Given the prognostic relevance of MCT1 and MCT4 mRNA expression in NDMM, lactate transport activity across the cell membrane in CD138 + MM cells was evaluated using SIRM-based tracing studies in various human myeloma cell lines (HMCLs) such as RPMI-8226, MM1S, and U266. Here, SLC16A1 is linked to plasma cell myeloma.