Activated cMET and IGF1R-Driven PI3K Signaling Predicts Poor Survival in Colorectal Cancers Independent of KRAS Mutational Status

Background

Oncogenic mutational analysis provides predictive guidance for therapeutics such as anti-EGFR antibodies, but it is successful only for a subset of colorectal cancer (CRC) patients.

Method

A comprehensive molecular profiling of 120 CRC patients, including 116 primary, 15 liver metastasis, and 1 peritoneal seeding tissue samples was performed to identify the relationship between v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) WT and mutant CRC tumors and clinical outcomes. This included determination of the protein activation patterns of human epidermal receptor 1 (HER1), HER2, HER3, c-MET, insulin-like growth factor 1 receptor (IGF1R), phosphatidylinositide 3-kinase (PI3K), Src homology 2 domain containing (Shc), protein kinase B (AKT), and extracellular signal-regulated kinase (ERK) kinases using multiplexed collaborative enzyme enhanced reactive (CEER) immunoassay.

Results

KRAS WT and mutated CRCs were not different with respect to the expression of the various signaling molecules. Poor prognosis in terms of early relapse (<2 years) and shorter disease-free survival (DFS) correlated with enhanced activation of PI3K signaling relative to the HER kinase pathway signaling, but not with the KRAS mutational status. KRAS WT CRCs were identified as a mixed prognosis population depending on their level of PI3K signaling. KRAS WT CRCs with high HER1/c-MET index ratio demonstrated a better DFS post-surgery. c-MET and IGF1R activities relative to HER axis activity were considerably higher in early relapse CRCs, suggesting a role for these alternative receptor tyrosine kinases (RTKs) in driving high PI3K signaling.

Conclusions

The presented data subclassified CRCs based on their activated signaling pathways and identify a role for c-MET and IGF1R-driven PI3K signaling in CRCs, which is superior to KRAS mutational tests alone. The results from this study can be utilized to identify aggressive CRCs, explain failure of currently approved therapeutics in specific CRC subsets, and, most importantly, generate hypotheses for pathway-guided therapeutic strategies that can be tested clinically.     

Asymmetric PI3K Activity in Lymphocytes Organized by a PI3K-Mediated Polarity Pathway

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Akt and PI 3-Kinase Signaling in Cardiomyocyte Hypertrophy and Survival

In many systems, activation of the “protein and lipid kinase” phosphoinositide 3-kinase (PI 3-kinase) and its downstream serine-threonine kinase effector, Akt (or Protein Kinase B), provide a potent stimulus for cell proliferation, growth, and survival. In the heart, constrained by the limited proliferative capacity of cardiomyocytes, this pathway plays a key role in regulating cardiomyocyte growth and survival, with little effect on proliferation. Simultaneously, PI 3-kinase and Akt are important modulators of metabolic substrate utilization and cardiomyocyte function. Thus, the convergent signaling pathways controlling so many clinical important phenotypes of the cardiomyocyte suggest it holds promise as a therapeutic target in a variety of cardiac diseases. However, the similar role of PI 3-kinase/Akt signaling in neoplasia suggests the difficulty of activating this pathway in the heart without invoking adverse consequences elsewhere. Here we review evidence regarding the role of PI 3-kinase/Akt in controlling cardiomyocyte growth and survival, and discuss the implications for therapeutic strategies.     

NPD1 Induction of Retinal Pigment Epithelial Cell Survival Involves PI3K/Akt Phosphorylation Signaling

Neuroprotectin D1 (NPD1), a docosahexaenoic acid (DHA)-derived lipid mediator, promotes survival in cells exposed to oxidative stress by inducing the activity of anti-inflammatory mediators and suppressing the expression of pro-inflammatory genes. Though retinal pigment epithelial (RPE) cells naturally produce NPD1 from DHA, investigating the mechanisms through which exogenous NPD1 induces cell survival is essential to assess mechanisms of actions and the potential of this lipid mediator for treatment of retinal degenerative diseases. The PI3K/Akt and mTOR/p70S6K pathways are responsible for supporting cell survival upon exposure to oxidative stress. In human ARPE-19 cells pretreated with NPD1 then exposed to varying concentrations of oxidative stress or repeated exposures to oxidative stress, Akt, mTOR, and p70S6K were phosphorylated to a greater extent and for a greater duration than cells not pretreated with NPD1. In addition to increased phosphorylation, a subsequent decreased rate of apoptosis was observed upon NPD1 treatment. Thus NPD1 bioactivity in RPE cells enhances activation of these pathways and promotes cell integrity and survival.     

