ILKAP, ILK and PINCH1 control cell survival of p53-wildtype glioblastoma cells after irradiation

New Perspectives on the Role of Integrin-Linked Kinase (ILK) Signaling in Cancer Metastasis

Simple Summary

Today, the vast majority of deaths from cancer are due to cancer metastasis. Metastasis requires that cancer cells escape from the initial tumor, travel through blood vessels, and form new tumors in distant host tissues. Integrin-linked kinase (ILK) is overexpressed by many types of cancer cells and provides both structural and signaling functions that are important for successful metastasis. Here, we discuss recent findings that show how ILK is involved in promoting physical changes important for cell motility and invasion, and how ILK relays signals to other machinery components during metastasis, including interactions with components of the immune system and communication between cancer cells and normal cells, to affect the process of metastasis. We also discuss the contribution of ILK to therapeutic resistance and examine efforts to target ILK for the treatment of metastatic disease.

Abstract

Cancer metastasis is a major barrier to the long-term survival of cancer patients. In cancer cells, integrin engagement downstream of cell-extracellular matrix (ECM) interactions results in the recruitment of cytoskeletal and signaling molecules to form multi-protein complexes to promote processes critical for metastasis. One of the major functional components of these complexes is Integrin Linked Kinase (ILK). Here, we discuss recent advances in our understanding of the importance of ILK as a signaling effector in processes linked to tumor progression and metastasis. New mechanistic insights as to the role of ILK in cellular plasticity, epithelial mesenchymal transition (EMT), migration, and invasion, including the impact of ILK on the formation of invadopodia, filopodia-like protrusions (FLPs), and Neutrophil Extracellular Trap (NET)-induced motility are highlighted. Recent findings detailing the contribution of ILK to therapeutic resistance and the importance of ILK as a potentially therapeutically tractable vulnerability in both solid tumors and hematologic malignancies are discussed. Indeed, pharmacologic inhibition of ILK activity using specific small molecule inhibitors is effective in curtailing the contribution of ILK to these processes, potentially offering a novel therapeutic avenue for inhibiting critical steps in the metastatic cascade leading to reduced drug resistance and increased therapeutic efficacy.

Identification of MAEL as a promoter for the drug resistance model of iPSCs derived from T-ALL

Significant progress has been made in the diagnosis and treatment of the drug‐resistant and highly recurrent refractory T cell acute lymphoblastic leukemia (T‐ALL). Primary tumor cell‐derived induced pluripotent stem cells (iPSCs) have become very useful tumor models for cancer research including drug sensitivity tests. In the present study, we investigated the mechanism underlying drug resistance in T‐ALL using the T‐ALL‐derived iPSCs (T‐iPSCs) model. T‐ALL cells were transformed using iPSC reprogramming factors (Sox‐2, Klf4, Oct4, and Myc) via nonintegrating Sendai virus. T‐iPSCs with the Notch1 mutation were then identified through genomic sequencing. Furthermore, T‐iPSCs resistant to 80 μM LY411575, a γ‐secretase and Notch signal inhibitor, were also established. We found a significant difference in the expression of drug resistance‐related genes between the drug‐resistant T‐iPSCs and drug‐sensitive groups. Among the 27 genes, six most differently expressed genes (DEGs) based on Log₂FC >5 were identified. Knockdown analyses using RNA interference (RNAi) revealed that MAEL is the most important gene associated with drug resistance in T‐ALL cells. Also, MAEL knockdown downregulated expression of MRP and LRP in drug‐resistant T‐iPSCs. Interestingly, this phenomenon partially restored the sensitivity of the cells to LY411575. Furthermore, overexpression of the MAEL gene enhanced drug resistance against LY411575. Conclusively, MAEL promotes LY411575 resistance in T‐ALL cells increasing the expression of MRP and LRP genes.

Reduced expression of enolase-1 correlates with high intracellular glucose levels and increased senescence in cisplatin-resistant ovarian cancer cells

