Knockdown of CLN5 inhibits the tumorigenic properties of glioblastoma cells via the Akt/mTOR signaling pathway

Gliomas are highly malignant tumors with a rapid progression and poor prognosis. The present study investigated the cellular effects of CLN5-knockdown in the glioblastoma (GBM) U251 and U87MG cell lines. The Cell Counting Kit-8 and colony formation assays indicated that CLN5-knockdown inhibited the proliferation of GBM cells. Additionally, the results of the Transwell and scratch assays revealed that CLN5-knockdown significantly inhibited migration and invasion, and the flow cytometry analysis confirmed that apoptosis was promoted. Knockdown of CLN5 downregulated the expression levels of MMP-2, Bcl-2, cyclin D1, CDK4 and CDK6, and upregulated the expression levels of Bax and activated caspase-9. Additionally, it blocked GBM cells in the G1-phase and induced early apoptosis. Knockdown of CLN5 inhibited the activation of the Akt and mTOR signaling pathways in GBM by decreasing the levels of phosphorylated (p)-Akt and p-mTOR. The present data suggested that downregulation of CLN5 may be a potential treatment option for GBM. Knockdown of CLN5 inhibited the development of GBM via the inhibition of the Akt and mTOR signaling pathways.     

Role of aquaporin-4 in the regulation of migration and invasion of human glioma cells

Glioblastoma is the most aggressive form of primary brain tumor with a tendency to invade surrounding healthy brain tissues, rendering tumors of this type largely incurable. Aquaporin-4 (AQP4) is a key molecule involved in maintaining water and ion homeostasis in the central nervous system and has been recently reported to play a role in cell migration in addition to its well-known function in brain edema. Increased AQP4 expression has been demonstrated in glioblastoma multiforme (GBM), suggesting that it is also involved in malignant brain tumors. Here, we identify a novel role for aquaporin-4 in glioblastoma cell migration and invasion. In the present study, we used small-interference RNA technology and a pharmacological inhibitor to knock down the expression of AQP4, which resulted in speci?c and massive impairment of glioblastoma cell migration and invasion in vitro and in vivo. In addition, we demonstrated the possible mechanisms by which AQP4 functions in the process of glioblastoma cell invasion. The downregulation of matrix metalloprotease-2 (MMP-2) expression in LN229 cells with AQP4 reduction coincided with decreased cell invasive ability. Furthermore, our study showed that AQP4 may also be involved in the regulation of glioblastoma cell adhesion. The expression of β-catenin and connexin 43 were increased in AQP4-downregulated LN229 cells consistent with their enhanced cell-cell adhesion ability. In summary, our results indicate that AQP4 is involved in the control of glioblastoma cell migration and invasion and may be a potential therapeutic target for glioblastoma cell in?ltration.     

CD155/PVR plays a key role in cell motility during tumor cell invasion and migration

Background

Invasion is an important early step of cancer metastasis that is not well understood. Developing therapeutics to limit metastasis requires the identification and validation of candidate proteins necessary for invasion and migration.

Methods

We developed a functional proteomic screen to identify mediators of tumor cell invasion. This screen couples Fluorophore Assisted Light Inactivation (FALI) to a scFv antibody library to systematically inactivate surface proteins expressed by human fibrosarcoma cells followed by a high-throughput assessment of transwell invasion.

Results

Using this screen, we have identified CD155 (the poliovirus receptor) as a mediator of tumor cell invasion through its role in migration. Knockdown of CD155 by FALI or by RNAi resulted in a significant decrease in transwell migration of HT1080 fibrosarcoma cells towards a serum chemoattractant. CD155 was found to be highly expressed in multiple cancer cell lines and primary tumors including glioblastoma (GBM). Knockdown of CD155 also decreased migration of U87MG GBM cells. CD155 is recruited to the leading edge of migrating cells where it colocalizes with actin and αv-integrin, known mediators of motility and adhesion. Knockdown of CD155 also altered cellular morphology, resulting in cells that were larger and more elongated than controls when plated on a Matrigel substrate.

