c-Jun N-terminal kinase is involved in the regulation of proliferation and apoptosis by integrin-linked kinase in human retinoblastoma cells

Insulin attenuates apoptosis in neuronal cells by an integrin-linked kinase-dependent mechanism

Insulin promotes neuronal survival by activating a phosphatidylinositol 3-kinase (PI 3-kinase)/AKT-dependent signaling pathway and reducing caspase activation. We investigated a role for integrin-linked kinase (ILK) in insulin-mediated cell survival in cultured neurons and differentiated R28 cells. We used a serum and depolarization withdrawal model to induce apoptosis in cerebellar granule neurons and a serum withdrawal model to induce apoptosis in differentiated R28 cells. ILK knock-out decreased insulin-mediated protection as did the addition of pharmacological inhibitors of ILK, KP-392 or QLT-0267. Prosurvival effects of insulin were rescued by Boc-Asp (O-methyl)-CH₂F (BAF), a pancaspase inhibitor, in the presence of KP-392. Insulin and IGF-1 decreased caspase-3 activation, an effect that was inhibited by KP-392 and QLT-0267. Western blot analysis indicates that insulin-induced stimulation of AKT Ser-473 phosphorylation was decreased after the ILK gene was conditionally knocked-out, following overexpression of AKT-DN or in the presence of QLT-0267. Insulin and IGF-1 stimulated ILK kinase activity in primary neurons and this was inhibited following ILK-DN overexpression. Western blot analysis indicates that insulin exposure upregulated the expression of the cellular inhibitor of apoptosis protein c-IAP2 in an extracellular matrix-dependent manner, an effect blocked by KP-392. These results indicate that ILK is an important effector in insulin-mediated neuroprotection.

The MAPK Pathway-Based Drug Therapeutic Targets in Pituitary Adenomas

Mitogen-activated protein kinases (MAPKs) include ERK, p38, and JNK MAPK subfamilies, which are crucial regulators of cellular physiology, cell pathology, and many diseases including cancers. For the MAPK signaling system in pituitary adenomas (PAs), the activation of ERK signaling is generally thought to promote cell proliferation and growth; whereas the activations of p38 and JNK signaling are generally thought to promote cell apoptosis. The role of MAPK in treatment of PAs is demonstrated through the effects of currently used medications such as somatostatin analogs such as SOM230 and OCT, dopamine agonists such as cabergoline and bromocriptine, and retinoic acid which inhibit the MAPK pathway. Further, there are potential novel therapies based on putative molecular targets of the MAPK pathway, including 18beta-glycyrrhetinic acid (GA), dopamine-somatostatin chimeric compound (BIM-23A760), ursolic acid (UA), fulvestrant, Raf kinase inhibitory protein (RKIP), epidermal growth factor pathway substrate number 8 (Eps8), transmembrane protein with EGF-like and two follistatin-like domains (TMEFF2), cold inducible RNA-binding protein (CIRP), miR-16, and mammaliansterile-20-like kinase (MST4). The combined use of ERK inhibitor (e.g., SOM230, OCT, or dopamine) plus p38 activator (e.g., cabergoline, bromocriptine, and fulvestrant) and/or JNK activator (e.g., UA), or the development of single drug (e.g., BIM-23A760) to target both ERK and p38 or JNK pathways, might produce better anti-tumor effects on PAs. This article reviews the advances in understanding the role of MAPK signaling in pituitary tumorigenesis, and the MAPK pathway-based potential therapeutic drugs for PAs.

CUL4B promotes metastasis and proliferation in pancreatic cancer cells by inducing epithelial-mesenchymal transition via the Wnt/β-catenin signaling pathway

This study determines whether cullin 4B (CUL4B) promotes pancreatic cancer (PC) metastasis by inducing epithelial-mesenchymal transition (EMT) via the Wnt/β-catenin signaling pathway. A total of 64 PC patients were enrolled in this study. Human PC cell lines were distributed into blank, negative control, shCUL4B, PLOC, PLOC-CUL4B, and PLOC-CUL4B + siRNA-β-catenin groups. The expressions of CUL4B, Wnt/β-catenin signaling pathway-related proteins, and EMT-related proteins were determined using RT-qPCR and Western blotting. The positive expressions of CUL4B and β-catenin protein in tissues were detected by immunohistochemistry. MTT assay and flow cytometry was performed for cell proliferation and cell cycle, scratch test, and transwell assay for cell migration and invasion ability. CUL4B and β-catenin were expressed at a higher level in PC tissues than in paracancerous tissues though paracancerous tissues had higher expressions of CUL4B and β-catenin than normal tissues. The PLOC-CUL4B group showed increased CUL4B, Wnt, β-catenin, LEF-1, c-Jun, Cyclin D1, N-cadherin, Vimentin, Snail, and ZEB1 expression; decreased E-cadherin expression; accelerated cell proliferation; increased S-phase cell percentages; increased cell migration ability; more liver metastases; and enlarged tumor than the PLOC and PLOC-CUL4B + siRNA-β-catenin groups. The shCUL4B group showed decreased CUL4B, Wnt, β-catenin, LEF-1, c-Jun, Cyclin D1, N-cadherin, Vimentin, Snail, and ZEB1 expression; increased E-cadherin expression; decelerated cell proliferation; decreased S-phase cell percentages; reduced cell migration ability; less liver metastases; and decreased tumor weight than the blank and negative control groups. We demonstrate that CUL4B promotes PC metastasis by inducing EMT via the Wnt/β-catenin signaling pathway. Therefore, CUL4B might be the clinical target for treating PC.

