APOLIPOPROTEIN-A-I REVERSE-TRANSCRIPTASE POLYMERASE-CHAIN-REACTION ANALYSIS FOR DETECTION OF HEMATOGENOUS COLON-CANCER DISSEMINATION

Detection of systemic tumor dissemination in colon carcinoma patients might be important for selection of appropriate treatment modalities. It has been previously shown that Apolipoprotein A-I (Apo A-I) is expr essed in human intestinal epithelial cells, and in some human colon ca rcinoma cell lines. We examined the expression of Apo A-I mRNA in 14 h uman primary colon carcinomas by Northern blot and/or reverse transcri ptase-polymerase chain reaction (RT-PCR) analysis. An Apo A-I specific transcript was found in up to 70% of the colon carcinomas. We develop ed an RT-PCR assay for Apo A-I transcripts, to identify circulating ca rcinoma cells in the peripheral blood of colon cancer patients. The Ap o A-I RT-PCR assay was optimized using limiting dilution of an Apo A-I positive cancer cell line mixed with peripheral blood from healthy do nor. In this system, up to 10 colon carcinoma cells were detected in 5 ml of peripheral blood. We examined Apo A-I mRNA expression in periph eral blood samples from 4 healthy donors, 20 colon carcinoma patients, and 11 individuals with tumor disease other than colon cancer. No Apo A-I mRNA was detected in the healthy donors and in the patients witho ut colon cancer. Two out of 10 patients with metastatic colon carcinom a were positive by this assay, whereas Apo A-I mRNA was not found in a ny of the blood samples from the 10 radically resected colon carcinoma patients. These data suggest that Apo A-I RT-PCR assay is a highly sp ecific and sensitive assay, although a low number of advanced colon ca rcinoma patients was found to be positive.