MCM2 expression levels predict diagnosis and prognosis in gastric cardiac cancer

Background: Gastric Cardiac Cancer (GCC) has high incidence and poor prognosis requiring early screening of high-risk populations. Minichromosome maintenance (MCM) proteins are used as diagnostic-biomarkers in many cancers but not validated for GCC. We evaluate MCM protein 2 (MCM2), comparing it with the validated markers Ki67 and PCNA. Methods: GCC and corresponding cardiac precancerous samples were immunostained with Ki67, MCM2 and PCNA antibodies. Results: 90% of dysplasia samples expressed MCM2, whereas Ki67 and PCNA were expressed in 67% and 80% respectively. The sensitivity and negative predictive values of MCM2 were also superior at 90% and 87%, respectively. Ki67 and PCNA expression was correlated with MCM2, but their expressions seldom reached surface layers, whereas MCM2 manifested mostly in easily accessible superficial layers. Labeling indices (LI) of Ki67 and PCNA were also lower. Significant associations between LI (MCM2), LI (PCNA), and TNM-stages, lymph node metastases and GCC grade were found (P<0.05). Increased protein expressions were associated with reduced overall and disease-free survival (P<0.05). Although Ki67 and PCNA were significant prognostic factors, there was no significant improvement in multivariate statistical analyses, in contrast to LI (MCM2) findings. Conclusions: MCM2 is a sensitive, specific and efficient biomarker of GCC having potential use in clinic.