Influence of MMP-2 and MMP-9 promoter polymorphisms on gene expression and clinical outcome of non-small cell lung cancer

Abstract

Matrix metalloproteinases (MMP) including MMP-2 and MMP-9 play a major role in tumour invasion by proteolysing the extracellular matrix. Their activation, particularly that of MMP-9, is partly dependent on plasmin that is inhibited by TFPI-2 (tissue factor pathway inhibitor-2), a serine protease inhibitor whose gene expression is decreased in about one-third of non-small cell lung cancers (NSCLC). In addition, MMP-2 and MMP-9 are essential in the development of NSCLC and can be regulated by functional promoter polymorphisms. In this study, the -1306C/T MMP-2, -735C/T MMP-2 and -1562C/T MMP-9 polymorphisms were analysed in 90 NSCLC patients and 90 controls. In addition, the promoter region of the TFPI-2 gene was screened for sequence variations in both groups by DHPLC. A -167G/A polymorphism was identified in 3% of controls whereas none of the 90 patients exhibited this genetic variation in the TFPI-2 promoter region. Moreover, no difference in -1306C/T MMP-2, -735C/T MMP-2 and -1562C/T MMP-9 genotypes was found between cases and controls. However, the homozygous -1562CC MMP-9 genotype was more frequent in patients with squamous cell carcinoma than in controls (p=0.018). When genotype distributions were compared to MMP-2 and MMP-9 gene expression in tumours, no relationship was found with the -1306 MMP-2 and -1562 MMP-9 polymorphisms. In contrast, tumour MMP-2 gene expression was lower in homozygous -735CC patients than in those with CT or TT genotypes. In addition, the survival time was longer in patients with the MMP-2 -735T allele than in those with the CC genotype (p=0.02). The relative risk of death was increased 2.6-fold in -735CC patients (p=0.045; 95% CI=1.0-6.7). The results of this study suggest that the -735C/T MMP-2 polymorphism might be an independent prognostic marker in NSCLC, but this should be confirmed in a larger cohort of patients.