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 candidate molecular or genetic changes specific to urothelial cancer or urothelium. In 1990, however, genes that encode urothelium-specific transmembrane proteins, uroplakins (UPs), were cloned. We have established a method of detecting circulating cancer cells in peripheral blood of patients with transitional cell carcinoma by nested reverse transcription-PCR assay for UP II. UP II mRNA-positive cells were detected in 3 (10.3%) of 29 patients with superficial cancers (pTa-1N0M0), 4 (28.6%) of 14 patients with muscularly invasive cancers (pT2-4N0M0), 2 (40.0%) of 5 loco-regional node-positive patients (pN1-2M0), and 6 (75.0%) of 8 patients with distant metastases. Positive rates, therefore, increased with tumor extension (P = 0.0033, Kruskal-Wallis test). Furthermore, sequential blood sampling was performed in three patients with metastases during and after systemic chemotherapy, and UP-II-positive cells were found to have disappeared in two patients who responded well to the systemic chemotherapy. These results suggest that 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 cancers, although the sensitivity is not so optimal.