PI3K/PTEN/AKT signaling regulates prostate tumor angiogenesis

PI3K pathway exerts its function through its downstream molecule AKT in regulating various cell functions including cell proliferation, cell transformation, cell apoptosis, tumor growth and angiogenesis. PTEN is an inhibitor of PI3K, and its loss or mutation is common in human prostate cancer. But the direct role and mechanism of PI3K/PTEN signaling in regulating angiogenesis and tumor growth in vivo remain to be elucidated. In this study, by using chicken chorioallantoic membrane (CAM) and in nude mice models, we demonstrated that inhibition of PI3K activity by LY294002 decreased PC-3 cells-induced angiogenesis. Reconstitution of PTEN, the molecular inhibitor of PI3K in PC-3 cells inhibited angiogenesis and tumor growth. Immunohistochemical staining indicated that PTEN expression suppressed HIF-1, VEGF and PCNA expression in the tumor xenographs. Similarly, expression of AKT dominant negative mutant also inhibited angiogenesis and tumor growth, and decreased the expression of HIF-1 and VEGF in the tumor xenographs. These results suggest that inhibition of PI3K signaling pathway by PTEN inhibits tumor angiogenesis and tumor growth. In addition, we found that AKT is the downstream target of PI3K in controlling angiogenesis and tumor growth, and PTEN could inhibit angiogenesis by regulating the expression of HIF-1 and VEGF expression through AKT activation in PC-3 cells.     

The TRAF3 adaptor protein drives proliferation of anaplastic large cell lymphoma cells by regulating multiple signaling pathways

T cells devoid of tumor necrosis factor receptor associated factor-3 (Traf3) exhibit decreased proliferation, sensitivity to apoptosis, and an improper response to antigen challenge. We therefore hypothesized that TRAF3 is critical to the growth of malignant T cells. By suppressing TRAF3 protein in different cancerous T cells, we found that anaplastic large cell lymphoma (ALCL) cells require TRAF3 for proliferation. Since reducing TRAF3 results in aberrant activation of the noncanonical nuclear factor-κB (NF-κB) pathway, we prevented noncanonical NF-κB signaling by suppressing RelB together with TRAF3. This revealed that TRAF3 regulates proliferation independent of the noncanonical NF-κB pathway. However, suppression of NF-κB-inducing kinase (NIK) along with TRAF3 showed that high levels of NIK have a partial role in blocking cell cycle progression. Further investigation into the mechanism by which TRAF3 regulates cell division demonstrated that TRAF3 is essential for continued PI3K/AKT and JAK/STAT signaling. In addition, we found that while NIK is dispensable for controlling JAK/STAT activity, NIK is critical to regulating the PI3K/AKT pathway. Analysis of the phosphatase and tensin homolog (PTEN) showed that NIK modulates PI3K/AKT signaling by altering the localization of PTEN. Together our findings implicate TRAF3 as a positive regulator of the PI3K/AKT and JAK/STAT pathways and reveal a novel function for NIK in controlling PI3K/AKT activity. These results provide further insight into the role of TRAF3 and NIK in T cell malignancies and indicate that TRAF3 differentially governs the growth of B and T cell cancers.     

Characteristics of the PI3K/AKT and MAPK/ERK pathways involved in the maintenance of self-renewal in lung cancer stem-like cells

