Expression levels and patterns of B-cell maturation antigen in newly diagnosed and relapsed multiple myeloma patients from Indian subcontinent

Abstract

Background

Many novel therapies are being evaluated for the treatment of Multiple myeloma (MM). The cell-surface protein B-cell maturation antigen (BCMA, CD269) has recently emerged as a promising target for CAR-T cell and monoclonal-antibody therapies in MM. However, the knowledge of the BCMA expression-pattern in myeloma patients from the Indian subcontinent is still not available. We present an in-depth study of BCMA expression-pattern on abnormal plasma cells (aPC) in Indian MM patients.

Methods

We studied BM samples from 217 MM patients (211-new and 6-relapsed) with a median age of 56 years (range, 30–78 years & M:F-2.29) and 20 control samples. Expression levels/patterns of CD269 (clone-19f2) were evaluated in aPCs from MM patients and in normal PCs (nPC) from uninvolved staging bone marrow samples (controls) using multicolor flow cytometry (MFC). Expression-level of CD269 was determined as a ratio of mean fluorescent intensity (MFI-R) of CD269 in PCs to that of non-B-lymphocytes and expression-pattern (homogenous/heterogeneous) as coefficient-of-variation of immunofluorescence (CVIF).

Results

Median (range) percentage of CD269-positive abnormal-PCs in total PCs was 71.6% (0.49–99.29%). The MFI-R (median, range) of CD269 was significantly higher in aPCs (4.13, 1.12–26.88) than nPCs (3.33, 1.23–12.87), p < .0001. Median (range) MFI of CD269 at diagnosis and relapse were 2.39 (0.77–9.57) and 2.66 (2.15–3.23) respectively. CD269 levels were similar at diagnosis and relapse, p = .5529.

Conclusions

We demonstrated that BCMA/CD269 is highly expressed in aPCs from a majority of MM patients, both at diagnosis and relapse. Thus, BCMA is a valuable target for therapy for Indian MM patients.