腺苷酸活化蛋白激酶途径与肿瘤的研究进展

腺苷酸活化蛋白激酶(AMPK)是哺乳动物细胞中高度保守的蛋白质,是细胞的重要的代谢感受器。哺乳动物雷帕霉素靶蛋白(m TOR)信号通路,是一种不典型的丝/苏氨酸激酶,在进化中也具有高度保守性,主要通过调控蛋白合成来调节细胞的生长,m TOR激酶通过多种信号通路来实现对细胞生长的调节作用,其中营养信号激活通路为细胞外的氨基酸通路LKB1-AMPK途径。二甲双胍(LKB1/AMPK的激活剂),可抑制m TOR的活性,从而可以应用于多种肿瘤的治疗,目前研究表明AMPK信号通路及其相关的信号通路与多种肿瘤的发生、发展有关。     

Low-Dose Rapamycin (Sirolimus) Effects in Autosomal Dominant Polycystic Kidney Disease: An Open-Label Randomized Controlled Pilot Study

Background and objectives

The two largest studies of mammalian target of rapamycin inhibitor treatment of autosomal dominant polycystic kidney disease (ADPKD) demonstrated no clear benefit on the primary endpoint of total kidney volume (TKV) or on eGFR. The present study evaluated two levels of rapamycin on the 12-month change in ¹²⁵I-iothalamate GFR (iGFR) as the primary endpoint and TKV secondarily.

Design, setting, participants, & measurements

In a 12-month open-label pilot study, 30 adult patients with ADPKD were randomly assigned to low-dose (LD) rapamycin (rapamycin trough blood level, 2–5 ng/ml) (LD group, n=10), standard-dose (STD) rapamycin trough level (>5–8 ng/ml) (STD group, n=10), or standard care (SC group, n=10). They were evaluated with iGFR and noncontrast computed tomography.

Results

Change in iGFR at 12 months was significantly higher in the LD group (7.7±12.5 ml/min per 1.73 m²; n=9) than in the SC group (−11.2±9.1 ml/min per 1.73 m²; n=9) (LD versus SC: P<0.01). Change in iGFR at 12 months in the STD group (1.6±12.1 ml/min per 1.73 m²; n=8) was not significantly greater than that in the SC group (P=0.07), but it was in the combined treatment groups (LD+STD versus SC: P<0.01). Neither eGFR calculated by the CKD-Epidemiology Collaboration equation nor TKV (secondary endpoint) changed significantly from baseline to 12 months in any of the groups. On the basis of results of the mixed model, during the study, patients in the LD group had significantly lower trough blood levels of rapamycin (mean range±SD, 2.40±0.64 to 2.90±1.20 ng/ml) compared with those in the STD group (3.93±2.27 to 5.77±1.06 ng/ml) (P<0.01).

Conclusion

Patients with ADPKD receiving LD rapamycin demonstrated a significant increase in iGFR compared with those receiving standard care, without a significant effect on TKV after 12 months.     

mTOR信号通路在克唑替尼诱导的EML4-ALK融合基因阳性肺癌细胞株H2228凋亡中的作用

 目的：探讨以磷脂酰肌醇3-激酶相关激酶蛋白家族成员哺乳动物雷帕霉素靶蛋白 (mTOR)为中心的信号通路在克唑替尼（crizotinib）诱导的棘皮动物微管结合蛋白样蛋白4-间变性淋巴瘤激酶（EML4-ALK）融合基因阳性的非小细胞肺癌细胞株H2228凋亡中的作用。方法：根据不同的实验目的处理H2228细胞后,荧光定量PCR检测基因状态,MTT法检测细胞抑制率;流式细胞术检测细胞凋亡和细胞周期;Western blotting检测细胞mTOR信号通路中关键蛋白的表达及活化水平。结果：Crizotinib对H2228细胞有促凋亡作用,呈时间和剂量依赖性,且能使H2228细胞阻滞在G1期。在使用crizotinib处理的凋亡细胞株中发现mTOR活化水平降低,mTOR上、下游关键蛋白的活化水平都呈下降趋势,肺癌细胞株H2228中特殊表达的融合蛋白EML4-ALK变异体3表达量未受影响,但其活化形式p-ALK明显受到抑制。结论：初步证实mTOR信号通路在crizotinib诱导含有EML4-ALK融合基因的肺癌细胞H2228凋亡中有一定作用,为crizotinib的作用机制提供了依据。     

