Inhibition of HuR and MMP-9 expression in macrophage-differentiated HL-60 myeloid leukemia cells by green tea polyphenol EGCg.

Matrix metalloproteinase (MMP)-9 expression is linked with myeloid cell differentiation, as well as inflammation and angiogenesis processes related to cancer progression. MMP-9 secretion and macrophage-like HL-60 myeloid leukemia cells differentiation were triggered by the tumor-promoting agent PMA. The chemopreventive effects of green tea catechins epigallocatechin-gallate, catechin-gallate, and epicatechin-gallate, but not those catechins that lack a 3'-galloyl group, inhibited in a time- and dose-dependent manner MMP-9 secretion. The gene and protein expression of MMP-9 and of the mRNA stabilizing factor HuR were also inhibited, while that of the 67 kDa laminin receptor remained unaffected. Specific catechins may help optimize current chemotherapeutic treatment protocols for leukemia.