The small molecule inhibitor QLT0267 Radiosensitizes squamous cell carcinoma cells of the head and neck

In Vitro Models of Head and Neck Cancer: From Primitive to Most Advanced

For several decades now, researchers have been trying to answer the demand of clinical oncologists to create an ideal preclinical model of head and neck squamous cell carcinoma (HNSCC) that is accessible, reproducible, and relevant. Over the past years, the development of cellular technologies has naturally allowed us to move from primitive short-lived primary 2D cell cultures to complex patient-derived 3D models that reproduce the cellular composition, architecture, mutational, or viral load of native tumor tissue. Depending on the tasks and capabilities, a scientific laboratory can choose from several types of models: primary cell cultures, immortalized cell lines, spheroids or heterospheroids, tissue engineering models, bioprinted models, organoids, tumor explants, and histocultures. HNSCC in vitro models make it possible to screen agents with potential antitumor activity, study the contribution of the tumor microenvironment to its progression and metastasis, determine the prognostic significance of individual biomarkers (including using genetic engineering methods), study the effect of viral infection on the pathogenesis of the disease, and adjust treatment tactics for a specific patient or groups of patients. Promising experimental results have created a scientific basis for the registration of several clinical studies using HNSCC in vitro models.

Optimisation of Conditions for the Formation of Spheroids of Head and Neck Squamous Cell Carcinoma Cell Lines for Use as Animal Alternatives

The use of in vitro 3-D cell culture models in cancer research has yielded substantial gains in knowledge on various aspects of tumour biology. Such cell culture models could be useful in the study of head and neck squamous cell carcinoma (HNSCC), where mimicking intratumoral and intertumoral heterogeneity is especially challenging. Our research aims to establish 3-D spheroid models for HNSCC that reproduce in vitro the connections between tumour cells and the surrounding microenvironment. The aims of this study were to determine the optimal conditions for the culture and use of spheroids from HNSCC cell lines and optimal timepoint for using the spheroids obtained, to evaluate the effects of coculture with tumour-specific fibroblasts on spheroid formation, and to investigate spheroid responses to cisplatin treatment. Four HNSCC cell lines (UMSCC-11A, UMSCC-11B, UMSCC-22B and UD-SCC-01) were seeded in flat or round bottom well ultra-low attachment spheroid plates, and spheroid formation was evaluated. The HNSCC cell lines were then cocultured with stromal cells of the tumour microenvironment, producing an accelerated formation of dense spheroids. The viability of cells within the spheroids was assessed during cell culture by using a fluorescent dye. Our results suggest that: three out of the four cell lines tested could form usable spheroids with acceptable viability; the addition of stromal cells did not improve the number of viable cells; and the use of round bottom well plates supported the formation of a single spheroid, whereas flat bottom well plates led to the formation of multiple spheroids of different sizes.

Precision Medicine Gains Momentum: Novel 3D Models and Stem Cell-Based Approaches in Head and Neck Cancer

Despite the current progress in the development of new concepts of precision medicine for head and neck squamous cell carcinoma (HNSCC), in particular targeted therapies and immune checkpoint inhibition (CPI), overall survival rates have not improved during the last decades. This is, on the one hand, caused by the fact that a significant number of patients presents with late stage disease at the time of diagnosis, on the other hand HNSCC frequently develop therapeutic resistance. Distinct intratumoral and intertumoral heterogeneity is one of the strongest features in HNSCC and has hindered both the identification of specific biomarkers and the establishment of targeted therapies for this disease so far. To date, there is a paucity of reliable preclinical models, particularly those that can predict responses to immune CPI, as these models require an intact tumor microenvironment (TME). The "ideal" preclinical cancer model is supposed to take both the TME as well as tumor heterogeneity into account. Although HNSCC patients are frequently studied in clinical trials, there is a lack of reliable prognostic biomarkers allowing a better stratification of individuals who might benefit from new concepts of targeted or immunotherapeutic strategies. Emerging evidence indicates that cancer stem cells (CSCs) are highly tumorigenic. Through the process of stemness, epithelial cells acquire an invasive phenotype contributing to metastasis and recurrence. Specific markers for CSC such as CD133 and CD44 expression and ALDH activity help to identify CSC in HNSCC. For the majority of patients, allocation of treatment regimens is simply based on histological diagnosis and on tumor location and disease staging (clinical risk assessments) rather than on specific or individual tumor biology. Hence there is an urgent need for tools to stratify HNSCC patients and pave the way for personalized therapeutic options. This work reviews the current literature on novel approaches in implementing three-dimensional (3D) HNSCC in vitro and in vivo tumor models in the clinical daily routine. Stem-cell based assays will be particularly discussed. Those models are highly anticipated to serve as a preclinical prediction platform for the evaluation of stable biomarkers and for therapeutic efficacy testing.

In vitro chemotherapeutic and antiangiogenic properties of cardenolides from Acokanthera oblongifolia (Hochst.) Codd

Acovenoside A (Acov-A) and acobioside A (Acob-A) were isolated from Acokanthera oblongifolia. Their anticancer properties were explored regarding, antiproliferative and antiangiogenic activities. The study included screening phase against six cancer cell lines followed by mechanistic investigation against HepG2 cancer cell line. The sulforhodamine-B (SRB) was used to determine their growth inhibitory power. In the other hand, flow cytometry techniques were recorded the cell death type and cell cycle analysis. The clonogenic (colony formation) and wound healing assays, enzyme-linked immunosorbent assay (ELISA) and molecular docking, were performed to evaluate the antiangiogenesis capability. Both compounds were strongly, inhibited four cancer cell lines at GI₅₀ less than 100 nM. The in vitro mechanistic investigation against HepG2 resulted in cell accumulations at G2M phase and induction of apoptosis upon treating cells separately, with 400 nM Acov-A and 200 nM Acob-A. Interestingly, the same concentrations were able to activate caspase-3 by 7.2 and 4.8-fold, respectively. Suppressing the clonogenic capacity of HepG2 cells (20 and 40 nM) and inhibiting the migration of the colon Caco-2 cancer cells were provoke the results of vascular endothelial growth factor receptor2 (VEGFR2) kinase enzyme inactivation. The docked study was highly supportive, to the antiangiogenic approach of both cardenolides. The isolated cardenolides could orchestrate pivotal events in fighting cancer.

