PSMA3 and plasma cell myeloma: In MSCs, PSMA3, which encodes proteasome 20S subunit α3 and lncPSMA3 antisense mRNA (lncPSMA3-antisense (AS)1)—which arises from the antisense strand of PSMA3—can be packed into exosomes and transferred to myeloma cells to render cells resistance to PIs in myeloma cells [22].