Aberrant methylation of secreted apoptosis-related protein 2 (SARP2) in pure pancreatic juice in the diagnosis of pancreatic neoplasms

Objective: Secreted apoptosis-related protein (SARP) families are considered to counteract the oncogenic Writ signaling pathway, and inactivation of this gene may aid cancer development and progression. Recently, the aberrant methylation of SARP2 has been frequently detected in pancreatic carcinoma (PCa) tissue, but not in normal pancreatic tissue. We evaluated the hypermethylation of SARP2 in pure pancreatic juices (PPJ) endoscopically aspirated from patients with PCa, intraductal papillary mucinous neoplasm of the pancreas (IPMN), chronic pancreatitis (CP), and a control group who were consequently free of pancreatic diseases according to the differential diagnosis of PCa. Methods: We investigated the aberrant methylation of SARP2 in 9 human PCa cell lines and in the PPJ samples from 33 patients with PCa, 20 with IPMN, 19 with CP, and 10 control patients. DNAs extracted from not only the sediment, but also the supernatant of the PPJ and PCa cell lines were treated with sodium bisulfite and analyzed by methylation-specific polymerase chain reaction (PCR) (MSP). Moreover, real-time MSP was also performed for the melting curve analysis and the quantitative analysis of SARP2 in PPJ. Results: The incidence of the aberrant methylation of SARP2 using MSP was 8/9 (89%) in PCa cell lines, 26/33 (79%) in the PPJ with PCa, and 17/20 (85%) with IPMN. However, it was only 1/19 (5%) in the PPJ with CP, and 0/10 (0%) in the PPJ of the control patients, respectively. The incidences of aberrant methylation of SARP2 in the PPJ with PCa and IPMN were significantly higher than that in the PPJ with CP (P < 0.001, P < 0.001). Melting curve analysis by real-time MSP revealed that the incidences of aberrant methylation of SARP2 in PPJ was 28/33 (85%) with PCa, 9/11 (82%) with the malignant group of IPN4N, 5/9 (56%) with the benign group of IPMN, and 5/19 (26%) with CP. In this analysis, there were significant differences between PCa and CP (P < 0.001) and between the malignant group of IPMN and CP (P < 0.005). In the quantitative analysis by real-time MSP with a suitable cutoff value, the incidences of aberrant methylation of SARP2 in the PPJ with PCa, the malignant group of IPMN, the benign group of IPMN, and CP were 19/33 (58%), 6/11 (55%), 3/9 (33%), and 2/19 (11%), respectively. The incidence of the aberrant methylation of SARP2 in the PPJ was significantly different between PCa and CP and between the malignant group of IPMN and CP (P < 0.005 and P < 0.05, respectively). Conclusions: Hypermethylation of SARP2 in the PPJ may be a highly sensitive and useful marker for the detection of pancreatic neoplasms, including PCa and the malignant group of IPMN.