Despite good responses to first-line treatment with platinum-based combination chemotherapy, most ovarian cancer patients will relapse and eventually develop a platinum-resistant disease with a poor overall prognosis. The molecular events leading to the cisplatin resistance of ovarian cancer cells are not fully understood. Here, we performed a proteomic analysis to identify protein candidates deregulated in a cisplatin-resistant ovarian cancer cell line (A2780CP20) in comparison to their sensitive counterpart (A2780). Forty-eight proteins were differentially abundant in A2780CP20, as compared with A2780, cells. Enolase-1 (ENO1) was significantly decreased in cisplatin-resistant ovarian cancer cells. Western blots and RT-PCR confirmed our findings. Ectopic ENO1 expression increased the sensitivity of ovarian cancer cells to cisplatin treatment. In contrast, small-interfering (siRNA)-based ENO1 silencing in A2780 cells reduced the sensitivity of these cells to cisplatin treatment. Whereas glucose consumption was lower, intracellular levels were higher in cisplatin-resistant ovarian cancer cells as compared with their cisplatin-sensitive counterparts. Senescence-associated β-galactosidase (β-Gal) levels were higher in cisplatin-resistant ovarian cancer cells as compared with cisplatin-sensitive ovarian cancer cells. β-Gal levels were decreased in ENO1 overexpressed clones. Protein levels of the cell cycle regulators and senescence markers p21 and p53 showed opposite expression patterns in cisplatin-resistant compared with cisplatin sensitive cells. Our studies suggest that decreased expression of ENO1 promotes glucose accumulation, induces senescence, and leads to cisplatin resistance of ovarian cancer cells.

Matrix stiffness modulates ILK-mediated YAP activation to control the drug resistance of breast cancer cells

One of the hallmarks of cancer progression is strong drug resistance during clinical treatments. The tumor microenvironment is closely associated with multidrug resistance, the optimization of tumor microenvironments may have a strong therapeutic effect. In this study, we configured polyacrylamide hydrogels of varying stiffness [low (10 kPa), intermediate (38 kPa) and high (57 kPa)] to simulate tissue physical matrix stiffness across different stages of breast cancer. After treatment with doxorubicin, cell survival rates on intermediate stiffness substrate are significantly higher. We find that high expression of ILK and YAP reduces the survival rates of breast cancer patients. Drug resistance is closely associated with the inactivation of the hippo pathway protein Merlin/MST/LATS and the activation of YAP. These results not only highlight the understanding of drug resistance mechanisms but also serve as a new basis for developing breast cancer treatment delivery systems.

High PINCH1 Expression in Human Laryngeal Carcinoma Associates with Poor Prognosis

Focal adhesion signaling to actin cytoskeleton is critically implicated in cell migration and cancer invasion and metastasis. Actin-binding proteins cofilin and N-WASP regulate actin filament turnover, and focal adhesion proteins parvins and PINCH mediate integrin signaling to the actin cytoskeleton. Altered expression of these proteins has been implicated in human cancer. This study addresses their expression and prognostic significance in human laryngeal carcinoma. Protein expressions of cofilin, N-WASP, α-parvin, β-parvin, and PINCH1 were examined by immunohistochemistry in 72 human laryngeal squamous cell carcinomas. Correlations with clinicopathological data and survival were evaluated. All proteins examined were overexpressed in human laryngeal carcinomas compared to adjacent nonneoplastic epithelium. High expression of PINCH1 was associated significantly with high grade, lymph node-positive, and advanced stage disease. Moreover, high PINCH1 expression significantly associated with poor overall and disease-free survival and high cytoplasmic PINCH1 expression was shown by multivariate analysis to independently predict poor overall survival. In conclusion, we provide novel evidence that focal adhesion signaling to actin cytoskeleton is implicated in human laryngeal carcinogenesis and PINCH1 has prognostic significance in the disease.

SuperQuant-assisted comparative proteome analysis of glioblastoma subpopulations allows for identification of potential novel therapeutic targets and cell markers

Glioblastoma (GBM) is a highly aggressive brain cancer with poor prognosis and low survival rate. Invasive cancer stem-like cells (CSCs) are responsible for tumor recurrence because they escape current treatments. Our main goal was to study the proteome of three GBM subpopulations to identify key molecules behind GBM cell phenotypes and potential cell markers for migrating cells. We used SuperQuant-an enhanced quantitative proteome approach-to increase proteome coverage. We found 148 proteins differentially regulated in migrating CSCs and 199 proteins differentially regulated in differentiated cells. We used Ingenuity Pathway Analysis (IPA) to predict upstream regulators, downstream effects and canonical pathways associated with regulated proteins. IPA analysis predicted activation of integrin-linked kinase (ILK) signaling, actin cytoskeleton signaling, and lysine demethylase 5B (KDM5B) in CSC migration. Moreover, our data suggested that microRNA-122 (miR-122) is a potential upstream regulator of GBM phenotypes as miR-122 activation was predicted for differentiated cells while its inhibition was predicted for migrating CSCs. Finally, we validated transferrin (TF) and procollagen-lysine 2-oxoglutarate 5-dioxygenase 2 (PLOD2) as potential markers for migrating cells.

