Am J Cancer Res 2016;6(1):91-96 www.ajcr.us /ISSN:2156-6976/ajcr0017795
Original Article CPA4 is a promising diagnostic serum biomarker for pancreatic cancer Lichao Sun1,2*, Joseph Burnett2*, Chunguang Guo3, Yibin Xie3, Jian Pan4, Zhihua Yang1, Yuliang Ran1, Duxin Sun2 1 State Key Laboratory of Molecular Oncology, Cancer Hospital, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing 100021, P. R. China; 2Department of Pharmaceutical Sciences, University of Michigan, Ann Arbor, MI 48109, USA; 3The Department of Abdominal Surgical Oncology Cancer Hospital, Chinese Academy of Medical Sciences (CAMS), Beijing 100021, P. R. China; 4Department of Hematology and Oncology, Children’s Hospital of Soochow University, Suzhou 215005, Jiangsu, P. R. China. *Equal contributors.
Received October 13, 2015; Accepted October 16, 2015; Epub December 15, 2015; Published January 1, 2016 Abstract: CPA4 belongs to a member of the metallocarboxypeptidase family, and its expression in pancreatic cancer samples and clinical significance are still not investigated until now. In this study, we aimed to evaluate the level of CPA4 in pancreatic cancer samples and study its clinical implications as a diagnostic marker for pancreatic cancer. The levels of CPA4 in pancreatic cancer tissues and serum samples were measured by immunohistochemistry (IHC) and enzyme-linked immunosorbent assay (ELISA), respectively. Among 150 pancreatic cancer tissues examined, 86.7% (130/150) of cases showed positive staining for CPA4. Clinicopathological relevance analysis showed that CPA4 expression was correlated with advanced clinical stage and lymph node metastasis. Also, we found that the levels of CPA4 in serum samples were significantly high in cases whose expression was also high in paired tissue samples (N=50). In a larger sample set, we found that serum CPA4 in pancreatic cancer patients was significantly higher than for healthy controls (P40% of cells as 3. Pancreatic cancer tissues that registered levels 0 and 1 were defined as negative for expression, whereas samples at levels 2 or 3 were defined as positive. Measurement of human plasma levels of CPA4 A commercially available ELISA kit (SEF317Hu, Cloud-Clone Corp.) was used to measure CPA4 level. The sensitivities of the immunoassays for CPA4 were 0.156 ng/mL-10 ng/mL respectively. Each serum sample was run in duplicate. Briefly, 100 ml of serum (1:2 dilution) were placed into each well of the ELISA plate and incubated for 45 min at 37°C. The plates were washed four times with buffer and incubated with 100 ml of detection antibody at 37°C for 45 min. After four washes, the plates were incubated with substrate solution for 15 min at room temperature, then the reaction was stopped and the plates were read by a spectrophotometer at wavelength 450 nm. A standard curve was generated with the provided standards and used to calculate the quantity of CPA4 in each serum sample. Statistical analysis The SPSS 15 software package (SPSS, Inc., Chicago, IL) was used for statistical analysis. Mean between-group values were compared using the χ2-test. The independent sample t test was used for ELISA group analysis. The association between the markers and clinicopathologic features was analyzed using χ2-test or two-sided t-test as appropriate. Receiver operating characteristics (ROC) curves were generated to compare the predictive sensitivity and specificity, and the area under the curve Am J Cancer Res 2016;6(1):91-96
CPA4 is a serum biomarker for pancreatic cancer
Figure 1. Expression of CPA4 in human primary pancreatic cancer tissues and normal adjacent tissues.
(AUC). All comparisons were two-tailed, and p values of