Lung cancer is the leading cause of cancer-related mortality worldwide due to its early asymptomatic and late metastasis. While cancer stem cells (CSCs) may play a vital role in oncogenesis and development of lung cancer, mechanisms underlying CSCs self‐renewal remain less clear. In the present study, we constructed a clinically relevant CSCs enrichment recognition model and evaluated the potential functions of phosphatidylinositol 3-kinase (PI3K)/AKT pathway (PI3K/AKT) and mitogen-activated protein kinases/extracellular signal-regulated kinase (MAPK/ERK) pathways in lung cancer via bioinformatic analysis, providing the basis for in depth mechanistic inquisition. Experimentally, we confirmed that PI3K/AKT pathway predominantly promotes proliferation through anti-apoptosis in lung adenocarcinoma cells, while MAPK/ERK pathway has an overwhelming superiority in regulating the proliferation in lung CSCs. Further, utilizing stemness score model, LLC-Symmetric Division (LLC-SD) cells and mouse orthotopic lung transplantation model, we elucidated an intricate cross-talk between the oncogenic pathway and the stem cell reprograming pathway that impact stem cell characteristics as well as cancer biology features of lung CSCs both in vitro and in vivo. In summary, our findings uncovered a new insight that PI3K/AKT and MAPK/ERK pathways as oncogenic signaling pathway and/or stem cell signaling pathway act distinctively and synergistically to regulate lung CSCs self-renewal.     

RNF7 promotes glioma growth via the PI3K/AKT signalling axis

RNF7 has been reported to play critical roles in various cancers. However, the underlying mechanisms of RNF7 in glioma development remain largely unknown. Herein, the expression level of RNF7 was examined in tissues by quantitative real-time PCR, Western blotting and immunohistochemistry. The effect of RNF7 on glioma progression was measured by performing CCK-8 and apoptosis assays, cell cycle-related experiments and animal experiments. The effect of RNF7 on PI3K/AKT signalling pathway was tested by Western blotting. First, we found that RNF7 was upregulated in tumour tissue compared with normal brain tissue, especially in high-grade glioma, and the high expression of RNF7 was significantly related to tumour size, Karnofsky Performance Scale score and a poor prognosis. Second, RNF7 overexpression facilitated tumour cell cycle progression and cell proliferation and suppressed apoptosis. Conversely, RNF7 knockdown suppressed tumour cell cycle progression and cell proliferation and facilitated apoptosis. Furthermore, follow-up mechanistic studies indicated that RNF7 could facilitate glioma cell proliferation and cell cycle progression and inhibit apoptosis by activating the PI3K/AKT signalling pathway. This study shows that RNF7 can clearly promote glioma cell proliferation by facilitating cell cycle progression and inhibiting apoptosis by activating the PI3K/AKT signalling pathway. Targeting the RNF7/PI3K/AKT axis may provide a new perspective on the prevention or treatment of glioma.     

microRNA-21在食管癌细胞增殖、迁移和凋亡中的作用

本研究检测了40例食管癌组织和40例癌旁组织中的miR-21、PTEN、PI3K和AKT表达,并通过转染miR-21抑制剂来敲低人食管癌细胞系EC9706的miR-21表达,考察了miR-21对食管癌细胞生长的影响。研究发现,食管癌组织中PTEN蛋白的阳性染色评分低于癌旁组织(p<0.05),而PI3K和AKT蛋白的阳性染色评分高于癌旁组织(p<0.05)。miR-21在人食管癌组织中被上调(3.56 vs 1.21,p<0.05)。转染miR-21抑制剂导致PTEN蛋白表达升高,而PI3K和AKT蛋白表达降低(p<0.05)。转染miR-21抑制剂抑制了EC9706细胞的增殖和迁移,但促进了细胞凋亡(p<0.05)。miR-21的上调可通过激活PTEN/PI3K/AKT信号通路来促进食道癌细胞的增殖和迁移,并抑制细胞凋亡。     

PTEN promotes intervertebral disc degeneration by regulating nucleus pulposus cell behaviors