Mammalian target of rapamycin inhibition in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death worldwide. It is associated with a poor prognosis and has limited treatment options. Sorafenib, a multi-targeted kinase inhibitor, is the only available systemic agent for treatment of HCC that improves overall survival for patients with advanced stage disease; unfortunately, an effective second-line agent for the treatment of progressive or sorafenib-resistant HCC has yet to be identified. This review focuses on components of the mammalian target of rapamycin (mTOR) pathway, its role in HCC pathogenesis, and dual mTOR inhibition as a therapeutic option with potential efficacy in advanced HCC. There are several important upstream and downstream signals in the mTOR pathway, and alternative tumor-promoting pathways are known to exist beyond mTORC1 inhibition in HCC. This review analyzes the relationships of the upstream and downstream regulators of mTORC1 and mTORC2 signaling; it also provides a comprehensive global picture of the interaction between mTORC1 and mTORC2 which demonstrates the pre-clinical relevance of the mTOR pathway in HCC pathogenesis and progression. Finally, it provides scientific rationale for dual mTORC1 and mTORC2 inhibition in the treatment of HCC. Clinical trials utilizing mTORC1 inhibitors and dual mTOR inhibitors in HCC are discussed as well. The mTOR pathway is comprised of two main components, mTORC1 and mTORC2; each has a unique role in the pathogenesis and progression of HCC. In phase III studies, mTORC1 inhibitors demonstrate anti-tumor activity in advanced HCC, but dual mTOR (mTORC1 and mTORC2) inhibition has greater therapeutic potential in HCC treatment which warrants further clinical investigation.     

Antileukaemic effect of PI3K‐mTOR inhibitors in acute myeloid leukaemia‐gene expression profiles reveal CDC25B expression as determinate of pharmacological effect

Acute myeloid leukaemia (AML) is a heterogeneous malignancy. Intracellular signalling through the phosphatidylinositol 3‐kinase (PI3K)‐Akt‐mammalian target of rapamycin (mTOR) pathway is important for regulation of cellular growth and metabolism, and inhibitors of this pathway is considered for AML treatment. Primary human AML cells, derived from 96 consecutive adult patients, were examined. The effects of two mTOR inhibitors (rapamycin, temsirolimus) and two PI3K inhibitors (GDC‐0941, 3‐methyladenine) were studied, and we investigated cytokine‐dependent proliferation, regulation of apoptosis and global gene expression profiles. Only a subset of patients demonstrated strong antiproliferative effects of PI3K‐mTOR inhibitors. Unsupervised hierarchical clustering analysis identified two main clusters of patients; one subset showing weak or absent antiproliferative effects (59%) and another group showing a strong growth inhibition for all drugs and concentrations examined (41%). Global gene expression analyses showed that patients with AML cell resistance against PI3K‐mTOR inhibitors showed increased mRNA expression of the CDC25B gene that encodes the cell cycle regulator Cell Division Cycle 25B. The antileukaemic effect of PI3K‐Akt‐mTOR inhibition varies between patients, and resistance to these inhibitors is associated with the expression of the cell cycle regulator CDC25B, which is known to crosstalk with the PI3K‐Akt‐mTOR pathway and mediate rapamycin resistance in experimental models.     

