Study on detecting colorectal cancer micrometastases in lymph nodes by nested reverse transcriptase-polymerase chain reaction amplification of cytokeratin 20

OBJECTIVE:To develop a nested reverse transcriptase polymerase chain reaction method to amplify cytokeratin 20 mRNA (CK20 mRNA) for detecting colorectal cancer micrometastases in lymph nodes and to evaluate its specificity and sensitivity.METHODS:The RT-PCR system was set up by using nest primer. The presence of CK20 mRNA was investigated by nested RT-PCR in 187 lymph nodes from 30 colorectal cancer patients who underwent curative operation. Tweenty-five lymph nodes from 10 patients with benign intestinal disease were served as negative control. The results of nested RT-PCR were compared with ones of routine histology.RESULTS:The positive rate of CK20 mRNA in 187 lymph nodes from 30 colorectalcancer patients was 51.87%(97/187), while only 57 samples were histologically positive.The expression of CK20 mRNA in 25 lymph nodes of 10 cases of the control group were all negative. CONCLUSIONS:Nested reverse transcriptasepolymerase chain reaction was a sensitive and specific method to detect the expression of CK20 mRNA in lymph nodes as a helpful marker of micrometastases of colorectal carcinoma cells. It is superior to routine histopathological assay in examing lymph node metastases. The detection of CK20mRNA in lymph nodes may contribute to improve the accuracy of clinical staging, determine patients' prognosis and provide information for adjuvant therapy.