Functional Role of mTORC2 versus Integrin-Linked Kinase in Mediating Ser473-Akt Phosphorylation in PTEN-Negative Prostate and Breast Cancer Cell Lines

Addressing the Reciprocal Crosstalk between the AR and the PI3K/AKT/mTOR Signaling Pathways for Prostate Cancer Treatment

The reduction in androgen synthesis and the blockade of the androgen receptor (AR) function by chemical castration and AR signaling inhibitors represent the main treatment lines for the initial stages of prostate cancer. Unfortunately, resistance mechanisms ultimately develop due to alterations in the AR pathway, such as gene amplification or mutations, and also the emergence of alternative pathways that render the tumor less or, more rarely, completely independent of androgen activation. An essential oncogenic axis activated in prostate cancer is the phosphatidylinositol-3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway, as evidenced by the frequent alterations of the negative regulator phosphatase and tensin homolog (PTEN) and by the activating mutations in PI3K subunits. Additionally, crosstalk and reciprocal feedback loops between androgen signaling and the PI3K/AKT/mTOR signaling cascade that activate pro-survival signals and play an essential role in disease recurrence and progression have been evidenced. Inhibitors addressing different players of the PI3K/AKT/mTOR pathway have been evaluated in the clinic. Only a limited benefit has been reported in prostate cancer up to now due to the associated side effects, so novel combination approaches and biomarkers predictive of patient response are urgently needed. Here, we reviewed recent data on the crosstalk between AR signaling and the PI3K/AKT/mTOR pathway, the selective inhibitors identified, and the most advanced clinical studies, with a focus on combination treatments. A deeper understanding of the complex molecular mechanisms involved in disease progression and treatment resistance is essential to further guide therapeutic approaches with improved outcomes.

Bile acid metabolism and signaling, the microbiota, and metabolic disease

The diversity, composition, and function of the bacterial community inhabiting the human gastrointestinal tract contributes to host health through its role in producing energy or signaling molecules that regulate metabolic and immunologic functions. Bile acids are potent metabolic and immune signaling molecules synthesized from cholesterol in the liver and then transported to the intestine where they can undergo metabolism by gut bacteria. The combination of host- and microbiota-derived enzymatic activities contribute to the composition of the bile acid pool and thus there can be great diversity in bile acid composition that depends in part on the differences in the gut bacteria species. Bile acids can profoundly impact host metabolic and immunological functions by activating different bile acid receptors to regulate signaling pathways that control a broad range of complex symbiotic metabolic networks, including glucose, lipid, steroid and xenobiotic metabolism, and modulation of energy homeostasis. Disruption of bile acid signaling due to perturbation of the gut microbiota or dysregulation of the gut microbiota-host interaction is associated with the pathogenesis and progression of metabolic disorders. The metabolic and immunological roles of bile acids in human health have led to novel therapeutic approaches to manipulate the bile acid pool size, composition, and function by targeting one or multiple components of the microbiota-bile acid-bile acid receptor axis.

Mammalian Target of Rapamycin as the Therapeutic Target of Vascular Proliferative Diseases: Past, Present, and Future

ABSTRACT

The abnormal proliferation of vascular smooth muscle cells (VSMCs) is a key pathological characteristic of vascular proliferative diseases. Mammalian target of rapamycin (mTOR) is an evolutionarily conserved serine/threonine kinase that plays an important role in regulating cell growth, motility, proliferation, and survival, as well as gene expression in response to hypoxia, growth factors, and nutrients. Increasing evidence shows that mTOR also regulates VSMC proliferation in vascular proliferative diseases and that mTOR inhibitors, such as rapamycin, effectively restrain VSMC proliferation. However, the molecular mechanisms linking mTOR to vascular proliferative diseases remain elusive. In our review, we summarize the key roles of the mTOR and the recent discoveries in vascular proliferative diseases, focusing on the therapeutic potential of mTOR inhibitors to target the mTOR signaling pathway for the treatment of vascular proliferative diseases. In this study, we discuss mTOR inhibitors as promising candidates to prevent VSMC-associated vascular proliferative diseases.

The focal adhesion protein Integrin-Linked Kinase (ILK) as an important player in breast cancer pathogenesis

Cell-extracellular matrix interactions, or focal adhesions (FA), are crucial for tissue homeostasis but are also implicated in cancer. Integrin-Linked Kinase (ILK) is an abundantly expressed FA protein involved in multiple signaling pathways. Here, we reviewed the current literature on the role of ILK in breast cancer (BC). Articles included in vitro and in vivo experiments as well as studies in human BC samples. ILK attenuation via silencing or pharmaceutical inhibition, leads to apoptosis or inhibition of epithelial-to-mesenchymal transition, and cell invasion whereas ILK overexpression suppresses anoikis and promotes tumor growth and metastasis. Finally, ILK is upregulated in BC tumors and its expression is associated with grade, and metastasis. Therefore, ILK should be evaluated as a potential anti-cancer pharmaceutical target.

HIF-1 α may play a role in late pregnancy hypoxia-induced autism-like behaviors in offspring rats

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that can be caused by various factors. The present study aimed to determine whether prenatal hypoxia can lead to ASD and the role of hypoxia-inducible factor-1α (HIF-1α) in this process. We constructed a prenatal hypoxia model of pregnant rats by piping nitrogen and oxygen mixed gas, with an oxygen concentration of 10 ± 0.5 %, into the self-made hypoxia chamber. Rats were subjected to different extents of hypoxia treatments at different points during pregnancy. The results showed that hypoxia for 6 h on the 17th gestation day is most likely to lead to autistic behavior in offspring rats, including social deficits, repetitive behaviors, and impaired learning and memory. The mRNA expression level of TNF-α also increased in hypoxia-induced autism group and valproic acid (VPA) group. Western blotting analysis showed increased levels of hypoxia inducible factor 1 alpha (HIF-1α) and decreased levels of phosphatase and tensin homolog (PTEN) in the hypoxic-induced autism group. Meanwhile, N-methyl d-aspartate receptor subtype 2 (NR2A) and glutamate ionotropic receptor AMPA type subunit 2 (GluR2) were upregulated in the hypoxic-induced autism group. HIF-1α might play a role in hypoxia-caused autism-like behavior and its regulatory effect is likely to be achieved by regulating synaptic plasticity.