MAEL contributes to gastric cancer progression by promoting ILKAP degradation

The cancer-testis gene MAEL is involved in the development and progression of bladder, liver and colorectal cancers. However, its role in other cancers is unclear. By systematically analyzing transcriptomics and genomics data from various cancer databases, we identified that the MAEL gene is aberrantly elevated in gastric cancer (GC) tissues and that its expression is strongly negatively correlated with DNA methylation (Pearson's correlation coefficient = −0.675). Survival analysis revealed that MAEL expression may serve as a prognostic marker for GC patients (overall survival: hazard ratio [HR] = 1.54, p = 1.2E-4; first progression: HR = 1.51, p = 8.7E-4). In vitro and in vivo experiments demonstrated that silencing MAEL expression in the GC cell lines HGC-27 and AGS inhibits proliferation, colony formation, migration, invasion and growth of xenograft tumors, whereas MAEL overexpression exerts the opposite effects in the normal gastric cell line GES-1. Mechanistically, MAEL promotes the lysosome-dependent degradation of the protein phosphatase ILKAP, leading to increased phosphorylation of its substrates (p38, CHK1 and RSK2). Moreover, adenovirus-mediated ILKAP overexpression reversed the oncogenic effects of MAEL in vitro and in vivo. Taken together, these results indicate that MAEL exerts its oncogenic function by promoting ILKAP degradation in the GC.

Tumor suppressive protein phosphatases in human cancer: Emerging targets for therapeutic intervention and tumor stratification

Aberrant protein phosphorylation is one of the hallmarks of cancer cells, and in many cases a prerequisite to sustain tumor development and progression. Like protein kinases, protein phosphatases are key regulators of cell signaling. However, their contribution to aberrant signaling in cancer cells is overall less well appreciated, and therefore, their clinical potential remains largely unexploited. In this review, we provide an overview of tumor suppressive protein phosphatases in human cancer. Along their mechanisms of inactivation in defined cancer contexts, we give an overview of their functional roles in diverse signaling pathways that contribute to their tumor suppressive abilities. Finally, we discuss their emerging roles as predictive or prognostic markers, their potential as synthetic lethality targets, and the current feasibility of their reactivation with pharmacologic compounds as promising new cancer therapies. We conclude that their inclusion in clinical practice has obvious potential to significantly improve therapeutic outcome in various ways, and should now definitely be pushed forward.

Interest of integrins targeting in glioblastoma according to tumor heterogeneity and cancer stem cell paradigm: an update

Glioblastomas are malignant brain tumors with dismal prognosis despite standard treatment with surgery and radio/chemotherapy. These tumors are defined by an important cellular heterogeneity and notably contain a particular subpopulation of Glioblastoma-initiating cells, which recapitulate the heterogeneity of the original Glioblastoma. In order to classify these heterogeneous tumors, genomic profiling has also been undertaken to classify these heterogeneous tumors into several subtypes. Current research focuses on developing therapies, which could take into account this cellular and genomic heterogeneity. Among these targets, integrins are the subject of numerous studies since these extracellular matrix transmembrane receptors notably controls tumor invasion and progression. Moreover, some of these integrins are considered as membrane markers for the Glioblastoma-initiating cells subpopulation. We reviewed here integrin expression according to glioblastoma molecular subtypes and cell heterogeneity. We discussed their roles in glioblastoma invasion, angiogenesis, therapeutic resistance, stemness and microenvironment modulations, and provide an overview of clinical trials investigating integrins in glioblastomas. This review highlights that specific integrins could be identified as selective glioblastoma cells markers and that their targeting represents new diagnostic and/or therapeutic strategies.

The cancer cell adhesion resistome: mechanisms, targeting and translational approaches

Cell adhesion-mediated resistance limits the success of cancer therapies and is a great obstacle to overcome in the clinic. Since the 1990s, where it became clear that adhesion of tumor cells to the extracellular matrix is an important mediator of therapy resistance, a lot of work has been conducted to understand the fundamental underlying mechanisms and two paradigms were deduced: cell adhesion-mediated radioresistance (CAM-RR) and cell adhesion-mediated drug resistance (CAM-DR). Preclinical work has evidently demonstrated that targeting of integrins, adapter proteins and associated kinases comprising the cell adhesion resistome is a promising strategy to sensitize cancer cells to both radiotherapy and chemotherapy. Moreover, the cell adhesion resistome fundamentally contributes to adaptation mechanisms induced by radiochemotherapy as well as molecular drugs to secure a balanced homeostasis of cancer cells for survival and growth. Intriguingly, this phenomenon provides a basis for synthetic lethal targeted therapies simultaneously administered to standard radiochemotherapy. In this review, we summarize current knowledge about the cell adhesion resistome and highlight targeting strategies to override CAM-RR and CAM-DR.

