PI3K/AKT/mTOR通路及其抑制剂在乳腺癌中的应用现状

磷脂酰肌醇3-激酶（phosphoinositide 3-kinase,PI3K）/蛋白激酶B（protein kinase B,AKT）/哺乳动物雷帕霉素靶蛋白（mammalian target of rapamycin,mTOR）信号转导通路在多种肿瘤中异常激活,参与肿瘤细胞增殖、分化和凋亡等生命过程的调控,是抗肿瘤药物研发的重要靶点。对目前已应用于乳腺癌临床或处于临床试验阶段的PI3K/AKT/mTOR信号通路抑制剂进行归纳,并综述该通路抑制剂的联合用药策略,以期为不同亚型乳腺癌提供个体化靶向治疗方案。     

Strategies for co-targeting the PI3K/AKT/mTOR pathway in NSCLC

The PI3K/AKT/mTOR pathway regulates cell growth and proliferation and is often dysregulated in cancer due to mutation, amplification, deletion, methylation and post-translational modifications. We and others have shown that activation of this pathway in non-small cell lung cancer (NSCLC) leads to a more aggressive disease which correlates to poor prognosis for patients. A multitude of selective inhibitors are in development which target key regulators in this pathway, however the success of PI3K targeted inhibition has been hampered by a high rate of innate and acquired resistance. Response to PI3K inhibition may be improved by co-targeting potential mediators of resistance, such as related cell surface receptors or other intracellular signaling pathways which cross-talk with the PI3K pathway. Inhibition of the PI3K pathway may also overcome radioresistance, chemoresistance and immune evasion in NSCLC. The identification of appropriate patient cohorts who will benefit from PI3K co-targeted inhibition strategies will be key to the success of these inhibitors.     

内质网激动剂调控PI3K/AKT/mTOR通路诱导人小细胞肺癌NCI-H446细胞凋亡

目的 检测内质网应激能否通过PI3K/AKT/mTOR通路对人小细胞肺癌NCI-H446细胞凋亡产生作用.方法 采用MTT法检测不同浓度衣霉素对人小细胞肺癌NCI-H446的细胞毒性,Annexin V/PI检测药物作用下人小细胞肺癌NCI-H446细胞凋亡情况,Western Blot检测PI3K/AKT/mTOR通路相关蛋白的表达.结果 衣霉素可抑制人小细胞肺癌NCI-H446细胞的活性,且呈时间和浓度依赖性.衣霉素能够激活内质网应激,抑制PI3K/AKT/mTOR信号通路,使PI3K、AKT、mTOR蛋白磷酸化下调,诱导细胞凋亡.结论 内质网激动剂能够调控PI3K/AKT/mTOR通路诱导人小细胞肺癌NCI-H446细胞凋亡.     

PI3K/AKT/mTOR信号通路抑制剂在淋巴瘤中的研究进展*

磷脂酰肌醇-3 激酶（phosphatidylinositol 3-kinase,PI 3K）- 蛋白激酶B（protein kinaseB ,PKB ,又称AKT ）- 雷帕霉素靶蛋白（mammalian target of? rapamycin,mTOR）信号通路与细胞的生长、增殖、分化、凋亡、代谢等密切相关,在多种实体肿瘤中已发现该信号通路的异常。近年来,以抑制该通路特定位点的靶向治疗已成为抗肿瘤的研究热点。许多该位点新型抑制剂也已进入淋巴瘤的临床试验中,本文就该通路在淋巴瘤中的活化状态及各个分子靶点抑制剂的研究进展做一综述。      

MCL-1-independent mechanisms of synergy between dual PI3K/mTOR and BCL-2 inhibition in diffuse large B cell lymphoma

The PI3K/AKT/mTOR axis promotes survival and is a frequently mutated pathway in cancer. Yet, inhibitors targeting this pathway are insufficient to induce cancer cell death as single agents in some contexts, including diffuse large B cell lymphoma (DLBCL). In these situations, combinations with inhibitors targeting BCL-2 survival proteins (ABT-199 and ABT-263) may hold potential. Indeed, studies have demonstrated marked synergy in contexts where PI3K/mTOR inhibitors suppress expression of the pro-survival protein, MCL-1. In this study, we use BH3 profiling to confirm that BCL-2 and BCL-X_L support survival following PI3K pathway inhibition, and that the dual PI3K/mTOR inhibitor BEZ235 strongly synergizes with BCL-2 antagonists in DLBCL. However, we identify an alternative mechanism of synergy between PI3K/mTOR and BCL-2 inhibitors, independent of MCL-1 down-regulation. Instead, we show that suppression of AKT activation by BEZ235 can induce the mitochondrial accumulation of pro-apoptotic BAD and BIM, and that expression of a constitutively active form of AKT prevents sensitization to BCL-2 antagonism. Thus, our work identifies an additional mechanism of synergy between PI3K pathway inhibitors and BCL-2 antagonists that strengthens the rationale for testing this combination in DLBCL.     

