Regulation of the Epithelial to Mesenchymal Transition in Osteosarcoma.

The epithelial to mesenchymal transition (EMT) is a cellular process that has been linked to the promotion of aggressive cellular features in many cancer types. It is characterized by the loss of the epithelial cell phenotype and a shift to a more mesenchymal phenotype and is accompanied by an associated change in cell markers. EMT is highly complex and regulated via multiple signaling pathways. While the importance of EMT is classically described for carcinomas-cancers of epithelial origin-it has also been clearly demonstrated in non-epithelial cancers, including osteosarcoma (OS), a primary bone cancer predominantly affecting children and young adults. Recent studies examining EMT in OS have highlighted regulatory roles for multiple proteins, non-coding nucleic acids, and components of the tumor micro-environment. This review serves to summarize these experimental findings, identify key families of regulatory molecules, and identify potential therapeutic targets specific to the EMT process in OS.

DNA damage response revisited: the p53 family and its regulators provide endless cancer therapy opportunities.

Antitumor therapeutic strategies that fundamentally rely on the induction of DNA damage to eradicate and inhibit the growth of cancer cells are integral approaches to cancer therapy. Although DNA-damaging therapies advance the battle with cancer, resistance, and recurrence following treatment are common. Thus, searching for vulnerabilities that facilitate the action of DNA-damaging agents by sensitizing cancer cells is an active research area. Therefore, it is crucial to decipher the detailed molecular events involved in DNA damage responses (DDRs) to DNA-damaging agents in cancer. The tumor suppressor p53 is active at the hub of the DDR. Researchers have identified an increasing number of genes regulated by p53 transcriptional functions that have been shown to be critical direct or indirect mediators of cell fate, cell cycle regulation, and DNA repair. Posttranslational modifications (PTMs) primarily orchestrate and direct the activity of p53 in response to DNA damage. Many molecules mediating PTMs on p53 have been identified. The anticancer potential realized by targeting these molecules has been shown through experiments and clinical trials to sensitize cancer cells to DNA-damaging agents. This review briefly acknowledges the complexity of DDR pathways/networks. We specifically focus on p53 regulators, protein kinases, and E3/E4 ubiquitin ligases and their anticancer potential.

Epithelial-mesenchymal transition, regulated by ß-catenin and Twist, leads to esophageal wall remodeling in pediatric eosinophilic esophagitis.

Eosinophilic Esophagitis (EoE) is an antigen-triggered inflammatory condition of the esophageal lining characterized by eosinophilic infiltration. EoE is associated with significant remodeling, and although this remodeling is reversed by current treatment regimens, symptoms of EoE and associated remodeling reappear upon cessation of therapies. We hypothesized that structural remodeling of cell-cell adhesion is a key factor in the pathogenesis of EoE and that epithelial to mesenchymal transition (EMT) was a viable molecular process to lead to this remodeling. Endoscopically obtained biopsy samples from 18 EoE and 18 control pediatric patients were evaluated by transmission electron microscopy to measure intercellular spaces (IS) between cells. Biopsy samples from all groups were analyzed for cellular levels of cell-cell adhesion proteins: E-cadherin, zonula occludens associated protein-1 (ZO-1), and N-cadherin. We also analyzed for cellular levels and localization two of transcription factors, Twist1 and ß-catenin, that are associated with promoting EMT. The IS was significantly increased in the EoE group compared to the control. We observed a significant decrease in E-cadherin and ZO-1 levels and a concomitant increase in N-cadherin levels in EoE samples compared to control. Further, while there was no significant change in cellular levels of ß-catenin, we observed an altered localization of the protein from the cell membrane in control tissue to a nuclear/perinuclear localization in EoE. We observed higher levels of the transcription factor Twist1 in the EoE group compared to normal which was localized mainly at the nucleus. Our results suggest that the integrity of normally sealed esophageal epithelia is compromised in the EoE patients compared to control subjects, and this is due to alterations in the expression of cell adhesion molecules at the esophageal epithelium. Our data also suggest that EMT, potentially regulated by transcription factors ß-catenin and Twist1, may be responsible for the molecular alteration which leads to the remodeling of esophageal epithelia in EoE.