Integrin-Linked Kinase Is a Novel Therapeutic Target in Ovarian Cancer

OBJECTIVE

The objective of this study is to identify and validate novel therapeutic target(s) in ovarian cancer.

BACKGROUND

Development of targeted therapeutics in ovarian cancer has been limited by molecular heterogeneity. Although gene expression datasets are available, most of them lack appropriate pair-matched controls to define the alterations that result in the transformation of normal ovarian cells to cancerous cells.

METHODS

We used microarray to compare the gene expression of treatment-naïve ovarian cancer tissue samples to pair-matched normal adjacent ovarian tissue from 24 patients. Ingenuity Pathway Analysis (IPA) was used to identify target pathways for further analysis. Integrin-linked kinase (ILK) expression in SKOV3 and OV90 cells was determined using Western blot. ILK was knocked down using CRISPR/Cas9 constructs. Subcutaneous xenograft study to determine the effect of ILK knockdown on tumor growth was performed in NOD SCID gamma mice.

RESULTS

Significant upregulation of the ILK pathway was identified in 22 of the 24 cancer specimens, identifying it as a potential player that could contribute to the transformation of normal ovarian cells to cancerous cells. Knockdown of ILK in SKOV3 cells resulted in decreased cell proliferation and tumor growth, and inhibition of downstream kinase, AKT (protein kinase B). These results were further validated using an ILK-1 chemical inhibitor, compound 22.

CONCLUSION

Our initial findings validate ILK as a potential therapeutic target for molecular inhibition in ovarian cancer, which warrants further investigation.

53BP1/RIF1 signaling promotes cell survival after multifractionated radiotherapy

Multifractionated irradiation is the mainstay of radiation treatment in cancer therapy. Yet, little is known about the cellular DNA repair processes that take place between radiation fractions, even though understanding the molecular mechanisms promoting cancer cell recovery and survival could improve patient outcome and identify new avenues for targeted intervention. To address this knowledge gap, we systematically characterized how cells respond differentially to multifractionated and single-dose radiotherapy, using a combination of genetics-based and functional approaches. We found that both cancer cells and normal fibroblasts exhibited enhanced survival after multifractionated irradiation compared with an equivalent single dose of irradiation, and this effect was entirely dependent on 53BP1-mediated NHEJ. Furthermore, we identified RIF1 as the critical effector of 53BP1. Inhibiting 53BP1 recruitment to damaged chromatin completely abolished the survival advantage after multifractionated irradiation and could not be reversed by suppressing excessive end resection. Analysis of the TCGA database revealed lower expression of 53BP1 pathway genes in prostate cancer, suggesting that multifractionated radiotherapy might be a favorable option for radio-oncologic treatment in this tumor type. We propose that elucidation of DNA repair mechanisms elicited by different irradiation dosing regimens could improve radiotherapy selection for the individual patient and maximize the efficacy of radiotherapy.

Stroma-Rich Co-Culture Multicellular Tumor Spheroids as a Tool for Photoactive Drugs Screening

Conventional 3D multicellular tumor spheroids of head and neck squamous cell carcinoma (HNSCC) consisting exclusively of cancer cells have some limitations. They are compact cell aggregates that do not interact with their extracellular milieu, thus suffering from both insufficient extracellular matrix (ECM) deposition and absence of different types of stromal cells. In order to better mimic in vivo HNSCC tumor microenvironment, we have constructed a 3D stroma-rich in vitro model of HNSCC, using cancer-associated MeWo skin fibroblasts and FaDu pharynx squamous cell carcinoma. The expression of stromal components in heterospheroids was confirmed by immunochemical staining. The generated co-culture FaDu/MeWo spheroids were applied to study penetration, distribution and antitumor efficacy of photoactive drugs such as Temoporfin and Chlorin e6 used in the photodynamic therapy flow cytometry and fluorescence microscopy techniques. We also investigated the distribution of photodiagnostic agent Indocyanine Green. We demonstrated that the presence of stroma influences the behavior of photoactive drugs in different ways: (i) No effect on Indocyanine Green distribution; (ii) lower accumulation of Chlorin e6; (iii) better penetration and PDT efficiency of Temoporfin. Overall, the developed stroma-rich spheroids enlarge the arsenal of in vitro pre-clinical models for high-throughput screening of anti-cancer drugs.

Long-term Tumor Adaptation after Radiotherapy: Therapeutic Implications for Targeting Integrins in Prostate Cancer

Adaptation of tumor cells to radiotherapy induces changes that are actionable by molecular targeted agents and immunotherapy. This report demonstrates that radiation-induced changes in integrin expression can be targeted 2 months later. Integrins are transmembrane cell adhesion molecules that are essential for cancer cell survival and proliferation. To analyze the short- and long-term effects of radiation on the integrin expression, prostate cancer cells (DU145, PC3, and LNCaP) were cultured in a 3D extracellular matrix and irradiated with either a single dose of radiation (2-10 Gy) or a multifractionated regimen (2-10 fractions of 1 Gy). Whole human genome microarrays, immunoblotting, immunoprecipitation assays, and immunofluorescence staining of integrins were performed. The results were confirmed in a prostate cancer xenograft model system. Interestingly, β1 and β4 integrins (ITGB1 and ITGB4) were upregulated after radiation in vitro and in vivo. This overexpression lasted for more than 2 months and was dose dependent. Moreover, radiation-induced upregulation of β1 and β4 integrin resulted in significantly increased tumor cell death after treatment with inhibitory antibodies. Combined, these findings indicate that long-term tumor adaptation to radiation can result in an increased susceptibility of surviving cancer cells to molecular targeted therapy due to a radiation-induced overexpression of the target. IMPLICATIONS: Radiation induces dose- and schedule-dependent adaptive changes that are targetable for an extended time; thus suggesting radiotherapy as a unique strategy to orchestrate molecular processes, thereby providing new radiation-drug treatment options within precision cancer medicine.