Epibrassinolide activates AKT to trigger autophagy with polyamine metabolism in SW480 and DLD-1 colon cancer cell lines

Epibrassinolide (EBR), a plant-derived polyhydroxylated derivative of 5α-cholestane, structurally shows similarities to animal steroid hormones. According to the present study, EBR treatment triggered a significant stress response via activating ER stress, autophagy, and apoptosis in cancer cells. EBR could also increase Akt phosphorylation in vitro. While the activation of Akt resulted in cellular metabolic activation in normal cells to proceed with cell survival, a rapid stress response was induced in cancer cells to reduce survival. Therefore, Akt as a mediator of cellular survival and death decision pathways is a crucial target in cancer cells. In this study, we determined that EBR induces stress responses through activating Akt, which reduced the mTOR complex I (mTORC1) activation in SW480 and DLD-1 colon cancer cells. As a consequence, EBR triggered macroautophagy and led to lipidation of LC3 most efficiently in SW480 cells. The cotreatment of spermidine (Spd) with EBR increased lipidation of LC3 synergistically in both cell lines. We also found that EBR promoted polyamine catabolism in SW480 cells. The retention of polyamine biosynthesis was remarkable following EBR treatment. We suggested that EBR-mediated Akt activation might determine the downstream cellular stress responses to induce autophagy related to polyamines.

An In silico Approach to Identify High Affinity Small Molecule Targeting m-TOR Inhibitors for the Clinical Treatment of Breast Cancer

Breast cancer is the most frequent malignancy among women. It is a heterogeneous disease with different subtypes defined by its hormone receptor. A hormone receptor is mainly concerned with the progression of the PI3K/AKT/mTOR pathway which is often dysregulated in breast cancer. This is a major signaling pathway that controls the activities such as cell growth, cell division, and cell proliferation. The present study aims to suppress mTOR protein by its various inhibitors and to select one with the highest binding affinity to the receptor protein. Out of 40 inhibitors of mTOR against breast cancer, SF1126 was identified to have the best docking score of -8.705, using Schrodinger Suite which was further subjected for high throughput screening to obtain best similar compound using Lipinski’s filters. The compound obtained after virtual screening, ID: ZINC85569445 is seen to have the highest affinity with the target protein mTOR. The same result based on the binding free energy analysis using MM-GBSA showed that the compound ZINC85569445 to have the the highest binding free energy. The next study of interaction between the ligand and receptor protein with the pharmacophore mapping showed the best conjugates, and the ZINC85569445 can be further studied for future benefits of treatment of breast cancer.

mTOR Complexes as a Nutrient Sensor for Driving Cancer Progression

Recent advancement in the field of molecular cancer research has clearly revealed that abnormality of oncogenes or tumor suppressor genes causes tumor progression thorough the promotion of intracellular metabolism. Metabolic reprogramming is one of the strategies for cancer cells to ensure their survival by enabling cancer cells to obtain the macromolecular precursors and energy needed for the rapid growth. However, an orchestration of appropriate metabolic reactions for the cancer cell survival requires the precise mechanism to sense and harness the nutrient in the microenvironment. Mammalian/mechanistic target of rapamycin (mTOR) complexes are known downstream effectors of many cancer-causing mutations, which are thought to regulate cancer cell survival and growth. Recent studies demonstrate the intriguing role of mTOR to achieve the feat through metabolic reprogramming in cancer. Importantly, not only mTORC1, a well-known regulator of metabolism both in normal and cancer cell, but mTORC2, an essential partner of mTORC1 downstream of growth factor receptor signaling, controls cooperatively specific metabolism, which nominates them as an essential regulator of cancer metabolism as well as a promising candidate to garner and convey the nutrient information from the surrounding environment. In this article, we depict the recent findings on the role of mTOR complexes in cancer as a master regulator of cancer metabolism and a potential sensor of nutrients, especially focusing on glucose and amino acid sensing in cancer. Novel and detailed molecular mechanisms that amino acids activate mTOR complexes signaling have been identified. We would also like to mention the intricate crosstalk between glucose and amino acid metabolism that ensures the survival of cancer cells, but at the same time it could be exploitable for the novel intervention to target the metabolic vulnerabilities of cancer cells.

Inhibition of mTORC2 component RICTOR impairs tumor growth in pancreatic cancer models

Mammalian Target of Rapamycin complex 2 (mTORC2) and its regulatory component Rapamycin-insensitive companion of mTOR (RICTOR) are increasingly recognized as important players in human cancer development and progression. However, the role of RICTOR in human pancreatic ductal adenocarcinoma (PDAC) is unclear so far. Here, we sought to analyze the effects of RICTOR inhibition in human pancreatic cancer cell lines in vitro and in vivo. Furthermore, RICTOR expression was determined in human PDAC samples. Results demonstrate that depletion of RICTOR with siRNA (transient knock-down) or shRNA (stable knock-down) has an inhibitory effect on tumor growth in vitro. Moreover, RICTOR inhibition led to impaired phosphorylation/activity of AGC kinases (AKT, SGK1). Interestingly, hypoxia-induced expression of hypoxia-induced factor-1α (HIF-1α) was diminished and secretion of vascular-endothelial growth factor-A (VEGF-A) was impaired upon targeting RICTOR. Stable RICTOR knock-down led to significant inhibition of tumor growth in subcutaneous and orthotopic tumor models which was accompanied by significant reduction of tumor cell proliferation. Finally, immunohistochemical analyses of 85 human PDAC samples revealed significantly poorer survival in patients with higher RICTOR expression. In conclusion, these findings provide first evidence for mTORC2/RICTOR as an attractive novel target for treatment of human PDAC.