Inhibition of triple negative breast cancer metastasis and invasiveness by novel drugs that target epithelial to mesenchymal transition.

Invasive breast cancer (BrCa) is predicted to affect 1 in 9 women in a lifetime;1 in 32 will die from this disease. The most aggressive forms of BrCa, basal-like/triple-negative phenotype (TNBC), are challenging to treat and result in higher mortality due high number of metastatic cases. There is a paucity of options for TNBC treatment, which highlights the need for additional innovative treatment approaches. NIH-III mice were injected in the abdominal mammary fat pad with luciferase-expressing derivative of the human TNBC cell line, MDA-MB-231 cells. Animals were gavage-fed with nitrofen at the doses of 1, 3 or 6 mg/kg/alternate days. However, several structural properties/components of nitrofen raise concerns, including its high lipophilicity (cLogP of nearly 5) and a potential toxophore in the form of a nitroarene group. Therefore, we developed analogues of nitrofen which lack the nitro group and/or have replaced the diaryl ether linker with a diarylamine that could allow modulation of polarity. In vitro anti-invasiveness activity of nitrofen analogues were evaluated by quantitative determination of invasion of MDA-MB-231-Luciferase cells through Matrigel using a Boyden chamber. Our in vivo data show that nitrofen efficiently blocks TNBC tumor metastasis. In vitro data suggest that this is not due to cytotoxicity, but rather is due to impairment of invasive capacity of the cells. Further, using an in vitro model of EMT, we show that nitrofen interferes with the process of EMT and promotes mesenchymal to epithelial transformation. In addition, we show that three of the nitrofen analogues significantly reduced invasive potential of TNBC cells, which may, at least partially, be attributed to the analogues' ability to promote mesenchymal to epithelial-like transformation of TNBC cells. Our study shows that nitrofen, and more importantly its analogues, are significantly effective in limiting the invasive potential of TNBC cell lines with minimal cytotoxic effect. Further, we demonstrate that nitrofen its analogues, are very effective in reversing mesenchymal phenotype to a more epithelial-like phenotype. This may be significant for the treatment of patients with mesenchymal-TNBC tumor subtype who are well known to exhibit high resistance to chemotherapy.

Sulforaphane (SFA) protects neuronal cells from oxygen & glucose deprivation (OGD).

