PI3 K/AKT/mTOR信号通路与肺癌TKI耐药性及放疗抵抗性

肺癌的发病率及病死率一直居高不下,目前针对表皮生长因子受体以及抗血管内皮生长因子受体等的靶向治疗药物已成为临床一线用药,并辅助以放疗、手术治疗等。但是,临床发现肺癌细胞容易对药物产生耐药性,对放疗的敏感性也容易下降。研究发现 PI3K/AKT/mTOR 通路广泛存在于多种癌症细胞中,在细胞生长、增殖、血管生成等过程中起重要调节作用。不少研究学者发现,该通路的激活与肺癌细胞对表皮生长因子受体-酪氨酸激酶抑制剂的耐药性和放疗的抵抗性呈现正相关。PI3K/AKT抑制剂或 mTOR抑制剂均可逆转肺癌细胞的耐药性及放疗抵抗性,并有望成为治疗肺癌的新型抗癌药物。本文就近几年该信号通路有关的报道进行总结。     

Involvement of PI3K/PTEN/AKT/mTOR pathway in invasion and metastasis in hepatocellular carcinoma: Association with MMP-9

Aim:  To investigate the status of Phosphatidylinositol 3-kinase (PI3K)/PTEN/AKT/mammalian target of rapamycin (mTOR) pathway and its correlation with clinicopathological features and matrix metalloproteinase-2, -9 (MMP-2, 9) in human hepatocellular carcinoma (HCC).
Methods:  PTEN, Phosphorylated AKT (p-AKT), Phosphorylated mTOR (p-mTOR), MMP-2, MMP-9 and Ki-67 expression levels were evaluated by immunohistochemistry on tissue microarrays containing 200 HCCs with paired adjacent non-cancerous liver tissues. PTEN, MMP-2 and MMP-9 mRNA levels were determined by real-time RT-PCR in 36 HCCs. The relationships between PI3K/PTEN/AKT/mTOR pathway and clinicopathological factors and MMP-2, 9 were analyzed in HCC.
Results:  In HCC, PTEN loss and overexpression of p-AKT and p-mTOR were associated with tumor grade, intrahepatic metastasis, vascular invasion, TNM stage and high Ki-67 labeling index ( P  < 0.05). PTEN loss was correlated with p-AKT, p-mTOR and MMP-9 overexpression. Furthermore, PTEN and MMP-2, 9 mRNA levels were down-regulated and up-regulated in HCC compared with paired non-cancerous liver tissues, respectively ( P  < 0.01). PTEN, MMP-2 and MMP-9 mRNA levels were correlated with tumor stage and metastasis. There was an inverse correlation between PTEN and MMP-9 mRNA expression. However, PI3K/PTEN/AKT/mTOR pathway was not correlated with MMP-2.
Conclusions:  PI3K/PTEN/AKT/mTOR pathway, which is activated in HCC, is involved in invasion and metastasis through up-regulating MMP-9 in HCC.     

Targeting PI3‐kinase (PI3K), AKT and mTOR axis in lymphoma

Targeted therapy represents a transformation in oncology, a field that has relied primarily on non‐selective cytotoxic therapies. Phosphatidylinositol 3‐kinase (PI3K) is a family of ubiquitous signalling molecules involved in a wide variety of cellular processes and likewise, in a broad selection of human cancers. The discovery that the p110‐δ form of PI3K is differentially expressed in normal and malignant lymphocytes has led to the development of specific inhibitors that are currently in clinical trials for lymphoma. Downstream effectors of PI3K, including v‐akt murine thymoma viral oncogene homolog 1 (AKT; also termed AKT1) and mechanistic target of rapamycin (serine/threonine kinase) (mTOR) are similarly important in lymphoma, and agents targeting these components of the PI3K‐AKT‐mTOR axis are also underway, although at earlier stages of development. In this review we examine the role of PI3K‐AKT‐mTOR in normal and malignant lymphocytes, as well as the preclinical and clinical status of a number of inhibitors of this pathway.     

Ribonucleotide reductase M2 subunit silencing suppresses tumorigenesis in pancreatic cancer via inactivation of PI3K/AKT/mTOR pathway

