K. Miyake1, R. Mori1, R. Matsuyama1, Y. Homma1, A. Okayama2, Y. Ota1, K. Taniguchi1, H. Hirano2, I. Endo1 2Yokohama City University,Graduate School Of Medical Life Science And Advanced Medical Research Center,Yokohama, KANAGAWA, Japan 1Yokohama City University,Department Of Gastroenterological Surgery,Yokohama, KANAGAWA, Japan
Introduction: Pancreatic ductal adenocarcinoma (PDAC) is classified to three types following the resectability in NCCN Guidelines, namely Resectable, Borderline resectable (BR), and Unresectable. BR cases invade to surrounding major arteries and/or vein. Therefore, it is not easy to achieve R0 resection by straightforward surgery. Recently, several studies have reported that NACRT for BR-PDAC improves prognosis and resectability, and eradicates micro metastases. Furthermore, it is presumed that NACRT induces antitumor immunity, and the accumulation of tumor infiltrating lymphocytes (TILs) correlate with prognosis. In our department, we have started clinical research of NACRT for BR-PDAC from Jan 2009. In fact, we have already reported that high CD8+ TILs might be a predictive marker of long survival for these cases. However, the feature of cases with high CD8+ TILs has not been clarified. In this study, we have performed proteomic analysis to reveal the predictive marker of high accumulation of CD8+ TILs.
Methods: We studied 72 resected BR-PDAC cases with NACRT from Jan 2009 to Mar 2014. Three matched pairs of high CD8+ TILs with good prognosis and low CD8+ TILs with poor prognosis cases were selected. Shotgun proteomics was performed using the cancerous part and tumor stroma which are extracted from formalin-fixed and paraffin-embedded tissue samples. For validation of identified proteins, immunohistochemistry (IHC) was performed. 44 PDAC cases with straight forward surgery from 2006 to 2014 were evaluated for comparison. Relationships between the identified proteins and NACRT, TILs, clinical outcomes were assessed by statistical analysis.
Results: 369 proteins were identified by shotgun proteomics, and there was statistic difference of expression in 6 proteins. From these candidates, we selected one protein; Marginal zone B and B1 cell specific protein (MZB1), which is known for B lineage cell specific protein. MZB1 expression were detected in only tumor stroma, and tumor cells were negative. IHC showed high expression of stromal MZB1 in long survival cases with high CD8+ TILs as with proteomic analysis. In the NACRT group (n=72), high expression of stromal MZB1 was positively correlated with the accumulation of CD8+ TILs (|R|=0.347, p=0.002). Patients with high accumulation of stromal MZB1 (?207) had a longer overall survival (OS) than others (3 year-survival; MZB1 high : low = 60.2% : 28.6%, p=0.014). Regarding the 36 patients with high CD8+ TILs in the NACRT group, there was statistic significant relationship between high expression of stromal MZB1 and OS (3 year-survival; MZB1 high : low = 72.9% : 42.9%, p=0.003). In straight forward group (n=44), there was no significant relationships between stromal MZB1 and accumulation of CD8+ TILs, or OS.
Conclusion: MZB1 might be a predictive marker of the high CD8+ TILs and long term survival of resected BR-PDAC cases after NACRT. Furthermore, MZB1 might have a promotive effect on anti-tumor immunity.