BACKGROUND: Perinatal brain injury results in neurodevelopmental disabilities (neuroDDs) that include cerebral palsy, autism, attention deficit disorder, epilepsy, learning disabilities and others. Commonly, injury occurs when placental circulation, that is responsible for transporting nutrients and oxygen to the fetus, is compromised. Placental insufficiency (PI) is a reduced supply of blood and oxygen to the fetus and results in a hypoxic-ischemic (HI) environment. A significant HI state in-utero leads to perinatal compromise, characterized by fetal growth restriction and brain injury. Given that over 80% of perinatal brain injuries that result in neuroDDs occur during gestation, prior to birth, preventive approaches are needed to reduce or eliminate the potential for injury and subsequent neuroDDs. Sulforaphane (SFA) derived from cruciferous vegetables such as broccoli sprouts (BrSps) is a phase-II enzyme inducer that acts via cytoplasmic Nrf2 to enhance the production of anti-oxidants in the brain through the glutathione pathway. We have previously shown a profound in vivo neuro-protective effect of BrSps/SFA as a dietary supplement in pregnant rat models of both PI and fetal inflammation. Strong evidence also points to a role for SFA as treatment for various cancers. Paradoxically, then SFA has the ability to enhance cell survival, and with conditions of cancer, enhance cell death. Given our findings of the benefit of SFA/Broccoli Sprouts as a dietary supplement during pregnancy, with improvement to the fetus, it is important to determine the beneficial and toxic dosing range of SFA. We therefore explored, in vitro, the dosing range of SFA for neuronal and glial protection and toxicity in normal and oxygen/glucose deprived (OGD) cell cultures. METHODS: OGD simulates, in vitro, the condition experienced by the fetal brain due to PI. We developed a cell culture model of primary cortical neuronal, astrocyte and combined brain cell co-cultures from newborn rodent brains. The cultures were exposed to an OGD environment for various durations of time to determine the LD50 (duration of OGD required for 50% cell death). Using the LD50 as the time point, we evaluated the efficacy of varying doses of SFA for neuroprotective and neurotoxicity effects. Control cultures were exposed to normal media without OGD, and cytotoxicity of varying doses of SFA was also evaluated. Immunofluorescence (IF) and Western blot analysis of cell specific markers were used for culture characterization, and quantification of LD50. Efficacy and toxicity effect of SFA was assessed by IF/high content microscopy and by AlamarBlue viability assay, respectively. RESULTS: We determined the LD50 to be 2 hours for neurons, 8 hours for astrocytes, and 10 hours for co-cultures. The protective effect of SFA was noticeable at 2.5 µM and 5 µM for neurons, although it was not significant. There was a significant protective effect of SFA at 2.5 µM (p<0.05) for astrocytes and co-cultures. Significant toxicity ranges were also confirmed in OGD cultures as ≥ 100 µM (p<0.05) for astrocytes, ≥ 50 µM (p<0.01) for co-cultures, but not toxic in neurons; and toxic in control cultures as ≥ 100 µM (p<0.01) for neurons, and ≥ 50 µM (p<0.01) for astrocytes and co-cultures. One Way ANOVA and Dunnett's Multiple Comparison Test were used for statistical analysis. CONCLUSIONS: Our results indicate that cell death shows a trend to reduction in neuronal and astrocyte cultures, and is significantly reduced in co-cultures treated with low doses of SFA exposed to OGD. Doses of SFA that were 10 times higher were toxic, not only under conditions of OGD, but in normal control cultures as well. The findings suggest that: 1. SFA shows promise as a preventative agent for fetal ischemic brain injury, and 2. Because the fetus is a rapidly growing organism with profound cell multiplication, dosing parameters must be established to insure safety within efficacious ranges. This study will influence the development of innovative therapies for the prevention of childhood neuroDD.

Graphene Oxide Nanoparticles Induce Apoptosis in wild-type and CRISPR/Cas9-IGF/IGFBP3 knocked-out Osteosarcoma Cells.

Osteosarcoma affects both adolescents and adults, and some improvement in the survival rate for affected patients has been reached in the last decade. Still, non-specificity and systemic toxicity may limit traditional therapeutic approaches to some extent. The insulin growth factor 1 (IGF1) and its binding protein (IGFBP3) have been implicated in the tumorigenesis. Nanoparticles, such as graphene oxide (GO), can provide an effective treatment for cancer as they can specifically target cancer cells while reducing undesired side effects. This study aimed to evaluate the toxicity of GO on osteosarcoma in vitro using tumor cell lines with and without knocking out the IGF and IGFBP3 genes. Human osteosarcoma cell lines, U2OS and SAOS2, and the normal osteoblast cell line hFOB1.19 were used. The IGF1 and IGFBP3 genes were eliminated using CRISPR/Cas9. Tumor cells were cultured and treated with GO. Apoptosis and reactive oxygen species (ROS) were analyzed by Annexin V-FITC and ROS assays. The nuclear factor erythroid 2-related factor 2 (NRF2), which is a crucial regulator of cellular resistance to oxidants, was investigated by Western blotting. We found a significantly higher rate of apoptosis in the OS than hFOB1.19, especially in U2OS cells in which IGF1 and IGFBP3 were knocked out. ROS increase due to GO exposure was remarkably time and concentration-dependent. Based on the rate of apoptosis, ROS, Nrf-2 decrease, and cytomorphological changes, GO has a significant cytotoxic effect against OS. Targeting the IGF1 and IGFBP3 signaling pathway may strengthen GO-related cytotoxicity with the potential to increase the survival of patients affected by this tumor.

