Green tea polyphenol (–)‐epigallocatechin‐3‐O‐gallate increases cGMP to inhibit tumor growth by activating apoptotic signaling via the Akt/eNOS/NO/cGMP/PKCδ pathway in multiple myeloma, gastric, pancreatic, and prostate cancers 25. Here, PRKCD is linked to plasma cell myeloma.