Ho Daniel W H, Chan Lo K, Chiu Yung T, Xu Iris M J, Poon Ronnie T P, Cheung Tan T, Tang Chung N, Tang Victor W L, Lo Irene L O, Lam Polly W Y, Yau Derek T W, Li Miao X, Wong Chun M, Ng Irene O L
Department of Pathology, The University of Hong Kong, Hong Kong, Hong Kong.
State Key Laboratory for Liver Research, The University of Hong Kong, Hong Kong, Hong Kong.
Gut. 2017 Aug;66(8):1496-1506. doi: 10.1136/gutjnl-2016-312734. Epub 2016 Dec 14.
We investigated the mutational landscape of mammalian target of rapamycin (mTOR) signalling cascade in hepatocellular carcinomas (HCCs) with chronic HBV background, aiming to evaluate and delineate mutation-dependent mechanism of mTOR hyperactivation in hepatocarcinogenesis.
We performed next-generation sequencing on human HCC samples and cell line panel. Systematic mutational screening of mTOR pathway-related genes was undertaken and mutant genes were evaluated based on their recurrence. Protein expressions of tuberous sclerosis complex (TSC)1, TSC2 and pRPS6 were assessed by immunohistochemistry in human HCC samples. Rapamycin sensitivity was estimated by colony-formation assay in HCC cell lines and the treatment was further tested using our patient-derived tumour xenograft (PDTX) models.
We identified and confirmed multiple mTOR components as recurrently mutated in HBV-associated HCCs. Of significance, we detected frequent (16.2%, n=18/111) mutations of and genes in the HCC samples. The spectrum of mutations likely disrupts the endogenous gene functions in suppressing the downstream mTOR activity through different mechanisms and leads to more aggressive tumour behaviour. Mutational disruption of and was also observed in HCC cell lines and our PDTX models. -mutant cells exhibited reduced colony-forming ability on rapamycin treatment. With the use of biologically relevant -mutant PDTXs, we demonstrated the therapeutic benefits of the hypersensitivity towards rapamycin treatment.
Taken together, our findings suggest the significance of previously undocumented mutation-dependent mTOR hyperactivation and frequent mutations in HBV-associated HCCs. They define a molecular subset of HCC having genetic aberrations in mTOR signalling, with potential significance of effective specific drug therapy.
我们研究了慢性乙肝背景下肝细胞癌（HCC）中雷帕霉素哺乳动物靶点（mTOR）信号级联的突变图谱，旨在评估和阐明肝癌发生过程中mTOR过度激活的突变依赖性机制。
我们对人类HCC样本和细胞系进行了二代测序。对mTOR通路相关基因进行了系统的突变筛查，并根据突变的复发情况对突变基因进行了评估。通过免疫组化检测了人类HCC样本中结节性硬化复合物（TSC）1、TSC2和pRPS6的蛋白表达。通过HCC细胞系中的集落形成试验评估雷帕霉素敏感性，并使用我们的患者来源肿瘤异种移植（PDTX）模型进一步测试该治疗方法。
我们鉴定并确认多个mTOR组分在HBV相关HCC中反复发生突变。重要的是，我们在HCC样本中检测到频繁（16.2%，n = 18/111）的 和 基因的突变。 突变谱可能通过不同机制破坏内源性基因在抑制下游mTOR活性方面的功能，并导致更具侵袭性的肿瘤行为。在HCC细胞系和我们的PDTX模型中也观察到 和 的突变破坏。 -突变细胞在雷帕霉素处理下表现出集落形成能力降低。通过使用生物学相关的 -突变PDTX，我们证明了对雷帕霉素治疗超敏的治疗益处。
综上所述，我们的研究结果表明，以前未记录的突变依赖性mTOR过度激活以及HBV相关HCC中频繁的 突变具有重要意义。它们定义了一个在mTOR信号传导中存在基因畸变的HCC分子亚群，具有有效特异性药物治疗的潜在意义。
