DETECTION OF CIRCULATING TUMOR-CELLS AND NODAL METASTASIS BY REVERSE TRANSCRIPTASE-POLYMERASE CHAIN-REACTION TECHNIQUE

Background In the search for occult metastases in lymph nodes or circu lating tumour cells, a reverse transcriptase-polymerase chain reaction (RT-PCR) assay was developed to detect tumour-specific splice variant s of the transcript of the CD44 gene. The assay was highly sensitive a nd could detect ten tumour cell per 10(6) leucocytes. Methods RNA was purified from peripheral blood (n = 24) and regional lymph nodes (n = 14) from patients with colorectal cancer. Complementary DNA was made a nd amplified using primers specific for the CD44 gene, Southern blotti ng with exon-specific probes was used to enhance the sensitivity. Resu lts Tumour cells were detected in peripheral blood samples in four pat ients and lymph nodes in nine, in one of whom conventional histology h ad not detected tumour cells. Conclusion This technique may be useful in the early diagnosis of primary or metastatic tumours, in assessing prognosis and in detecting residual disease after treatment.