Conclusion

These results implicate a role for CD155 in mediating tumor cell invasion and migration and suggest that CD155 may contribute to tumorigenesis.     

SRC抑制胶质母细胞瘤的增殖、迁移、侵袭和干性维持的分子机制

目的 研究SRC在胶质母细胞瘤发生发展中的作用,并初步探讨可能的分子机制。方法  采用生物信息学的方法分析SRC在胶质母细胞瘤中的表达变化;利用shRNA下调胶质瘤母细胞系U87MG中SRC的表达,通过RT-PCR和免疫印迹法验证其抑制效率,并筛选出稳定干涉的细胞株;采用WST-1法、划痕愈合实验和Transwell迁移实验检测SRC shRNA干涉后细胞增殖、迁移和侵袭能力的变化;利用干细胞培养液筛选出SRC shRNA稳定干涉的胶质瘤干细胞,观察SRC shRNA对肿瘤干细胞干性的影响;利用细胞免疫荧光法观察干性基因SOX2的表达变化。结果 在胶质母细胞瘤标本中SRC的表达水平高于对照组,筛选到两条有效的SRC shRNA序列;通过shRNA下调SRC的表达后可以显著抑制胶质瘤母细胞U87MG的增殖、迁移、侵袭和肿瘤干细胞干性维持,并且可以明显抑制SOX2的表达。结论 SRC通过调控胶质母细胞瘤的增殖、迁移、侵袭和干性维持影响其发生发展,其对干性维持的作用可能是通过影响SOX2的表达实现的。     

microRNA-133b对胶质母细胞瘤细胞迁移和侵袭的影响

目的探讨microRNA(miR)-133b对胶质母细胞瘤(GBM)细胞的作用,并分析其作用的分子机制。方法应用实时逆转录聚合酶链反应(RT-PCR)检测20例人GBM标本及正常人脑胶质细胞系HEB中miR-133b的表达水平。Transwell侵袭实验评估miR-133b对GBM细胞迁移和侵袭的影响。Western blotting和荧光素酶报告实验来确定miR-133b的靶基因。结果与正常人脑胶质细胞系HEB比较,miR-133b在GBM标本中的相对表达量明显降低(1.0±0.17 vs.2.42±0.69,P<0.05);转染miR-133b mimic后GBM迁移和侵袭跨膜细胞数分别为66±17和60±14,均低于转染NC组(P<0.05);与转染NC组比较,转染miR-133b mimic后MMP-14蛋白表达水平明显下降(P<0.05)。荧光素酶报告基因分析实验进一步验证mir-133b靶向调节MMP-14。结论 miR-133b通过直接靶向调节MMP-14抑制GBM的迁移和侵袭能力,可作为GBM诊断和治疗的候选靶点。     

ILK mediates actin filament rearrangements and cell migration and invasion through PI3K/Akt/Rac1 signaling

One of the hallmarks of integrin signaling is an increase in cell migration and invasion, both of which are associated with actin filament rearrangements. Integrin-linked kinase (ILK) is a cytoplasmic effector of integrin receptors. ILK is known to be involved in multiple cellular functions. However, the signaling pathways involved in ILK-mediated cellular structure and motility remain to be elucidated. Here, we have demonstrated that overexpression of ILK was sufficient to induce actin filament rearrangements, to form cell motility structures, and to increase cell migration and invasion in a phosphatidylinositol 3-kinase (PI3K)-dependent manner. This corresponds with the activation of both Akt and p70 ribosomal protein S6 kinase (p70S6K1). Overexpression of dominant-negative mutants of Akt inhibited ILK-dependent activation of p70S6K1, indicating that Akt is upstream of p70S6K1 in response to ILK signaling. Overexpression of ILK was sufficient to induce Rac1 activation, which was abolish by a PI3K inhibitor, indicating that Rac1 activity is involved in ILK signaling in a PI3K dependent manner. Inhibition of Akt, Rac1, or p70S6K1 inhibited the effects of ILK on actin filaments and cell migration, suggesting a regulatory role of the PI3K/Akt/p70S6K1/Rac1 signaling pathway in response to ILK signaling. We have shown that overexpression of a dominant-negative ILK was sufficient to abolish fibronectin peptide (PHSRN)-induced rearrangements of actin filaments and cell migration and invasion. Taken together, our results identify a mechanism through which ILK can regulate both integrin-associated rearrangements of actin filaments and cell migration and invasion at the integrin receptor-proximal region.     