PI3K/AKT/mTOR通路抑制剂在膀胱癌中的研究进展

磷脂酰肌醇3-激酶(PI3K)/AKT/哺乳动物雷帕霉素靶标(mTOR)通路在人类肿瘤的恶性转化及其随后的生长、增殖和转移中起重要作用。临床前研究表明,PI3K/AKT/mTOR通路在膀胱癌中经常被激活。因此,这一通路被认为是膀胱癌治疗干预的候选通路,针对该通路不同成分的抑制剂正处于临床开发的不同阶段。在这里,重点介绍我们对PI3K/AKT/mTOR通路的最新研究进展,并讨论以该通路为靶点的治疗药物作为膀胱癌治疗药物的发展障碍及发展潜力。     

Differentiating mTOR inhibitors in renal cell carcinoma

PI3K/Akt/mTOR signalling is dysregulated in many cancers, including renal cell carcinoma (RCC), and activation of this pathway has been suggested to correlate with aggressive behavior and poor prognosis in RCC tumors. mTOR inhibition plays a principal role in the targeted treatment of many cancer types, including RCC. Although mTOR inhibitors share the same mechanism of action, differences in metabolism, formulation and dosing schedule underpin distinct PK/PD profiles such that they may be differentiated for use in a variety of treatment niches. Approved mTOR inhibitors temsirolimus and everolimus serve as important therapeutic options within the current RCC treatment paradigm, although their recommended applications differ in setting and patient population characteristics. Clinical practice guidelines recommend temsirolimus for use in treatment-naive patients with poor-prognosis metastatic RCC of any histology (predominant clear cell or non-clear cell histology). Everolimus provides a standard-of-care therapy for patients with metastatic RCC whose disease has progressed after previous vascular endothelial growth factor receptor-tyrosine kinase inhibitor therapy. As therapeutic failure impacts the vast majority of patients with RCC, sequencing strategies of available agents or simultaneous targeting of multiple members of the PI3K/Akt/mTOR pathway may provide additional clinical benefit. Various classes of agents targeting the PI3K/Akt/mTOR pathway are currently being investigated, including mTORC1/mTORC2 kinase domain inhibitors, mTOR/PI3K dual inhibitors, PI3K-selective inhibitors, and programmed cell death 6 modulators. Clinical trials of mTOR inhibitors in a variety of tumor types are ongoing, and the role of mTOR inhibitors continues to evolve across the RCC treatment landscape.     

Multipoint targeting of the PI3K/mTOR pathway in mesothelioma

Background:

Mesothelioma is a notoriously chemotherapy-resistant neoplasm, as is evident in the dismal overall survival for patients with those of asbestos-associated disease. We previously demonstrated co-activation of multiple receptor tyrosine kinases (RTKs), including epidermal growth factor receptor (EGFR), MET, and AXL in mesothelioma cell lines, suggesting that these kinases could serve as novel therapeutic targets. Although clinical trials have not shown activity for EGFR inhibitors in mesothelioma, concurrent inhibition of various activated RTKs has pro-apoptotic and anti-proliferative effects in mesothelioma cell lines. Thus, we hypothesised that a coordinated network of multi-RTK activation contributes to mesothelioma tumorigenesis.

Methods:

Activation of PI3K/AKT/mTOR, Raf/MAPK, and co-activation of RTKs were evaluated in mesotheliomas. Effects of RTK and downstream inhibitors/shRNAs were assessed by measuring mesothelioma cell viability/growth, apoptosis, activation of signalling intermediates, expression of cell-cycle checkpoints, and cell-cycle alterations.

