Expression and prognostic roles of magnesium-dependent phosphatase-1 in gastric cancer

Gastric cancer is a leading cause of cancer deaths and has a poor prognosis after diagnosis. Previous studies showed that Magnesium-Dependent Phosphatase-1 (MDP-1) might be a key component for glycosylation in human protein repair, and an alteration of its function has been involved in some aspects of cellular metabolic networks linked to either normal or pathological processe. In this study, we investigate the MDP-1 status in patients with gastric carcinoma, and determine the potential relationship between MDP-1 and clinical outcome.

One hundred and seventy-one consecutive patients with stage I-III gastric carcinoma who had received a D2 gastrectomy were recruited. The MDP-1 expression was determined by immunohistochemistry (IHC). Disease-free survival (DFS) and overall survival (OS) were evaluated.

We generate an IHC score on a continuous scale of 0-7. The IHC cutoff point generated by ROC analysis and the threshold IHC score was 2. Low MDP-1 expression was scored for 61 (35.7%) and high MDP-1 expression for 110 (64.3%) patients. We saw a significant down-regulation of MDP-1 expression in G3-4 and stage III tumor tissue compared with G1-2 and stage I-II tumors, p=0.023 and p=0.047. In univariate survival analysis, high expression of MDP-1 predicted a significantly better DFS (56.0 months vs. 25.0 months, p=0.029) and OS (59.0 months vs. 41.0 months, p=0.043) compared with low expression. In a multivariate analysis, the tumor stage was a significant predictor for DFS and OS even after adjustment for all other covariates. The MDP-1 status was a joint predictor for DFS and OS with a multivariate HR 0.728, 95% CI 0.530-0.999, p=0.049 and a multivariate HR 0.745, 95% CI 0.543-1.022, p=0.068, respectively.

We showed that down-regulation of MDP-1 expression was correlated with poorly differentiated carcinoma and later tumor stage, and it predicted a significantly poorer DFS and OS. Down-regulation of MDP-1 expression was a predictor of a poor prognosis for gastric cancer patients, and it may refer to tumor cells that have lost a protective enzymatic system.