A conjugate of camptothecin and a somatostatin analog against prostate cancer cell invasion via a possible signaling pathway involving PI3K/Akt, alphaVbeta3/alphaVbeta5 and MMP-2/-9

Camptothecin (CPT) was conjugated to the N-terminal of a somatostatin analog (SSA) directly via a carbamate group and a basic N-terminal linking motif, D-Lys-D-Tyr-Lys-D-Tyr-D-Lys. This new CPT-SSA conjugate termed JF-10-81 was evaluated as a receptor-specific delivery system for its anti-invasive and anti-angiogenic activities. It was found that, in addition to blocking migration and invasion of highly invasive prostate cancer PC-3 cells, this conjugate also inhibited in vitro capillary-like tube formation of endothelial cells and in vivo angiogenesis in C57B1/6N female mice. JF-10-81 was found to block PC-3 cell attachment to various extracellular matrix components, mainly to vitronectin, the ligand of cell surface receptors integrin alphaVbeta3 and alphaVbeta5. Additionally, JF-10-81 reduced expression of integrins alphaVbeta3 and alphaVbeta5 on PC-3 cell surfaces, without effects on beta1 or any alphabeta1 heterodimers. This conjugate also inactivated phosphorylation of protein kinase B (PKB/Akt), down-regulated the expression of latent matrix metalloproteinase (MMP) -2 and MMP-9, but had little effect on MMP-3/-10. Meanwhile, membrane type-1 matrix metalloproteinase (MT1-MMP) and the tissue inhibitor of matrix metalloproteinase-2 (TIMP-2) were not detectable in PC-3 cells. alphaVbeta3/alphaVbeta5 and MMP-2/-9 are known to be highly expressed in many tumor cells and play an important role in tumor progression. Our results support that this conjugate could possibly inhibit prostate cancer PC-3 cell invasion through a signaling pathway involving PI3K/Akt, alphaVbeta3/alphaVbeta5 and MMP-2/-9, and this SSA could be used as an efficient vector to deliver CPT or other cytotoxic agents to target sites for cancer therapy.     

lncRNA MNX1-AS1 Promotes Glioblastoma Progression Through Inhibition of miR-4443

Long noncoding RNAs (lncRNAs) have been acknowledged as important regulators in various human cancers. lncRNA MNX1-AS1 has been shown to be an oncogene in epithelial ovarian cancer. However, the function of MNX1-AS1 in glioblastoma (GBM) remains largely unknown. Here we found that the expression of MNX1-AS1 was significantly upregulated in GBM tissues and cell lines. Knockdown of MNX1-AS1 significantly inhibited the proliferation, migration, and invasion of GBM cells. In terms of mechanism, we found that MNX1-AS1 could bind to miR-4443 in GBM cells. Overexpression of miR-4443 significantly inhibited the expression of MNX1-AS1 and vice versa. Moreover, there was an inverse correlation between the expression levels of MNX1-AS1 and miR-4443 in GBM tissues. We found that overexpression of miR-4443 inhibited the proliferation, migration, and invasion of GBM cells. We also showed that inhibition of miR-4443 reversed the effects of MNX1-AS1 knockdown on GBM cell proliferation, migration, and invasion. Taken together, we found that MNX1-AS1 promoted the proliferation, migration, and invasion of GBM cells through inhibiting miR-4443.     

