Targeting FGFR3 in multiple myeloma: inhibition of t(4;14)-positive cells by SU5402 and PD173074.

The t(4;14)(p16.3;q32), associated with 10-20% of cases of multiple myeloma (MM), deregulates the expression of MMSET and FGFR3. To assess the potential of FGFR3 as a drug target, we evaluated the effects of selective inhibitors on MM and control cell lines. SU5402 and PD173074 specifically inhibited the growth of the two t(4;14)-positive MM lines, KMS-11 and OPM-2. Importantly, inhibition was still observed in the presence of IL-6, a growth factor known to play an important role in MM. Both compounds induced a dose-dependent reduction in cell viability and an increase in apoptosis, accompanied by a decrease in extracellular signal-related kinase phosphorylation. In contrast, no inhibition was seen with either compound against t(4;14)-negative cell lines or NCI-H929, a t(4;14)-positive, FGFR3-negative MM cell line. FGFR3 is thus a plausible candidate for targeted therapy in a subset of MM patients.