Genetic Association Of Matrix Metalloproteinases Polymorphisms With Susceptibility To Hepatocellular Carcinoma And Nasopharyngeal Carcinoma In The Chinese Population

Hepatocellular carcinoma (HCC) and nasopharyngeal carcinoma (NPC) are common cancers in the world, which incidence and mortality are particularly higher in China. At present, the difficulty of early diagnosis, high rate of recurrence and metastasis, and the deficiency of directed therapy are the major problem in the treatment of the two cancers. Hence, the research on the pathogenesis of these cancers and the development of new technology on diagnosis and treatment are of great importance. The main risk factors for HCC development include chronic infection with hepatitis B virus (HBV) or hepatitis C virus (HCV), dietary exposure to aflatoxinB1 contaminated foodstuffs and consumption of alcohol; the main risk factors for NPC development include infection with EB virus and exposure to chemical carcinogen. The control of the risk factors may decrease the risk of tumorigenesis. HCC and NPC are multi-factorial cancers, and the notably family-clustered phenomenon in the occurrence indicates the important role of host genetic factors in the development of these cancers. The identification of susceptility genes and the elucidation of the interaction between these genes and other risk factors may provide specific genetic biomarkers and targets for early diagnosis and clinic treatment, which may also be applied in the detection of recurrence and metastasis after operation.Matrix metalloproteinases (MMPs) are a family of enzymes that proteolytically degrade a wide spectrum of extracellular matrix (ECM), and participate in the turnover of ECM. Physiologically, these enzymes play a role in normal tissue remodeling such as embryonic development, tissue morphogenesis, ovulation and wound healing. However, in the development of cancers, beyond the classical role of ECM disruption, MMPs also contributes to the formation of a complex microenvironment that promotes the malignant transformation in early stages of cancer by proteolytic processing of bioactive molecules. The additional functions mediated by MMPs include activation of growth factors, suppression of tumour cell apoptosis, destruction of chemokine gradients developed by host immune response, or release of angiogenic factors. Previous studies have identified the pro-tumorigenic role of MMPs in HCC and NPC development such as cancer-cell growth, angiogenesis, invasion and metastasis. Therefore, MMPs are considered to be excellent biologically candidate susceptibility genes.Functional polymorphisms in MMPs gene are known to influence gene expression, protein activity, protein stability and protein-protein interactions. These polymorphisms are found to be associated with the onset and progression of common cancers. The most common polymorphism in human genome is the substitution of single nucleotide, which is described as single nucleotide polymorphisms (SNPs). Previously, we have assessed the association between seven functional polymorphisms of MMPs (MMP-1 -1602 1G/2G, MMP-2 C-1306T and C-735T, MMP-3 -1612 5A/6A, MMP-9 C-1562T, MMP-12 G-82A and MMP-13 G-77A) and HCC and NPC risk. Our results indicated that these polymorphisms do not significantly confer an increased risk of HCC. However, the functional polymorphisms and haplotypes of MMP-2 C-1306T and C-735T are associated with NPC risk. The MMPs family consists of 23 members. Thus, in addition to the SNPs above, it is expected that the other MMPs polymorphisms are also possibly to be associated with the onset and progression HCC and NPC. These SNPs include MMP-7 A-181G and C-153T, MMP-8 C-799T, A-381G and C+17G, MMP-10 A+180G and MMP-21 C+572T. By use of DNA sequencing in 96 individuals randomly chosen from the control population, we found that only MMP-7 A-181G, MMP-8 C-799T and MMP-21 C+572T polymorphisms exist in our population. The association between these polymorphisms and HCC and NPC risk was evaluated while controlling for confounding factors. We found no significant association between these polymorphisms and HCC and NPC risk in the overall sample. In addition, further analyses stratified by various risk factors also showed no significant association between these polymorphisms and HCC and NPC risk. Meanwhile, there was no association between these polymorphisms and NPC severity.Recently, we focus on the MMP-14 gene. It was reported that the MMP-14 play an important role in tumorigenesis. However, the role of MMP-14 polymorphisms in susceptibility to HCC and NPC has not been investigated systematically. We screened SNPs in ~7.2-kb promoter region of MMP-14 gene and constructed a refined linkage disequilibrium (LD) block map. Five SNPs (SNP2,SNP12,SNP17,SNP21 and SNP22) were chosen to subsequent genotype analyse. The association study results showed that in HCC overall sample, the SNP12 was associated with susceptibility to HCC and the G allele is related to the increased risk of HCC. Further analysis stratified by HBV status also showed significant association between the SNP12 and the HCC risk. Moreover, SNP17 was found to be associated with HCC risk. In HBV carriers, the AA genotype was associated with decreased risk of HCC; while in non-HBV carriers, the AG genotype was associated with increased risk of HCC. The haplotype analysis showed that number 1 (TAAGC) and number 2 (GAGGT) haplotypes were associated with decreased risk of HCC. In the further stratification analysis, the association remained significant. In NPC overall sample, SNP12, SNP17 and SNP21 were associated with susceptibility to NPC. SNP12 G allele and SNP21 GA genotype were associated with decreased risk of NPC; SNP17 G allele was associated with increased risk of NPC. Number 2 (GAGGT) and number 3 (TGGAT) haplotypes were associated with decreased risk of NPC.Our associaton studies have found that SNP12 and SNP17 of MMP-14 gene are associated with susceptibility to HCC, while SNP12,SNP17 and SNP21 are associated with susceptibility to NPC. These SNPs may have a causal role in tumorigenesis or be in LD with the real causal polymorphism, so we continue to carry out the functional studies on thses SNPs. By in vivo and in vitro functional assays including EMSA, reporter gene assay and quantitation of MMP-14 mRNA, we demonstrated in DNA and RNA level that SNP12 was a functional regulatory polymorphism in the MMP-14 promoter. This polymorphism could regulate the expression of MMP-14 gene in an allele-specific manner and the G allele was related with increased expression of MMP-14 gene.