The Expression of Melanoma-Associated Antigen D2 Both in Surgically Resected and Serum Samples Serves as Clinically Relevant Biomarker of Gastric Cancer Progression

Background: Sensitive biomarkers are necessary for risk classification of patients with gastric cancer (GC), especially ones at risk of distant metastases. Melanoma-associated antigen (MAGE)-D2 has been reported to play a role in the process of cell adhesion and metastatic potential of tumor cells in colorectal cancer. The purpose of this study was to identify a novel clinically relevant biomarker of GC. Methods: Expression analysis of MAGE-D2 was conducted in GC cell lines and clinical samples (surgical specimen and serum) in both mRNA and protein level. Correlations between MAGE-D2 expression status and clinicopathological factors were evaluated. Results: MAGE-D2 mRNA expression levels were similar between GC tissues and the corresponding normal adjacent tissues and were independent of GC differentiation or subtype. In 101 (45 %) of 225 patients, the expression level of MAGE-D2 mRNA was increased in GC tissues compared with the corresponding normal adjacent tissues. Increased expression of MAGE-D2 mRNA in GC tissues was associated with distant metastasis and early recurrence and was an independent prognostic factor (hazard ratio 2.27, 95 % confidence interval 1.39–3.74, P = 0.001). There was a stepwise increase in serum MAGE-D2 level going from healthy volunteers to patients with localized GC and then to those with extended GC (stage IV). Patients with preoperative serum MAGE-D2 levels >130 pg/ml had a more unfavorable prognosis than those with levels ≤130 pg/ml. Conclusion: MAGE-D2 was associated with metastatic potential of GC and may represent a promising biomarker, both in gastric tissues and serum samples, for malignant behavior of GC.