OSU-T315 as an Interesting Lead Molecule for Novel B Cell-Specific Therapeutics

B cells are pathogenic in various disease processes and therefore represent an interesting target for the development of novel immunosuppressants. In the search for new therapeutic molecules, we utilized an in vitro B cell activation assay with ODN2006-stimulated Namalwa cells to screen a chemical library of small molecules for B cell modulating effects. OSU-T315, described as an inhibitor of integrin-linked kinase (ILK), was hereby identified as a hit. On human and murine primary B cells, OSU-T315 potently suppressed the proliferation and the production of antibodies and cytokines upon stimulation, suggesting that ILK could be a promising target in the modulation of B cell activity. Mice with B cell-specific knockout of ILK were generated. Surprisingly, knockout of ILK in murine B cells did not affect B cell function as assessed by several in vivo and ex vivo B cell assays and did not alter the B cell immunosuppressive activity of OSU-T315. In conclusion, OSU-T315 displays potency as B cell modulator, probably through a mechanism of action independent of ILK, and might serve as lead drug molecule for the development of novel B cell-selective drugs.

PPARβ/δ Agonist GW501516 Inhibits Tumorigenicity of Undifferentiated Nasopharyngeal Carcinoma in C666-1 Cells by Promoting Apoptosis

Activation of peroxisome proliferator-activated receptor β/δ (PPARβ/δ) had been linked to inhibition on the proliferation and apoptosis in a few cancer cell lines. However, limited data exists regarding the role of PPARβ/δ in nasopharyngeal carcinoma (NPC). This study was undertaken to determine the effect of PPARβ/δ on cell proliferation, anchorage-dependent clonogenicity, and ectopic xenografts in the human NPC cell lines. Gene and protein expression of PPARβ/δ were reduced specifically in the poor- and un-differentiated NPC cell lines as compared with the control NP-69 cells. Ligand activation of PPARβ/δ by GW501516, a specific PPARβ/δ selective agonist, inhibited cell proliferation and colony formation strikingly, and induced a G2/M phase arrest in the EBV positive undifferentiated NPC C666-1 cells relative to the control cells. Moreover, GW501516 induced C666-1 cell apoptosis in a caspase and BAX dependent manner. In accordance with the in vitro result, GW501516 significantly suppressed the ectopic NPC xenograft tumorigenicity that derived from the C666-1 NPC cells in BALB/c nu/nu mice. This effect is greatly associated with its inhibition on the gene and protein expression of integrin-linked kinase (ILK) through activation of the AMPKα-dependent signaling pathways. Collectively, we showed that PPARβ/δ expression is in reverse correlation with the degree of differentiation in the NPC cell lines, and revealed the anti-tumorigenic effects of GW501516 in NPC cells by activation of AMPKα. This study suggested that PPARβ/δ targeting molecules may be useful for the poor-, and particularly un-differentiated NPC chemoprevention.

The Small Molecule Inhibitor QLT-0267 Decreases the Production of Fibrin-Induced Inflammatory Cytokines and Prevents Post-Surgical Peritoneal Adhesions

Peritoneal adhesions develop after abdominal surgery, trauma or intraperitoneal infections, and have important consequences. The deposition of peritoneal fibrin is a common pathophysiological pathway for the formation of adhesions. Here, we aimed to examine the effects of fibrin-induced cytokine production on peritoneal mesothelial cells (PMCs), and to block the effects of fibrin using an integrin-linked kinase (ILK) inhibitor, QLT-0267. PMCs were cultured from the enzymatic disaggregation of rat omentum. After the PMCs were covered with fibrin, the expression of IL-1β, IL-6, TNFα and VEGF-A increased. This increase in cytokine production was attenuated by QLT-0267, which acted via the inhibition of both the ILK and focal adhesion kinase (FAK) pathways, and subsequently via the GSK-3β pathway. We found that QLT-0267 decreased both the severity of peritoneal adhesion and the serum levels of IL-6 in our post-surgical adhesion mouse model. In conclusion, our study provides novel evidence that fibrin-induced cytokine production may involve in the mechanism of peritoneal adhesion formation. Furthermore, the use of the small molecule inhibitor QLT-0267 is a new strategy in preventing peritoneal adhesion in patients undergoing abdominal surgery.

Exploiting Radiation-Induced Signaling to Increase the Susceptibility of Resistant Cancer Cells to Targeted Drugs: AKT and mTOR Inhibitors as an Example

Implementing targeted drug therapy in radio-oncologic treatment regimens has greatly improved the outcome of cancer patients. However, the efficacy of molecular targeted drugs such as inhibitory antibodies or small molecule inhibitors essentially depends on target expression and activity, which both can change during the course of treatment. Radiotherapy has previously been shown to activate prosurvival pathways, which can help tumor cells to adapt and thereby survive treatment. Therefore, we aimed to identify changes in signaling induced by radiation and evaluate the potential of targeting these changes with small molecules to increase the therapeutic efficacy on cancer cell survival. Analysis of "The Cancer Genome Atlas" database disclosed a significant overexpression of AKT1, AKT2, and MTOR genes in human prostate cancer samples compared with normal prostate gland tissue. Multifractionated radiation of three-dimensional-cultured prostate cancer cell lines with a dose of 2 Gy/day as a clinically relevant schedule resulted in an increased protein phosphorylation and enhanced protein-protein interaction between AKT and mTOR, whereas gene expression of AKT, MTOR, and related kinases was not altered by radiation. Similar results were found in a xenograft model of prostate cancer. Pharmacologic inhibition of mTOR/AKT signaling after activation by multifractionated radiation was more effective than treatment prior to radiotherapy. Taken together, our findings provide a proof-of-concept that targeting signaling molecules after activation by radiotherapy may be a novel and promising treatment strategy for cancers treated with multifractionated radiation regimens such as prostate cancer to increase the sensitivity of tumor cells to molecular targeted drugs. Mol Cancer Ther; 17(2); 355-67. ©2017 AACRSee all articles in this MCT Focus section, "Developmental Therapeutics in Radiation Oncology."

In cancer cell lines inhibition of SCF/c-Kit pathway leads to radiosensitization only when SCF is strongly over-expressed

Background and purpose

The SCF/c-Kit pathway is often overexpressed in human tumors leading to an enhanced tumorigenesis, proliferation and migration. It was now tested for NSCLC and prostate cancer cells growing in 2D and 3D whether the inhibition of this pathway can be used to achieve a significant radiosensitization and whether a respective biomarker may be identified.