Cancer stem-like cells of glioblastoma characteristically express MMP-13 and display highly invasive activity

Glioblastoma is the most malignant type of primary brain tumor that has been shown to contain a small population of cancer stem cells. Recent studies have suggested that cancer stem cells cause tumor recurrence based on their resistance to radiotherapy and chemotherapy. Although the highly invasive nature of glioblastoma cells is also implicated in the failure of current therapies, it is not clear whether cancer stem cells are involved in invasiveness. In this study, we isolated tumor sphere-forming cells bearing cancer stem-like characteristics such as self-renewal, multipotency, drug-resistibility, and in vivo tumorigenicity, from the human glioblastoma cell line U251, under serum-free neural stem cell culture condition, and assessed their migratory and invasive ability. These cells showed enhanced migratory and invasive ability on both Matrigel and organotypic brain slices compared to parental U251 cells. The expression of matrix metalloproteinase (MMP)-13 was specifically expressed in tumor sphere-forming cells derived from U251 and primary human glioma cells. Knockdown of MMP-13 expression by shRNA suppressed the migration and invasion of these cells. The results suggest that the highly invasive potential of cancer stem cells depends on MMP-13 enzymatic activity, thus MMP-13 might be a potential therapeutic target for glioblastomas.     

Human chorionic gonadotropin β induces cell motility via ERK1/2 and MMP-2 activation in human glioblastoma U87MG cells

Human chorionic gonadotropin β (hCGβ) promotes tumorigenesis in a variety of tumors including glioblastoma, breast and prostate cancer cells, etc. However, the involved mechanisms remain elusive. Distinct from the other tumors, glioblastoma is a highly invasive brain tumor; invasion causes high recurrence and mortality. Characterization of hCGβ signaling is to determine therapeutic targets to inhibit invasion and lower recurrence. Through both a stable cell line over-expressing hCGβ and hCGβ standards, we tested hCGβ signaling, migration and invasion in human glioblastoma U87MG cells. ELISA showed that hCGβ secreted into culture medium at an amount of 237.8 ± 7.8 ng/10⁷ cells in hCGβ transfected stable cells after the cells were grown for 24 h. Through Western blot and Gelatin zymography, we found that hCGβ standards phosphorylated ERK1/2 and upregulated MMP-2 expression in dose- and time-dependent manners. Meanwhile, overexpressed hCGβ phosphorylated ERK1/2, and upregulated MMP-2 expression and activity, whereas ERK1/2 blocker PD98059 (25 μM) significantly decreased both ERK1/2 and MMP-2 expression and activity. In addition, in the same conditions as the signaling test, hCGβ promoted cell migration and invasion, whereas the PD98059 diminished these effects. These findings demonstrated that hCGβ phosphorylated ERK1/2 upregulating MMP-2 expression and activity leading to cell migration and invasion, suggesting that hCGβ, ERK1/2 and MMP-2 are the potential targets to inhibit glioblastoma invasion.     

Na+/K+-ATPase β2-subunit (AMOG) expression abrogates invasion of glioblastoma-derived brain tumor-initiating cells

Background

Mechanisms of glioma invasion remain to be fully elucidated. Glioma cells within glioblastoma multiforme (GBM) range from well-differentiated tumor cells to less-differentiated brain tumor-initiating cells (BTICs). The β2-subunit of Na⁺/K⁺-ATPase, called the adhesion molecule on glia (AMOG), is highly expressed in normal glia but is thought to be universally downregulated in GBM. To test our hypothesis that expression of AMOG is heterogeneous in GBM and confers a less invasive phenotype, we compared it between BTICs and differentiated cells from patient-matched GBM and then tested GBM invasion in vitro after AMOG overexpression.

