Aggressive FLC Escape in a Patient with IgD Myeloma

Characterization and use of the novel human multiple myeloma cell line MC-B11/14 to study biological consequences of CRISPR-mediated loss of immunoglobulin A heavy chain

The genetic abnormalities underlying multiple myeloma (MM) are notoriously complex and intraclonal heterogeneity is a common disease feature. In the current study, we describe the establishment of a monoclonal immunoglobulin A (IgA) kappa (κ) MM cell line designated MC-B11/14. Cytogenetic and fluorescence in situ hybridization analyses of the original and relapse patient samples revealed that the MM clone was nonhyperdiploid and possessed an 11;14 chromosomal translocation. The MC-B11/14 cell line, established from the relapse sample, is tetraploid and houses the t(11;14) abnormality. Given our long-standing interest in Ig function and secretion, we next used CRISPR technology to knock out IgA heavy-chain expression in the MC-B11/14 cells to assess the biological consequences of converting this cell line to one only expressing κ light chains. As expected, secretion of intact IgA was undetectable from MC-B11/14^IgA- cells. Sensitivity to pomalidomide treatment was similar between the MC-B11/14^WT and MC-B11/14^IgA- cells; however, MC-B11/14^IgA- cells were found to be significantly more resistant to bortezomib treatment. This study describes the establishment of a new human MM cell line tool with which to study disease biology and the use of CRISPR technology to create a potentially useful model with which to study MM light-chain escape.