Intervertebral disc degeneration (IDD) is induced by multiple factors including increased apoptosis, decreased survival, and reduced extracellular matrix (ECM) synthesis in the nucleus pulposus (NP) cells. The tumor suppressor phosphatase and tensin homolog deleted from chromosome 10 (PTEN) is the only known lipid phosphatase counteracting the PI3K/AKT pathway. Loss of PTEN leads to activated PI3K/AKT signaling, which plays a key role in a variety of cancers. However, the role of PTEN/PI3K/AKT signaling nexus in IDD remains unknown. Here, we report that PTEN is overexpressed in degenerative NP, which correlates with inactivated AKT. Using the PTEN knockdown approach by lentivirus‐mediated short interfering RNA gene transfer technique, we report that PTEN decreases survival but induces apoptosis and senescence of NP cells. PTEN also inhibits expression and production of ECM components including collagen II, aggrecan, and proteoglycan. Furthermore, PTEN modulates the expression of ECM regulatory molecules SOX‐9 and matrix metalloproteinase‐3 (MMP‐3). Using small‐molecule AKT inhibitor GDC‐0068, we confirm that PTEN regulates NP cell behaviors through its direct targeting of PI3K/AKT. These findings demonstrate for the first time that PTEN/PI3K/AKT signaling axis plays an important role in the pathogenesis of IDD. Targeting PTEN using gene therapy may represent a promising therapeutic approach against disc degenerative diseases.     

HIV-1 Nef and KSHV oncogene K1 synergistically promote angiogenesis by inducing cellular miR-718 to regulate the PTEN/AKT/mTOR signaling pathway

Kaposi''s sarcoma (KS) is an AIDS-defining cancer with aberrant neovascularization caused by KS-associated herpesvirus (KSHV). Although the interaction between HIV-1 and KSHV plays a pivotal role in promoting the aggressive manifestations of KS, the pathogenesis underlying AIDS-KS remains largely unknown. Here we examined HIV-1 Nef protein promotion of KSHV oncoprotein K1-induced angiogenesis. We showed that both internalized and ectopic expression of Nef in endothelial cells synergized with K1 to facilitate vascular tube formation and cell proliferation, and enhance angiogenesis in a chicken CAM model. In vivo experiments further indicated that Nef accelerated K1-induced angiogenesis and tumorigenesis in athymic nu/nu mice. Mechanistic studies revealed that Nef and K1 synergistically activated PI3K/AKT/mTOR signaling by downregulating PTEN. Furthermore, Nef and K1 induced cellular miR-718, which inhibited PTEN expression by directly targeting a seed sequence in the 3′ UTR of its mRNA. Inhibition of miR-718 expression increased PTEN synthesis and suppressed the synergistic effect of Nef- and K1-induced angiogenesis and tumorigenesis. These results indicate that, by targeting PTEN, miR-718 mediates Nef- and K1-induced angiogenesis via activation of AKT/mTOR signaling. Our results demonstrate an essential role of miR-718/AKT/mTOR axis in AIDS-KS and thus may represent an attractive therapeutic target.     

Glucose metabolism measured by [¹⁸F]fluorodeoxyglucose positron emission tomography is independent of PTEN/AKT status in human colon carcinoma cells

The phosphoinositide 3-kinase (PI3K) signaling pathway is one of the most altered in cancer, leading to a range of cellular responses including enhanced proliferation, survival, and metabolism, and is thus an attractive target for anticancer drug development. Stimulation of the PI3K pathway can be initiated by alterations at different levels of the signaling cascade including growth factor receptor activation, as well as mutations in PIK3CA, PTEN, and AKT genes frequently found in a broad range of cancers. Given its role in glucose metabolism, we investigated the utility of [(18)F]fluorodeoxyglucose positron emission tomography ([(18)F]FDG PET) as a pharmacodynamic biomarker of PI3K pathway-induced glucose metabolism. PTEN deletion in human colon carcinoma cells led to constitutive AKT activation but did not confer a phenotype of increased cell proliferation or glucose metabolism advantage in vivo relative to isogenic tumors derived from cells with a wild-type allele. This was not due to the activation context, that is, phosphatase activity, per se because PIK3CA activation in xenografts derived from the same lineage failed to increase glucose metabolism. Acute inhibition of PI3K activity by LY294002, and hence decreased activated AKT expression, led to a significant reduction in tumor [(18)F]FDG uptake that could be explained at least in part by decreased membrane glucose transporter 1 expression. The pharmacodynamic effect was again independent of PTEN status. In conclusion, [(18)F]FDG PET is a promising pharmacodynamic biomarker of PI3K pathway inhibition; however, its utility to detect glucose metabolism is not directly linked to the magnitude of activated AKT protein expression.     

