Serum cytokeratin 18 as a biomarker for gastric cancer

Cytokeratin 18 (CK18) fragments are released into circulation during epithelial cell death. M30 (reflects caspase-cleaved CK18 fragment) and M65 (reflects total CK18 fragment) enzyme-linked immunosorbent assay (ELISA) detect circulating CK18 fragments released during caspase-dependent or total cell death, respectively; thus, CK18 has the potential of being a biomarker for epithelial cancers. In the present study, we investigated the serum levels of M30 and M65 in patients with gastric cancer, determined correlation of these levels with clinical features, and evaluated the usefulness of these enzymes as diagnostic and prognostic markers. We enrolled 54 gastric cancer patients and 12 healthy volunteers in this study. We measured the serum levels of M30 and M65 by quantitative ELISA. The levels of M30 and M65 in gastric cancer patients were significantly higher than those in healthy volunteers (P = 0.001, P < 0.001). The enzyme levels were elevated with the progress of gastric cancer. The sensitivity and specificity of M30 as a diagnostic marker were 67.5 and 90.9 %, respectively, and those of M65 were 70.1 and 90.9 %, respectively. The serum levels of M30 and M65 in patient with early gastric cancer were elevated in 38.1 and 66.7 %, respectively. Further, increased serum level of M65 is an independent indicator of poor prognosis (P = 0.036). The serum levels of M30 and M65 may be useful biomarkers for gastric cancer as diagnostic markers that can reflect the extent of cancer. Moreover, M65 levels can be used as a prognostic indicator.