Expression analysis of two SLAM family receptors, SLAMF2 and SLAMF7, in patients with multiple myeloma.

Monoclonal antibodies against surface antigens on MM cells, such as anti-SLAMF7 and anti-CD38 antibodies, represent an attractive therapeutic modality for the eradication of multiple myeloma (MM) cells. However, further exploration of target molecules is urgently needed for the development of more effective therapies. In the present study, we studied the expression of CD48 in a total of 74 primary MM samples derived from patients to evaluate SLAMF2 (CD48) as a candidate in mAb therapy for MM. Of 74 samples, 39 were subjected to SLAMF7 analysis. Most of the MM cells, defined as CD38 and CD138 double-positive cells, showed strong expression of CD48 or SLAMF7 independent of disease stage or treatment history. In these 39 samples, most MM cells showed expression of both SLAMF7 and CD48; however, several samples showed expression of either only CD48 or only SLAMF7, including seven cases that were only highly positive for SLAMF7, and five that were only highly positive for CD48. Our study demonstrates that the immune receptor CD48 is overexpressed on MM cells together with SLAMF7, and that CD48 may be considered as an alternative target for treatment of MM in cases showing weak expression of SLAMF7.