CD274 and plasma cell myeloma: Existing studies suggested that the activation of the extracellular signal‐regulated kinase (ERK) pathway induces the expression of IFNγ, which subsequently stimulates the STAT1 pathway to promote PD‐L1 expression in myeloma cells.[18] Moreover, it is posited that the JAK or p38–mitogen activated protein kinase (MAPK) pathway also promotes PD‐L1 expression in myeloma cells.[19] The influence of chemotherapeutic drugs on alterations in PD‐L1 expression in myeloma cells, however, remains ambiguous.