Detection for therapeutic targets specifically expressed in myeloma side population cells

: ATP binding membrane transporter such as multi drug resistant protein (MDR1) and breast cancer resistance protein (BCRP) are highly activated in side population (SP) of various normal organs. It has been demonstrated that various primary as well as cancer cell lines also possess SP. Since SP cells have been also known as the cancer initiating cell rich population in various cancers, the population might play a crucial role in the pathogenesis of multiple myeloma. Recent our works demonstrated that G2/M (e.g. CCNB1, CDC2), centrosome (e.g.AURKB, CENP), polycomb (e.g. EPC1, EZH2) and proteasome (e.g. UBE3C, PSMA5) related genes were upregulated in the SP of myeloma cell lines and CD138-positive primary samples. Although myeloma has been known as incurable disease, discovery of new agents such as immunomodulatory drugs (lenalidomide) and proteasome inhibitor (bortezomib) provide improvement of prognosis of the tumor entity. These drugs might be effective to downregulate aforementioned aberrantly upregulated gene products in myeloma SP. Here we show some evidences of use of these drugs for targeting myeloma-SP cells.