Results:

We demonstrate activation of the PI3K/AKT/p70S6K and RAF/MEK/MAPK pathways in mesothelioma, but not in non-neoplastic mesothelial cells. The AKT activation, but not MAPK activation, was dependent on coordinated activation of RTKs EGFR, MET, and AXL. In addition, PI3K/AKT/mTOR pathway inhibition recapitulated the anti-proliferative effects of concurrent inhibition of EGFR, MET, and AXL. Dual targeting of PI3K/mTOR by BEZ235 or a combination of RAD001 and AKT knockdown had a greater effect on mesothelioma proliferation and viability than inhibition of individual activated RTKs or downstream signalling intermediates. Inhibition of PI3K/AKT was also associated with MDM2-p53 cell-cycle regulation.

Conclusions:

These findings show that PI3K/AKT/mTOR is a crucial survival pathway downstream of multiple activated RTKs in mesothelioma, underscoring that PI3K/mTOR is a compelling target for therapeutic intervention.     

Targeting mTOR signaling pathways and related negative feedback loops for the treatment of acute myeloid leukemia

An accumulating understanding of the complex pathogenesis of acute myeloid leukemia (AML) continues to lead to promising therapeutic approaches. Among the key aberrant intracellular signaling pathways involved in AML, the phosphatidylinositol 3-kinase/AKT/mammalian target of rapamycin (PI3K/AKT/mTOR) axis is of major interest. This axis modulates a wide array of critical cellular functions, including proliferation, metabolism, and survival. Pharmacologic inhibitors of components of this pathway have been developed over the past decade, but none has an established role in the treatment of AML. This review will discuss the preclinical data and clinical results driving ongoing attempts to exploit the PI3K/AKT/mTOR pathway in patients with AML and address issues related to negative feedback loops that account for leukemic cell survival. Targeting the PI3K/AKT/mTOR pathway is of high interest for the treatment of AML, but combination therapies with other targeted agents may be needed to block negative feedback loops in leukemia cells.     

Targeting the PI3K pathway and DNA damage response as a therapeutic strategy in ovarian cancer

Ovarian cancer is the most lethal gynecological malignancy worldwide although exponential progress has been made in its treatment over the last decade. New agents and novel combination treatments are on the horizon. Among many new drugs, a series of PI3K/AKT/mTOR pathway (referred to as the PI3K pathway) inhibitors are under development or already in clinical testing. The PI3K pathway is frequently upregulated in ovarian cancer and activated PI3K signaling contributes to increased cell survival and chemoresistance. However, no significant clinical success has been achieved with the PI3K pathway inhibitor(s) to date, reflecting the complex biology and also highlighting the need for combination treatment strategies. DNA damage repair pathways have been active therapeutic targets in ovarian cancer. Emerging data suggest the PI3K pathway is also involved in DNA replication and genome stability, making DNA damage response (DDR) inhibitors as an attractive combination treatment for PI3K pathway blockades. This review describes an expanded role for the PI3K pathway in the context of DDR and cell cycle regulation. We also present the novel treatment strategies combining PI3K pathway inhibitors with DDR blockades to improve the efficacy of these inhibitors for ovarian cancer.     

靶向PI3K/AKT/mTOR信号通路治疗急性T淋巴细胞白血病的研究进展

急性T淋巴细胞白血病(T-ALL)是来源于胸腺T细胞祖细胞的具有强侵袭性和异质性的血液系统恶性肿瘤。T-ALL约占儿童急性淋巴细胞白血病(ALL)的15%,在成人ALL中的比例约为25%。强化化疗方案的应用使儿童T-ALL患者预后显著提高,但成人及复发耐药T-ALL患者的预后仍较差。研制新型靶向药物特异性阻断T-ALL细胞内生存及耐药相关的异常激活信号通路近年来被认为是治疗成人及复发难治T-ALL患者的新策略。PI3K/AKT/mTOR通路是T-ALL细胞内异常激活信号通路中具有代表性的一条。目前靶向该通路的多种小分子抑制剂已被成功研制,并在治疗T-ALL的研究中取得良好效果。PI3K/AKT/mTOR通路相关抑制剂较传统化疗药物具有更高的特异性和更低的毒副作用,且诸多研究表明其与低剂量化疗药物或其他靶向药物联合治疗T-ALL能发挥协同效应。本综述将总结近年来在PI3K/AKT/mTOR通路与T-ALL相关领域的研究成果,并对基于靶向该通路治疗T-ALL的研究进展一并阐述。     