Methods

Immunohistochemistry, immunoblotting, and real-time PCR were used to characterize AMOG protein and mRNA expression in tumor samples, BTICs, and differentiated cells. Matrigel invasion assay, scratch assay, and direct cell counting were used for testing in vitro invasion, migration, and proliferation, respectively.

Results

While AMOG expression is heterogeneous in astrocytomas of grades II–IV, it is lost in most GBM. BTICs express higher levels of AMOG mRNA and protein compared with patient-matched differentiated tumor cells. Overexpression of AMOG decreased GBM cell and BTIC invasion without affecting migration or proliferation. Knockdown of AMOG expression in normal human astrocytes increased invasion.

Conclusions

AMOG expression inhibits GBM invasion. Its downregulation increases invasion in glial cells and may also represent an important step in BTIC differentiation. These data provide compelling evidence implicating the role of AMOG in glioma invasion and provide impetus for further investigation.     

Rictor regulates MMP-9 activity and invasion through Raf-1-MEK-ERK signaling pathway in glioma cells

Glioblastoma multiforme (GBM) is the most common and highly aggressive type of primary brain tumor. Tumor-associated macrophages (TAMs) secrete TNF-α that activates important survival pathways including Akt (PKB)/mTOR network. The mammalian target of rapamycin (mTOR) network functions downstream of PI3K/Akt pathway to regulate cell growth, proliferation and survival. mTOR exists in two distinct complexes-mTORC1 and mTORC2 that differ in their components and sensitivity to rapamycin. The rapamycin-insensitive complex (mTORC2) consists of mTOR, mLST8, Rictor, mSin1 and Protor and regulates the actin cytoskeleton in addition to activating Akt (protein kinase B). The present study aimed to investigate the role of Rictor-a core component of mTORC2 in regulating proliferation, survival, and invasion in gliomas. siRNA-mediated loss of Rictor function in human glioma cell lines, LN18 and LN229 and in primary GBM cells resulted in elevated expression and activity of MMP-9 and significant increase in the invasive potential of these cells. Mechanistic studies revealed that the activation of Raf-1-MEK-ERK pathway was essential for induction of MMP-9 activity and enhanced invasion. Interestingly, ablation of Rictor did not affect TNF-α-induced MMP-9 activity and invasiveness suggesting that TNF-α in the microenvironment of tumor might overrule the function of Rictor as a negative regulator of MMP-9 and invasion. Silencing Rictor had no effect on the survival or proliferation in the cell lines in the presence or absence of TNF-α. Our findings identify a role for Rictor in bridging two major pathways-Akt (PKB)/mTOR and Raf-1-MEK-ERK in regulating MMP-9 activity and invasion of glioma tumor cells.     

17AEP-GA, an HSP90 antagonist, is a potent inhibitor of glioblastoma cell proliferation, survival, migration and invasion

Glioblastoma multiforme (GBM) is the most frequent and the most malignant human brain tumor. The expression of receptor tyrosine kinase MET and its ligand hepatocyte growth factor (HGF) is strongly increased in GBM, where they promote tumor proliferation, cell survival, migration, invasion and angiogenesis. We used geldanamycins (GAs) (inhibitors of HSP90) in order to block glioblastoma growth and HGF-dependent cell migration and invasion. The effect of GAs on three GBM cell lines was tested and we found their antiproliferative effect on tumor cells. The maximum level of inhibition reached 70%. After treatment with GAs, cells also became apoptotic as determined by Annexin?V-positive staining and activation of the caspase-3 pathway. We examined the expression and activity of the MET?receptor on GBM cell lines and we observed phosphorylation of AKT and MAPK after HGF stimulation by western blot analysis. Since GBM?cells express high level of MET?receptor and were shown to respond to HGF by increased motility we tested if GAs could negatively affect GBM cell movement. In our study, we found that GAs inhibited the chemotaxis of glioblastoma cells toward the hepatocyte growth factor gradient. The GAs also blocked migration of tumor cells through a Matrigel layer in invasion assays. The strongest inhibitory effect was observed for GA and its analog, 17AEP-GA. Based on our results, GAs, particularly 17AEP-GA, could be considered as a new potential agent to treat glioblastoma multiforme.     

