Microsatellite instability and hMLH1/hMSH2 expression in Barrett esophagus-associated adenocarcinoma

Correlation between hMLH1 and RASSF1A expression and prognosis of esophageal carcinoma

AIM: To investigate the expression of human mutL homologue 1 (hMLH1) and Ras association domain family 1A (RASSF1A) in esophageal squamous cell carcinoma (ESCC) and to analyze their prognostic value.

METHODS: The expression of hMLH1 mRNA and RASSF1A protein in 60 specimens of esophageal cancer was detected by in situ hybridization (ISH) and immunohistochemistry, respectively. The relationship of hMLH1 and RASSF1A expression with ESCC prognosis was evaluated using Cox regression model and Kaplan-Meier survival curve analysis.

RESULTS: The positive rates of hMLH1 and RASSF1A expression in esophageal carcinoma were significantly lower than those in normal esophageal tissue (41.67% vs 90.00%, 80.00% vs 100.00%; both P < 0.05). The expression of hMLH1 and RASSF1A was correlated with tumor TNM stage, invasion depth, lymph node metastasis, and tumor size (all P < 0.05), but not with patient's nationality (P > 0.05). The expression of RASSF1A was positively correlated with that of hMLH1 (r = 0.338, P < 0.01). The five-year overall survival rate for all the patients was 35% (21/60). Univariate survival analysis suggested that the five-year survival rate for patients with positive expression of RASSF1A was higher than that for patients with negative expression of RASSF1A though the difference was not significant (P > 0.05). Patients with positive expression of hMLH1 had a significantly higher survival rate compared to those with negative expression of hMLH1 (P < 0.05). Cox multivariate analysis indicated that tumor invasion depth and TNM stage were independent prognostic factors affecting survival of ESCC patients (both P < 0.05).

CONCLUSION: Both hMLH1 and RASSF1A were weakly expressed in ESCC. The expression of hMLH1 and RASSF1A was positively correlated with ESCC progression. Expression of hMLH1 and RASSF1A might be used as a prognostic parameter in ESCC patients.

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.

Relationship between mismatch repair gene hMSH2 promoter methylation and gastric carcinoma

AIM: To detect the role of methylation of the 5'CpG island located in the promoter region of the human mutS homolog-2 (hMSH2) gene in the pathogenesis of gastric carcinoma.

METHODS: The methylation of the hMSH2 promoter was examined by methylation-specific polymerase chain reaction (MSP) in 40 gastric carcinoma specimens, 40 matched cancer-adjacent mucosa specimens, 14 chronic atrophic gastritis (CAG) specimens, and 6 chronic superficial gastritis (CSG) specimens.

RESULTS: The methylation of the hMSH2 promoter was detected in 24 out of the 40 (60%) gastric cancer specimens, 15 out of the 40 (37.5%) cancer-adjacent mucosa specimens, and 5 out of the 14 (35.7%) CAG specimens. No methylation was detected in 6 CSG specimens. The rate of hMSH2 promoter methylation was significantly higher in gastric cancer tissue than in non-carcinoma tissue (P < 0.05). No significant differences were detected in the rates of hMSH2 promoter methylation among cancer-adjacent mucosa specimens, CAG specimens and CSG specimens. The rate of hMSH2 promoter methylation is not correlated with the clinicopathological parameters of gastric cancer.

CONCLUSION: The hMSH2 promoter methylation may be a main mechanism responsible for mismatch repair (MMR) dysfunction that is involved in the development, but not the progression, of gastric cancer.

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.