Functional Redundancy of Class I Phosphoinositide 3-Kinase (PI3K) Isoforms in Signaling Growth Factor-Mediated Human Neutrophil Survival

We have investigated the contribution of individual phosphoinositide 3-kinase (PI3K) Class I isoforms to the regulation of neutrophil survival using (i) a panel of commercially available small molecule isoform-selective PI3K Class I inhibitors, (ii) novel inhibitors, which target single or multiple Class I isoforms (PI3Kα, PI3Kβ, PI3Kδ, and PI3Kγ), and (iii) transgenic mice lacking functional PI3K isoforms (p110δ^KOγ^KO or p110γ^KO). Our data suggest that there is considerable functional redundancy amongst Class I PI3Ks (both Class IA and Class IB) with regard to GM-CSF-mediated suppression of neutrophil apoptosis. Hence pharmacological inhibition of any 3 or more PI3K isoforms was required to block the GM-CSF survival response in human neutrophils, with inhibition of individual or any two isoforms having little or no effect. Likewise, isolated blood neutrophils derived from double knockout PI3K p110δ^KOγ^KO mice underwent normal time-dependent constitutive apoptosis and displayed identical GM-CSF mediated survival to wild type cells, but were sensitized to pharmacological inhibition of the remaining PI3K isoforms. Surprisingly, the pro-survival neutrophil phenotype observed in patients with an acute exacerbation of chronic obstructive pulmonary disease (COPD) was resilient to inactivation of the PI3K pathway.     

PI3K/AKT信号通路与心力衰竭

丝氨酸/苏氨酸激酶(serine/threonine kinase,AKT)是真核细胞中参与细胞信号转导的关键分子。目前已经证实PI3K(phosphatidylinositol-3-kinase,PI3K)/AKT信号通路在人类肿瘤、代谢紊乱、肾脏疾病以及精神障碍等疾病中发挥着重要的作用。近年来的研究还发现PI3K/AKT信号通路的激活会对心肌细胞的生长、代谢以及凋亡等活动产生影响,且该通路及其中的很多受体、激酶被证实与心力衰竭关系密切,这使该信号通路在心力衰竭的发病机制、诊断及治疗等方面的研究日益受到重视。总结PI3K/AKT的结构特点、相关信号转导机制及其与心力衰竭的关系将有利于更好地理解心力衰竭的发病机制。     

Nrf2 Negatively Regulates Melanogenesis by Modulating PI3K/Akt Signaling

Nrf2 plays a role in protection of cells against oxidative stress and xenobiotic damage by regulating cytoprotective genes. In this study, we investigated the effect of Nrf2 on melanogenesis in normal human melanocytes (NHMCs). When NHMCs were transduced with a recombinant adenovirus expressing Nrf2, melanin synthesis was significantly decreased. Consistent with this result, overexpression of Nrf2 decreased the expression of tyrosinase and tyrosinase-related protein 1. The inhibitory effect of Nrf2 was reversed by overexpression of Keap1, an intracellular regulator of Nrf2. Interestingly, Nrf2 overexpression resulted in marked activation of PI3K/Akt signaling. Conversely, inhibition of PI3K activity by treatment with wortmannin reversed the depigmentary effects of Nrf2. Taken together, these results strongly suggest that Nrf2 negatively regulates melanogenesis by modulating the PI3K/Akt signaling pathway.     

Synergistic Effects of Targeted PI3K Signaling Inhibition and Chemotherapy in Liposarcoma

While liposarcoma is the second most common soft tissue malignant tumor, the molecular pathogenesis in this malignancy is poorly understood. Our goal was therefore to expand the understanding of molecular mechanisms that drive liposarcoma and identify therapeutically-susceptible genetic alterations. We studied a cohort of high-grade liposarcomas and benign lipomas across multiple disease sites, as well as two liposarcoma cell lines, using multiplexed mutational analysis. Nucleic acids extracted from diagnostic patient tissue were simultaneously interrogated for 150 common mutations across 15 essential cancer genes using a clinically-validated platform for cancer genotyping. Western blot analysis was implemented to detect activation of downstream pathways. Liposarcoma cell lines were used to determine the effects of PI3K targeted drug treatment with or without chemotherapy. We identified mutations in the PIK3CA gene in 4 of 18 human liposarcoma patients (22%). No PIK3CA mutations were identified in benign lipomas. Western blot analysis confirmed downstream activation of AKT in both PIK3CA mutant and non-mutant liposarcoma samples. PI-103, a dual PI3K/mTOR inhibitor, effectively inhibited the activation of the PI3K/AKT in liposarcoma cell lines and induced apoptosis. Importantly, combination with PI-103 treatment strongly synergized the growth-inhibitory effects of the chemotherapy drugs doxorubicin and cisplatin in liposarcoma cells. Taken together, these findings suggest that activation of the PI3K/AKT pathway is an important cancer mechanism in liposarcoma. Targeting the PI3K/AKT/pathway with small molecule inhibitors in combination with chemotherapy could be exploited as a novel strategy in the treatment of liposarcoma.     