Mitochondria-Endoplasmic Reticulum Contact Sites Function as Immunometabolic Hubs that Orchestrate the Rapid Recall Response of Memory CD8+ T Cells

Glycolysis is linked to the rapid response of memory CD8⁺ T cells, but the molecular and subcellular structural elements enabling enhanced glucose metabolism in nascent activated memory CD8⁺ T cells are unknown. We found that rapid activation of protein kinase B (PKB or AKT) by mammalian target of rapamycin complex 2 (mTORC2) led to inhibition of glycogen synthase kinase 3β (GSK3β) at mitochondria-endoplasmic reticulum (ER) junctions. This enabled recruitment of hexokinase I (HK-I) to the voltage-dependent anion channel (VDAC) on mitochondria. Binding of HK-I to VDAC promoted respiration by facilitating metabolite flux into mitochondria. Glucose tracing pinpointed pyruvate oxidation in mitochondria, which was the metabolic requirement for rapid generation of interferon-γ (IFN-γ) in memory T cells. Subcellular organization of mTORC2-AKT-GSK3β at mitochondria-ER contact sites, promoting HK-I recruitment to VDAC, thus underpins the metabolic reprogramming needed for memory CD8⁺ T cells to rapidly acquire effector function.

mTOR is a fine tuning molecule in CDK inhibitors-induced distinct cell death mechanisms via PI3K/AKT/mTOR signaling axis in prostate cancer cells

Purvalanol and roscovitine are cyclin dependent kinase (CDK) inhibitors that induce cell cycle arrest and apoptosis in various cancer cells. We further hypothesized that co-treatment of CDK inhibitors with rapamycin, an mTOR inhibitor, would be an effective combinatory strategy for the inhibition of prostate cancer regard to androgen receptor (AR) status due to inhibition of proliferative pathway, PI3K/AKT/mTOR, and induction of cell death mechanisms. Androgen responsive (AR+), PTEN(-/-) LNCaP and androgen independent (AR-), PTEN(+/-) DU145 prostate cancer cells were exposed to purvalanol (20 µM) and roscovitine (30 µM) with or without rapamycin for 24 h. Cell viability assay, immunoblotting, flow cytometry and fluorescence microscopy was used to define the effect of CDK inhibitors with or without rapamycin on proliferative pathway and cell death mechanisms in LNCaP and DU145 prostate cancer cells. Co-treatment of rapamycin modulated CDK inhibitors-induced cytotoxicity and apoptosis that CDK inhibitors were more potent to induce cell death in AR (+) LNCaP cells than AR (-) DU145 cells. CDK inhibitors in the presence or absence of rapamycin induced cell death via modulating upstream PI3K/AKT/mTOR signaling pathway in LNCaP cells, exclusively only treatment of purvalanol have strong potential to inhibit both upstream and downstream targets of mTOR in LNCaP and DU145 cells. However, co-treatment of rapamycin with CDK inhibitors protects DU145 cells from apoptosis via induction of autophagy mechanism. We confirmed that purvalanol and roscovitine were strong apoptotic and autophagy inducers that based on regulation of PI3K/AKT/mTOR signaling pathway. Co-treatment of rapamycin with purvalanol and roscovitine exerted different effects on cell survival and death mechanisms in LNCaP and DU145 cell due to their AR receptor status. Our studies show that co-treatment of rapamycin with CDK inhibitors inhibit prostate cancer cell viability more effectively than either agent alone, in part, by targeting the mTOR signaling cascade in AR (+) LNCaP cells. In this point, mTOR is a fine-tuning player in purvalanol and roscovitine-induced apoptosis and autophagy via regulation of PI3K/AKT and the downstream targets, which related with cell proliferation.

Hypoxia-inducible ERO1α promotes cancer progression through modulation of integrin-β1 modification and signalling in HCT116 colorectal cancer cells

Endoplasmic reticulum disulphide oxidase 1α (ERO1α) is an oxidase localized in the endoplasmic reticulum that plays a role in the formation of disulphide bonds of secreted and cell-surface proteins. We previously showed that ERO1α is overexpressed in various types of cancer and we further identified ERO1α expression as a novel factor related to poor prognosis in cancer. However, the biological functions of ERO1α in cancer remain unclear. Here, we investigated the cell biological roles of ERO1α in the human colon-cancer cell line HCT116. ERO1α knockout (KO) by using CRISPR/Cas9 resulted in decreased tumourigenicity in vivo and reduced cell proliferation only under hypoxia in vitro, which suggested that ERO1α promotes cancer progression specifically in a low-oxygen environment. Thus, we evaluated the function of ERO1α in cell proliferation under hypoxia, and found that under hypoxic conditions, ERO1α KO resulted in a contact-inhibited morphology and diminished motility of cells. We further showed that ERO1α KO induced a change in integrin-β1 glycosylation and thus an attenuation of cell-surface integrin-β1 expression, which resulted in the aforementioned phenotype. Our study has established a previously unrecognized link between ERO1α expression and integrin activation, and thus provides new evidence for the effectiveness of ERO1α-targeted therapy for colorectal carcinoma.

