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Objective: To investigate the expressions of mismatch repair (MMR) proteins, i.e. MLH1 (mutL homolog 1), MSH2 (mutS homolog 2), MSH6 (mutS homolog 6) and PMS2 (postmeiotic segregation increased 2) in sporadic colorectal carcinoma (SCRC) and their correlation with clinicopathological characteristics. Methods: Cancer tissue samples of the SCRC patients who underwent radical resection of colorectal cancer at Tongren Hospital, Shanghai Jiao Tong University School of Medicine from April 2014 to August 2018 were collected. MLH1, MSH2, MSH6, PMS2 and p53 proteins in colorectal cancer tissue samples from 209 patients who met the criteria were detected by immunohistochemistry, and 67 samples were detected by real-time PCR for KRAS oncogene mutation. Results: In 209 cases of cancer tissues, MLH1, MSH2, MSH6 and PMS2 deficiency rates were 17.2% (36/209), 2.4% (5/209), 12.9% (27/209), and 16.7% (35/209), respectively. The total deficiency rate of MMR system proteins was 30.1% (63/209), which was higher in the patients under 55 years old, with tumor at the right colon, with tumor bigger than 6 cm or with mucinous adenocarcinoma (all P<0.05). MLH1 deficiency rate of the patients with p53 mutation was significantly higher than that of unmutated patients (P=0.012); MLH1 deficiency rate of the patients with KRAS mutation was significantly lower than that of unmutant patients (P=0.044). There was no significant difference in the positive expression rates of MLH1 and PMS2 in these SCRC patients (P=1.000). Conclusion: MMR systemic protein deletion may be associated with patient age, tumor location, tumor size, and histopathological typing; MLH1 protein deletion may be associated with mutations of p53 and KRAS genes.
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Objective To explore the expression and clinical significance of mismatch repair (MMR)protein and MLH1 promoter methylation testing in endometrial cancer(EC). Methods A total of 420 cases with EC diagnosed by the surgical pathology examination from the Department of Pathology of PLA General Hospital, MLH1,MSH2,MSH6 and PMS2 protein in EC were detected by immunohistochemistry and methylation-specific multiplex ligation-dependent probe amplification(MS-MLPA) testing. Results (1)Of the 420 tumor cases, the total expression loss rate of MMR protein was 34.5%(145/420), the expression loss rates of MLH1,MSH2,MSH6 and PMS2 protein were respectively 17.1%(72/420), 8.1% (34/420), 7.4%(31/420), 26.2%(110/420)and loss rates of MLH1 and PMS2,MSH2 and MSH6 were 16.7%(70/420), 6.2%(26/420). When there was a loss of MMR protein expression, any one or more protein expression deletions in MLH1, PMS2, MSH2 and MSH6, it could be Lynch syndrome related endometrial carcinoma(LS-EC). The expression loss rate of MMR protein in the poorly differentiated endometrioid adenocarcinoma was higher than that in the well differentiated endometrioid adenocarcinoma(P<0.05).(2) The expression loss rate of MMR and PMS2 protein had statistically significant between the endometrioid adenocarcinoma and non-endometrioid adenocarcinoma(P<0.01). The expression loss rate of MSH2 protein had statistically significant in the stage Ⅲ(P<0.01). Moreover, there were also significant differences in depth of myometrial invasion and lymph node metastasis between the expression loss rate of MMR protein (P<0.05).(3)The expression loss rate of MLH1 protein was 72 cases and 57 cases had MLH1 promoter methylation testing(excluding those who were not qualified for DNA testing). The positive rate was 47.4% (27/57). Therefore, these patients were sporadic endometrial cancer, not non-LS-EC. Conclusions MMR protein may be play an important role in the development of endometrial cancer and be indicated poor prognosis. Immunohistochemical staining and MLH1 promoter methylation detection may be play an important role in the screening of the LS-EC.
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MutL and MutS or their homologues are two crucial proteins of DNA mismatch repair (MMR) system. A new method was described for observation of the interaction between MutS and MutL which is based on the fusion gene/fusion protein technique. Three fusion proteins, MutL-GFP fusion (Trx-His6-GFP-(Ser-Gly)6-MutL), MutL-Strep tag Ⅱ fusion (Trx-His6-(Ser-Gly)6-Strep tagⅡ-(Ser-Gly)6-MutL) and MutS fusion (Trx-His6-(Ser-Gly)6-MutS), were constructed and expressed in E. coli AD494 (DE3). Interaction assay between MutS and MutL was performed in a 96-well microtiter plate.MutS fusion protein was immobilized on the wells and provided a surface for the interaction between MutS and MutL.Results showed that only after binding of MutS to the mismatched DNA, there was an interaction between MutS and MutL.The binding events could be indicated by GFP signal or the signal generated from alkaline phosphatase and its substrate. In addition, the method based on fusion molecular system also serve as a model for studies on the interactions among other proteins or biomolecules.
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Objective: To observe the expression of hMLH1 protein in esophagus squamous cell carcinoma, atypical hyperplasia tissue and normal esophagus tissue, so as to discuss the relationship between hMLH1 expression and esophagus carcinogenesis. Methods: The specimens of esophagus squamous cell carcinoma, atypical hyperplasia and normal esophagus tissue were obtained from 92 esophagus carcinoma patients. Immunohistochemistry (IHC) staining technique was used to detect expression of hMLH1 protein. The relationship between hMLH1 expression with clinical parameters, such as gender, age, cancer differentiation level, infiltration depth, tumor stage, lymphatic metastasis, was analyzed. Results: The positive rates of hMLH1 protein in esophagus squamous cell carcinoma, and atypical hyperplasia tissue and normal esophagus tissue were 36.96%,56.52%, and 84.78%,respectively,with the former 2 significantly lower than the latter (P