PI3K-Akt信号传导通路对糖代谢的调控作用

磷脂酰肌醇3-激酶(PI3Ks)作为酪氨酸激酶和G蛋白偶联受体的主要下游分子,通过催化产生第二信使3,4,5-三磷酸磷脂酰肌醇(PIP3)并激活Akt、糖原合酶激酶-3(GSK-3)、Forkhead转录因子FoxO1、mTOR(mammalian target of rapamycin)等下游分子,将多种生长因子及细胞因子的信号传递到细胞内,从而对细胞增殖、分化、凋亡和葡萄糖转运等多种生物过程起重要的调节作用.PTEN(phosphatase and tensin homologue)是PI3K信号通路的重要负调节因子.本文将对PI3K-Akt信号通路在糖代谢中的作用予以简要综述.     

The PI3K pathway in B cell metabolism

B cell growth and proliferation is tightly regulated by signaling through the B cell receptor and by other membrane bound receptors responding to different cytokines. The PI3K signaling pathway has been shown to play a crucial role in B cell activation, differentiation and survival. Activated B cells undergo metabolic reprograming in response to changing energetic and biosynthetic demands. B cells also need to be able to coordinate metabolic activity and proliferation with nutrient availability. The PI3K signaling network has been implicated in regulating nutrient acquisition, utilization and biosynthesis, thus integrating receptor-mediated signaling with cell metabolism. In this review, we discuss the current knowledge about metabolic changes induced in activated B cells, strategies to adapt to metabolic stress and the role of PI3K signaling in these processes.     

TGF-beta1 通过PI3K及ERK信号通路调节肺动脉高压过程中IGFBPs蛋白表达

目的：探讨大鼠肺动脉高压(PAH)过程中TGF-beta1对胰岛素样生长因子结合蛋白（IGFBP）表达调节是否依赖于PI3K及ERK 信号通路。方法：取健康成年SD 大鼠26 只,随机分成2 组：PAH组,腹腔注射1%的野百合碱,剂量为60 mg/kg;对照(C)组腹腔 注射生理盐水。于4 周后超声检测肺动脉平均压力,取肺组织做HE 染色,应用NIS-Element 系统测量中膜厚度。原代培养肺动脉 平滑肌（PASMC）细胞,分别加入TGF-beta1 及TGF-beta1 中和抗体后,Western-blot 检测IGFBP3,IGFBP5,Smad2/Smad3 表达。加入 ERK特异性抑制剂PD98059 或PI3K 抑制剂LY294002,检测IGFBP3,IGFBP5 表达。结果：野百合碱处理4 周后,肺动脉高压组 的平均肺动脉压力及右室/(左室+室间隔)比值显著高于对照组。TGF-茁1 可显著升高IGFBP3,IGFBP5 及p-Smad3 的表达（P<0. 05）,而抑制TGF-beta1 则可显著降低三种蛋白的表达（P<0.05）。加入LY294002 抑制PI3K ERK 后,IGFBP3 和p-Smad2 两种蛋白的 表达量显著下调（P<0.05）。加入PD98059 抑制ERK 后可显著降低IGFBP3 及IGFBP5 的表达水平（P<0.05）。结论：PAH 中 TGF-茁1 升高可通过活化Smad2/Smad3 上调IGFBP3和IGFBP5 的表达。TGF-beta1 促进IGFBP3,IGFBP5表达的作用依赖于PI3K 及ERK 信号通路。     

mTOR Activation by PI3K/Akt and ERK Signaling in Short ELF-EMF Exposed Human Keratinocytes