Osteosarcoma progression is associated with increased nuclear levels and transcriptional activity of activated ß-Catenin.

Osteosarcoma (OS) is an aggressive primary bone malignancy that has peak incidence in children and young adults <25 years of age. Despite current multimodal treatments, no significant change in patient outcome has been observed in two decades. Presently, there is a lack of established, reliable baseline prognostic markers for aggressive OS, other than extent and site of disease involvement. The canonical Wnt/ß-catenin pathway controls multiple cellular processes, and is known to be a critical pathway in OS progression. This pathway regulates cellular levels of ß-catenin, which is a significant player in the oncogenesis and progression of many cancers. We investigated the relationship between ß-catenin, more specifically, the transcriptionally active form of ß-catenin, Activated ß-Catenin (ABC), and OS progression. Using an in vitro model, we observed that cellular/nuclear ABC levels, but not cellular/nuclear ß-catenin levels, increase with the degree of aggressiveness in OS. Our results demonstrate a strong association between nuclear-ABC levels and aggressive OS in vitro. Furthermore, we observed significant correlation between positive nuclear-ABC and patient age and tumor stage. Our results support the potential use of ABC as a predictive marker for risk stratification in OS.

Osteogenic Sarcoma: A 21st Century Review.

Compared to other bone tumors, bone osteogenic sarcoma (BOS) continues to confer a much grimmer prognosis as the survival benefit of traditional chemotherapy treatment regimens is still unsatisfactory. Chemotherapy was demonstrated to be effective in eradicating both primary tumor and pulmonary metastases in the last century, with effective agents used in various combination regimens having changed the survival rate from less than 10% to 75%. The most common primary bone cancer, BOS is conventionally a primary intramedullary high-grade malignant tumor characterized by malignant cells forming immature bone or osteoid. BOS is a disease with diverse morphological presentations. The treatment of all morphological variants seem to have been the same for over 30 years. The introduction of antiproliferative agents such as insulin growth factor-binding protein 3 hold promise of a potentially veritable therapeutic target. In this review, we highlight recent data on osteosarcoma to consolidate a platform able to connect bench and bedside.

Active ß-catenin is regulated by the PTEN/PI3 kinase pathway: a role for protein phosphatase PP2A.

Dysregulation of Wnt/ß-catenin signaling has been associated with the development and progression of many cancers. The stability and subcellular localization of ß-catenin, a dual functional protein that plays a role in intracellular adhesion and in regulating gene expression, is tightly regulated. However, little is known about the transcriptionally active form of ß-catenin, Active Beta Catenin (ABC), that is unphosphorylated at serine 37 (Ser37) and threonine 41 (Thr41). Elucidating the mechanism by which ß-catenin is activated to generate ABC is vital to the development of therapeutic strategies to block ß-catenin signaling for cancer treatment. Using melanoma, breast and prostate cancer cell lines, we show that while cellular ß-catenin levels are regulated by the Wnt pathway, cellular ABC levels are mainly regulated by the PI3K pathway and are dependent on the phosphatase activity of the protein phosphatase PP2A. Furthermore, we demonstrate that although the PI3K/PTEN pathway does not regulate total ß-catenin protein levels within the cell, it plays a role in regulating the subcellular localization of ß-catenin. Our results support a novel functional interaction/cross-talk between the PTEN/PI3K and Wnt pathways in the regulation of the subcellular/nuclear levels of ABC, which is crucially important for the protein's activity as a transcription factor and its biological effects in health and disease.

Intestinal and gastric permeability in children with eosinophilic esophagitis and reflux esophagitis.

