Impact of CD34/CD309 expression in circulating endothelial progenitor cells on prognosis and response to bortezomib therapy in multiple myeloma.

Multiple myeloma (MM) is a prevalent yet incurable hematologic malignancy. Despite the proven efficacy of proteasome inhibitors in treating MM, resistance to Bortezomib-based treatments persists in a subset of patients. This case control study explores the potential of circulating endothelial progenitor cells (EPCs) as biomarkers for predicting response to Proteasome Inhibitor based therapy combined with Dexamethasone in MM patients. This study was conducted on 105 MM patients receiving bortezomib plus dexamethasone therapy and 90 healthy individuals as a control group. Utilizing 8-color multi-parameter flow cytometry, we assessed the levels of circulating EPCs, identified through CD34 FITC and CD309 PE markers at diagnosis and after one treatment cycle (4 weeks). Our findings revealed that patients exhibiting poor response to therapy showed significantly higher CD34/CD309 values than those with a good response (p < 0.001). The delineation of response based on CD34/CD309 expression was established with a cutoff ≤ 0.9 for percentage (yielding 100% sensitivity and 94.1% specificity) and ≤ 12.5 for absolute value (also with 100% sensitivity and 94.1% specificity). These results underscore the potential of EPC population levels, as quantified by CD34/CD309, to serve as a predictive biomarker for immunomodulatory treatment in MM patients undergoing Proteasome Inhibitor and Dexamethasone therapy.