Several reports suggest that ELF-EMF exposures interact with biological processes including promotion of cell proliferation. However, the molecular mechanisms by which ELF-EMF controls cell growth are not completely understood. The present study aimed to investigate the effect of ELF-EMF on keratinocytes proliferation and molecular mechanisms involved. Effect of ELF-EMF (50 Hz, 1 mT) on HaCaT cell cycle and cells growth and viability was monitored by FACS analysis and BrdU assay. Gene expression profile by microarray and qRT-PCR validation was performed in HaCaT cells exposed or not to ELF-EMF. mTOR, Akt and MAPKs expressions were evaluated by Western blot analysis. In HaCaT cells, short ELF-EMF exposure modulates distinct patterns of gene expression involved in cell proliferation and in the cell cycle. mTOR activation resulted the main molecular target of ELF-EMF on HaCaT cells. Our data showed the increase of the canonical pathway of mTOR regulation (PI3K/Akt) and activation of ERK signaling pathways. Our results indicate that ELF-EMF selectively modulated the expression of multiple genes related to pivotal biological processes and functions that play a key role in physio-pathological mechanisms such as wound healing.     

PI3K/Akt/mTOR信号通路及临床相关肿瘤抑制剂

哺乳动物雷帕霉素靶（mTOR）和蛋白激酶B（Akt/PKB）与肿瘤发生的密切关系已被广泛地认可.mTOR是一种丝/苏氨酸激酶,可以通过影响mRNA转录、代谢、自噬等方式调控细胞的生长.它既是PI3K的效应分子,也可以是PI3K的反馈调控因子.mTORC1 和mTORC2是mTOR的两种不同复合物. 对雷帕霉素敏感的mTORC1受到营养、生长因子、能量和应激4种因素的影响.生长因子通过PI3K/Akt信号通路调控mTORC1是最具特征性调节路径.而mTORC2最为人熟知的是作为Akt473磷酸化位点的上游激酶. 同样,Akt/PKB在细胞增殖分化、迁移生长过程中发挥着重要作用. 随着Thr308和Ser473两个位点激活,Akt/PKB也得以全面活化.因此,mTORC2-Akt-mTORC1的信号通路在肿瘤形成和生长中是可以存在的.目前临床肿瘤治疗中,PI3K/Akt/mTOR是重要的靶向治疗信号通路.然而,仅抑制mTORC1活性,不是所有的肿瘤都能得到预期控制.雷帕霉素虽然能抑制mTORC1,但也能反馈性地增加PI3K信号活跃度,从而影响治疗预后.近来发现的第二代抑制剂可以同时抑制mTORC1/2和PI3K活性,这种抑制剂被认为在肿瘤治疗上颇具前景.本综述着重阐述了PI3K/Akt/mTOR信号通路的传导、各因子之间的相互调控以及相关抑制剂的发展.     

Dual Inhibition of PI3K/Akt Signaling and the DNA Damage Checkpoint in p53-Deficient Cells with Strong Survival Signaling: Implications for Cancer Therapy

Natural (intrinsic) resistance of many tumor types to DNA damaging agents is closely associated with their capacity to undergo robust cell cycle arrest in G2/M. G2 arrest is regulated by the DNA damage checkpoint and by survival signaling, with a potential role of PI3K/Akt in checkpoint function. In this work, we wanted to clarify if inhibition of multiple checkpoint/survival pathways may confer better efficacy in the potentiation of genotoxic agents compared to inhibition of either pathway alone. We compared the influence of UCN-01, which affects both the DNA damage checkpoint and PI3K/Akt-mediated survival signaling, with the PI3K inhibitors wortmannin and LY294002 in p53-deficient M1 acute myeloid leukemia cells treated with the DNA damaging agent cisplatin. Our results show that direct inhibition of PI3K/Akt in G2-arrested cells by wortmannin or LY294002 strongly enhanced the cytotoxicity of cisplatin without influencing the G2 checkpoint. Unexpectedly, dual inhibition of both survival and checkpoint signaling by UCN-01, also increased the cytotoxicity of cisplatin, but to a lesser degree than wortmannin or LY294002. The differences in cytotoxicity were accompanied by differences in cell death pathways: direct inhibition of PI3K/Akt was accompanied by rapid apoptotic cell death during G2, whereas cells underwent mitotic transit and cell division followed by cell death during G1 when both checkpoint and survival signaling were inhibited. Our results elucidate a novel function for PI3K/Akt as a survival factor during DNA damage-induced G2 arrest and could have important pharmacological consequences for the application of response modulators in p53-deficient tumors with strong survival signaling.