The Study Of Colorectal Neoplasm's Micrometastases In Peritoneal Cavity

Free cancer cells exfoliated from primary foci usually lead to local recurrence or peritoneal dissemination after resection of primary foci, which will strongly affect the prognosis of patients with colorectal carcinoma. So, examination ana elimination of these cells may help patients to improve their survival fundamentlly. Conventional cytology and immunocytoche-mistry, however, lack sensitivity and fail to precisely identify malignant cells. Although nested RT-PCR technique with extreme sensitivity and specificity has been adoptted in the study of colorectal cancer cells in the peritoneal cavity. It was still difficult to efficiently detect free cancer cells in peritoneal cavity only by CEA , the single tumour marker, on account of hetero- geneity of tumour associated genes and multiple genie formation of a successful metastasis. MMP-7, a member of the matrix metalloproteinase(MMP) gene family, which is capable of degradingexternal cell matrix(ECM) and participation in tumour invasion, is mainly present in epithelial cancer cells and absent in stromal cells. CK-20, a member of cytokeratin(CK), being predominantly confined to gastric and intestinal epithelium and absent in the peritoneal mesothelium. In addition, CK-20 is steadily expressed during tumour metastasis. By detection of expression of three tumor associated genes in peritoneal washes from patients with colorectal neoplasm , the objective of the study was to explore whether detection by combination of these three markers can significantly improve the sensitivity of examination and to find out a new and more reliable method to diagnose peritoneal micrometastases of colorectal neoplasm.Patients and Methods Nested RT-PCR analysis with three tumour associated gene markers(CEA , MMP-7 and CK-20) and conventional cytologic examination by HE staining were performed on peritoneal washes collected at laparotomy from 52 patients with colorectal carcinoma locating in peritoneal cavity. Sensitivity and specificity of the nested RT-PCR analysis for individual markers were assessed using colorectal carcinoma cell line(LS~174T), 10 colorectal carcinoma tissues, peritoneum tissues from 10 patients with benign disease and peritoneal washes from 30 patients with benign disease as controls. Results 1.A11 three gene markers(CEA , MMP-7 and CK-20) were expressed incolorectal cancer cell line(LS-174T) and 10 colorectal carcinoma tissues, whereas peritoneum tissues and 29 of 30 peritoneal washes as negative controls tested negative for all markers; the remaining one peritoneal wash was positive for CEA.2. In sensitivity tests, CEA RT-PCR, MMP-7 RT-PCR and CK-20 RT-PCR all proved to be capable of detecting 10 carcinoma cells per sample.3. There was a positive correlation between detection rate of three markers and Duke's stage (p< 0.05) and there was also a positive one between detection rate of three markers and peritoneal dissemination (p< 0.05).4. In 52 samples, the rate of positive detection by CEA mRNA, CK-20 mRNA, MMP-7 mRNA and cytology was 38.5% (20/52), 36. 5%(19/52), 25.0%(13/52) and 17. 3%(9/52), respectively. The positive rate of CEA mRNA and CK-20 mRNA was significantly higher than that of cytology (P<0. 05). Compared with the positive rate of cytology, that of MMP-7 mRNA wasn't significantly higher (P>0. 05), but 4 more samples were detected by MMP-7 mRNA than by cytology. Moreover, 32 peritoneal washes, including all 9 samples with positive cytology results, proved positive for the nested RT-PCR assay.5. The rate of positive detection by combination of three markers was 61. 5%(32/52) and significantly higher than that by any marker alone (P<0. 05).Conclusions1.As CEA, both MMP-7 and CK-20 can be regarded as useful markers ain the study of colorectal neoplasm's micrometastases in peritoneal cavity.2. The correlation analysis between detection rate of three markers and Duke's stage and that between detection rate of three markers and peritoneal dissemination suggest that with the progression of tumor, the rate of free...