Increased serum midkine concentration as a possible tumor marker in patients with superficial esophageal cancer

Midkine, a heparin-binding growth factor, is expressed in numerous cancer tissues and is reportedly elevated in patients with various neoplasms. The aim of this study was to evaluate the clinicopathological significance of serum midkine concentration (S-MK) in patients with superficial esophageal squamous cell carcinoma (SCC). Pretreatment S-MK was measured by enzyme-linked immunosorbent assay in 135 healthy controls, 16 patients with benign esophageal disease, and 60 patients with primary superficial esophageal squamous cell cancer (SESCC). All patients with SESCC underwent curative resection. The disease was staged according to TNM/UICC guidelines. Serum concentrations of carcinoembryonic antigen (CEA), squamous cell carcinoma antigen (SCC-Ag), and cytokeratin 19 fragment (CYFRA21-1) were also evaluated in the same populations. S-MK in patients with SESCC (388+/-411 pg/ml) was significantly higher than in benign esophageal disease or healthy controls (183+/-73 and 154+/-76 pg/ml, respectively). Using the mean + 2 standard deviations of healthy control S-MK (300 pg/ml) as the cut-off level, 50% of patients with esophageal SESCC were deemed positive. This S-MK positivity rate for detecting SESCC was significantly higher than for other tumor markers. Thus, S-MK may be useful as a tumor marker to detect SESCC.