Subcurative radiation significantly increases cell proliferation,invasion, and migration of primary glioblastoma multiforme in vivo

Tumor cell proliferation, infiltration, migration, and neovascularization are known causes of treatment resistance in glioblastoma multiforme(GBM). The purpose of this study was to determine the effect of radiation on the growth characteristics of primary human GBM developed in a nude rat. Primary GBM cells grown from explanted GBM tissues were implanted orthotopically in nude rats. Tumor growth was confirmed by magnetic resonance imaging on day 77(baseline) after implantation. The rats underwent irradiation to a dose of 50 Gy delivered subcuratively on day 84 postimplantation(n = 8), or underwent no radiation(n = 8). Brain tissues were obtained on day 112(nonirradiated) or day 133(irradiated). Immunohistochemistry was performed to determine tumor cell proliferation(Ki-67) and to assess the expression of infiltration marker(matrix metalloproteinase-2, MMP-2) and cell migration marker(CD44). Tumor neovascularization was assessed by microvessel density using von-Willebrand factor(vWF) staining. Magnetic resonance imaging showed well-developed, infiltrative tumors in 11 weeks postimplantation. The proportion of Ki-67-positive cells in tumors undergoing radiation was(71 ± 15)% compared with(25 ± 12)% in the nonirradiated group(P = 0.02). The number of MMP-2-positive areas and proportion of CD44-positive cells were also high in tumors receiving radiation, indicating great invasion and infiltration. Microvessel density analysis did not show a significant difference between nonirradiated and irradiated tumors. Taken together, we found that subcurative radiation significantly increased proliferation, invasion, and migration of primary GBM. Our study provides insights into possible mechanisms of treatment resistance following radiation therapy for GBM.     

Epidermal growth factor induces matrix metalloproteinase-1 (MMP-1) expression and invasion in glioma cell lines via the MAPK pathway

Glioblastoma multiforme (GBM) is an aggressive cancer with a poor survival rate. A key component that contributes to the poor prognosis is the capacity of glioma cells to invade local brain tissue in a diffuse manner. Among various proteases that aid in the process of invasion, matrix metalloproteinase-1 (MMP-1) has been identified as an important contributory factor in various cancers. Apart from its traditional role in cleaving its primary extracellular matrix (ECM) substrates, and like other members of the matrix metalloproteinase family, MMP-1 can activate latent forms of bio-active molecules initiating downstream pro-invasive and pro-oncogenic signaling mechanisms. MMP-1 expression is regulated by several growth factors including epidermal growth factor (EGF). Due to the fact that the epidermal growth factor receptor (EGFR) is aberrantly overexpressed in GBM, we wanted to examine in greater detail the signaling mechanisms by which MMP-1 expression and invasion is driven by EGF in GBM cells. T98G cells treated with EGF resulted in an induction of MMP-1 expression following EGFR activation. Inhibition of EGFR by both pharmacologic and genetic approaches abrogated this induction. Repression of the mitogen activated protein kinase (MAPK) signaling led to the inhibition of EGF-induced MMP-1 whereas the PI3-kinase/AKT signaling was not associated with EGFR-mediated MMP-1 induction. Inhibition of EGFR signaling also led to a decrease in T98G invasion. These data suggest that EGFR mediated MMP-1 regulation is mainly via the MAPK pathway in T98G cells and inhibition of EGFR and MMP-1 results in a decrease in T98G cell invasion.     