Oxymatrine induces apoptosis and inhibits invasion in Gallbladder carcinoma via PTEN/PI3K/AKT pathway

Oxymatrine extracted from Sophora flavescens Ait as a natural polyphenolic phytochemical has been demonstrated to exhibit anti-tumor effects on various cancers, including Gallbladder carcinoma (GBC). However, its underlying mechanisms of function are largely unknown in GBC cells. The present study is conducted to investigate the anti-tumor effects and the underlying mechanisms of oxymatrine on GBC cells in vitro and in vivo. The results showed that oxymatrine inhibited cell viability, metastatic ability and induced cell apoptosis in dose-dependent manners. Furthermore, we found that the expression of p-AKT, MMP-2, MMP-9 and the ratio of Bcl-2/Bax were significantly down-regulated, while the expression of PTEN was up-regulated in GBC cells. In addition, pretreatment with a specific PI3K/AKT activator (IGF-1) significantly antagonized the oxymatrine-mediated inhibition of GBC–SD cells. Subsequently, our in vivo studies showed that administration of oxymatrine induced a significant dose-dependent decrease in tumor growth. In conclusion, these findings indicated that the inhibition of cells proliferation, migration, invasion and the induction of apoptosis in response to oxymatrine in GBC cells, may function through the suppression of PTEN/PI3K/AKT pathway, which was considered as the vital signaling pathway in regulating tumorigenesis. These results suggested that oxymatrine might be a novel effective candidate as chemotherapeutic agent against GBC.     

PER1 suppresses glycolysis and cell proliferation in oral squamous cell carcinoma via the PER1/RACK1/PI3K signaling complex

There is increasing evidence that the core clock gene Period 1 (PER1) plays important roles in the formation of various tumors. However, the biological functions and mechanism of PER1 in promoting tumor progression remain largely unknown. Here, we discovered that PER1 was markedly downregulated in oral squamous cell carcinoma (OSCC). Then, OSCC cell lines with stable overexpression, knockdown, and mutation of PER1 were established. We found that PER1 overexpression significantly inhibited glycolysis, glucose uptake, proliferation, and the PI3K/AKT pathway in OSCC cells. The opposite effects were observed in PER1-knockdown OSCC cells. After treatment of PER1-overexpressing OSCC cells with an AKT activator or treatment of PER1-knockdown OSCC cells with an AKT inhibitor, glycolysis, glucose uptake, and proliferation were markedly rescued. In addition, after treatment of PER1-knockdown OSCC cells with a glycolysis inhibitor, the increase in cell proliferation was significantly reversed. Further, coimmunoprecipitation (Co-IP) and cycloheximide (CHX) chase experiment demonstrated that PER1 can bind with RACK1 and PI3K to form the PER1/RACK1/PI3K complex in OSCC cells. In PER1-overexpressing OSCC cells, the abundance of the PER1/RACK1/PI3K complex was significantly increased, the half-life of PI3K was markedly decreased, and glycolysis, proliferation, and the PI3K/AKT pathway were significantly inhibited. However, these effects were markedly reversed in PER1-mutant OSCC cells. In vivo tumorigenicity assays confirmed that PER1 overexpression inhibited tumor growth while suppressing glycolysis, proliferation, and the PI3K/AKT pathway. Collectively, this study generated the novel findings that PER1 suppresses OSCC progression by inhibiting glycolysis-mediated cell proliferation via the formation of the PER1/RACK1/PI3K complex to regulate the stability of PI3K and the PI3K/AKT pathway-dependent manner and that PER1 could potentially be a valuable therapeutic target in OSCC.Subject terms: Oral cancer, Cell growth, RNAi     