Background/objectivesRibonucleotide Reductase M2 subunit (RRM2) is elevated in pancreatic cancer and involved in DNA synthesis and cell proliferation. But its specific mechanism including genetic differences and upstream regulatory pathways remains unclear.MethodsWe analyzed RRM2 expression of 178 pancreatic cancer patients in Gene Expression Profiling Interactive Analysis (GEPIA) database. Besides, more pancreatic cancer specimens were collected and detected RRM2 expression by immunohistochemistry. RRM2 knockdown by shRNA was applied for functional and mechanism analysis in vitro. Xenograft tumor growth was significantly slower by RRM2 silencing in vivo.ResultsIt showed that high RRM2 expression had a poorer overall survival and disease free survival. RRM2 expression was higher in tumor grade 2 and 3 than grade 1. Immunohistochemistry data validated that high RRM2 expression predicted worse survival. RRM2 knockdown significantly reduced cell proliferation, inhibited colony formation and suppressed cell cycle progress. Further mechanism assay showed silencing RRM2 lead to inactivation of PI3K/AKT/mTOR pathway and inhibition of mutant p53, which induce S phase arrest and/or apoptosis. In panc-1 cells, S-phase arrest mediated by mutant p53 inhibition, p21 increase and cell cycle related proteins change. While in miapaca-2 cells, induction of apoptosis and S-phase arrest mediated by CDK1 played a coordinated role.ConclusionTaken together, high RRM2 expression was associated with worse prognosis. Importantly, RRM2 knockdown deactivated PI3K/AKT/mTOR pathway, resulting in cell cycle arrest and/or apoptosis. This study shed light on the molecular mechanism of RRM2 in pancreatic tumor progression and is expected to provide a new theoretical basis for pancreatic cancer treatment.     

Deguelin, A PI3K/AKT inhibitor, enhances chemosensitivity of leukaemia cells with an active PI3K/AKT pathway

Activation of the phosphoinositide 3 kinase (PI3K)/Akt signalling pathway has been linked with resistance to chemotherapeutic drugs, and its downregulation, by means of PI3K inhibitors, lowers resistance to various types of therapy in tumour cell lines. Recently, it has been reported that deguelin, a naturally occurring rotenoid, is a powerful inhibitor of PI3K. We investigated whether or not deguelin could enhance the sensitivity to chemotherapeutic drugs of human U937 leukaemia cells and acute myeloid leukaemia (AML) blasts with an activated PI3K/Akt network. Deguelin (10 nmol/l) induced S phase arrest with interference of progression to G2/M, and at 100 nmol/l significantly increased apoptotic cell death of U937. At 10-100 nmol/l concentrations, deguelin downregulated Akt phosphorylation of leukaemia cells and markedly increased sensitivity of U937 cells to etoposide or cytarabine. A 10 nmol/l concentration of deguelin did not negatively affect the survival rate of human cord blood CD34+ cells, whereas it increased sensitivity of AML blasts to cytarabine. Deguelin was less toxic than wortmannin on erythropoietin- and stem cell factor-induced erythropoiesis from CD34+ progenitor cells. Overall, our results indicate that deguelin might be used in the future for increasing sensitivity to therapeutic treatments of leukaemia cells with an active PI3K/Akt signalling network.     

Overexpression of CREG attenuates atherosclerotic endothelium apoptosis via VEGF/PI3K/AKT pathway

Aims

Cellular repressor of E1A-stimulated genes (CREG) is a homeostasis-modulating gene abundantly expressed in adult artery endothelium. Previous studies have demonstrated a protective effect of CREG against atherosclerosis through prevention of vascular smooth muscle cell apoptosis. However, the role of CREG in endothelial cells (ECs) apoptosis and the underlying signaling mechanisms are unknown.

Method and results

We ascertained that CREG expression was decreased in atherogenesis-prone endothelium in apolipoprotein E-null (apoE^−/−) mice compared with their wild-type littermates using in situ immunofluorescent staining. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) staining and caspase-3 activity assays determined that treatment of apoE^−/− mice arteries with staurosporine (STS) significantly induced endothelial apoptosis associated with a reduction of CREG expression. Gain- and loss-of-function analyses revealed that silencing CREG expression significantly enhanced ECs apoptosis, whereas CREG overexpression abrogated apoptosis stimulated by STS or etoposide (VP-16). Blocking assays using the neutralizing antibody for vascular endothelial growth factor (VEGF) and the specific inhibitor of phosphoinositide 3-kinase (PI3K), such as LY294002 or wortmannin, demonstrated that the protective effect of CREG on ECs apoptosis was mainly mediated by activation of the VEGF/PI3K/AKT signaling pathway.

Conclusions

These data demonstrate that CREG plays a critical role in protecting the vascular endothelium from apoptosis, and the protective effort of CREG against ECs apoptosis is through the activation of the VEGF/PI3K/AKT signaling pathway.     

PI3K/AKT/mTOR信号通路在糖皮质激素性股骨头坏死中的表达与作用

糖皮质激素性股骨头坏死(steroid-induced avascularnecrosis of femoral head,SANFH)是一类致残率较高的疾病,长期损害人类与社会健康,已成为亟待解决的社会问题。PI3K/AKT/mTOR信号通路是一条与细胞分化凋亡自噬等密切相关的转导通路。近年随着分子生物学和细胞生物学的进步发展,表明以此信号通路为切入点能够对SANFH进行有效的靶向调控,并通过促进成骨分化,抑制凋亡,修复血管内皮细胞以及调控自噬等多种途径,对骨细胞产生显著调控和影响。本文就PI3K/AKT/mTOR通路在SANFH中所发挥的调控机制和作用,以及各部分在激素性股骨头坏死中的表达作简要综述,为以后的研究治疗提供思路与依据。     