Integrin-linked kinase regulates senescence in an Rb-dependent manner in cancer cell lines

Anti-integrin-linked kinase (ILK) therapies result in aberrant mitosis including altered mitotic spindle organization, centrosome declustering and mitotic arrest. In contrast to cells that expressed the retinoblastoma tumor suppressor protein Rb, we have shown that in retinoblastoma cell lines that do not express Rb, anti-ILK therapies induced aberrant mitosis that led to the accumulation of temporarily viable multinucleated cells. The present work was undertaken to: 1) determine the ultimate fate of cells that had survived anti-ILK therapies and 2) determine whether or not Rb expression altered the outcome of these cells. Our data indicate that ILK, a chemotherapy drug target is expressed in both well-differentiated, Rb-negative and relatively undifferentiated, Rb-positive retinoblastoma tissue. We show that small molecule targeting of ILK in Rb-positive and Rb-deficient cancer cells results in increased centrosomal declustering, aberrant mitotic spindle formation and multinucleation. However, anti-ILK therapies in vitro have different outcomes in retinoblastoma and glioblastoma cell lines that depend on Rb expression. TUNEL labeling and propidium iodide FACS analysis indicate that Rb-positive cells exposed to anti-ILK therapies are more susceptible to apoptosis and senescence than their Rb-deficient counterparts wherein aberrant mitosis induced by anti-ILK therapies exhibit mitotic arrest instead. These studies are the first to show a role for ILK in chemotherapy-induced senescence in Rb-positive cancer lines. Taken together these results indicate that the oncosuppressive outcomes for anti-ILK therapies in vitro, depend on the expression of the tumor suppressor Rb, a known G1 checkpoint and senescence regulator.

Using Pharmacokinetic Profiles and Digital Quantification of Stained Tissue Microarrays as a Medium-Throughput, Quantitative Method for Measuring the Kinetics of Early Signaling Changes Following Integrin-Linked Kinase Inhibition in an In Vivo Model of Cancer

A small molecule inhibitor (QLT0267) targeting integrin-linked kinase is able to slow breast tumor growth in vivo; however, the mechanism of action remains unknown. Understanding how targeting molecules involved in intersecting signaling pathways impact disease is challenging. To facilitate this understanding, we used tumor tissue microarrays (TMA) and digital image analysis for quantification of immunohistochemistry (IHC) in order to investigate how QLT0267 affects signaling pathways in an orthotopic model of breast cancer over time. Female NCR nude mice were inoculated with luciferase-positive human breast tumor cells (LCC6^Luc) and tumor growth was assessed by bioluminescent imaging (BLI). The plasma levels of QLT0267 were determined by LC-MS/MS methods following oral dosing of QLT0267 (200 mg/kg). A TMA was constructed using tumor tissue collected at 2, 4, 6, 24, 78 and 168 hr after treatment. IHC methods were used to assess changes in ILK-related signaling. The TMA was digitized, and Aperio ScanScope and ImageScope software were used to provide semi-quantitative assessments of staining levels. Using medium-throughput IHC quantitation, we show that ILK targeting by QLT0267 in vivo influences tumor physiology through transient changes in pathways involving AKT, GSK-3 and TWIST accompanied by the translocation of the pro-apoptotic protein BAD and an increase in Caspase-3 activity.

Regulation of mitotic cytoskeleton dynamics and cytokinesis by integrin-linked kinase in retinoblastoma cells

During cell division integrin-linked kinase (ILK) has been shown to regulate microtubule dynamics and centrosome clustering, processes involved in cell cycle progression, and malignant transformation. In this study, we examine the effects of downregulating ILK on mitotic function in human retinoblastoma cell lines. These retinal cancer cells, caused by the loss of function of two gene alleles (Rb1) that encode the retinoblastoma tumour suppressor, have elevated expression of ILK. Here we show that inhibition of ILK activity results in a concentration-dependent increase in nuclear area and multinucleated cells. Moreover, inhibition of ILK activity and expression increased the accumulation of multinucleated cells over time. In these cells, aberrant cytokinesis and karyokinesis correlate with altered mitotic spindle organization, decreased levels of cortical F-actin and centrosome de-clustering. Centrosome de-clustering, induced by ILK siRNA, was rescued in FLAG-ILK expressing Y79 cells as compared to those expressing FLAG-tag alone. Inhibition of ILK increased the proportion of cells exhibiting mitotic spindles and caused a significant G2/M arrest as early as 24 hours after exposure to QLT-0267. Live cell analysis indicate ILK downregulation causes an increase in multipolar anaphases and failed cytokinesis (bipolar and multipolar) of viable cells. These studies extend those indicating a critical function for ILK in mitotic cytoskeletal organization and describe a novel role for ILK in cytokinesis of Rb deficient cells.

Role of the JNK pathway in human diseases

The c-Jun-NH(2)-terminal kinase (JNK) signaling pathway plays a critical role in regulating cell fate, being implicated in a multitude of diseases ranging from cancer to neurological and immunological/inflammatory conditions. Not surprisingly, therefore, it has been sought after for therapeutic intervention, and its inhibition has been shown to ameliorate many pathological conditions in experimental systems, paving the way for initial clinical trials. However, the fundamental problem in fully harnessing the potential provided by the JNK pathway has been the lack of specificity, due to the multiple JNK forms that are involved in multiple cellular processes in various cell types. Moreover, lack of sufficient knowledge of all JNK-interacting proteins and substrates has also hindered progress. This review will therefore focus on the role of the JNKs in human diseases and appraise the efforts to inhibit JNK signaling to ameliorate disease conditions, assessing potential challenges and providing insights into possible future directions to efficiently target this pathway for therapeutic use.