showed a potent in vitro cytotoxic response to JQ1 in a panel of primary ALL cells. This response was independent of prognostic features but did depend on high expression of MYC and coupled with transcriptional downregulation of various pro-survival pathways. JQ1 decreased c-MYC protein stability and also reduced progression of DNA replication forks.