The Microsatellite Instability Of Cancer Tissues In Esophageal Carcinoma

Objective: Esophageal carcinoma is still a dangerous disease worldwide because of its high mortality and morbidity. It is the forth most common cancer in China, with a mortality rate of 9.7 per 10,000 population per year. Although many efforts have been made to improve diagnoses and treatments of esophageal carcinoma, the longterm results were still disapointing because the disease could not be diagnosed usually in early strage. With the development of the molecular biology, it is becoming possible to diagnose the disease at early strage. More recently, a tumor correlatting gene-mismatch repair gene (MMR), in addition to oncogene and antioncogene, and these genes are associated with occurrence and development of tumor. The most common MMR's expression is microsatellite instability (MSI). It is microsatellite and MSI that become the hotspot in tumor investigation. So, MSI is a serious evolution anent tumor pathogenesis after oncogene and antioncogene. Microsatellite DNA is a kind of nucleotide repetitive sequences existing in the genome, whose number can be changed. MSI is the change of the simple repeatedsequences, whose occur because of the replication errors, and the expression of MSI is the change of allelics' sizes which existed in the tumor or non-tumor tissue. MSI had been documented in maligenancies associated with non-polyposis colorectal carcinoma (HNPCC) in 1993, and had be discovered in the malignancies of the colon, stomach, pancreas, endometrium, ovary in addition of small cell lung cancer. Up to now, it is demonstrated that almost every tumor has the MSI. MSI caused by the defective functions of MMR plays an important role in the carcinogenesis. However, little is known about the role of MSI in esophageal carcinogenesis. In the present study, we research the relationship between the esophageal carcinoma and MSI, and try to find out a new molecule method. So, we can find out the predisposition to esophageal malignancies at forepart of the disease, in favor of designing the treatment project. Methods: Thirty pairs of tumor and surrounding normal tissue samples were obtained from 30 patients (17 males and 13 females, average age is 57.2 years). All patients were treated in the Department of thoracic surgery the Forth Hospital of Hebei Medical University between August 2001 and January 2003. The tumors were clinically and microscopically classified according to the criteria set by Union Internationale Contre le Cancer (UICC) and the World Health Organization (WHO).The samples' pathological types: squamous cell carcinoma 23 cases, adenocarcinoma 2 cases, small cell carcinoma 5 cases; There were 20 cases high to middle differentiation, 5 cases low differentiation, and 5 cases undifferenciation tumor. These tumors had been classified as three different types by PTNM staging system: stage Ⅰ 1 cases, stage Ⅱ 16 cases, stage Ⅲ 13 cases. The 14 cases had the lymph node metastasis and 16 cases had not. Thirty tumors were obtained at surgery. No patients had tumor family history and no patients had received any therapy prior to the surgical oprtation. All patients had enregistered the living habits.The tumor and surrounding 5 cm normal tissue samples were obtained from every 30 patients. A part of each these tissues was frozen and stored at －80℃ until DNA extraction. The DNA was isolated using proteinase K digestion and standard phenol-chloroform extraction procedure. Two microsatellite markers were studied: D3S1067 (located in chromosome 3p21.1～3p14.3) and D18S58 (located in chromosome 18q22.3～18q23). Isolated DNA was amplified by 40 cycles of PCR for D3S1067: Each cycle consisted of a denaturation step at 94℃ for 30s, an annealing step at 59℃ for 30s, and an elongation step at 72℃ for 30s. Isolated DNA was amplified by 35 cycles of PCR for D18S58. Each cycle consised of a denaturationstep at 94℃ for 45s, an annealing step at 59℃ for 30s, and an elongation step at 72℃ for 45s. The PCR production were loaded on 7% denaturalized polyacrylamide gel ele...