Material and methods

Experiments were performed with different cancer cell lines (NSCLC: H23, H520, H226, H1975 and PrCa: DU145) growing either under 2D or 3D conditions. Expression of SCF and c-Kit was determined by RT-PCR and Western blot, SCF was knocked down by siRNA, c-Kit was inhibited by ISCK03 inhibitor and cell survival was determined by colony formation assay.

Results

There is a profound variation in the expression of both c-Kit and SCF with no association between each other. Neither levels did correlate with the respective cellular radiosensitivity determined for 2D or 3D with only a trend seen for SCF. Knock-down of SCF was generally found to result in no or only minor reduction of plating efficiency or cellular radioresistance. A significant reduction was only obtained for H520 cells characterized by an extreme over-expression of SCF. The inhibition of c-Kit by a specific inhibitor was also found to result only in minor radiosensitization.

Conclusion

Generally, the SCF/c-Kit pathway does not have a dominant effect on both, cell survival and radioresponse and, as a consequence, knockdown of this pathway does not result in a strong effect on radioresistance, except when SCF is strongly over-expressed.

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

The prognosis is generally poor for patients suffering from glioblastoma multiforme (GBM) due to radiation and drug resistance. Prosurvival signaling originating from focal adhesion hubs essentially contributes to therapy resistance and tumor aggressiveness. As the underlying molecular mechanisms remain largely elusive, we addressed whether targeting of the focal adhesion proteins particularly interesting new cysteine-histidine-rich 1 (PINCH1), integrin-linked kinase (ILK) and ILK associated phosphatase (ILKAP) modulates GBM cell radioresistance. Intriguingly, PINCH1, ILK and ILKAP depletion sensitized p53-wildtype, but not p53-mutant, GBM cells to radiotherapy. Concomitantly, these cells showed inactivated Glycogen synthase kinase-3β (GSK3β) and reduced proliferation. For PINCH1 and ILKAP knockdown, elevated levels of radiation-induced γH2AX/53BP1-positive foci, as a marker for DNA double strand breaks, were observed. Mechanistically, we identified radiation-induced phosphorylation of DNA protein kinase (DNAPK), an important DNA repair protein, to be dependent on ILKAP. This interaction was fundamental to radiation survival of p53-wildtype GBM cells. Conclusively, our data suggest an essential role of PINCH1, ILK and ILKAP for the radioresistance of p53-wildtype GBM cells and provide evidence for DNAPK functioning as a central mediator of ILKAP signaling. Strategies for targeting focal adhesion proteins in combination with radiotherapy might be a promising approach for patients with GBM.

ILK-PI3K/AKT pathway participates in cutaneous wound contraction by regulating fibroblast migration and differentiation to myofibroblast

The interactions between fibroblasts and the extracellular matrix in wound contraction are mainly mediated via integrin signaling. Integrin-linked kinase (ILK) is a key mediator in integrin signal transduction. We investigated the role of ILK in cutaneous wound contraction. We found that ILK was involved in cutaneous wound healing in rats, and ILK and PI3K/AKT inhibitors inhibited wound contraction and re-epithelialization, consequently delaying wound healing in vivo. Further, using in vitro studies, we demonstrated that ILK and PI3K/AKT inhibitors suppressed the contraction of fibroblast-populated collagen lattices, inhibited fibroblast migration, and interrupted the effect of TGF-β1 on promoting alpha smooth muscle actin (α-SMA) expression in fibroblasts. When ILK expression was directly blocked by ILK small interfering RNA transfection, the migration and α-SMA expression of normal dermal fibroblasts were significantly suppressed as well. The data suggest that the ILK-PI3K/AKT signaling pathway mediates cutaneous wound contraction by regulating fibroblast migration and differentiation to myofibroblasts.

Cancer cell motility is affected through 3D cell culturing and SCF/c-Kit pathway but not by X-irradiation

BACKGROUND AND PURPOSE

Success of radiotherapy is often limited by therapy resistance and metastasis resulting from cancer cell motility. It was tested in vitro whether this cancer cell motility is affected by growth condition, active SCF/c-Kit pathway or X-irradiation.

MATERIALS AND METHODS

Cell motility was measured with BioCoat™ Matrigel™ invasion chamber using four different cancer cell lines (NSCLC: H23, H520, H226 and PrCa: DU145). Cells were grown in 2D or 3D, SCF was knocked down by siRNA and cells were irradiated with 2 or 6Gy.

RESULTS

All cell lines except H520 showed a 2-3-fold increase in cell motility when grown in 3D. This effect was considered to result from the EMT-like change seen when cells were grown in 3D as indicated by the enhanced expression of vimentin and N-cadherin and reduction of E-cadherin. Just the opposite trends were found for H520 cells. Knockdown of SCF was found to result in reduced cell motility for both 2D and 3D. In contrast, X-irradiation did not modulate cell motility neither under 2D nor 3D. In line with this, X-irradiation did neither induce the expression of EMT-associated genes nor SCF.

CONCLUSION

X-irradiation affects neither the expression of important EMT genes such as vimentin, E-cadherin and N-cadherin nor SCF/c-Kit signaling and, as a consequence, does not alter cell motility.

Comprehensive analysis of signal transduction in three-dimensional ECM-based tumor cell cultures

Analysis of signal transduction and protein phosphorylation is fundamental to understanding physiological and pathological cell behavior and identifying novel therapeutic targets. Despite the fact that the use of physiological three-dimensional cell culture assays is increasing, 3D proteomics and phosphoproteomics remain challenging due to difficulties with easy, robust and reproducible sample preparation. Here, we present an easy-to-perform, reliable and time-efficient method for the production of 3D cell lysates that does not compromise cell adhesion before cell lysis. The samples can be used for western blotting as well as phosphoproteome array technology. This technique will be of interest for researchers working in all fields of biology and drug development.

3D matrix-based cell cultures: Automated analysis of tumor cell survival and proliferation

Three-dimensional ex vivo cell cultures mimic physiological in vivo growth conditions thereby significantly contributing to our understanding of tumor cell growth and survival, therapy resistance and identification of novel potent cancer targets. In the present study, we describe advanced three-dimensional cell culture methodology for investigating cellular survival and proliferation in human carcinoma cells after cancer therapy including molecular therapeutics. Single cells are embedded into laminin-rich extracellular matrix and can be treated with cytotoxic drugs, ionizing or UV radiation or any other substance of interest when consolidated and approximating in vivo morphology. Subsequently, cells are allowed to grow for automated determination of clonogenic survival (colony number) or proliferation (colony size). The entire protocol of 3D cell plating takes ~1 h working time and pursues for ~7 days before evaluation. This newly developed method broadens the spectrum of exploration of malignant tumors and other diseases and enables the obtainment of more reliable data on cancer treatment efficacy.

