Abstract. Autophagy pathways promote the growth of pancreatic ductal adenocarcinoma (PDAC), but the critical role is yet to be determined. Transcription factor EB (TFEB) centrally controls lysosomal and autophagy biogenesis. This study aimed to explore the role of TFEB for autophagy regulation in PDAC. We found that TFEB expression was significantly elevated in human PDAC samples (n=45), and localized to the cytoplasm and nucleus in 11 of 15 cases. In primary PDAC cell lines, TFEB nuclear expression was evident even under basal conditions, and further nuclear enrichment was achieved by starvation. Transient RNA interference reduced TFEB expression to 11-23%, but starvation-induced accumulation of the lipidated, autophagosome-associated LC3-II and the autophago-to-lysosome route was maintained after TFEB silencing. Likewise, gemcitabine treatment of the cancer cells augmented apoptosis and LC3-II as an indicator of autophagy, regardless of the TFEB expression levels. Moreover, the interplay of oncogenic KRAS with TFEB and autophagy was investigated. KRAS silencing caused PDAC cell apoptosis and a reciprocal increase in TFEB expression. This inverse correlation could be confirmed in published data sets of genetically engineered mouse models and human PDAC samples using the the Pubmed GEO and BioPortal databases, and was independent of KRAS mutation status. In conclusion, the central autophagy regulator TFEB is expressed and active in PDAC, but autophagy is sustained after TFEB knockdown, suggesting alternative bypass signaling. TFEB is dispensable for gemcitabine-induced cell death, but inversely correlated with KRAS expression.
Background The present study aimed to examine the impact of microscopically tumour-infiltrated resection margins (R1) in pancreatic ductal adenocarcinoma (PDAC) patients with advanced lymphonodular metastasis (pN1–pN2) on overall survival (OS). Methods This retrospective, multi-institutional analysis included patients undergoing surgical resection for PDAC at three tertiary university centres between 2005 and 2018. Subcohorts of patients with lymph node status pN0–N2 were stratified according to the histopathological resection status using Kaplan-Meier survival analysis. Results The OS of the entire cohort (n = 620) correlated inversely with the pN status (26 [pN0], 18 [pN1], 11.8 [pN2] months, P < 0.001) and R status (21.7 [R0], 12.5 [R1] months, P < 0.001). However, there was no statistically significant OS difference between R0 versus R1 in cases with advanced lymphonodular metastases: 19.6 months (95% CI: 17.4–20.9) versus 13.6 months (95% CI: 10.7–18.0) for pN1 stage and 13.7 months (95% CI: 10.7–18.9) versus 10.1 months (95% CI: 7.9–19.1) for pN2, respectively. Accordingly, N stage–dependent Cox regression analysis revealed that R status was a prognostic factor in pN0 cases only. Furthermore, there was no significant survival disadvantage for patients with R0 resection but circumferential resection margin invasion (≤ 1 mm; CRM+; 10.7 months) versus CRM-negative (13.7 months) cases in pN2 stages (P = 0.5). Conclusions An R1 resection is not associated with worse OS in pN2 cases. If there is evidence of advanced lymph node metastasis and a re-resection due to an R1 situation (e.g. at venous or arterial vessels) may substantially increase the perioperative risk, margin clearance in order to reach local control might be avoided with respect to the OS.
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