Mapping of microsatellite instability in endoscopic normal colon

Prevalence and implications of elevated microsatellite alterations at selected tetranucleotides in cancer

Elevated microsatellite alterations at selected tetranucleotides (EMAST), a variation of microsatellite instability (MSI), has been reported in a variety of malignancies (e.g., neoplasias of the lung, head and neck, colorectal region, skin, urinary tract and reproductive organs). EMAST is more prominent at organ sites with potential external exposure to carcinogens (e.g., head, neck, lung, urinary bladder and colon), although the specific molecular mechanisms leading to EMAST remain elusive. Because it is often associated with advanced stages of malignancy, EMAST may be a consequence of rapid cell proliferation and increased mutagenesis. Moreover, defects in DNA mismatch repair enzyme complexes, TP53 mutation status and peritumoural inflammation involving T cells have been described in EMAST tumours. At various tumour sites, EMAST and high-frequency MSI share no clinicopathological features or molecular mechanisms, suggesting their existence as separate entities. Thus EMAST should be explored, because its presence in human cells may reflect both increased risk and the potential for early detection. In particular, the potential use of EMAST in prognosis and prediction may yield novel types of therapeutic intervention, particularly those involving the immune system. This review will summarise the current information concerning EMAST in cancer to highlight the knowledge gaps that require further research.

Vascular endothelial growth factor (VEGF) gene polymorphisms and colorectal cancer: a meta-analysis of epidemiologic studies

BACKGROUND

Studies investigating the association between vascular endothelial growth factor (VEGF) polymorphisms and colorectal cancer (CRC) risk report conflicting results. To clarify the effect of four VEGF (-460T/C, -634G/C, +936C/T, and -2578C/A) gene polymorphisms on the risk of developing CRC, we carried out a meta-analysis using published data to obtain more precise estimates of risk.

METHODS

Electronic searches of PubMed and EMBASE were conducted to select studies for this meta-analysis. The principal outcome measure was the odds ratio (OR) with 95% confidence interval (CI) for the risk of CRC associated with four VEGF (-460T/C, -634G/C, +936C/T, and -2578C/A) gene polymorphisms.

RESULTS

We identified 12 epidemiologic studies, which included 2770 CRC cases and 2568 controls. The combined results based on all studies showed that CRC cases had a significantly higher frequency of VEGF -634GG (OR=1.24, 95% CI=1.06, 1.44) and -2578AA (OR=1.37, 95% CI=1.12, 1.66) genotype and a lower frequency of -634CG (OR=0.82, 95% CI=0.71, 0.95) than controls. When stratifying for race, we found that patients with CRC had a significantly higher frequency of -460TC (OR=1.54, 95% CI=1.22, 1.94), -460CC (OR=2.00, 95% CI=1.50, 2.67), and -2578AA (OR=1.38, 95% CI=1.12, 1.69) and a lower frequency of -2578AA (OR=0.78, 95% CI=0.65, 0.93) genotypes of VEGF than controls, among Caucasians. We also found that patients with CRC had a significantly higher frequency of -634GG (OR=1.61, 95% CI=1.20, 2.15) and a lower frequency of -634CG (OR=0.60, 95% CI=0.46, 0.79) genotypes of VEGF than controls, among Asians.

CONCLUSIONS

Our meta-analysis suggests that the VEGF -460T/C, -634G/C, and -2578C/A gene polymorphisms are associated with a risk of CRC.