Evaluation of spheroid head and neck squamous cell carcinoma cell models in comparison to monolayer cultures

Two-dimensional (2D) monolayer cell culture models are the most common method used to investigate tumor cells in vitro. In the few last decades, a multicellular spheroid model has gained attention due to its adjacency to tumors in vivo. The aim of the present study was to investigate immunohistochemical differences between these two cell culture systems. The FaDu, CAL27 and SCC25 head and neck squamous cell carcinoma (HNSCC) cell lines were seeded out in monolayer and multicellular spheroids. The FaDu and SCC25 cells were treated with increasing doses of cisplatin and irradiation. CAL27 cells were not used in theproliferation experiments, since the spheroids of CAL27 cells were not able to process the reagent in CCK-8 assays. Furthermore, they were stained to present alterations of the following antigens: Ki-67, vascular endothelial growth factor receptor, epithelial growth factor and survivin. Differences in growth rates and expression patterns were detected in certain HNSCC cell lines. The proliferation rates showed a significant divergence of cells grown in the three-dimensional model compared with cells grown in the 2D model. Overall, multicellular spheroids are a promising method to reproduce the immunohistochemical aspects and characteristics of tumor cells, and may show different response rates to therapeutic options.

Patient-Derived Xenografts as a Model System for Radiation Research

The cancer literature is filled with promising preclinical studies demonstrating impressive efficacy for new therapeutics, yet translation of these approaches into clinical successes has been rare, indicating that current methods used to predict efficacy are suboptimal. The most likely reason for the limitation of these studies is the disconnect between preclinical models and cancers treated in the clinic. Specifically, most preclinical models are poor representations of human disease. Immortalized cancer cell lines that dominate the cancer literature may be, in a sense, "paper tigers" that have been selected by decades of culture to be artificially driven by highly targetable proteins. Thus, although effective in treating these cell lines either in vitro or as artificial tumors transplanted from culture into experimental animals as xenografts, the identified therapies would likely underperform in a clinical setting. This inherent limitation applies not only to drug testing but also to experiments with radiation therapy. Indeed, traditional radiobiology methods rely on monolayer culture systems, with emphasis on colony formation and DNA damage assessment that may have limited clinical translation. As such, there has been keen interest in developing tumor explant systems in which patient tumors are directly transplanted into and solely maintained in vivo, using immunocompromised mice. These so-called patient-derived xenografts (PDXs) represent a robust model system that has been garnering support in academia and industry as a superior preclinical approach to drug testing. Likewise, PDX models have the potential to improve radiation research. In this review, we describe how PDX models are currently being used for both drug and radiation testing and how they can be incorporated into a translational research program.

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.

Focal adhesion signaling and therapy resistance in cancer

Interlocking gene mutations, epigenetic alterations and microenvironmental features perpetuate tumor development, growth, infiltration and spread. Consequently, intrinsic and acquired therapy resistance arises and presents one of the major goals to solve in oncologic research today. Among the myriad of microenvironmental factors impacting on cancer cell resistance, cell adhesion to the extracellular matrix (ECM) has recently been identified as key determinant. Despite the differentiation between cell adhesion-mediated drug resistance (CAMDR) and cell adhesion-mediated radioresistance (CAMRR), the underlying mechanisms share great overlap in integrin and focal adhesion hub signaling and differ further downstream in the complexity of signaling networks between tumor entities. Intriguingly, cell adhesion to ECM is per se also essential for cancer cells similar to their normal counterparts. However, based on the overexpression of focal adhesion hub signaling receptors and proteins and a distinct addiction to particular integrin receptors, targeting of focal adhesion proteins has been shown to potently sensitize cancer cells to different treatment regimes including radiotherapy, chemotherapy and novel molecular therapeutics. In this review, we will give insight into the role of integrins in carcinogenesis, tumor progression and metastasis. Additionally, literature and data about the function of focal adhesion molecules including integrins, integrin-associated proteins and growth factor receptors in tumor cell resistance to radio- and chemotherapy will be elucidated and discussed.

Integrin-linked kinase regulates the rate of platelet activation and is essential for the formation of stable thrombi

BACKGROUND

Integrin-linked kinase (ILK) and its associated complex of proteins are involved in many cellular activation processes, including cell adhesion and integrin signaling. We have previously demonstrated that mice with induced platelet ILK deficiency show reduced platelet activation and aggregation, but only a minor bleeding defect. Here, we explore this apparent disparity between the cellular and hemostatic phenotypes.

METHODS

The impact of ILK inhibition on integrin αII b β3 activation and degranulation was assessed with the ILK-specific inhibitor QLT0267, and a conditional ILK-deficient mouse model was used to assess the impact of ILK deficiency on in vivo platelet aggregation and thrombus formation.

RESULTS

Inhibition of ILK reduced the rate of both fibrinogen binding and α-granule secretion, but was accompanied by only a moderate reduction in the maximum extent of platelet activation or aggregation in vitro. The reduction in the rate of fibrinogen binding occurred prior to degranulation or translocation of αII b β3 to the platelet surface. The change in the rate of platelet activation in the absence of functional ILK led to a reduction in platelet aggregation in vivo, but did not change the size of thrombi formed following laser injury of the cremaster arteriole wall in ILK-deficient mice. It did, however, result in a marked decrease in the stability of thrombi formed in ILK-deficient mice.

CONCLUSION

Taken together, the findings of this study indicate that, although ILK is not essential for platelet activation, it plays a critical role in facilitating rapid platelet activation, which is essential for stable thrombus formation.