Regulation of PI3K effector signalling in cancer by the phosphoinositide phosphatases

Class I phosphoinositide 3-kinase (PI3K) generates phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P₃) at the plasma membrane in response to growth factors, activating a signalling cascade that regulates many cellular functions including cell growth, proliferation, survival, migration and metabolism. The PI3K pathway is commonly dysregulated in human cancer, and drives tumorigenesis by promoting aberrant cell growth and transformation. PtdIns(3,4,5)P₃ facilitates the activation of many pleckstrin homology (PH) domain-containing proteins including the serine/threonine kinase AKT. There are three AKT isoforms that are frequently hyperactivated in cancer through mutation, amplification or dysregulation of upstream regulatory proteins. AKT isoforms have converging and opposing functions in tumorigenesis. PtdIns(3,4,5)P₃ signalling is degraded and terminated by phosphoinositide phosphatases such as phosphatase and tensin homologue (PTEN), proline-rich inositol polyphosphate 5-phosphatase (PIPP) (INPP5J) and inositol polyphosphate 4-phosphatase type II (INPP4B). PtdIns(3,4,5)P₃ is rapidly hydrolysed by PIPP to generate phosphatidylinositol 3,4-bisphosphate (PtdIns(3,4)P₂), which is further hydrolysed by INPP4B to form phosphatidylinositol 3-phosphate (PtdIns3P). PtdIns(3,4)P₂ and PtdIns3P are also important signalling molecules; PtdIns(3,4)P₂ together with PtdIns(3,4,5)P₃ are required for maximal AKT activation and PtdIns3P activates PI3K-dependent serum and glucocorticoid-regulated kinase (SGK3) signalling. Loss of Pten, Pipp or Inpp4b expression or function promotes tumour growth in murine cancer models through enhanced AKT isoform-specific signalling. INPP4B inhibits PtdIns(3,4)P₂-mediated AKT activation in breast and prostate cancer; however, INPP4B expression is increased in acute myeloid leukaemia (AML), melanoma and colon cancer where it paradoxically promotes cell proliferation, transformation and/or drug resistance. This review will discuss how PTEN, PIPP and INPP4B distinctly regulate PtdIns(3,4,5)P₃ signalling downstream of PI3K and how dysregulation of these phosphatases affects cancer outcomes.

Overexpression of ILK promotes temozolomide resistance in glioma cells

The present study aimed to investigate whether overexpression of integrin-linked kinase (ILK) affects drug resistance to temozolomide (TMZ) in glioma cells. To do this, a plasmid containing the ILK gene was transfected into the SHG‑44 human glioma cell line, and cells were subsequently cultured in the absence or presence of TMZ. The expression levels of ILK, multidrug resistance‑associated protein (MRP) and multi‑drug resistance protein (MDR) were assessed in these cells. Cell growth and apoptosis were measured by MTT and Hoechst staining, and flow cytometry, respectively. In addition, the expression levels of B‑cell lymphoma 2 (Bcl‑2) and Bcl‑2‑associated x protein (Bax), and caspase‑3 activity, were evaluated. The ILK‑overexpressing SHG‑44 cell was successfully constructed, and demonstrated increased expression levels of ILK, MDR and MRP compared with untransfected cells. Cell growth in the ILK+TMZ group was significantly greater, and the percentage of apoptotic cells in the ILK+TMZ group was significantly reduced, compared with the p enhanced green fluorescent protein (EGFP)‑C1+ TMZ empty vector control group. Expression levels of the anti‑apoptotic protein Bcl‑2 were significantly increased and those of the pro‑apoptotic protein Bax were significantly decreased (P<0.01) in the ILK+TMZ group compared with the pEGFP‑C1+TMZ group. In addition, the activity of caspase‑3 in ILK+TMZ group was significantly decreased compared with the pEGFP‑C1+TMZ group (P<0.01). Overexpression of ILK therefore promoted the proliferation of SHG‑44 human glioma cells, reduced apoptosis and reduced sensitivity to TMZ via decreasing the activity of caspase‑3.

mTORC2 activation is regulated by the urokinase receptor (uPAR) in bladder cancer

Mammalian target of rapamycin complex 2 (mTORC2) has been identified as a major regulator of bladder cancer cell migration and invasion. Upstream pathways that mediate mTORC2 activation remain poorly defined. Urokinase-type plasminogen activator receptor (uPAR) is a GPI-anchored membrane protein and known activator of cell-signaling. We identified increased uPAR expression in 94% of invasive human bladder cancers and in 54-71% of non-invasive bladder cancers, depending on grade. Normal urothelium was uPAR-immunonegative. Analysis of publicly available datasets identified uPAR gene amplification or mRNA upregulation in a subset of bladder cancer patients with reduced overall survival. Using biochemical approaches, we showed that uPAR activates mTORC2 in bladder cancer cells. Highly invasive bladder cancer cell lines, including T24, J82 and UM-UC-3 cells, showed increased uPAR mRNA expression and protein levels compared with the less aggressive cell lines, UROtsa and RT4. uPAR gene-silencing significantly reduced phosphorylation of Serine-473 in Akt, an mTORC2 target. uPAR gene-silencing also reduced bladder cancer cell migration and Matrigel invasion. S473 phosphorylation was observed by immunohistochemistry in human bladder cancers only when the tumors expressed high levels of uPAR. S473 phosphorylation was not controlled by uPAR in bladder cancer cell lines that are PTEN-negative; however, this result probably did not reflect altered mTORC2 regulation. Instead, PTEN deficiency de-repressed alternative kinases that phosphorylate S473. Our results suggest that uPAR and mTORC2 are components of a single cell-signaling pathway. Targeting uPAR or mTORC2 may be beneficial in patients with bladder cancer.

