FGFR3 and B-cell chronic lymphocytic leukemia: To interrogate if AXL and FGFR3 are also regulated, at least in part, by HSP90, expression of both the RTKs was examined in CLL cells treated with AUY922 or transduced with a HSP90-targeted shRNA. Western blot analyses find a significant reduction of FGFR3 expression but not AXL (Figure 4E) upon pharmacologic inhibition (upper panel; P1, P4, P5) or shRNA-mediated partial depletion (lower panel; P16 – P18) of HSP90 in CLL cells.