Head and neck cancer cell radiosensitization upon dual targeting of c-Abl and beta1-integrin

Integrin-mediated cell adhesion to extracellular matrix (ECM) critically contributes to cancer cell therapy resistance and DNA double strand break (DSB) repair. c-Abl tyrosine kinase has been linked to both of these processes. Based on our previous findings indicating c-Abl hyperphosphorylation on tyrosine (Y) 412 and threonine (T) 735 upon beta1-integrin inhibition, we hypothesized c-Abl tyrosine kinase as an important mediator of beta1-integrin signaling for radioresistance. In a panel of 8 cell lines from different solid cancer types grown in 3D laminin-rich ECM cultures, we targeted beta1 integrin with AIIB2 (mAb) and c-Abl with Imatinib with and without X-ray irradiation and subsequently examined clonogenic survival, residual DSBs, protein expression and phosphorylation. Single or combined treatment with AIIB2 and Imatinib resulted in cell line-dependent cytotoxicity. Intriguingly, we identified a subgroup of this cell line panel that responded with a higher degree of radiosensitization to AIIB2/Imatinib relative to both single treatments. In this subgroup, we observed a non-statistically significant trend between the radioresponse and phospho-c-Abl Y412. Mechanistically, impairment of DNA repair seems to be associated with radiosensitization upon AIIB2/Imatinib and AIIB2/Imatinib-related radiosensitization could be reduced by exogenous overexpression of either wildtype or constitutively active c-Abl forms relative to controls. Our data generated in more physiological 3D cancer cell culture models suggest c-Abl as further determinant of radioresistance and DNA repair downstream of beta1-integrin. For solid cancers, c-Abl phosphorylation status might be an indicator for reasonable Imatinib application as adjuvant for conventional radio(chemo)therapy.

Interplay between intergrin-linked kinase and ribonuclease inhibitor affects growth and metastasis of bladder cancer through signaling ILK pathways

Background

Integrin-linked kinase (ILK) is a multifunctional adaptor protein which is involved with protein signalling within cells to modulate malignant (cancer) cell movement, cell cycle, metastasis and epithelial–mesenchymal transition (EMT). Our previous experiment demonstrated that ILK siRNA inhibited the growth and induced apoptosis of bladder cancer cells as well as increased the expression of Ribonuclease inhibitor (RI), an important cytoplasmic protein with many functions. We also reported that RI overexpression inhibited ILK and phosphorylation of AKT and GSK3β. ILK and RI gene both locate on chromosome 11p15 and the two genes are always at the adjacent position of same chromosome during evolution, which suggest that ILK and RI could have some relationship. However, underlying interacting mechanisms remain unclear between them. Here, we postulate that RI might regulate ILK signaling pathway via interacting with ILK.

Methods

Co-immunoprecipitation, GST pull-down and co-localization under laser confocal microscope assay were used to determine the interaction between ILK and RI exogenously and endogenously. Furthermore, we further verified that there is a direct binding between the two proteins by fluorescence resonance energy transfer (FRET) in cells. Next, The effects of interplay between ILK and RI on the key target protein expressions of PI3K/AKT/mTOR signaling pathway were determined by western blot, immunohistochemistry and immunofluorescence assay in vivo and in vitro. Finally, the interaction was assessed using nude mice xenograft model.

Results

We first found that ILK could combine with RI both in vivo and in vitro by GST pull-down, co-immunoprecipitation (Co-IP) and FRET. The protein levels of ILK and RI revealed a significant inverse correlation in vivo and in vitro. Subsequently, The results showed that up-regulating ILK could increase cell proliferation, change cell morphology and regulate cell cycle. We also demonstrated that the overexpression of ILK remarkably promoted EMT and expressions of target molecules of ILK signaling pathways in vitro and in vivo. Finally, we found that ILK overexpression significantly enhanced growth, metastasis and angiogenesis of xenograft tumor; Whereas, RI has a contrary role compared to ILK in vivo and in vitro.

Conclusions

Our findings, for the first time, directly proved that the interplay between ILK and RI regulated EMT via ILK/PI3K/AKT signaling pathways for bladder cancer, which highlights the possibilities that ILK/RI could be valuable markers together for the therapy and diagnosis of human carcinoma of urinary bladder.