Utilizing quantitative polymerase chain reaction to evaluate prostate stem cell antigen as a tumor marker in pancreatic cancer

Background: Real-time quantitative polymerase chain reaction (qPCR) may prove to be a sensitive technique by which to evaluate potential tumor markers in pancreatic cancer. Methods: The prostate stem cell antigen (PSCA) gene was identified as a marker highly expressed in pancreatic adenocarcinoma and not normal pancreas. RNA from pancreatic and nonpancreatic cancer cell lines as well as tissue and blood from pancreatic cancer and control patients was reverse-transcribed and PSCA quantified by qPCR. Results: Individual operator experience affects the results of qPCR, with significantly different copy numbers at experiment numbers 5, 15, and 40. Five of six pancreatic cell lines had PSCA/actin ratios 10-fold greater than nonpancreatic cancer lines. Mean PSCA expression in pancreatic tumor tissue was significantly higher (P < 0.05, Student's t-test) than in the tissue of benign pancreatic processes. The close correlation of PSCA/actin copy number with number of tumor cells in the blood was demonstrated by regression analysis (r = 0.768, P = 0.0001). PSCA copy number was significantly higher in the blood of patients with metastatic pancreatic cancer than in that of normal patients (P < 0.05, Student's t-test). Conclusions: Such trends suggest that PSCA may prove to be a valuable pancreatic cancer tumor marker. More generally, the technique of qPCR is shown to provide a sensitive method of evaluating markers in cancer patients.