Detection of circulating MN/CA9 positive renal cell carcinoma cells during operation

Our previous study demonstrated the clear detection of MN/CA9 mRNA in peripheral blood samples from RCC patients. However, approximately 30 % of control blood samples from healthy volunteers showed MN/CA9 expression. We have developed a new primer set and optimized the PCR conditions, now resulting in a specificity of 100 %. In tissue samples, all clear cell type carcinomas but none of the spindle cell type and pleomorphic cell type tumors expressed the MN/CA9 message. Analysis of MN/CA9 messages in peripheral blood samples from RCC patients gave positive results for 0/2, 1/9, 0/4 and 4/12 of stage I, II, III and IV cases, respectively. RT-PCR analysis using preoperative renal venous blood samples resulted in clear detection of MN/CA9 positive cells in 2/4, 3/13, 2/6 and 1/1 of stage I, II, III and IV cases, respectively. Our results suggest that assessment of MN/CA9 expression by RT-PCR is a promising method for detecting cancer cells in the circulation of patients with RCC.