PI3K/AKT/mTOR信号通路在Burkitt淋巴瘤中的研究进展

 Burkitt淋巴瘤是一种高度侵袭性的非霍奇金淋巴瘤，是人类生长最快的肿瘤。根据流行病学及miRNA不同，分为地方型、散发型与免疫缺陷相关型。该病主要发生在儿童及青少年，少数发生于成年人。经短期、强效化疗后疗效显著，但成年、晚期、耐药的患者预后较差。PI3K/AKT/mTOR信号通路在细胞的生长、分化、代谢、生存以及增殖等方面发挥重要作用，研究发现，该信号通路在Burkitt淋巴瘤中呈激活状态，且针对该通路的抑制剂对Burkitt淋巴瘤细胞有抑制作用。通过对该信号通路与PTEN、c-Myc、自噬在Burkitt淋巴瘤中作用及相互关系的研究，了解其发病机制，设计该通路抑制剂与其他相关通路抑制剂或与单克隆抗体的联合用药，为晚期、耐药的患者寻找精准、高效、低毒的靶向治疗方案。     

Inhibition of PI3K/Akt/mTOR signaling pathway enhances the sensitivity of the SKOV3/DDP ovarian cancer cell line to cisplatin in vitro

The activation of the PI3K/AKT/m TOR pathway plays a key role in ovarian cancer tumorigenesis, progression and chemotherapy resistance. This study aimed to explore the possible mechanism that PI-103, a dual inhibitor of phosphatidylinositide 3-kinase and m TOR, enhances the sensitivity of SKOV3/DDP ovarian cancer cell line to cisplatin chemotherapy. The results showed that PI-103 could significantly increase the sensitivity of SKVO3/DDP cells to cisplatin through inhibiting the activation of PI3K/Akt/m TOR signaling pathway and inducing cell cycle arrest and apoptosis.     

PI3K/AKT/mTOR信号通路介导索拉非尼治疗原发性肝癌耐药机制的研究进展

索拉非尼（sorafenib）作为原发性肝癌（hepatocellular carcinoma,HCC）靶向治疗的一线药物已广泛应用于临床,然而部分HCC患者对索拉非尼治疗耐药导致临床疗效欠佳,联合其他靶向药物的临床实验仍未取得突破,故深入研究索拉非尼耐药机制,逆转索拉非尼耐药对于改善肝癌治疗的预后具有重要意义。最新研究发现,PI3K/AKT/mTOR信号通路在索拉非尼耐药机制中起重要作用,本文将从PI3K/AKT/mTOR信号通路促进肿瘤血管生成、参与细胞自噬、抑制肿瘤细胞凋亡并促进其增殖、与RAS/RAF/ERK/MEK信号通路交联及其促进上皮-间质转化等几个方面,概述其在索拉非尼治疗原发性肝癌时产生耐药的机制,为进一步开发治疗原发性肝癌的新型药物提供研究方向。     

Regulation of O2 consumption by the PI3K and mTOR pathways contributes to tumor hypoxia

Background

Inhibitors of the phosphatidylinositol 3-kinase (PI3K) and the mammalian target of rapamycin (mTOR) pathway are currently in clinical trials. In addition to antiproliferative and proapoptotic effects, these agents also diminish tumor hypoxia. Since hypoxia is a major cause of resistance to radiotherapy, we sought to understand how it is regulated by PI3K/mTOR inhibition.

Methods

Whole cell, mitochondrial, coupled and uncoupled oxygen consumption were measured in cancer cells after inhibition of PI3K (Class I) and mTOR by pharmacological means or by RNAi. Mitochondrial composition was assessed by immunoblotting. Hypoxia was measured in spheroids, in tumor xenografts and predicted with mathematical modeling.

Results

Inhibition of PI3K and mTOR reduced oxygen consumption by cancer cell lines is predominantly due to reduction of mitochondrial respiration coupled to ATP production. Hypoxia in tumor spheroids was reduced, but returned after removal of the drug. Murine tumors had increased oxygenation even in the absence of average perfusion changes or tumor necrosis.

Conclusions

Targeting the PI3K/mTOR pathway substantially reduces mitochondrial oxygen consumption thereby reducing tumor hypoxia. These alterations in tumor hypoxia should be considered in the design of clinical trials using PI3K/mTOR inhibitors, particularly in conjunction with radiotherapy.     

