A subset of metastatic pancreatic ductal adenocarcinomas depends quantitatively on oncogenic Kras/Mek/Erk-induced hyperactive mTOR signalling. Mus musculus

Objective Oncogenic Kras-activated robust Mek/Erk signals phosphorylate to the tuberous sclerosis complex (Tsc) and deactivates mammalian target of rapamycin (mTOR) suppression in pancreatic ductal adenocarcinoma (PDAC); however, Mek and mTOR inhibitors alone have demonstrated minimal clinical antitumor activity. Design We generated transgenic mouse models in which mTOR was hyperactivated either through the Kras/Mek/Erk cascade, by loss of Pten or through Tsc1 haploinsufficiency. Primary cancer cells were isolated from mouse tumours. Oncogenic signalling was assessed in vitro and in vivo, with and without single or multiple targeted molecule inhibition. Transcriptional profiling was used to identify biomarkers predictive of the underlying pathway alterations and of therapeutic response. Results from the preclinical models were confirmed on human material. Results Reduction of Tsc1 function facilitated activation of Kras/Mek/Erk-mediated mTOR signalling, which promoted the development of metastatic PDACs. Single inhibition of mTOR or Mek elicited strong feedback activation of Erk or Akt, respectively. Only dual inhibition of Mek and PI3K reduced mTOR activity and effectively induced cancer cell apoptosis. Analysis of downstream targets demonstrated that oncogenic activity of the Mek/Erk/Tsc/mTOR axis relied on Aldh1a3 function. Moreover, in clinical PDAC samples, ALDH1A3 specifically labelled an aggressive subtype. Conclusions These results advance our understanding of Mek/Erk-driven mTOR activation and its downstream targets in PDAC, and provide a mechanistic rationale for effective therapeutic matching for Aldh1a3-positive PDACs. Overall design: We performed gene expression microarray analysis in duplicates on 11 cell lines representing three experimental models

研究目的：致癌性Kras激活的强活性Mek/Erk信号可对结节性硬化复合物（Tuberous sclerosis complex, Tsc）进行磷酸化修饰，并解除胰腺导管腺癌（pancreatic ductal adenocarcinoma, PDAC）中雷帕霉素靶蛋白（mammalian target of rapamycin, mTOR）的抑制作用；然而，单独使用Mek或mTOR抑制剂仅展现出微弱的临床抗肿瘤活性。
实验设计：我们构建了转基因小鼠模型，通过Kras/Mek/Erk级联反应、Pten缺失或Tsc1单倍体剂量不足使mTOR过度激活。从小鼠肿瘤中分离原代癌细胞，在施加或不施加单靶点或多靶点靶向药物抑制的条件下，于体外和体内环境中评估致癌信号通路的活化情况。通过转录组谱分析，鉴定可预测通路异常及治疗响应的生物标志物。临床前模型的研究结果在人体样本中得到验证。
研究结果：Tsc1功能缺失可增强Kras/Mek/Erk介导的mTOR信号活化，进而促进转移性胰腺导管腺癌的发生发展。单独抑制mTOR或Mek可分别引发Erk或蛋白激酶B（Protein Kinase B, Akt）的强烈反馈激活。仅联合抑制Mek与磷脂酰肌醇3-激酶（phosphoinositide 3-kinase, PI3K）才能降低mTOR活性，并有效诱导癌细胞凋亡。对下游靶点的分析显示，Mek/Erk/Tsc/mTOR信号轴的致癌活性依赖于Aldh1a3的功能。此外，在临床PDAC样本中，ALDH1A3可特异性标记侵袭性亚型。
研究结论：本研究加深了我们对PDAC中Mek/Erk调控的mTOR活化及其下游靶点的认识，并为Aldh1a3阳性PDAC的精准治疗方案匹配提供了机制依据。
整体实验设计：我们对代表3种实验模型的11株细胞系进行了重复基因表达微阵列分析。