Multiple myeloma is among the most common leukemias in elder patients. Genetic abnormalities causing expression of a protein called FGFR3 or mutant Ras proteins have been found in about 15% or 40% of multiple myeloma patients, respectively. We have found a protein called p90RSK as a critical "partner protein" that may be activated ("turned-on") by FGFR3 or Ras in myeloma cells. In this proposal, we will test whether p90RSK is a "good" target in myeloma treatment. We will test the ability of a drug called fmk, which is a highly specific inhibitor of p90RSK, to kill myeloma cells in cell assays and mouse disease models.