PF4 and plasma cell myeloma: We further investigated the effects of PF4 and the p17-70 fragment on cell proliferation, and showed that both of them expressed in U266, RPMI8226, and LP-1 myeloma cells markedly inhibited the proliferation of human EPCs to 67%, 73%, 58%, and 49%, 56%, 42%, respectively (all P < 0.05; Figure 2B).