Recent advances in targeting mTOR signaling pathway using small molecule inhibitors

Targeted-based cancer therapy (TBCT) or personalized medicine is one of the main treatment modalities for cancer that has been developed to decrease the undesirable effects of chemotherapy. Targeted therapy inhibits the growth of tumor cells by interrupting with particular molecules required for tumorigenesis and proliferation of tumor cells rather than interfering with dividing normal cells. Therefore, targeted therapies are anticipated to be more efficient than former tumor treatment agents with minimal side effects on non-tumor cells. Small molecule inhibitors (SMIs) are currently one of the most investigated anti-tumor agents of TBCT. These small organic agents target several vital molecules involved in cell biological processes and induce target cells apoptosis and necrosis. Mechanistic (mammalian) target of rapamycin (mTOR) complexes (mTORC1/2) control different intracellular processes, including growth, proliferation, angiogenesis and metabolism. Signaling pathways, in which mTOR complexes are involved in are usually dysregulated in various tumors and have been shown to be ideal targets for SMIs. Currently, different mTOR-SMIs are in the clinic for the treatment of cancer patients, and several others are in preclinical or clinical settings. In this review, we summarize recent advances in developing different mTOR inhibitors, which are currently in preclinical and clinical investigations or have been approved for cancer treatment.

A novel HIF-1α-integrin-linked kinase regulatory loop that facilitates hypoxia-induced HIF-1α expression and epithelial-mesenchymal transition in cancer cells

Here, we described a novel regulatory feedback loop in which hypoxia induces integrin-linked kinase (ILK) expression through a HIF-1α-dependent mechanism and ILK, in turn, stimulates HIF-1α expression through cell type- and cell context-dependent pathways. HIF-1α increased ILK via transcriptional activation. ILK increased HIF-1α levels by promoting mTOR-mediated translation in PC-3 and MCF-7 cells, and by blocking GSK3β-mediated degradation in LNCaP cells, consistent with the cell line-/cellular context-specific functions of ILK as a Ser473-Akt kinase. We show that ILK can account for the effects of hypoxia on Akt, mTOR, and GSK3β phosphorylation. Also, ILK can de-repress HIF-1α signaling through the YB-1-mediated inhibition of Foxo3a expression. In concert with HIF-1α, these downstream effectors promote epithelial-mesenchymal transition (EMT) through modulation of Snail and Zeb1. Thus, the ILK-HIF-1α regulatory loop could underlie the maintenance of high HIF-1α expression levels and the promotion of EMT under hypoxic conditions. Finally, we show that the small-molecule ILK inhibitor T315 can disrupt this regulatory loop in vivo and suppress xenograft tumor growth, thereby providing proof-of-concept that targeting ILK represents an effective strategy to block HIF-1α expression and aggressive phenotype in cancer cells.

The Novel Small Molecule Inhibitor, OSU-T315, Suppresses Vestibular Schwannoma and Meningioma Growth by Inhibiting PDK2 Function in the AKT Pathway Activation

Activation of PKB/AKT signaling, which requires PDK1 and PDK2 function, drives Vestibular Schwannoma (VS) and meningioma growth. PDK2 function is defined as a molecule that phosphorylates AKT-Ser473. Integrin-Linked Kinase (ILK) functions as PDK2 in PKB/AKT activation in many cancers; therefore, we hypothesized that OSU-T315, a small molecule ILK inhibitor, will inhibit the ILK-PDK2 function in PKB/AKT signaling activation in VS and meningioma cell growth. OSU-T315 decreased cell viability at IC50 < 2μM in VS (HEI193) and meningioma (Ben-Men-1) cell lines, in primary cells at < 3.5μM, while in normal primary Schwann cells at 7.1μM. OSU-T315 inhibits AKT signaling by decreasing phosphorylation at AKT-Ser473, AKT-Thr308, ILK-Ser246 and ILK-Thr173. In addition, OSU-T315 affected the phosphorylation or expression levels of AKT downstream proliferation effectors as well as autophagy markers. Flow cytometry shows that OSU-T315 increased the percentage of cells arrested at G2/M for both, HEI193 (39.99%) and Ben-Men-1 (26.96%) cells, compared to controls (21.54%, 8.47%). Two hours of OSU-T315 treatment increased cell death in both cell lines (34.3%, 9.1%) versus untreated (12.1%, 8.1%). Though longer exposure increased cell death in Ben-Men-1, TUNEL assays showed that OSU-T315 does not induce apoptosis. OSU-T315 was primarily cytotoxic for HEI193 and Ben-Men-1 inducing a dysregulated autophagy. Our studies suggest that OSU-T315 has translational potential as a chemotherapeutic agent against VS and meningioma.

Targeting PRAS40 for multiple diseases

Proline-rich Akt substrate 40kDa (PRAS40) bridges cell signaling between protein kinase B (Akt) and the mammalian target of rapamycin complex 1 (mTORC1). Both Akt and mTORC1 can phosphorylate PRAS40. As a negative regulator of mTORC1, PRAS40 prevents the binding of mTOR to its substrates. The phosphorylation of PRAS40 results in its dissociation from mTORC1 and enhanced mTOR activation. PRAS40 in conjunction with mTORC1 has been closely associated with programmed cell death and is implicated in diabetes mellitus (DM), cardiovascular diseases, cancer, and neurological diseases. Thus, targeting PRAS40 might hold great promise for innovative therapeutic strategies for these diseases.

