Current status of tumor M2 pyruvate kinase (tumor M2-PK) as a biomarker of gastrointestinal malignancy

Background: Tumor pyruvate kinase M2 (tumor M2-PK) is a key enzyme in the altered metabolism of tumor tissue. In cancer, it is known to be present in high concentrations in malignant tissue, plasma and other body fluids. A commercial enzyme-linked immunosorbent assay (ELISA) method exists for the detection of tumor M2-PK. This study undertakes a systematic review of the current literature on tumor M2-PK as a diagnostic tool and provides an overview of the current usage and scope of this emerging biomarker. Methods: The MEDINE and EMBASE databases were searched for English-language articles containing original data. MeSH headings used were pyruvate kinase, tumor and cancer. All case reports and review articles were excluded and a final study population of 30 manuscripts containing original data was obtained. Results: Eight articles evaluated plasma tumor M2-PK in 511 esophago-gastric cancer, 226 pancreatobiliary cancer and 470 colorectal cancer patients. Although there are inter-study variations in cut-off points, consistent findings include elevated levels in patients with malignancy with the degree of elevation corresponding to extent of disease. Conclusion: Tumor M2-PK is elevated in a range of gastrointestinal malignancy. In pancreatobiliary malignancy, the weight of evidence suggests that the test can be used as an adjunctive diagnostic test in conjunction with CA 19-9 and also that it may be a valuable biomarker of adverse prognosis. Stool tumor M2-PK appears to be a promising test for colon cancer.