EGFR抑制剂对肿瘤的抑制和放疗增敏作用研究进展

放射治疗是治疗肿瘤的重要手段,提高放疗疗效仍是目前肿瘤放射治疗学领域亟待解决的难题。表皮生长因子受体（epidermal growth factor receptor ,EGFR）是ErbB家族成员之一,具有酪氨酸激酶活性,是一种重要的跨膜受体。EGFR 可介导细胞迁移、黏附、增殖、分化、凋亡,且与肿瘤的形成和恶化密切相关。EGFR 抑制剂具有放射增敏性,EGFR 抑制剂可通过影响细胞周期进展、DNA 损伤修复及抗血管形成等多种途径发挥放疗增敏作用。合理应用EGFR 抑制剂,将有效地提高恶性肿瘤放射敏感性,从而改善患者生活质量,减少肿瘤局部复发,延长患者的生存时间。      

mTOR抑制剂联合阿霉素在肝癌细胞株对化疗药物协同增敏中的作用研究

目的 初步探讨mTOR抑制剂Temsirolimus联合阿霉素对肝癌细胞的抗肿瘤作用机制及化疗增敏作用.方法 体外培养肝癌细胞,取增殖期细胞进行实验,用MTT法检测单用Temsirolimus、阿霉素以及两者联合应用时对肿瘤细胞生长的影响,用流式细胞术检测细胞凋亡情况.结果 在体外肝癌细胞株PLC/PRF/5、BEL7402、HuH7中,与单独用药相比,Temsirolimus联合阿霉素提高了细胞增殖抑制率及凋亡率.Temsirolimus联合阿霉素的抗肿瘤作用高于将阿霉素浓度增加1倍时的抗肿瘤作用.结论 联合应用mTOR抑制剂及阿霉素可以提高抗肿瘤作用,前者对化疗药物有一定的增敏效应,两者联合可以通过减少阿霉素的剂量来减轻不良反应,同时不降低药物效能,有临床应用的前景.     

mTOR功能及其抑制剂研究进展

哺乳动物雷帕霉素靶蛋白（mammalian target of rapamycin mTOR）是一种丝／苏氨酸蛋白激酶，mTOR在肿瘤细胞生长、增殖过程中起重要作用，mTOR信号通路活动异常与肿瘤的发生有密切关系，mTOR足肿瘤药物治疗作用的理想靶点，目前新的mTOR抑制剂不断出现。本文对mTOR蛋白的结构、功能和mTOR信号通路及其抑制剂进行了综述。     

端粒酶抑制剂对小鼠胃癌放疗的增敏作用研究

目的：探讨端粒酶抑制剂对动物在体肿瘤的治疗作用及对放射治疗的增敏价值。方法：将SGC-7901胃癌细胞接种BALB/c小鼠，采用端粒酶抑制剂AZT联合放疗治疗小鼠胃癌，观察其对肿瘤体积和肿瘤端粒酶活性的影响。结果：未治疗组小鼠肿瘤体积增加了2.5倍，而AZT组、放疗组及AZT联合放疗组肿瘤体积分别缩小了26.3%、36.8%及70.5%。肿瘤端粒酶活性检测，未治疗组、AZT、放疗均能使肿瘤体积缩小并降低前几天粒酶活性分别为100、55.2、24.5及12.1。结论：AZT放疗均能使肿瘤体积缩小并降低端粒酶活性，且AZT能增加肿瘤的放射敏感性。     

放疗增敏PD-1/PD-L1抑制剂疗效的研究进展

程序性死亡受体-1(PD-1)/程序性死亡受体-配体(PD-L1)抑制剂治疗现已批准用于多种肿瘤,但其单药治疗疗效偏低。如何通过放疗来增敏PD-1/PD-L1抑制剂的疗效,是放疗业界研究的热点。放疗与PD-1/PD-L1抑制剂的联合应用,在多项研究中已显示出生存获益。然而电离辐射对于PD-1/PD-L1免疫治疗而言,是一把双刃剑。如何在充分发挥放疗免疫激活作用的同时,尽量避免放疗的免疫抑制效应,这与放疗的剂量选择、分割模式、治疗时机选择及治疗部位数目等密切相关。为此,本文针对晚期转移性肿瘤治疗中,如何优化放疗联合抗PD-1/PD-L1治疗做一综述。     