Integrin-linked kinase as a novel molecular switch of the IL-6-NF-κB signaling loop in breast cancer

Substantial evidence has clearly demonstrated the role of the IL-6-NF-κB signaling loop in promoting aggressive phenotypes in breast cancer. However, the exact mechanism by which this inflammatory loop is regulated remains to be defined. Here, we report that integrin-linked kinase (ILK) acts as a molecular switch for this feedback loop. Specifically, we show that IL-6 induces ILK expression via E2F1 upregulation, which, in turn, activates NF-κB signaling to facilitate IL-6 production. shRNA-mediated knockdown or pharmacological inhibition of ILK disrupted this IL-6-NF-κB signaling loop, and blocked IL-6-induced cancer stem cells in vitro and estrogen-independent tumor growth in vivo Together, these findings establish ILK as an intermediary effector of the IL-6-NF-κB feedback loop and a promising therapeutic target for breast cancer.

Regulation of oncogenic KRAS signaling via a novel KRAS-integrin-linked kinase-hnRNPA1 regulatory loop in human pancreatic cancer cells

Integrin-linked kinase (ILK) is a mediator of aggressive phenotype in pancreatic cancer. On the basis of our finding that knockdown of either KRAS or ILK has a reciprocal effect on the other's expression, we hypothesized the presence of an ILK-KRAS regulatory loop that enables pancreatic cancer cells to regulate KRAS expression. This study aimed to elucidate the mechanism by which this regulatory circuitry is regulated and to investigate the translational potential of targeting ILK to suppress oncogenic KRAS signaling in pancreatic cancer. Interplay between KRAS and ILK and the roles of E2F1, c-Myc and heterogeneous nuclear ribonucleoprotein as intermediary effectors in this feedback loop was interrogated by genetic manipulations through small interfering RNA/short hairpin RNA knockdown and ectopic expression, western blotting, PCR, promoter-luciferase reporter assays, chromatin immunoprecipitation and pull-down analyses. In vivo efficacy of ILK inhibition was evaluated in two murine xenograft models. Our data show that KRAS regulated the expression of ILK through E2F1-mediated transcriptional activation, which, in turn, controlled KRAS gene expression via hnRNPA1-mediated destabilization of the G-quadruplex on the KRAS promoter. Moreover, ILK inhibition blocked KRAS-driven epithelial-mesenchymal transition and growth factor-stimulated KRAS expression. The knockdown or pharmacological inhibition of ILK suppressed pancreatic tumor growth, in part, by suppressing KRAS signaling. These studies suggest that this KRAS-E2F1-ILK-hnRNPA1 regulatory loop enables pancreatic cancer cells to promote oncogenic KRAS signaling and to interact with the tumor microenvironment to promote aggressive phenotypes. This regulatory loop provides a mechanistic rationale for targeting ILK to suppress oncogenic KRAS signaling, which might foster new therapeutic strategies for pancreatic cancer.

A novel curcumin derivative increases the cytotoxicity of raloxifene in estrogen receptor-negative breast cancer cell lines

There is a need for new, safe and efficacious drug therapies for the treatment of estrogen receptor (ER)-negative breast cancers. Raloxifene and the 2nd generation curcumin derivative 2,6-bis(pyridin-4-ylmethylene)-cyclohexanone (RL91) have been shown to inhibit the growth of ER-negative breast cancer cells in vitro and in vivo. We investigated whether RL91 could enhance the growth-suppressive effects mediated by raloxifene in MDA-MB-231, MDA-MB-468, Hs578t and SkBr3 human breast cancer cell lines. The cytotoxicity was consistent across the cell lines but RL91 was more potent. EC50 values for RL91 were 1.2-2 µM while EC50 values for raloxifene were 9.6-11.2 µM. When the cells were treated with raloxifene (15 µM), RL91 (1 µM) or a combination of the two for 6-72 h, the combination treatment consistently elicited significantly greater cytotoxicity compared to all other treatments. In SkBr3 cells the combination treatment caused significantly more cells to undergo G1 arrest compared to raloxifene. In all cell lines apoptosis was synergistically induced by the combination treatment, as shown by both flow cytometery and cleaved caspase-3. Furthermore, the stress kinase p38 was increased and EFGR isoforms were decreased by both raloxifene and raloxifene + RL91. The anti-angiogenic anti-metastatic potential of raloxifene was not increased by RL91, as MDA-MB-231 cell migration and invasion as well as endothelial tube formation by HUVEC cells was not different between raloxifene (10 µM) and the combination of raloxifene + RL91. Thus, our findings provide evidence that RL91 increases the ability of raloxifene to suppress ER-negative cancer cell growth by increasing the number of apoptotic cells. The broad effect of this drug combination across a range of ER-negative breast cancer cell lines indicates that this drug combination should be explored further in order to find a safe and efficacious therapy for ER-negative breast cancer.

Integrin-linked kinase affects signaling pathways and migration in thyroid cancer cells and is a potential therapeutic target

BACKGROUND

Integrin-linked kinase (ILK) is a serine-threonine kinase that regulates interactions between the cell and the extracellular matrix. In many cancers, overexpression of ILK leads to increased cell proliferation, motility, and invasion. We hypothesized that ILK functions as a regulator of viability and migration in thyroid cancer cells.

METHODS

Eleven human thyroid cancer cell lines were screened for ILK protein expression. The cell lines with the greatest expression were treated with either ILK small interfering RNA (siRNA) or a novel ILK inhibitor, T315, and the effects were evaluated via Western blot and migration assay. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assays were performed to assess cell viability.