Inactivation of the Hippo tumour suppressor pathway by integrin-linked kinase

One of the hallmarks of cancers is the silencing of tumour suppressor genes and pathways. The Hippo tumour suppressor pathway is inactivated in many types of cancers, leading to tumour progression and metastasis. However, the mechanisms of pathway inactivation in tumours remain unclear. Here we demonstrate that integrin-linked kinase (ILK) plays a critical role in the suppression of the Hippo pathway via phospho-inhibition of MYPT1-PP1, leading to inactivation of Merlin. Inhibition of ILK in breast, prostate and colon tumour cells results in the activation of the Hippo pathway components MST1 and LATS1 with concomitant inactivation of YAP/TAZ (Yes-associated protein/transcriptional co-activator with PDZ-binding motif) transcriptional co-activators and TEAD-mediated transcription. Genetic deletion of ILK suppresses ErbB2-driven YAP/TAZ activation in mammary tumours, and its pharmacological inhibition suppresses YAP activation and tumour growth in vivo. Our data demonstrate a role for ILK as a multiple receptor proximal regulator of Hippo tumour suppressor pathway and as a cancer therapeutic target.

The Hippo tumour suppressor pathway is inactivated in many cancer types, but how this occurs is unclear. Here, the authors show that integrin-linked kinase (ILK) has a role in inhibiting the Hippo pathway and pharmacological inhibition of ILK reduces the size of tumours in mice.

High expression of integrin-linked kinase predicts aggressiveness and poor prognosis in patients with gastric cancer

Integrin-linked kinase (ILK), an intracellular serine/threonine protein kinase, has been reported to be highly expressed in many human malignancies, including gastric cancer. However, the prognostic significance of ILK expression in gastric cancer remains to be elucidated. In the present study, ILK expression in 95 gastric tumor tissues and 30 adjacent non-cancerous gastric mucosa was evaluated by immunohistochemistry and correlated with clinicopathological characteristics and patients' outcome. The results showed that high ILK expression was observed in 47.4% (45/95) of gastric cancer tissues, but only in 20.0% (6/30) of adjacent gastric mucosa. Clinicopathological analysis indicated that high ILK expression was significantly associated with poor tumor differentiation (P=0.024), advanced TNM stage (P=0.006), tumor invasion (P=0.001), and lymph node metastasis (P=0.014). Kaplan-Meier survival curves demonstrated that patients with high ILK expression had substantially shorter overall survival that those with low ILK expression (P=0.043, log-rank test). Furthermore, Cox multivariate regression analysis identified ILK expression as an independent prognostic factor for overall survival of gastric cancer patients (hazard ratio, 1.95; 95% confidence interval, 1.02-3.13; P=0.026). In conclusion, our data suggest that ILK may contribute to the malignant progression of gastric cancer and serve as a novel prognostic indicator for gastric cancer patients.

APPL proteins modulate DNA repair and radiation survival of pancreatic carcinoma cells by regulating ATM

Despite intensive multimodal therapies, the overall survival rate of patients with ductal adenocarcinoma of the pancreas is still poor. The chemo- and radioresistance mechanisms of this tumor entity remain to be determined in order to develop novel treatment strategies. In cancer, endocytosis and membrane trafficking proteins are known to be utilized and they also critically regulate essential cell functions like survival and proliferation. On the basis of these data, we evaluated the role of the endosomal proteins adaptor proteins containing pleckstrin homology domain, phosphotyrosine binding domain and a leucine zipper motif (APPL)1 and 2 for the radioresistance of pancreatic carcinoma cells. Here, we show that APPL2 expression in pancreatic cancer cells is upregulated after irradiation and that depletion of APPL proteins by small interfering RNA (siRNA) significantly reduced radiation survival in parallel to impairing DNA double strand break (DSB) repair. In addition, APPL knockdown diminished radiogenic hyperphosphorylation of ataxia telangiectasia mutated (ATM). Activated ATM and APPL1 were also shown to interact after irradiation, suggesting that APPL has a more direct role in the phosphorylation of ATM. Double targeting of APPL proteins and ATM caused similar radiosensitization and concomitant DSB repair perturbation to that observed after depletion of single proteins, indicating that ATM is the central modulator of APPL-mediated effects on radiosensitivity and DNA repair. These data strongly suggest that endosomal APPL proteins contribute to the DNA damage response. Whether targeting of APPL proteins is beneficial for the survival of patients with pancreatic adenocarcinoma remains to be elucidated.

β1 integrin signaling maintains human epithelial progenitor cell survival in situ and controls proliferation, apoptosis and migration of their progeny

β1 integrin regulates multiple epithelial cell functions by connecting cells with the extracellular matrix (ECM). While β1 integrin-mediated signaling in murine epithelial stem cells is well-studied, its role in human adult epithelial progenitor cells (ePCs) in situ remains to be defined. Using microdissected, organ-cultured human scalp hair follicles (HFs) as a clinically relevant model for studying human ePCs within their natural topobiological habitat, β1 integrin-mediated signaling in ePC biology was explored by β1 integrin siRNA silencing, specific β1 integrin-binding antibodies and pharmacological inhibition of integrin-linked kinase (ILK), a key component of the integrin-induced signaling cascade. β1 integrin knock down reduced keratin 15 (K15) expression as well as the proliferation of outer root sheath keratinocytes (ORSKs). Embedding of HF epithelium into an ECM rich in β1 integrin ligands that mimic the HF mesenchyme significantly enhanced proliferation and migration of ORSKs, while K15 and CD200 gene and protein expression were inhibited. Employing ECM-embedded β1 integrin-activating or -inhibiting antibodies allowed to identify functionally distinct human ePC subpopulations in different compartments of the HF epithelium. The β1 integrin-inhibitory antibody reduced β1 integrin expression in situ and selectively enhanced proliferation of bulge ePCs, while the β1 integrin-stimulating antibody decreased hair matrix keratinocyte apoptosis and enhanced transferrin receptor (CD71) immunoreactivity, a marker of transit amplifying cells, but did not affect bulge ePC proliferation. That the putative ILK inhibitor QLT0267 significantly reduced ORSK migration and proliferation and induced massive ORSK apoptosis suggests a key role for ILK in mediating the ß1 integrin effects. Taken together, these findings demonstrate that ePCs in human HFs require β1 integrin-mediated signaling for survival, adhesion, and migration, and that different human HF ePC subpopulations differ in their response to β1 integrin signaling. These insights may be exploited for cell-based regenerative medicine strategies that employ human HF-derived ePCs.