OBJECTIVES: Eosinophilic esophagitis (EoE) is an allergic and immune-mediated entity that leads to a characteristic inflammation of esophageal mucosa. Patients complain of dysphagia and reflux-like symptoms. As many as 80% of patients with EoE may also have a history of atopy, and patients with asthma and eczema have previously been shown to have increased intestinal permeability. This study was designed to assess small intestinal and gastric permeability in patients with EoE and to see whether it differed from healthy individuals and patients with reflux esophagitis (RE). METHODS: Gastric and small intestinal permeability was measured using sugar probe tests containing lactulose, mannitol, and sucrose. Lactulose-to-mannitol (L/M) ratios in the patient's urine were a measure for intestinal permeability, and total sucrose was a measure for gastric permeability. RESULTS: We analyzed samples from 23 patients with EoE, 20 RE, 14 normal upper endoscopy with gastrointestinal symptoms, and 26 healthy controls. All of the 4 groups had L/M ratios less than the upper limit of normal (<0.025). There was no statistically significant difference in gastric permeability between the 4 groups (L/M P = 0.26, sucrose P = 0.46). CONCLUSIONS: Our data suggest that an alteration in gastric and intestinal permeability does not play a role in EoE or RE pathogenesis.

ß-catenin is O-GlcNAc glycosylated at Serine 23: implications for ß-catenin's subcellular localization and transactivator function.

BACKGROUND: We have previously reported that ß-catenin is post-translationally modified with a single O-linked attachment of ß-N-acetyl-glucosamine (O-GlcNAc). We showed that O-GlcNAc regulated ß-catenin's subcellular localization and transcriptional activity. OBJECTIVE: The objectives of this investigation were to identify the putative O-GlcNAc sites of ß-catenin and the relevance of identified sites in the regulation of ß-catenin's localization and transcriptional activity. METHOD: Missense mutations were introduced to potential O-GlcNAc sites of pEGFP-C2-N-Terminal- or pEGFP-C2-Wild Type-ß-catenin by site-directed mutagenesis. We determined the levels of O-GlcNAc-ß-catenin, subcellular localization, interaction with binding partners and transcriptional activity of the various constructs. RESULTS: Serine 23 of ß-catenin was determined as a site for O-GlcNAc modification which regulated its subcellular distribution, its interactions with cellular partners and consequently its transcriptional activity. SIGNIFICANCE: O-GlcNAcylation of Serine 23 is a novel regulatory modification for ß-catenin's subcellular localization and transcriptional activity. This study is the first report to characterize site specific regulation of ß-catenin by the O-GlcNAc modification.

Angiogenic remodeling in pediatric EoE is associated with increased levels of VEGF-A, angiogenin, IL-8, and activation of the TNF-α-NFκB pathway.

OBJECTIVES: Eosinophilic esophagitis (EoE) is a clinicopathologic diagnosis characterized by inflammation and infiltration of eosinophils at the esophageal mucosa. The underlying etiology of EoE remains elusive. Inflammatory diseases, such as asthma, are associated with structural remodeling of the airways, which includes angiogenesis. The aims of this study were to determine the angiogenic profile of esophageal mucosa in children presenting with EoE and to evaluate the putative mechanism(s) underlying the early inflammatory angiogenic response observed in EoE. METHODS: Endoscopically obtained biopsy samples from 18 EoE and 18 control pediatric patients were analyzed for angiogenic markers (CD31, von Willebrand factor, vascular cell adhesion molecule-1) and tissue levels of angiogenic factors (vascular endothelial growth factor [VEGF]-A, VEGF-R2, angiogenin and interleukin [IL]-8). Expression levels of angiogenic factors and markers in EoE and control samples were characterized by immunofluorescence analysis and quantitative reverse transcriptase-polymerase chain reaction. Vascular density of biopsy samples was evaluated by immunofluorescence analysis. RESULTS: Samples from patients with EoE exhibited higher levels of von Willebrand factor, CD31, and vascular cell adhesion molecule-1, which is suggestive of neovascularization and an activated endothelium. Moreover, EoE biopsies showed greater levels of the angiogenesis promoters VEGFA, angiogenin, and IL-8. Interestingly, there were greater cellular levels of tumor necrosis factor-α in EoE samples compared with controls. Furthermore, there were higher nuclear levels of p50 and p65 subunits of NFκB and lower cellular levels of the inhibitor of NFκB, IκB-α, in EoE samples compared with controls. CONCLUSIONS: We demonstrate increased angiogenesis in the esophageal mucosa of pediatric patients with EoE. The data also provided evidence that the angiogenic factors VEGF-A, angiogenin, and IL-8 were prominently involved in promoting angiogenic remodeling.