RESULTS

siRNA against ILK decreased phosphorylation of downstream effectors Akt and MLC, as well as decreased migration. Treatment with T315 showed a dose-related decrease in both Akt and MLC phosphorylation, as well as decreased migration. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assays showed T315 to have an half maximal inhibitory concentration of less than 1 μM in cell lines with high ILK expression.

CONCLUSION

ILK is expressed differentially in thyroid cancer cell lines. Both ILK siRNA and T315 inhibit motility of thyroid cancer cell lines, and T315 is shown to be cytotoxic at low concentrations. Altogether, our study suggests that ILK may represent an important kinase in aggressive thyroid cancers.

Molecular changes in the medial prefrontal cortex and nucleus accumbens are associated with blocking the behavioral sensitization to cocaine

Previous studies have demonstrated that cocaine-induced behavioral sensitization is associated with persistent functional and structural alterations in the medial prefrontal cortex (mPFC) and nucleus accumbens (NAc); however, the molecular mechanisms underlying these changes have not been elucidated. In this study, the behavioral sensitization to cocaine was established in Sprague Dawley rats and was measured by locomotion and behavioral rating. The brain tissue homogenization was used for measuring the level of brain-derived neurotrophic factor (BDNF), the expression and activity of integrin-linked kinase (ILK), level of protein kinase B (Akt) phosphorylation at serine 473 and threonine 308, and the expression of p75(NTR), TrkA, and TrkB protein. The Results showed that cocaine sensitization was associated with increased BDNF, ILK activity, phospho-Akt Ser(473), p75(NTR), and TrkB protein levels in the mPFC and NAc core. The combination of pergolide and ondansetron normalized not only behavioral sensitization, but also the increases in these molecular markers. Dual immunofluoresence staining showed that ILK expression is co-distributed with p75(NTR) and TrkA expression in both the mPFC and NAc core. Results suggested that the BDNF-TrkA/p75(NTR)-ILK-Akt signaling pathway may be active in cocaine sensitization and associated neural plasticity in the mPFC and NAc core.

Releasing 'brakes' to nerve regeneration: intrinsic molecular targets

Restoring critical neuronal architecture after peripheral nerve injury is challenging. Although immediate regenerative responses to peripheral axon injury involve the synthesis of regeneration-associated proteins in neurons and Schwann cells, an unfavorable balance between growth facilitatory and growth inhibitory signaling impairs the growth continuum of injured peripheral nerves. Molecules involved with the signaling network of tumor suppressors play crucial roles in shifting the balance between growth and restraint during axon regeneration. An understanding of the molecular framework of tumor suppressor molecules in injured neurons and its impact on stage-specific regeneration events may expose therapeutic intervention points. In this review we discuss how signaling networks of the specific tumor suppressors PTEN, Rb1, p53, p27 and p21 are altered in injured peripheral nerves and how this impacts peripheral nerve regeneration. Insights into the roles and importance of these pathways may open new avenues for improving the neurological deficits associated with nerve injury.

SPARC Controls Melanoma Cell Plasticity through Rac1

Cell transition to a more aggressive mesenchymal-like phenotype is a hallmark of cancer progression that involves different steps and requires tightly regulated cell plasticity. SPARC (Secreted Protein Acidic and Rich in Cysteine) is a matricellular protein that promotes this transition in various malignant cell types, including melanoma cells. We found that suppression of SPARC expression in human melanoma cells compromised cell migration, adhesion, cytoskeleton structure, and cell size. These changes involved the Akt/mTOR pathway. Re-expression of SPARC or protein addition restored all the cell features. Suppression of SPARC expression was associated with increased Rac1-GTP levels and its membrane localization. Expression of the dominant negative mutant of Rac1 counteracted almost all the changes observed in SPARC-deficient cells. Overall, these data suggest that most of the SPARC-mediated effects occurred mainly through the blockade of Rac1 activity.

Identification of kinases and regulatory proteins required for cell migration using a transfected cell-microarray system

Background

Cell migration plays a major role in a variety of normal biological processes, and a detailed understanding of the associated mechanisms should lead to advances in the medical sciences in areas such as cancer therapy. Previously, we developed a simple chip, based on transfected-cell microarray (TCM) technology, for the identification of genes related to cell migration. In the present study, we used the TCM chip for high-throughput screening (HTS) of a kinome siRNA library to identify genes involved in the motility of highly invasive NBT-L2b cells.

Results

We performed HTS using TCM coupled with a programmed image tracer to capture time-lapse fluorescence images of siRNA-transfected cells and calculated speeds of cell movement. This first screening allowed us to identify 52 genes. After quantitative PCR (qPCR) and a second screening by a conventional transfection method, we confirmed that 32 of these genes were associated with the migration of NBT-L2b cells. We investigated the subcellular localization of proteins and levels of expression of these 32 genes, and then we used our results and databases of protein-protein interactions (PPIs) to construct a hypothetic but comprehensive signal network for cell migration.

Conclusions

The genes that we identified belonged to several functional categories, and our pathway analysis suggested that some of the encoded proteins functioned as the hubs of networks required for cell migration. Our signal pathways suggest that epidermal growth factor receptor (EGFR) is an upstream regulator in the network, while Src and GRB2 seem to represent nodes for control of respective the downstream proteins that are required to coordinate the many cellular events that are involved in migration. Our microarray appears to be a useful tool for the analysis of protein networks and signal pathways related to cancer metastasis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12863-015-0170-7) contains supplementary material, which is available to authorized users.