HCMV glycoprotein B is expressed in primary glioblastomas and enhances growth and invasiveness via PDGFR-alpha activation

Our laboratory first demonstrated that human cytomegalovirus (HCMV) is associated with the most deadly form of primary brain tumor, glioblastoma (GBM). We showed that HCMV glycoprotein B (gB) mediates viral cellular entry via the receptor tyrosine kinase PDGFR-alpha (PDGFRα), resulting in activation of the PI3K/Akt pathway, a critical signaling axis gliomagenesis. Here, we investigated the effects of gB overexpression on glioma progression. We demonstrate that gB is endogenously expressed in primary GBM samples and show that ectopic gB expression in glioma cells induced sustained phosphorylation of PDGFRα, Akt, and Src. Recombinant gB protein and the whole virus enhanced invasion of primary glioblastoma cells into Matrigel and rat brain slices, and this effect was specifically inhibited by neutralizing antibodies to either gB or PDGFRα. Importantly, neutralizing antibodies to gB significantly inhibited the invasiveness of patient-derived HCMV-positive glioblastoma cells, suggesting that functional inhibition of this viral protein could hinder glioblastoma progression. gB overexpression promoted in vivo glioma growth and enhanced phosphor-Akt levels and tumor cell dispersal relative to controls. Taken together, our results demonstrate that HCMV gB promotes key hallmarks of glioblastoma and suggest that targeting gB may have therapeutic benefits for patients with HCMV -positive gliomas.     

Angiopoietin-2 stimulates breast cancer metastasis through the alpha(5)beta(1) integrin-mediated pathway

Acquisition of a metastatic phenotype by breast cancer cells includes alternations of multigenic programs that permit tumor cells to metastasize to distant organs. Here, we report that angiopoietin-2 (Ang2), a known growth factor, is capable of promoting breast cancer cell invasion leading to metastasis. Analysis of 185 primary human breast cancer specimens that include 97 tumors showing lymph node and/or distant metastasis reveals a significant correlation between the expression of Ang2 and E-cadherin, Snail, metastatic potential, tumor grade, and lymph-vascular invasion during breast cancer progression. Using a xenograft model, we show that overexpression of Ang2 in poorly metastatic MCF-7 breast cancer cells suppresses expression of E-cadherin and induces Snail expression and phosphorylation of Akt and glycogen synthase kinase-3beta (GSK-3beta) promoting metastasis to the lymph nodes and lung. In cell culture, Ang2 promotes cell migration and invasion in Tie2-deficient breast cancer cells through the alpha(5)beta(1) integrin/integrin-linked kinase (ILK)/Akt, GSK-3beta/Snail/E-cadherin signaling pathway. Inhibition of ILK and the alpha(5)beta(1) integrin abrogates Ang2 modulation of Akt, GSK-3beta, Snail, and E-cadherin and Ang2-stimulated breast cancer cell migration and invasion. Together, these results underscore the significant contribution of Ang2 in cancer progression, not only by stimulating angiogenesis but also by promoting metastasis, and provide a mechanism by which breast cancer cells acquire an enhanced invasive phenotype contributing to metastasis.     

Abrogation of PIK3CA or PIK3R1 reduces proliferation, migration, and invasion in glioblastoma multiforme cells

Glioblastoma multiforme (GBM) is a highly invasive and deadly brain tumor. Tumor cell invasion makes complete surgical resection impossible and reduces the efficacy of other therapies. Genome-wide analyses of mutations, copy-number changes, and expression patterns have provided new insights into genetic abnormalities common in GBM. We analyzed published data and identified the invasion and motility pathways most frequently altered in GBM. These were most notably the focal adhesion and integrin signaling, and extracellular matrix interactions pathways. We mapped alterations in each of these pathways and found that they included the catalytic PIK3CA and regulatory PIK3R1 subunit genes of the class IA PI3K. Knockdown of either of these genes separately in GBM cell lines by lentiviral-mediated shRNA expression resulted in decreased proliferation, migration, and invasion in all lines tested. FAK activity was reduced by knockdown of either PIK3CA or PIK3R1, and MMP2 levels were reduced by knockdown of PIK3R1. We conclude that PIK3R1, like PIK3CA, is a potential therapeutic target in GBM and that it also influences tumor cell growth and motility.