Proteomic studies of rat tibialis anterior muscle during postnatal growth and development

Phosphoinositide 3-kinase (PI3K) pathway exerts its effects through Akt, its downstream target molecule, and thereby regulates various cell functions including cell proliferation, cell transformation, apoptosis, tumor growth, and angiogenesis. Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) has been implicated in regulating cell survival signaling through the PI3K/Akt pathway. However, the mechanism by PI3K/PTEN signaling regulates angiogenesis and tumor growth in vivo remains to be elucidated. Vascular endothelial growth factor (VEGF) plays a pivotal role in tumor angiogenesis. The effect of PTEN on VEGF-mediated signal in pancreatic cancer is unknown. This study aimed to determine the effect of PTEN on both the expression of VEGF and angiogenesis. Toward that end, we used the siRNA knockdown method to specifically define the role of PTEN in the expression of VEGF and angiogenesis. We found that siRNA-mediated inhibition of PTEN gene expression in pancreatic cancer cells increase their VEGF secretion, up-modulated the proliferation, and migration of co-cultured vascular endothelial cell and enhanced tubule formation by HUVEC. In addition, PTEN modulated VEGF-mediated signaling and affected tumor angiogenesis through PI3K/Akt/VEGF/eNOS pathway.     

GRP94 promotes muscle differentiation by inhibiting the PI3K/AKT/mTOR signaling pathway

The glucose-regulated endoplasmic reticulum chaperone protein 94 (GRP94) is required for many biological processes, such as secretion of immune factors and mesoderm induction. Here, we demonstrated that GRP94 promotes muscle differentiation in vitro and in vivo. Moreover, GRP94 inhibited the PI3K/AKT/mTOR signaling pathway. Using both in vitro and in vivo approaches, in myoblasts, we found that this inhibition resulted in reduced proliferation and increased differentiation. To further investigate the mechanism of GRP94-induced muscle differentiation, we used co-immunoprecipitation and proximity ligation assays and found that GRP94 interacted with PI3K-interacting protein 1 (Pik3ip1). The latter protein promoted muscle differentiation by inhibiting the PI3K/AKT/mTOR pathway. Furthermore, GRP94 was found to regulate Pik3ip1 expression. Finally, when Pik3ip1 expression was inhibited, GRP94-induced promotion of muscle differentiation was diminished. Taken together, our data demonstrated that GRP94 promoted muscle differentiation, mediated by Pik3ip1-dependent inhibition of the PI3K/AKT/mTOR signaling pathway.     

Atorvastatin overcomes gefitinib resistance in KRAS mutant human non-small cell lung carcinoma cells

The exact influence of statins on gefitinib resistance in human non-small cell lung cancer (NSCLC) cells with KRAS mutation alone or KRAS/PIK3CA and KRAS/PTEN comutations remains unclear. This work found that transfection of mutant KRAS plasmids significantly suppressed the gefitinib cytotoxicity in Calu3 cells (wild-type KRAS). Gefitinib disrupted the Kras/PI3K and Kras/Raf complexes in Calu3 cells, whereas not in Calu3 KRAS mutant cells. These trends were corresponding to the expression of pAKT and pERK in gefitinib treatment. Atorvastatin (1 μM) plus gefitinib treatment inhibited proliferation, promoted cell apoptosis, and reduced the AKT activity in KRAS mutant NSCLC cells compared with gefitinib alone. Atorvastatin (5 μM) further enhanced the gefitinib cytotoxicity through concomitant inhibition of AKT and ERK activity. Atorvastatin could interrupt Kras/PI3K and Kras/Raf complexes, leading to suppression of AKT and ERK activity. Similar results were also obtained in comutant KRAS/PTEN or KRAS/PIK3CA NSCLC cells. Furthermore, mevalonate administration reversed the effects of atorvastatin on the Kras/Raf and Kras/PI3K complexes, as well as AKT and ERK activity in both A549 and Calu1 cells. The in vivo results were similar to those obtained in vitro. Therefore, mutant KRAS-mediated gefitinib insensitivity is mainly derived from failure to disrupt the Kras/Raf and Kras/PI3K complexes in KRAS mutant NSCLC cells. Atorvastatin overcomes gefitinib resistance in KRAS mutant NSCLC cells irrespective of PIK3CA and PTEN statuses through inhibition of HMG-CoA reductase-dependent disruption of the Kras/Raf and Kras/PI3K complexes.     

