Treatment of myeloma cells with EPO was followed by JAK-2 and ERK-1/2 phosphorylation while knockdown of EPOR expression in the myeloma cell line INA-6 reduced JAK-2 and ERK-1/2 phosphorylation, again demonstrating the specificity of active EPO/EPOR signaling in myeloma cells. This evidence concerns the gene MAPK3 and plasma cell myeloma.