Prediction of Prognosis in Pancreatic Cancer According to Methionyl-tRNA Synthetase 1 Expression as Determined by Immunohistochemical Staining

SIMPLE SUMMARY: Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer-related deaths worldwide, but effective prognostic markers are lacking. Methionyl-tRNA synthetase 1 (MARS1), a critical enzyme in translation initiation that transfers Met to the initiator tRNA, has been implicated in cancer development and progression. MARS1 expression was significantly increased in PDAC versus normal pancreatic duct tissues. Additionally, high expression of MARS1 was associated with a poor prognosis in patients with PDAC. Our findings suggest that MARS1 is involved in pancreatic carcinogenesis and has potential as a novel prognostic marker for PDAC. ABSTRACT: The serum level of CA 19-9 is a prognostic marker for pancreatic ductal adenocarcinoma (PDAC). We evaluated the ability of the expression level of methionyl-tRNA synthetase 1 (MARS1)—which facilitates cancer growth by modulating protein synthesis and the cell cycle—to predict the prognosis of PDAC. Immunohistochemical (IHC) staining was performed on pancreatic specimens obtained from patients with PDAC who were undergoing surgery. High MARS1 expression was defined as equal to, or greater than, that in normal acinar cells. Low MARS1 expression was defined as weaker than in normal acinar cells, and stronger than in the pancreatic duct epithelium. Univariate and multivariate analyses were performed on other factors related to prognosis. Among 137 PDAC patients, no significant differences in baseline characteristics were found between those with high (n = 82) and low (n = 55) MARS1 expression. The median overall survival time of patients with high MARS1 expression was shorter than that of those with low expression (15.2 versus 17.2 months, log-rank test p = 0.044). The median disease-free survival (DFS) was not significantly different between the two groups. However, the DFS was shorter in patients with high than in those with low MARS1 expression (8.9 versus 11.2 months, log-rank test p = 0.067). In a multivariate analysis, lymph node metastasis and high MARS1 expression were associated with a poor prognosis of PDAC. Elevated MARS1 expression detected by IHC staining is associated with a poor prognosis of PDAC, suggesting that MARS1 has potential as a prognostic marker.