Induction of matrix metalloproteinase gene transcription by nitric oxide and mechanisms of MMP‐1 gene induction in human melanoma cell lines

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Abstract
Expression of 12 matrix metalloproteinases (MMPs) after exposure of human melanoma cell lines C32TG and Mewo to nitric oxide (NO) was investigated by the reverse transcription‐polymerase chain reaction. Expression of the mRNA of MMP‐1, ‐3, ‐10 and ‐13 in C32TG cells was transcriptionally enhanced in a dose‐dependent manner by exposure to an NO donor, S‐nitroso‐N‐acetyl‐DL‐penicillamine (SNAP) and mRNA expression of MMP‐1 and ‐10 was similarly enhanced in Mewo cells. Exposure of C32TG cells to NO increased the MMP‐1 protein concentration in the culture medium. Testing with the luciferase gene fused to the 1.5 Kbp 5′‐flanking region of the human MMP‐1 gene showed that exposure to NO upregulated MMP‐1 promoter activity in C32TG cells. Endogenous NO production after introduction of inducible NO synthase cDNA also enhanced MMP‐1 promoter activity in C32TG cells. Deletion and mutational analysis identified a critical AP‐1 binding site required for NO regulation of MMP‐1. A neighboring Ets motif from the AP‐1 site in the promoter region acted as an accessory to enhance MMP‐1 expression. Electromobility shift analysis using the AP‐1 binding site showed that NO enhanced the AP‐1 binding ability of nuclear factors in C32TG cells. PD98059, a selective MEK inhibitor and SB202190, a p38 MAPK inhibitor, attenuated the MMP‐1 mRNA expression enhanced by NO. Thus, MMP‐1 was transcriptionally enhanced by NO via MAPK (ERK and p38) pathways. The results of our study suggest that the increased expression of MMPs in response to NO may be associated with tumor progression under inflammation.

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