Expression of E-cadherin and ß-catenin in two cholangiocarcinoma cell lines (OZ and HuCCT1) with different degree of invasiveness of the primary tumor.

BACKGROUND: Cholangiocarcinoma (CC) is the most frequent malignant epithelial tumor of the biliary system. CC has received increasing interest due to its different etiologic factors, invasiveness, and the difficulty of diagnosis at an early stage. The pathogenesis of CC has not been clearly defined, but cohesiveness of tumor cells seems to be a critical factor. Calcium-dependent adherence proteins or cadherins are a family of proteins essential for connecting the plasma membrane of adjacent cells. Linkage of cadherins with the cytoskeleton occurs through another class of proteins, called catenins. E-cadherin forms a mutually exclusive complex or unit with ß-catenin. Loss of E-cadherin -ß-catenin adhesion represents an important step in the progression of many epithelial malignancies. Cell lines arising from CC are not often investigated and may show a differential expression of cell adhesion molecules, particularly E-cadherin - ß-catenin. We hypothesized that a moderately invasive cell line of CC may co-localize both molecules in cytoplasm and cytoplasmic membrane, indicating a greater "tightness" of the tumor cells, while a metastasizing cell line may show isolated cytoplasmic membrane localization, indicating tumor cells probably more keen to reach the blood stream and give metastases. Thus, our aim was to investigate the expression and localization of E-cadherin and ß-catenin in two CC cell lines, including a rapidly metastasizing cell line and a moderately invasive cell line, correlating to a different degree of invasiveness of the primary tumor. MATERIALS AND METHODS: OZ and HuCCT1 cells represent homogeneous, functional human biliary epithelial tumor cell lines that were originally isolated in Japan. Following cell line growth we extracted total proteins. Western blot analysis, immunofluorescence and confocal laser microscopy were used to identify the protein expression and their cyto-localization and co-localization. RESULTS: Both CC cell lines expressed E-cadherin and ß-catenin, but they showed remarkably different localization patterns. In HuCCT1, both E-cadherin and ß-catenin were localized in the cytoplasm, while in OZ these proteins were localized in the cytoplasmic membrane only. This was attributed to a different degree of invasiveness of the primitive CC from which the cell lines were characterized, OZ being a metastasizing cell line, HuCCT1 being a moderately invasive cell line. CONCLUSION: To the best of our knowledge, this is the first time that E-cadherin and ß-catenin have been studied in detail in these two cell lines. These data seem to be very promising in terms of adding insight into the cell biology of CC and initiating investigations that aim to identify cytoskeletal dynamics and ultimately provide guidelines for developing new therapeutic strategies.

O-GlcNAc-glycosylation of beta-catenin regulates its nuclear localization and transcriptional activity.

Beta-catenin plays a role in intracellular adhesion and regulating gene expression. The latter role is associated with its oncogenic properties. Phosphorylation of beta-catenin controls its intracellular expression but mechanism/s that regulates the nuclear localization of beta-catenin is unknown. We demonstrate that O-GlcNAc glycosylation (O-GlcNAcylation) of beta-catenin negatively regulates its levels in the nucleus. We show that normal prostate cells (PNT1A) have significantly higher amounts of O-GlcNAcylated beta-catenin compared to prostate cancer (CaP) cells. The total nuclear levels of beta-catenin are higher in the CaP cells than PNT1A but only a minimal fraction of the nuclear beta-catenin in the CaP cells are O-GlcNAcylated. Increasing the levels of O-GlcNAcylated beta-catenin in the CaP cells with PUGNAc (O- (2-acetamido-2-deoxy-d-gluco-pyranosylidene) amino-N-phenylcarbamate) treatment is associated with a progressive decrease in the levels of beta-catenin in the nucleus. TOPFlash reporter assay and mRNA expressions of beta-catenin's target genes indicate that O-GlcNAcylation of beta-catenin results in a decrease in its transcriptional activity. We define a novel modification of beta-catenin that regulates its nuclear localization and transcriptional function.