基于纳米技术的肿瘤热放疗增敏的研究进展

放疗是治疗恶性肿瘤的重要手段之一,通过物理技术提高放疗的治疗增益比是现代精确放疗技术的发展方向。由于高能放射线固有的物理特性,通过放射物理技术提高放疗的治疗增益比必然遭遇瓶颈。应用热疗增敏放疗,可提高肿瘤细胞的放射敏感性、降低肿瘤细胞的放射抵抗性,在放疗中具有非常重要的临床实用价值。具有良好的生物相容性和安全性的多功能纳米材料在肿瘤光热疗治疗研究中已经受到广泛的关注并展现出了良好的潜力,将纳米热疗技术作为增敏载体结合放疗,在热放疗增敏的同时,高原子序数纳米材料亦可单独作为放疗增敏载体,使肿瘤热疗和放疗二者协同增效,有可能克服目前制约肿瘤放疗的诸多难题,为推动放疗的进一步发展提供了新的发展机遇。本文对基于纳米技术的肿瘤热放疗增敏的研究进展进行综述。      

mTOR信号通路与非小细胞肺癌放疗敏感性的关系

目的:研究mTOR信号通路与非小细胞肺癌放疗敏感性的关系。方法:采用不同剂量的雷帕霉素抑制非小细胞肺癌细胞系A549中的mTOR信号通路;Western blot检测雷帕霉素作用后下游信号分子的表达;将A549细胞分为空白对照组及雷帕霉素作用的实验组,将对照组和实验组经不同剂量射线作用;用MTT实验（噻唑蓝）及克隆形成能力检测细胞增殖能力,流式细胞仪检测细胞凋亡的变化。结果:雷帕霉素药物作用抑制了mTOR信号通路及下游分子的表达,经不同剂量射线照射后细胞的增殖能力和克隆形成能力显著低于对照组,凋亡显著高于对照组。结论:抑制mTOR信号通路可以增加非小细胞肺癌对放疗的敏感性。     

mTOR抑制剂在乳腺癌内分泌治疗耐药中的研究进展

PI3K/Akt/mTOR信号转导通路可抑制肿瘤细胞凋亡、促进细胞生存、调节细胞周期,促进肿瘤新生血管的形成以及侵袭与转移,在肿瘤的发生、发展、治疗及转归中发挥着重要作用。该信号通路与乳腺癌关系非常密切,是乳腺癌新的治疗靶点及研究热点。mTOR抑制剂通过不同的靶点作用于PI3K/Akt/mTOR信号转导通路上,从而达到其抗癌作用。内分泌治疗是乳腺癌的重要治疗方式之一,与化疗等其他治疗方式一样,内分泌治疗同样也面临治疗耐受这一难题。随着越来越多的信号通路被揭示,单一阻断某一位点已经不能满足治疗的需要,寻找多条通路的共同抑制位点成为研究人员关注的焦点。本文就mTOR抑制剂在乳腺癌内分泌治疗耐药中的作用及其临床试验结果进行综述,以期进一步了解mTOR抑制剂的临床作用。      

mTOR抑制剂依维莫司在乳腺癌治疗中的研究进展

正乳腺癌是威胁妇女健康的主要恶性肿瘤之一,随着肿瘤分子生物学研究的发展,分子靶向药物在乳腺癌治疗中取得了一定的疗效,单克隆抗体赫赛汀(Herceptin)是针对乳腺癌Her-2基因的第一个分子靶向药物,为乳腺癌临床治疗带来了突破,但是只有30%的Her-2阳性的乳腺癌患者能从单药中获益,而部分患者可能出现该药物的原发耐药和继发耐药,随着分子靶向药物研究的不断深入,选择     