Oncogenic signaling in amphiregulin and EGFR-expressing PTEN-null human breast cancer

A subset of triple negative breast cancer (TNBC) is characterized by overexpression of the epidermal growth factor receptor (EGFR) and loss of PTEN, and patients with these determinants have a poor prognosis. We used cell line models of EGFR‐positive/PTEN null TNBC to elucidate the signaling networks that drive the malignant features of these cells and cause resistance to EGFR inhibitors. In these cells, amphiregulin (AREG)‐mediated activation of EGFR results in up‐regulation of fibronectin (FN1), which is known to be a mediator of invasive capacity via interaction with integrin β1. EGFR activity in this PTEN null background also results in Wnt/beta‐catenin signaling and activation of NF‐κB. In addition, AKT is constitutively phosphorylated in these cells and is resistant to gefitinib. Expression profiling demonstrated that AREG‐activated EGFR regulates gene expression differently than EGF‐activated EGFR, and functional analysis via genome‐scale shRNA screening identified a set of genes, including PLK1 and BIRC5, that are essential for survival of SUM‐149 cells, but are uncoupled from EGFR signaling. Thus, our results demonstrate that in cells with constitutive EGFR activation and PTEN loss, critical survival genes are uncoupled from regulation by EGFR, which likely mediates resistance to EGFR inhibitors.

Activation of EGFR by AREG alters signaling and gene expression compared to EGF.

Activation of EGFR by AREG reduces mTORC1 pathway expression and phosphorylation.

EGF‐positive, PTEN‐null TNBC cells are poised for Wnt/beta‐catenin signaling.

Wnt/beta‐catenin activity occurs in a subset of cells and is enhanced in mammospheres.

Regulation of growth/survival genes is uncoupled from EGFR in PTEN‐null TNBC cells.

Targeting EMT in cancer: opportunities for pharmacological intervention

The spread of cancer cells to distant organs represents a major clinical challenge in the treatment of cancer. Epithelial-mesenchymal transition (EMT) has emerged as a key regulator of metastasis in some cancers by conferring an invasive phenotype. As well as facilitating metastasis, EMT is thought to generate cancer stem cells and contribute to therapy resistance. Therefore, the EMT pathway is of great therapeutic interest in the treatment of cancer and could be targeted either to prevent tumor dissemination in patients at high risk of developing metastatic lesions or to eradicate existing metastatic cancer cells in patients with more advanced disease. In this review, we discuss approaches for the design of EMT-based therapies in cancer, summarize evidence for some of the proposed EMT targets, and review the potential advantages and pitfalls of each approach.

Dysregulation of the IGF-I/PI3K/AKT/mTOR signaling pathway in autism spectrum disorders

The IGF-I/PI3K/AKT/mTOR signaling pathway plays an important role in the regulation of cell growth, proliferation, differentiation, motility, survival, metabolism and protein synthesis. Insulin-like growth factor-I (IGF-I) is synthesized in the liver and fibroblasts, and its biological actions are mediated by the IGF-I receptor (IGF-IR). The binding of IGF-I to IGF-IR leads to the activation of phosphatidylinositol 3-kinase (PI3K). Activated PI3K stimulates the production of phosphatidylinositol (4,5)-bisphosphate [PI(4,5)P2] and phosphatidylinositol (3,4,5)-trisphosphate [PI(3,4,5)P3]. The PH domain of AKT (protein kinase B, PKB) (v-AKT murine thymoma viral oncogene homolog) binds to PI(4,5)P2 and PI(3,4,5)P3, followed by phosphorylation of the Thr308 and Ser473 regulatory sites. Tuberous sclerosis complex 1 (TSC1) and TSC2 are upstream regulators of mammalian target of rapamycin (mTOR) and downstream effectors of the PI3K/AKT signaling pathway. The activation of AKT suppresses the TSC1/TSC2 heterodimer, which is an upstream regulator of mTOR. Dysregulated IGF-I/PI3K/AKT/mTOR signaling has been shown to be associated with autism spectrum disorders (ASDs). In this review, we discuss the emerging evidence for a functional relationship between the IGF-I/PI3K/AKT/mTOR pathway and ASDs, as well as a possible role of this signaling pathway in the diagnosis and treatment of ASDs.

SPARC promotes leukemic cell growth and predicts acute myeloid leukemia outcome

Aberrant expression of the secreted protein, acidic, cysteine-rich (osteonectin) (SPARC) gene, which encodes a matricellular protein that participates in normal tissue remodeling, is associated with a variety of diseases including cancer, but the contribution of SPARC to malignant growth remains controversial. We previously reported that SPARC was among the most upregulated genes in cytogenetically normal acute myeloid leukemia (CN-AML) patients with gene-expression profiles predictive of unfavorable outcome, such as mutations in isocitrate dehydrogenase 2 (IDH2-R172) and overexpression of the oncogenes brain and acute leukemia, cytoplasmic (BAALC) and v-ets erythroblastosis virus E26 oncogene homolog (ERG). In contrast, SPARC was downregulated in CN-AML patients harboring mutations in nucleophosmin (NPM1) that are associated with favorable prognosis. Based on these observations, we hypothesized that SPARC expression is clinically relevant in AML. Here, we found that SPARC overexpression is associated with adverse outcome in CN-AML patients and promotes aggressive leukemia growth in murine models of AML. In leukemia cells, SPARC expression was mediated by the SP1/NF-κB transactivation complex. Furthermore, secreted SPARC activated the integrin-linked kinase/AKT (ILK/AKT) pathway, likely via integrin interaction, and subsequent β-catenin signaling, which is involved in leukemia cell self-renewal. Pharmacologic inhibition of the SP1/NF-κB complex resulted in SPARC downregulation and leukemia growth inhibition. Together, our data indicate that evaluation of SPARC expression has prognosticative value and SPARC is a potential therapeutic target for AML.