Role of IGF-1/IGF-1R in regulation of invasion in DU145 prostate cancer cells.

BACKGROUND: Prostate cancer progression to androgen independence is the primary cause of mortality by this tumor type. The IGF-1/IGF-1R axis is well known to contribute to prostate cancer initiation, but its contribution to invasiveness and the downstream signalling mechanisms that are involved are unclear at present. RESULTS: We examined the invasive response of androgen independent DU145 prostate carcinoma cells to IGF-1 stimulation using Matrigel assays. We then examined the signaling mechanisms and protease activities that are associated with this response. IGF-1 significantly increased the invasive capacity of DU145 cells in vitro, and this increase was inhibited by blocking IGF-1R. We further demonstrated that specific inhibitors of the MAPK and PI3-K pathways decrease IGF-1-mediated invasion. To determine potential molecular mechanisms for this change in invasive capacity, we examined changes in expression and activity of matrix metalloproteinases. We observed that IGF-1 increases the enzymatic activity of MMP-2 and MMP-9 in DU145 cells. These changes in activity are due to differences in expression in the case of MMP-9 but not in the case of MMP-2. This observation is corroborated by the fact that correlated changes of expression in a regulator of MMP-2, TIMP-2, were also seen. CONCLUSION: This work identifies a specific effect of IGF-1 on the invasive capacity of DU145 prostate cancer cells, and furthermore delineates mechanisms that contribute to this effect.

The role of integrin-linked kinase (ILK) in cancer progression.

Integrin-linked kinase (ILK) is an intracellular protein, which interacts with the cytoplasmic domains of integrin beta and beta3 subunits. ILK is a 59 kDa protein containing a phosphoinositide phospholipid-binding domain flanked by an N-terminal ankyrin repeat domain and a C-terminal serine/threonine protein kinase domain. Genetic and biochemical evidence have established an essential role of ILK in connecting integrins to the actin cytoskeleton. Apart from integrins, ILK interacts with several adaptor and signaling proteins resulting in its activation and localization to focal adhesion plaques. The kinase activity of ILK is stimulated upon integrin engagement, as well as by growth factors and chemokines in a PI-3Kinase-dependent manner. ILK can mediate the phosphorylation of a variety of intracellular substrates, most notable of which are: protein kinase B (PKB/Akt), glycogen synthase kinase-3 (GSK-3) and myosin light chain. Gain and loss of function strategies have shown that overexpression, and/or constitutive activation of ILK results in oncogenic transformation and progression to invasive and metastatic phenotypes. In addition ILK expression and activity are upregulated in several types of cancers. In this review, we summarize the adaptor and signaling properties ofILK, and also progress in the identification of therapeutic strategies for inhibition of ILK activity.

Overexpression of vimentin: role in the invasive phenotype in an androgen-independent model of prostate cancer.

The androgen-sensitive LNCaP prostate cancer cell line is less invasive than hormone-insensitive lines. CL1, an aggressive, hormone-insensitive LNCaP subline derived by continuous passaging in hormone-depleted medium, was compared with the parental cell line by cDNA microarray analysis. The gene coding for the intermediate filament protein vimentin was found to be highly up-regulated in the CL1 subline. This difference was confirmed by Northern and Western blots and visualized by immunofluorescence microscopy. To assess the contribution of vimentin to the invasive phenotype, LNCaP cells were stably transfected to overexpress vimentin, and the CL1 cells were transfected with vimentin antisense construct. The invasiveness of the transfected cells was tested using an in vitro invasion assay. We were able to demonstrate that decreasing vimentin expression in the constitutively vimentin-expressing CL1 cells led to a significant decrease in their invasiveness but that forcing expression of vimentin in the LNCaP cells did not augment their invasiveness. These findings imply that vimentin expression contributes to the invasive phenotype but cannot confer it alone.