肺炎支原体LAMPs经PI3K/Nrf2诱导人单核细胞表达HO-1

目的 探讨肺炎支原体(Mycoplasma pneumoniae,Mp)脂质相关膜蛋白(lipid-associated membrane protein,LAMPs)对人单核细胞表达血红素氧合酶-1(heme oxygenase-1,HO-1)的影响,并探讨可能的调控机制。方法 体外培养THP-1细胞,用不同浓度的LAMPs作用后,分别采用realtime-PCR和Western blot检测HO-1 mRNA和蛋白的表达。同时采用不同浓度的放线菌素D(ActD)和放线菌酮(CHX)预处理细胞,观察其对HO-1表达的影响,以证实HO-1的表达是否通过转录和翻译水平;提取LAMPs作用前后的核蛋白,凝胶迁移率实验检测Nrf2的核转位、Western blot检测Akt的磷酸化情况;同时采用PI3K抑制剂LY294002处理细胞,观察其对LAMPs诱导Nrf2核转位及HO-1表达的影响;最后采用 siRNA干扰Nrf2表达,以证实Nrf2是否参与调控HO-1表达。结果 (1)0~5 μg/mL LAMPs能以剂量依赖性方式诱导THP-1表达HO-1 mRNA和蛋白;(2)5 μg/mL LAMPs能诱导THP-1细胞Akt磷酸化,并能增强其DNA结合活性;PI3K抑制剂LY294002处理后,可明显抑制LAMPs诱导的HO-1表达和Nrf2核转位;(3)干扰Nrf2表达后,可明显下调LAMPs诱导THP-1细胞表达HO-1。结论 LAMPs可诱导THP-1细胞表达HO-1,其机制可能与PI3K/Nrf2通路有关。     

PRDM1 expression and its relationship with PI3K/AKT pathway activation in extranodal NK/T cell lymphoma-nasal type

<正>Objective To investigate the expression of PRDM1and its relationship with PI3K/AKT pathway activation in extranodal NK/T cell lymphoma-nasal type. Methods Immunocytochemistry and Western blot were used to detect the expression of PRDM1 and p-AKT in 10 EN-NK/T-NT tissue or 3 cell lines (PRDM1-positive YT cell line, PRDM1-negative NKL and NK92 cell lines).     

Insulin stimulates IGFBP-2 expression in 3T3-L1 adipocytes through the PI3K/mTOR pathway

Insulin-like growth factor binding protein 2 (IGFBP-2) has been implicated in the etiology of several diseases, including the metabolic syndrome. Although IGFBP-2 derives mostly from the liver, recent evidence in mice and humans indicate that aging and obesity are associated with altered IGFBP-2 levels in white adipocytes. The present study was aimed at determining the mechanisms that control IGFBP-2 expression in mature adipocytes. IGFBP-2 mRNA and protein expression in serum-deprived 3T3-L1 adipocytes were twofold increased by acute insulin treatment. Co-treatments with the phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin or the mammalian target of rapamycin (mTOR) inhibitor rapamycin blunted the effects of insulin. Coherently, IGFBP-2 mRNA levels were robustly increased in adipocytes lacking either TSC2 or 4E-BP1. Insulin triggered the recruitment of CAAT/enhancer binding protein α (C/EBPα) to the IGFBP-2 proximal promoter. These findings suggest that insulin upregulates IGFBP-2 expression through a PI3K/mTOR/C/EBPα pathway in white adipocytes.     

Thrombopoietin/MPL participates in initiating and maintaining RUNX1-ETO acute myeloid leukemia via PI3K/AKT signaling

Oncogenic mutations in components of cytokine signaling pathways elicit ligand-independent activation of downstream signaling, enhancing proliferation and survival in acute myeloid leukemia (AML). The myeloproliferative leukemia virus oncogene, MPL, a homodimeric receptor activated by thrombopoietin (THPO), is mutated in myeloproliferative disorders but rarely in AML. Here we show that wild-type MPL expression is increased in a fraction of human AML samples expressing RUNX1-ETO, a fusion protein created by chromosome translocation t(8;21), and that up-regulation of Mpl expression in mice induces AML when coexpressed with RUNX1-ETO. The leukemic cells are sensitive to THPO, activating survival and proliferative responses. Mpl expression is not regulated by RUNX1-ETO in mouse hematopoietic progenitors or leukemic cells. Moreover, we find that activation of PI3K/AKT but not ERK/MEK pathway is a critical mediator of the MPL-directed antiapoptotic function in leukemic cells. Hence, this study provides evidence that up-regulation of wild-type MPL levels promotes leukemia development and maintenance through activation of the PI3K/AKT axis, and suggests that inhibitors of this axis could be effective for treatment of MPL-positive AML.