MicroRNAs as important players in regulating cancer through PTEN/PI3K/AKT signalling pathways

Cancer being the leading cause of mortality has become a great threat worldwide. Current cancer therapeutics lack specificity and have side effects due to a lack of understanding of the molecular mechanisms and signalling pathways involved in carcinogenesis. In recent years, researchers have been focusing on several signalling pathways to pave the way for novel therapeutics. The PTEN/PI3K/AKT pathway is one of the important pathways involved in cell proliferation and apoptosis, leading to tumour growth. In addition, the PTEN/PI3K/AKT axis has several downstream pathways that could lead to tumour malignancy, metastasis and chemoresistance. On the other hand, microRNAs (miRNAs) are important regulators of various genes leading to disease pathogenesis. Hence studies of the role of miRNAs in regulating the PTEN/PI3K/AKT axis could lead to the development of novel therapeutics for cancer. Thus, in this review, we have focused on various miRNAs involved in the carcinogenesis of various cancer via the PTEN/PI3K/AKT axis.     

TRIM59 predicts poor prognosis and promotes pancreatic cancer progression via the PI3K/AKT/mTOR-glycolysis signaling axis

Aberrant expression of the tripartite motif containing 59 (TRIM59) has been reported to participate in the development and progression of various human cancers. However, its expression pattern and cellular roles in pancreatic cancer (PC) remains unclear. In our study, we found that TRIM59 expression was significantly increased in PC tissues and was positively correlated with several malignant behaviors and poor overall survival of PC patients based on bioinformatics analysis and immunohistochemistry staining. Functionally, small interfering RNA–mediated TRIM59 depletion inhibited cell proliferation and migration in vitro, while TRIM59 overexpression promoted cell proliferation and migration in vitro and drove tumor growth and liver metastasis in vivo. Mechanically, TRIM59 was found to enhance glycolysis through activating the PI3K/AKT/mTOR pathway, ultimately contributing to PC progression. Taken together, our results demonstrate that TRIM59 may be a potential predictor for PC and promotes PC progression via the PI3K/AKT/mTOR-glycolysis signaling pathway, which establishes the rationale for targeting the TRIM59-related pathways to treat PC.     

Synergistic Therapeutic Effect of Cisplatin and Phosphatidylinositol 3-Kinase (PI3K) Inhibitors in Cancer Growth and Metastasis of Brca1 Mutant Tumors

Drug resistance and cancer metastasis are two major problems in cancer research. During a course of therapeutic treatment in Brca1-associated tumors, we found that breast cancer stem cells (CSCs) exhibit an intrinsic ability to metastasize and acquire drug resistance through distinct signaling pathways. Microarray analysis indicated that the cytoskeletal remodeling pathway was differentially regulated in CSCs, and this was further evidenced by the inhibitory role of reagents that impair this pathway in the motility of cancer cells. We showed that cisplatin treatment, although initially inhibiting cancer growth, preventing metastasis through blocking cytoskeletal remodeling, and retarding CSC motility, eventually led to drug resistance associated with a marked increase in the number of CSCs. This event was at least partially attributed to the activation of PI3K signaling, and it could be significantly inhibited by co-treatment with rapamycin. These results provide strong evidence that cytoskeletal rearrangement and PI3K/AKT signaling play distinct roles in mediating CSC mobility and viability, respectively, and blocking both pathways synergistically may inhibit primary and metastatic cancer growth.