Detection of circulating cancer cells by reverse transcription-polymerase chain reaction for uroplakin II in peripheral blood of patients with urothelial cancer

Few attempts have been made at the molecular detection of urothelial cancer cells in the blood or lymph nodes mainly because of an absence of good can didate molecular or genetic changes specific to urothelial cancer or urothe lium, In 1990, however, genes that encode urothelium-specific transmembrane proteins, uroplakins (UPs), were cloned. We have established a method of d etecting circulating cancer cells in peripheral blood of patients with tran sitional cell carcinoma by nested reverse transcription-PCR assay for UP II . UP IT mRNA-positive cells were detected in 3 (10.3%) of 29 patients with superficial cancers (pT(a.1)N(0)M(0)), 4 (28.6%) of 14 patients with muscul arly invasive cancers (pT(2-4)N(0)M(0)), 2 (40.0%) of 5 loco-regional node- positive patients (pN(1-2)M(0)), and 6 (75.0%) of 8 patients with distant m etastases. Positive rates, therefore, increased with tumor extension (P = 0 .0033, Kruskal-Wallis test). Furthermore, sequential blood sampling was per formed in three patients with metastases during and after systemic chemothe rapy, and UP-II-positive cells were found to have disappeared in two patien ts who responded well to the systemic chemotherapy, These results suggest t hat our nested reverse transcription-PCR assay for UP II is highly specific and might be used as a tumor marker for molecular staging of urothelial ca ncers, although the sensitivity is not so optimal.