Department of Visceral, Thoracic and Vascular Surgery, University Hospital Carl Gustav Carus, Technische Universität Dresden, D-01307 Dresden, Germany.
Department of General, Visceral and Transplantation Surgery, University of Heidelberg, D-69120 Heidelberg, Germany.
Int J Oncol. 2016 Jul;49(1):164-72. doi: 10.3892/ijo.2016.3505. Epub 2016 May 5.
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.
自噬途径促进胰腺导管腺癌（PDAC）的生长，但关键作用尚待确定。转录因子 EB（TFEB）集中控制溶酶体和自噬生物发生。本研究旨在探索 TFEB 在 PDAC 中对自噬调节的作用。我们发现 TFEB 在人 PDAC 样本（n=45）中表达显著上调，在 15 例中有 11 例定位于细胞质和核内。在原发性 PDAC 细胞系中，TFEB 核表达在基础条件下也很明显，饥饿可进一步增强核富集。瞬时 RNA 干扰使 TFEB 表达降低 11-23%，但 TFEB 沉默后，饥饿诱导的脂化、与自噬体相关的 LC3-II 的积累和自噬体到溶酶体的途径仍得以维持。同样，吉西他滨处理癌细胞可增强凋亡和 LC3-II（自噬的标志物），无论 TFEB 表达水平如何。此外，还研究了致癌 KRAS 与 TFEB 和自噬的相互作用。KRAS 沉默导致 PDAC 细胞凋亡和 TFEB 表达的反向增加。这种反向相关性可以在使用 Pubmed GEO 和 BioPortal 数据库的遗传工程小鼠模型和人 PDAC 样本的已发表数据集中得到证实，并且与 KRAS 突变状态无关。总之，中央自噬调节剂 TFEB 在 PDAC 中表达并活跃，但 TFEB 敲低后自噬仍能维持，提示存在替代旁路信号。TFEB 对于吉西他滨诱导的细胞死亡不是必需的，但与 KRAS 表达呈负相关。