Two hits are better than one: targeting both phosphatidylinositol 3-kinase and mammalian target of rapamycin as a therapeutic strategy for acute leukemia treatment

Phosphatidylinositol 3-kinase (PI3K) and mammalian target of rapamycin (mTOR) are two key components of the PI3K/Akt/mTOR signaling pathway. This signal transduction cascade regulates a wide range of physiological cell processes, that include differentiation, proliferation, apoptosis, autophagy, metabolism, motility, and exocytosis. However, constitutively active PI3K/Akt/mTOR signaling characterizes many types of tumors where it negatively influences response to therapeutic treatments. Hence, targeting PI3K/Akt/mTOR signaling with small molecule inhibitors may improve cancer patient outcome. The PI3K/Akt/mTOR signaling cascade is overactive in acute leukemias, where it correlates with enhanced drug-resistance and poor prognosis. The catalytic sites of PI3K and mTOR share a high degree of sequence homology. This feature has allowed the synthesis of ATP-competitive compounds targeting the catalytic site of both kinases. In preclinical models, dual PI3K/mTOR inhibitors displayed a much stronger cytotoxicity against acute leukemia cells than either PI3K inhibitors or allosteric mTOR inhibitors, such as rapamycin. At variance with rapamycin, dual PI3K/mTOR inhibitors targeted both mTOR complex 1 and mTOR complex 2, and inhibited the rapamycin-resistant phosphorylation of eukaryotic initiation factor 4E-binding protein 1, resulting in a marked inhibition of oncogenic protein translation. Therefore, they strongly reduced cell proliferation and induced an important apoptotic response. Here, we reviewed the evidence documenting that dual PI3K/mTOR inhibitors may represent a promising option for future targeted therapies of acute leukemia patients.     

Will PI3K pathway inhibitors be effective as single agents in patients with cancer?

The phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) axis regulates essential cellular functions including cell survival, proliferation, metabolism, migration, and angiogenesis. The PI3K pathway is activated in human cancers by mutation, amplification, and deletion of genes encoding components of this pathway. The critical role of PI3K in cancer has led to the development of drugs targeting the effector mechanisms of this signaling network. Recent studies have shown that inhibition at multiple levels of the PI3K pathway results in FOXO-dependent feedback reactivation of several receptor tyrosine kinases (RTKs) which, in turn, limit the sustained inhibition of this pathway and attenuates the action of therapeutic antagonists. This suggests that if used as single agents, PI3K pathway inhibitors may have limited clinical activity. We propose herein that to successfully target the output of the PI3K pathway in cancer cells, combination therapies that hinder these compensatory mechanisms should be used. Thus, combination therapies that target RTKs, PI3K, and mTOR activities may be required to maximize the clinical benefit derived from treatment with these inhibitors.     

Reciprocal feedback inhibition of the androgen receptor and PI3K as a novel therapy for castrate-sensitive and -resistant prostate cancer

Gain-of-function of the androgen receptor (AR) and activation of PI3K/AKT/mTOR pathway have been demonstrated to correlate with progression to castration-resistant prostate cancer (CRPC). However, inhibition of AR or PI3K/mTOR alone results in a reciprocal feedback activation. Therefore, we hypothesized that dual inhibition of the AR and PI3K/mTOR pathway might lead to a synergistic inhibition of cell growth and overcome drug resistance in CRPC. Here, we reported that androgen-depletion increased AR protein level and Akt phosphorylation at Ser473 and Thr308 in LNCaP cells. Moreover, we developed resistance cell lines of LNCaP to Enzalutamide (or MDV3100), an AR inhibitor (named as LNCaP ‘MDV-R’) and PF-04691502, a PI3K/mTOR inhibitor (named as LNCaP ‘PF-R’). MTS analysis showed that LNCaP ‘PF-R’ was strongly resistant to Enzalutamide treatment, and on the other hand, LNCaP ‘MDV-R’ was 6-fold resistant to PF-04691502 treatment. Mechanistically, LNCaP ‘MDV-R’ cells had significantly reduced AR, loss of PSA and increase Akt activity in contrast with LNCaP ‘PF-R’ cells. Combined inhibition of PI3K/mTOR and AR pathways with a variety of small molecular inhibitors led to a synergistic suppression of cell proliferation and a profound increase of apoptosis and cell cycle arrest in both androgen-dependent LNCaP and independent CRPC 22Rv1 cell lines. In conclusion, this study provides preclinical proof-of-concept that the combination of a PI3K/mTOR inhibitor with an AR inhibitor results in a synergistic anti-tumor response in non-CRPC and CRPC models.