非小细胞肺癌大分割放疗敏感性与PI3K/AKT/mTOR信号通路研究进展

常规分割放疗在中晚期非小细胞肺癌治疗中疗效有限,大分割放疗地位越来越重要,但仍有相当部分肿瘤细胞具有放射线抗拒,其分子机制未明。PI3K/AKT/mTOR信号通路与非小细胞肺癌常规分割放疗抗拒有关,但与大分割放疗抗拒关系尚未明确。调控PI3K/AKT/mTOR信号通路的基因表达及蛋白磷酸化水平有望增加NSCLC肿瘤细胞对大分割放疗的敏感性,并可能达到逆转放疗抗拒的效果;在PI3K/AKT/mTOR信号通路的诸多基因中,有望从临床样本中筛选获得预测NSCLC大分割放疗疗效的分子标记。      

mTOR inhibitors in cancer therapy

The mammalian target of rapamycin (mTOR) plays a key role in regulation of cellular metabolism, growth, and proliferation. The frequent hyperactivation of mTOR signaling makes it an attractive target for therapeutic intervention and has driven the development of a number of mTOR inhibitors. Encouraging data from preclinical studies have resulted in initiation of multiple clinical trials. Furthermore, combinational strategies are being studied in an effort to overcome resistance and enhance efficacy. Although additional studies are required to determine their specific role in the clinical setting, mTOR inhibitors remain a promising therapeutic option for the treatment of cancer.     

Catalytic mTOR inhibitors can overcome intrinsic and acquired resistance to allosteric mTOR inhibitors

We tested the antitumor efficacy of mTOR catalytic site inhibitor MLN0128 in models with intrinsic or acquired rapamycin-resistance. Cell lines that were intrinsically rapamycin-resistant as well as those that were intrinsically rapamycinsensitive were sensitive to MLN0128 in vitro. MLN0128 inhibited both mTORC1 and mTORC2 signaling, with more robust inhibition of downstream 4E-BP1 phosphorylation and cap-dependent translation compared to rapamycin in vitro. Rapamycin-sensitive BT474 cell line acquired rapamycin resistance (BT474 RR) with prolonged rapamycin treatment in vitro. This cell line acquired an mTOR mutation (S2035F) in the FKBP12-rapamycin binding domain; mTORC1 signaling was not inhibited by rapalogs but was inhibited by MLN0128. In BT474 RR cells, MLN0128 had significantly higher growth inhibition compared to rapamycin in vitro and in vivo. Our results demonstrate that MLN0128 may be effective in tumors with intrinsic as well as acquired rapalog resistance. mTOR mutations are a mechanism of acquired resistance in vitro; the clinical relevance of this observation needs to be further evaluated.     

mTOR inhibitors in urinary bladder cancer

Despite the great scientific advances that have been made in cancer treatment, there is still much to do, particularly with regard to urinary bladder cancer. Some of the drugs used in urinary bladder cancer treatment have been in use for more than 30 years and show reduced effectiveness and high recurrence rates. There have been several attempts to find new and more effective drugs, to be used alone or in combination with the drugs already in use, in order to overcome this situation.The biologically important mammalian target of rapamycin (mTOR) pathway is altered in cancer and mTOR inhibitors have raised many expectations as potentially important anticancer drugs. In this article, the authors will review the mTOR pathway and present their experiences of the use of some mTOR inhibitors, sirolimus, everolimus and temsirolimus, in isolation and in conjunction with non-mTOR inhibitors cisplatin and gemcitabine, on urinary bladder tumour cell lines. The non-muscle-invasive cell line, 5637, is the only one that exhibits a small alteration in the mTOR and AKT phosphorylation after rapalogs exposure. Also, there was a small inhibition of cell proliferation. With gemcitabine plus everolimus or temsirolimus, the results were encouraging as a more effective response was noticed with both combinations, especially in the 5637 and T24 cell lines. Cisplatin associated with everolimus or temsirolimus also gave promising results, as an antiproliferative effect was observed when the drugs were associated, in particular on the 5637 and HT1376 cell lines. Everolimus or temsirolimus in conjunction with gemcitabine or cisplatin could have an important role to play in urinary bladder cancer treatment, depending on the tumour grading.     

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.     

