Microsatellite instability, MLH-1 promoter hypermethylation, and frameshift mutations at coding mononucleotide repeat microsatellites in ovarian tumors

Clinical significance of detection of hMLH1 and hPMS2 mRNA expression in gastric cancer by real-time fluorescent quantitative RT-PCR

AIM: To investigate the expression of DNA mismatch repair genes hMLH1/hPMS2 and to analyze their clinical significance in gastric cancer.

METHODS: The expression of hMLH1/hPMS2 mRNAs in 40 specimens of gastric cancer and cancer-adjacent mucosa tissue and 21 specimens of chronic gastritis tissue was detected by real-time fluorescent quantitative reverse transcription-polymerase chain reaction (RT-PCR). The human glyceraldehydes-3-phosphate dehydrogenase (hGAPDH) gene was used for normalization of gene expression levels.

RESULTS: The level of hMLH1 mRNA in gastric cancer was significantly higher than those in cancer-adjacent mucosa tissue and chronic gastritis tissue (7.23 ± 11.91 vs 3.80 ± 5.13 and 2.01 ± 1.25, respectively; both P < 0.05). The level of hMLH1 mRNA was significantly higher in cancer-adjacent mucosa tissue than in chronic gastritis tissue (P < 0.05). The level of hPMS2 mRNA was significantly higher in gastric cancer and cancer-adjacent mucosa tissue than in chronic gastritis tissue (0.43 ± 0.35 and 0.55 ± 0.39 vs 0.32 ± 0.15, respectively; both P < 0.05). No significant difference was noted in the level of hPMS2 mRNA between gastric cancer and cancer-adjacent mucosa tissue. The expression levels of hMLH1/hPMS2 mRNAs in gastric cancer showed no significant correlation with tumor size, infiltration degree, and lymph node metastasis. However, the expression level of hMLH1 mRNA was significantly higher in gastric cancer with lymph node metastasis than in that without lymph node metastasis (all P < 0.05).

CONCLUSION: The expression levels of hMLH1 /hPMS2 gene in gastric cancer and cancer-adjacent mucosa tissue are abnormal when compared with that in chronic gastritis. Abnormal transcription of hMLH1/hPMS2 may be related with the genesis of gastric cancer, but not involved in the progression of the disease.

Significance of mismatch repair genes hMLH1 and hMSH2 expression in gastric cancer

AIM: To investigate the role of mismatch repair genes human mutL homolog 1 (hMLH1) and human mutL homolog 2 (hMSH2) in the carcinogenesis of gastric cancer.

METHODS: A total of 40 gastric cancer patients who underwent surgical resection at our hospital were included in the study, of which 33 were pathologically diagnosed as adenocarcinoma, and 7 as mucinous adenocarcinoma. All the patients did not underwent preoperative chemotherapy or immunotherapy. The gastric cancer specimens, matched cancer-adjacent tissue specimens, and 20 chronic gastritis mucosa specimens (10 diagnosed as chronic superficial gastritis by gastroscopic biopsy, and 10 as chronic atrophic gastritis) were collected. The expression of hMLH1 and hMSH2 proteins in these specimens was detected by Western blot.

RESULTS: The positive rate of hMSH2 expression in cancer tissue was significantly higher than those in cancer-adjacent tissue and gastritis mucosa tissue (0.28 ± 0.10 vs 0.23 ± 0.07 and 0.11 ± 0.10, respectively; both P < 0.01). The positive rate of hMLH1 expression in cancer tissue was significantly lower than those in cancer-adjacent tissue and gastritis mucosa tissue (0.22 ± 0.06 vs 0.28 ± 0.07, 0.26 ± 0.06, both P < 0.01). The positive rates of hMLH1 and hMSH2 expression were not correlated with various clinicopathological parameters in gastric cancer.

CONCLUSION: High hMSH2 expression and low hMLH1 expression may be potential markers for prediction of the development of gastric cancer.