Matrix metalloproteinase-1 (MMP-1) Promoter polymorphisms are well linked with lower stomach tumor formation in eastern Indian population

Abstract

Expression of matrix metalloproteinase-1 (MMP-1), an interstitial collagenase, plays a major role in cellular invasion during development of gastric cancer, a leading cause of death worldwide. A single-nucleotide polymorphism (SNP) -1607 1G/2G site of the MMP-1 gene promoter has been reported to alter transcription level. While the importance's of other SNPs in the MMP-1 promoter have not yet been studied in gastric cancer, our aim was to investigate MMP-1 gene promoter polymorphisms and gastric cancer susceptibility in eastern Indian population. A total of 145 gastric cancer patients and 145 healthy controls were genotyped for MMP-1 -1607 1G/2G (rs1799750) by PCR-restriction fragment length polymorphism (RFLP), while MMP-1 -519 A/G (rs1144393), MMP-1 -422 T/A (rs475007), MMP-1 -340 T/C (rs514921) and MMP-1 -320 T/C (rs494379) were genotyped by DNA sequencing. A positive association was found with MMP-1 -422 T/A SNP that showed significant risk for regional lymph node metastasis (P = 0.021, Odd's ratio (OR) = 3.044, Confidence intervals (CI) = 1.187-7.807). In addition, we found a significant association with lower stomach tumor formation among gastric cancer patients for three adjacent polymorphisms near the transcriptional start sites of [MMP-1 -422 T/A (P = 0.043, OR = 2.182, CI = 1.03-4.643), MMP-1 -340 T/C (P = 0.075, OR = 1.97, CI = 0.94-4.158) and MMP-1 -320 T/C (P = 0.034, OR = 2.224, CI = 1.064-40731)]. MMP-1 level in patients' serum was correlated with MMP-1 promoter haplotypes conferring these three SNPs to evaluate the functional importance of these polymorphisms in lower stomach tumor formation and significant correlation was observed. Furthermore, MMP-1 -519 A/G polymorphism displayed poor cellular differentiation (P = 0.024, OR = 3.8, CI = 1.69-8.56) attributing a higher risk of cancer progression. In conclusion, MMP-1 proximal promoter SNPs are associated with the risk of lower stomach tumor formation and node metastasis in eastern Indian population.

Figure 1. Gene map and LD structure of MMP-1 promoter locus.

(A) SNP positions in the gene map of MMP-1 gene (prepared using NCBI sequence viewer) in human chromosome 11. Different color schemes are assigned to show each SNP position in the map by marking the map according to the reference assembly (HuRef NCBI Build 36.7) position of the SNP in the chromosome. The number in different colored boxes indicates the SNP alias number used in our study. (B) LD structure of MMP-1 promoter locus SNPs. Linkage disequilibrium plots follows the GOLD heat map Haploview 4.2 color scheme. Block definition is based on the method of Gabriel et al. . Haploview plot of MMP-1 SNPs genotyped in 290 subjects (145 patients and 145 controls common for all SNPs studied) in our study. Numbers in squares are pair wise D' values between SNPs.

Figure 2. Haplotype effect on serum MMP-1 concentration.

Serum MMP-1 level in patients with lower stomach cancer with risk haplotypes (n = 54), and upper stomach cancer with non risk haplotypes (n = 15) were compared by ELISA. Results showed patients with lower stomach cancer exhibit a 1.43 fold higher MMP-1 level than in upper stomach cancer patients (p<0.05 by t-test) (box whisker diagram).