Aspects of mTOR biology and the use of mTOR inhibitors in non-Hodgkin's lymphoma

The mammalian target of rapamycin (mTOR) is a large and highly conserved kinase that integrates growth factor stimulation, energy and nutrient availability to modulate translation of proteins responsible for cellular growth and proliferation. Its importance in malignant cells provides strong rationale for the development of mTOR inhibitors (mTORi) in a broad variety of solid tumors and hematological malignancies. However several questions regarding mTOR biology and its interaction with pharmacological inhibitors remain unanswered and are relevant for further development of this novel family of cancer drugs. Nevertheless, mTORi have demonstrated activity in lymphoma cells either alone or in combination with cytotoxic agents. The most promising results have been seen in mantle cell lymphoma (MCL), likely because of its dependence on Cyclin D, the translation of which is largely regulated by mTOR activity. The currently knowledge of mTOR biology will here be reviewed along with the status of clinical development of mTORi in non-Hodgkin's lymphomas.     

Clinical development of mTOR inhibitors in breast cancer

The mammalian target of rapamycin (mTOR) pathway is a central pathway that regulates mRNA translation, protein synthesis, glucose metabolism, lipid synthesis and autophagy, and is involved in malignant transformation. Several randomized trials have shown that the use of mTOR inhibitors could improve patient outcome with hormone receptor-positive or human epidermal growth factor receptor-2-positive breast cancer. This review analyzes new perspectives from these trials. Preclinical studies have suggested that the mTOR pathway may play a role in the resistance to hormone therapy, trastuzumab and chemotherapy for breast cancer. This concept has been tested in clinical trials for neoadjuvant treatment and for metastatic breast cancer patients. Also, much effort has gone into the identification of biomarkers that will allow for more precise stratification of patients. Findings from these studies will provide indispensable tools for the design of future clinical trials and identify new perspectives and challenges for researchers and clinicians.     

Antihormonal therapy in breast cancer and mTOR inhibitors

Hormonal dependence of breast cancer has been known for a long time, yet about half of breast cancers with estrogen receptor will not respond to antihormonal therapy. Now, we know that this resistance may be related to a dysfunction of the estrogen pathway, or that of growth factors and particularly the pathway of cell activation PI3K/Akt/mTOR. Prevention of these different mechanisms of resistance could involve combination therapies such as anti-estrogens (SERMs, aromatase inhibitors) with inhibitors of the activity of growth factors that are particularly temsirolimus and everolimus for the activation pathway cell PI3K/Akt/mTOR.     

Updating progress in sarcoma therapy with mTOR inhibitors

BackgroundSarcomas are a diverse group of difficult-to-treat connective tissue neoplasms. The mammalian target of rapamycin (mTOR) pathway has been identified as a therapeutic target in many sarcomas and this article reviews the role of this pathway and updates clinical data for the available mTOR inhibitors.DesignReference sources were selected by the author for searches in PubMed and EMBASE, with search terms dependent on the particular subtopic.ResultsmTOR is a protein kinase that regulates cell growth and proliferation and is abnormally activated in many human tumours. Several disruptions of phosphatidylinositol-3′ kinase (PI3K)–Akt signalling are associated with different sarcoma types. The macrolide antibiotic rapamycin and synthetic derivatives sirolimus, temsirolimus, everolimus and ridaforolimus have been investigated in several tumour types and their potential for the treatment of sarcoma is being explored, with varying degrees of success. The PI3K–Akt–mTOR pathway is also implicated in resistance mechanisms to antineoplastic therapies, and mTOR inhibitors therefore have the potential to restore sensitivity to patients with treatment-resistant disease.ConclusionsThe PI3K–Akt–mTOR pathway is an exciting target for therapy in many types of solid malignancies and its blockade represents an opportunity to improve outcomes in poor-prognosis sarcoma.     

Predicted mechanisms of resistance to mTOR inhibitors

The serine/threonine kinase, mTOR (mammalian Target of Rapamycin) has become a focus for cancer drug development. Rapamycins are highly specific inhibitors of mTOR and potently suppress tumour cell growth by retarding cells in G1 phase or potentially inducing apoptosis. Currently, both rapamycin and several analogues are being evaluated as anticancer agents in clinical trials. Results indicate that many human cancers have intrinsic resistance and tumours initially sensitive to rapamycins become refractory, demonstrating acquired resistance. Here, we consider mechanisms of resistance to inhibitors of mTOR.