Synergistic anti-tumor effects of RAD001 with MEK inhibitors in neuroendocrine tumors: a potential mechanism of therapeutic limitation of mTOR inhibitor

Mammalian target of rapamycin (mTOR) inhibitors have been clinically used as anticancer agents in several types of human malignancies including neuroendocrine tumor (NET) but the development of clinical resistances or their therapeutic limitations have been also reported. This clinical resistance has been proposed to be partly due to a compensatory activation of an mTOR upstream factor Akt and MEK/ERK pathway in NET cells but its details have not necessarily been reported. Therefore, in this study, we examined the effects of mTOR inhibitors on these activations and of the concomitant treatment of mTOR and MEK inhibitors in two NET cell lines, NCI-H727 and COLO320. We evaluated the effects of RAD001, mTOR inhibitor, and U0126, MEK inhibitor, on cell proliferation and migration of these cells. In addition, an alteration of the factors involved in Akt/mTOR and MEK/ERK pathways was also examined under administration of these agents. RAD001 and U0126 treatment significantly inhibited cell proliferation and their combined treatment synergistically decreased it in both cell lines. Additionally, these treatments above decreased the expression of cell cycle-related factors, suggestive of an involvement of cell cycle arrest in therapeutic effects. The combined treatment also inhibited the cell migration in NCI-H727 via the decrement of MMP2 and 9 in an additive manner. We demonstrated the potential synergistic/combined effects of inhibitors of mTOR and MEK on cell proliferation and migration. These results suggest the potential therapeutic efficacy of the combined therapy of mTOR and MEK inhibitors or a dual inhibitor for the treatment of NET patients.     

Des-acyl ghrelin exhibits pro-anabolic and anti-catabolic effects on C2C12 myotubes exposed to cytokines and reduces burn-induced muscle proteolysis in rats

Although ghrelin and GHRP-2 have been shown to inhibit skeletal muscle proteolysis in rats with burn injury, the effects of des-acyl ghrelin (DAG) have not been reported. In this paper, we demonstrate that continuous 24h administration of DAG attenuated burn-induced EDL muscle proteolysis, and normalized elevated TNFα mRNA. Combined treatment of cultured C2C12 myotubes with TNFα and IFN-γ (TNF+IFN) inhibited protein synthesis and increased protein breakdown; DAG abolished both effects. PI3 kinase inhibition by LY294002 and mTOR inhibition by rapamycin blocked the reversal of the anti-anabolic effects of TNF+IFN-treated myotubes by DAG. DAG also reversed or attenuated the TNF+IFN-induced reduction in phosphorylation of Akt, FOXO1, 4E-BP-1, and GSK-3β in myotubes. Furthermore, DAG attenuated the atrophy signal, phospho-NF-κB, and the mRNA expression of MAFbx and MuRF1, upregulated by TNF+IFN in C2C12 myotubes. We conclude that DAG reduces muscle cachexia produced by injury and proinflammatory cytokines, and that DAG or DAG-based compounds may be useful in treating wasting disorders.     

mTOR inhibition with rapamycin causes impaired insulin signalling and glucose uptake in human subcutaneous and omental adipocytes

Rapamycin is an immunosuppressive agent used after organ transplantation, but its molecular effects on glucose metabolism needs further evaluation. We explored rapamycin effects on glucose uptake and insulin signalling proteins in adipocytes obtained via subcutaneous (n=62) and omental (n=10) fat biopsies in human donors. At therapeutic concentration (0.01 μM) rapamycin reduced basal and insulin-stimulated glucose uptake by 20-30%, after short-term (15 min) or long-term (20 h) culture of subcutaneous (n=23 and n=10) and omental adipocytes (n=6 and n=7). Rapamycin reduced PKB Ser473 and AS160 Thr642 phosphorylation, and IRS2 protein levels in subcutaneous adipocytes. Additionally, it reduced mTOR-raptor, mTOR-rictor and mTOR-Sin1 interactions, suggesting decreased mTORC1 and mTORC2 formation. Rapamycin also reduced IR Tyr1146 and IRS1 Ser307/Ser616/Ser636 phosphorylation, whereas no effects were observed on the insulin stimulated IRS1-Tyr and TSC2 Thr1462 phosphorylation. This is the first study to show that rapamycin reduces glucose uptake in human adipocytes through impaired insulin signalling and this may contribute to the development of insulin resistance associated with rapamycin therapy.