Comparison of Methylation-specific Polymerase Chain Reaction (MSP) with Reverse Transcriptase-polymerase Chain Reaction (RT-PCR) in Peripheral Blood of Gastric Cancer Patients

Background And Objectives: To achieve a complete cure in gastric cancer, primary and recurrent tumors must be detected at an early stage. This study was designed to compare carcinoembryonic antigen (CEA)-specific reverse transcriptase-polymerase chain reaction (RT-PCR) and methylation-specific polymerase chain reaction (MSP) for p16, E-cadherin, and retinoic acid receptor beta (RARbeta) genes using blood samples from gastric cancer patients.

Methods: Preoperative blood samples obtained from 41 patients with gastric cancer, including 9 with early-stage disease, and were subjected to RT-PCR and MSP assays.

Results: Ten of 41 (24%) patients exhibited a CEA-specific signal by RT-PCR. Positive rates were 11, 13, 50, and 50% in stages I, II, III, and IV, respectively. A significant association was found between RT-PCR results and stage (P< 0.01). The MSP assay detected hypermethylation of p16 in 9 patients (22%), E-cadherin in 9 patients (22%), and RARbeta in 6 patients (15%). Altogether, 18 patients (44%) showed hypermethylation. The positive rates were 37, 50, 40, and 75% in stages I, II, III, and IV, respectively. A significant association was found between aberrant methylation and venous invasion (P< 0.05). Neither the CEA-specific signal nor hypermethylation was detected in serum from control volunteers.

Conclusions: The detection rate of MSP was higher than that of RT-PCR in gastric cancer. Both assays can serve as markers that allow selection of those cases requiring more intensive screening and aggressive postoperative treatment.