Repression of integrin-linked kinase by antidiabetes drugs through cross-talk of PPARγ- and AMPKα-dependent signaling: role of AP-2α and Sp1

Nasopharyngeal carcinoma (NPC) is one of the most common cancers of the head and neck, particularly in Southern China and Southeast Asia with high treatment failure due to the development of local recurrence and distant metastasis. The molecular mechanisms related to the progression of NPC have not been fully understood. In this study, we showed that antidiabetes drugs rosiglitazone and metformin inhibit NPC cell growth through reducing the expression of integrin-linked kinase (ILK). Blockade of PPARγ and AMPKα overcame the effects of rosiglitazone and metformin on ILK protein. Importantly, overexpression of ILK abrogated the effect of rosiglitazone and metformin on NPC cell growth. Furthermore, these agents reduced ILK promoter activity, which was not observed in AP-2α, but not Sp1 site mutation in ILK gene promoter. In addition, silencing of AP-2α or overexpression of Sp1 reversed the effect of these agents on ILK protein expression and cell growth. Chromatin immunoprecipitation (ChIP) assay showed that rosiglitazone induced AP-2α, while metformin reduced Sp1 protein binding to the DNA sequences in the ILK gene promoter. Intriguingly, overexpression of Sp1 abolished the effect of rosiglitazone on AP-2α protein expression. Collectively, we show that rosiglitazone and metformin inhibit ILK gene expression through PPARγ- and AMPKα-dependent signaling pathways that are involved in the regulation of AP-2α and Sp1 protein expressions. The effect of combination of rosiglitazone and metformin demonstrates greater extent than single agent alone. The cross-talk of PPARγ and AMPKα signaling enhances the synergistic effects of rosiglitazone and metformin. This study unveils novel mechanisms by which oral antidiabetes drugs inhibit the growth of human NPC cells.

Cetuximab attenuates its cytotoxic and radiosensitizing potential by inducing fibronectin biosynthesis

Inherent and acquired resistance to targeted therapeutics continues to emerge as a major clinical obstacle. For example, resistance to EGF receptor targeting occurs commonly, more so than was expected, on the basis of preclinical work. Given emerging evidence that cancer cell-substrate interactions are important determinants of therapeutic sensitivity, we examined the impact of cell-fibronectin interactions on the efficacy of the EGF receptor antibody cetuximab, which is used widely for lung cancer treatment. Our results revealed the potential for cell-fibronectin interactions to induce radioresistance of human non-small cell lung cancer cells. Cell adhesion to fibronectin enhanced tumor cell radioresistance and attenuated the cytotoxic and radiosensitizing effects of cetuximab. Both in vitro and in vivo, we found that cetuximab treatment led to a remarkable induction of fibronectin biosynthesis. Mechanistic analyses revealed the induction was mediated by a p38-MAPK-ATF2 signaling pathway and that RNAi-mediated inhibition of fibronectin could elevate the cytotoxic and radiosensitizing potential of cetuximab. Taken together, our findings show how cell adhesion blunts cetuximab, which, by inducing fibronectin, generates a self-attenuating mechanism of drug resistance.

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

Although the rictor-mTOR complex (mTORC2) has been shown to act as phosphoinositide-dependent kinase (PDK)2 in many cell types, other kinases have also been implicated in mediating Ser473-Akt phosphorylation. Here, we demonstrated the cell line specificity of integrin-linked kinase (ILK) versus mTORC2 as PDK2 in LNCaP and PC-3 prostate and MDA-MB-468 breast cancer cells, of which the PTEN-negative status allowed the study of Ser473-Akt phosphorylation independent of external stimulation. PC-3 and MDA-MB-468 cells showed upregulated ILK expression relative to LNCaP cells, which expressed a high abundance of mTOR. Exposure to Ku-0063794, a second-generation mTOR inhibitor, decreased Ser473-Akt phosphorylation in LNCaP cells, but not in PC-3 or MDA-MB-468 cells. In contrast, treatment with T315, a novel ILK inhibitor, reduced the phosphorylation of Ser473-Akt in PC-3 and MDA-MB-468 cells without affecting that in LNCaP cells. This cell line specificity was verified by comparing Ser473-Akt phosphorylation status after genetic knockdown of rictor, ILK, and other putative Ser-473-Akt kinases. Genetic knockdown of rictor, but not ILK or the other kinases examined, inhibited Ser473-Akt phosphorylation in LNCaP cells. Conversely, PC-3 and MDA-MB-468 cells were susceptible to the effect of ILK silencing on Ser473-Akt phosphorylation, while knockdown of rictor or any of the other target kinases had no appreciable effect. Co-immunoprecipitation analysis demonstrated the physical interaction between ILK and Akt in PC-3 cells, and T315 blocked ILK-mediated Ser473 phosphorylation of bacterially expressed Akt. ILK also formed complexes with rictor in PC-3 and MDA-MB-468 cells that were disrupted by T315, but such complexes were not observed in LNCaP cells. In the PTEN-functional MDA-MB-231 cell line, both T315 and Ku-0063794 suppressed EGF-induced Ser473-Akt phosphorylation. Inhibition of ILK by T315 or siRNA-mediated knockdown suppressed epithelial-mesenchymal transition in MDA-MB-468 and PC-3 cells. Thus, we hypothesize that ILK might bestow growth advantage and metastatic potential in the course of tumor progression.

Radiation-induced mitotic cell death and glioblastoma radioresistance: a new regulating pathway controlled by integrin-linked kinase, hypoxia-inducible factor 1 alpha and survivin in U87 cells

We have previously shown that integrin-linked kinase (ILK) regulates U87 glioblastoma cell radioresistance by modulating the main radiation-induced cell death mechanism in solid tumours, the mitotic cell death. To decipher the biological pathways involved in these mechanisms, we constructed a U87 glioblastoma cell model expressing an inducible shRNA directed against ILK (U87shILK). We then demonstrated that silencing ILK enhanced radiation-induced centrosome overduplication, leading to radiation-induced mitotic cell death. In this model, ionising radiations induce hypoxia-inducible factor 1 alpha (HIF-1α) stabilisation which is inhibited by silencing ILK. Moreover, silencing HIF-1α in U87 cells reduced the surviving fraction after 2 Gy irradiation by increasing cell sensitivity to radiation-induced mitotic cell death and centrosome amplification. Because it is known that HIF-1α controls survivin expression, we then looked at the ILK silencing effect on survivin expression. We show that survivin expression is decreased in U87shILK cells. Furthermore, treating U87 cells with the specific survivin suppressor YM155 significantly increased the percentage of giant multinucleated cells, centrosomal overduplication and thus U87 cell radiosensitivity. In consequence, we decipher here a new pathway of glioma radioresistance via the regulation of radiation-induced centrosome duplication and therefore mitotic cell death by ILK, HIF-1α and survivin. This work identifies new targets in glioblastoma with the intention of radiosensitising these highly radioresistant tumours.

