The Significance of CD319 and CD269 in the Detection of Immunophenotyping and Minimal Residual Disease in Multiple Myeloma Patients

OBJECTIVE To investigate the expression of CD319 and CD269 in plasma cells of patients with multiple myeloma (MM) and the feasibility of using CD319 instead of CD38 as a gating antigen in immunophenotyping and minimal residual disease (MRD) monitoring. METHODS The expression levels of CD319 and CD269 antigens in clonal bone marrow plasma cells of 387 patients were detected by CD38/CD138 gating strategy with 8-color flow cytometry, and the stability of antigens was also analyzed, and the sensitivity and correlation of two different gating strategies employing CD319/CD138 and CD38/CD138 were compared as well. The control group consisted of 53 cases with non-malignant blood disease matched by age and sex. RESULTS Monoclonal plasma cells were detected in 303 of 387 MM patients, among which 277 cases (91.42%) were positive for CD269, and all cases were positive for CD319 (100%). In newly diagnosed MM (NDMM) and recurrent refractory MM (RRMM) patients, the expression levels of CD269 were 97.53% (0-99.92%) and 94.96% (0.22%-99.99%), respectively, while levels of CD319 were 99.90% (87.77%-100%) and 99.78% (63.12%-100%), respectively. The expression levels of CD269 and CD319 in the control group were 97.00% (77.00%-100%) and 100% (89.00%-100%), respectively. There were no significant differences in the expression levels of CD269 and CD319 among NDMM, RRMM and the control group. Patients acquiring therapeutic effects were divided into complete remission (CR) group, very good partial response (VGPR) group and partial response (PR) group. Gating with CD38/CD138, median MRD values were 0.76% (0-1.88%), 0.77% (0-4.96%) and 1.75% (0.09%-10.90%) in the three groups, respectively, while gating with CD319/CD138, median MRD values were 0.57% (0.18%-1.96%), 1.07% (0.12%-4.85%) and 1.77% (0.08%-8.22%), respectively. There was no significant difference in MRD level by the two gating strategies, but a good correlation between the two (r=0.808, P<0.05). In addition, in 4 patients treated by CD38 monoclonal antibody (DARA), the expression level of CD38 was observed to be down-regulated or even negative after treatment. When the MRD level was very low, CD38/CD138 gating resulted in false MRD-, while CD319/CD138 gating resulted in MRD+. CONCLUSION CD319 and CD269 express stably and continuously in plasma cells of MM patients at different disease stages. CD319 can be used as an alternative of CD38 for immunophenotyping and MRD detection, especially for MRD detection after DARA treatment, while CD269 is suitable for detection before BCMA-CAR-T treatment.