MZB1 in borderline resectable pancreatic cancer resected after neoadjuvant chemoradiotherapy.

BACKGROUND: A high accumulation of CD8+ tumor-infiltrating lymphocytes (TILs) induced by neoadjuvant chemoradiotherapy (NACRT) is associated with a favorable prognosis in patients with pancreatic ductal adenocarcinoma (PDAC). However, the correlation between a high accumulation of CD8+ TILs and a favorable prognosis has yet to be fully clarified. The aim of this study was to determine predictive markers of a high accumulation of CD8+ TILs, with a favorable prognosis, using proteomic analysis.

MATERIALS AND METHODS: We studied 72 resected borderline resectable PDAC patients treated with NACRT between April 2009 and March 2014. Three matched pairs of high CD8+ TIL patients with a favorable prognosis and low CD8+ TIL patients with a poor prognosis were selected. Shotgun proteomics of the stroma and cancerous lesion was performed using formalin-fixed, paraffin-embedded tissue. Validation of the identified proteins was performed using immunohistochemical staining. Relationships between the identified proteins and TILs and clinical outcomes were assessed.

RESULTS: Marginal zone B- and B1-cell-specific protein (MZB1) was detected in the tumor stroma. MZB1 expression was positively correlated with a high accumulation of CD8+ TILs. High stromal MZB1 expression also correlated with disease-free and overall survival. In a subgroup analysis of CD8+ expression, there was a significant association between stromal MZB1 expression and disease-free and overall survival in the high CD8+ TIL group.

CONCLUSIONS: MZB1 is a potential marker of a high accumulation of CD8+ TILs in borderline resectable PDACs resected after NACRT. Combination of CD8+ TILs with MZB1 may be a new biomarker of resected cases after NACRT.