N-acetyl cysteine as an osteogenesis-enhancing molecule for bone regeneration

Bone regeneration often requires cues from osteogenesis-inducing factors for successful outcome. N-acetyl cysteine (NAC), an anti-oxidant small molecule, possibly modulates osteoblastic differentiation. This study investigated the potential of NAC as an osteogenesis-enhancing molecule in vitro and in vivo. Various concentrations of NAC (0, 2.5, 5.0, and 10 mM) were added to rat bone marrow stromal cell or osteoblastic cell culture in media with or without dexamethasone. The results showed marked enhancement of alkaline phosphatase activity and mineralized matrix formation together with consistent upregulation of bone-related gene markers such as collagen I, osteopontin, and osteocalcin in the osteoblastic culture with addition of 2.5 or 5.0 mM NAC regardless of the presence of dexamethasone. Micro-CT-based analysis and histological observation revealed that addition of NAC to a collagenous sponge implanted in a critical size cortical bone defect (3.0 mm × 5.0 mm) in rat femur yielded acceleration and completion of defect closure, with thick, compact, and contiguous bone after 6 weeks of healing. In contrast, with sponge alone, only sparse and incomplete bone regeneration was observed during the matching healing period. These results indicate that NAC can function as an osteogenesis-enhancing molecule to accelerate bone regeneration by activating differentiation of osteogenic lineages.

EGFR/JIP-4/JNK2 signaling attenuates cetuximab-mediated radiosensitization of squamous cell carcinoma cells

EGF receptor (EGFR) promotes tumor growth as well as radio- and chemoresistance in various human malignancies including squamous cell carcinomas (SCC). In addition to deactivation of prosurvival signaling, cetuximab-mediated EGFR targeting might concomitantly induce self-attenuating signaling bypasses. Identification of such bypass mechanisms is key to improve the efficacy of targeted approaches. Here, we show great similarity of EGFR signaling and radiation survival in cetuximab-treated SCC cells grown in a more physiologic three-dimensional extracellular matrix and as tumor xenografts in contrast to conventional monolayer cell cultures. Using phosphoproteome arrays, we observed strong induction of JNK2 phosphorylation potentially resulting from cetuximab-inhibited EGFR through c-jun-NH(2)-kinase (JNK)-interacting protein-4 (JIP-4), which was identified using an immunoprecipitation-mass spectrometric approach. Inhibition of this signaling bypass by JIP-4 or JNK2 knockdown or pharmacologic JNK2 inhibition enhanced cetuximab efficacy and tumor cell radiosensitivity. Our findings add new facets to EGFR signaling and indicate signaling bypass possibilities of cancer cells to improve their survival on cetuximab treatment. By deactivation of cetuximab-self-attenuating JNK2-dependent signaling, the cytotoxicity, and radiosensitizing potential of cetuximab can be augmented.

The effect of growth architecture on the induction and decay of bleomycin and X-ray-induced bystander response and genomic instability in lung adenocarcinoma cells and blood lymphocytes

PURPOSE

Cancer patients treated with radiomimetic drug bleomycin (BLM) have shown incidence of 7% second malignancy. Studies regarding BLM-induced genomic instability in bystander cells are scarce, and experiments with cells grown on three-dimensional (3D) cultures to mimic the in-vivo condition have never been attempted.

MATERIALS AND METHODS

A549 and NCI-H23 (human lung adenocarcinoma) cells were grown as 3D cultures using Cytomatrix(™), exposed to BLM or X-radiation and co-cultured with their respective unexposed cells. The DNA damage in direct and bystander cells were assessed by the induction of micronuclei (MN) or phosphorylated serine-15 residue in protein 53 (p53(ser-15)), a reflection of DNA damage, and by up-regulation of protein 21 (p21Waf1). The persistence of DNA damage was measured using MN assay and fluorescence in situ hybridization (FISH) in cancer cells and human peripheral blood lymphocytes (PBL) respectively.

RESULTS

BLM or X-irradiation induced DNA damage in both A549 and NCI-H23 cells and their respective bystander cells grown in 2D or 3D cultures. Further persistence of these damages in bystander PBL at delayed times indicated genomic instability in these cells.

CONCLUSION

BLM-induced genomic instability in the progeny of bystander cells and their significance in therapy-induced second malignancy may not be eliminated completely.

The impact of cell-cell contact, E-cadherin and EGF receptor on the cellular radiosensitivity of A431 cancer cells

Cell-cell contact is thought to be critically involved in mechanisms leading to radioresistance. Here, we assessed the influence of confluent compared to subconfluent cell culture conditions and the radiosensitizing ability of E-cadherin inhibition alone or in combination with C225-mediated EGFR inhibition in human squamous cell carcinoma cells. Our results show higher radioresistance under subconfluent growth conditions than under confluency. Delayed plating only resulted in higher radiation survival in confluently growing cells. While E-cadherin depletion significantly reduced basal clonogenic survival, increased the rate of apoptosis, and diminished cell adhesion, the cellular radiosensitivity remained unchanged under both subconfluent and confluent conditions. C225 decreased basal cell survival but failed to modify radiation survival. Additional treatment of E-cadherin knockdown cell cultures with C225 did not further reduce basal cell survival or lead to radiosensitization. Interestingly, E-cadherin silencing in 3D cell cultures did not alter radiosensitivity. Our data indicate that cell-cell contact and E-cadherin are not prominently involved in the regulation of radioresistance of human squamous cell carcinoma cells. In addition, no regulatory interaction between E-cadherin and EGFR in the radiation response was observed.

A bioinformatics filtering strategy for identifying radiation response biomarker candidates

The number of biomarker candidates is often much larger than the number of clinical patient data points available, which motivates the use of a rational candidate variable filtering methodology. The goal of this paper is to apply such a bioinformatics filtering process to isolate a modest number (<10) of key interacting genes and their associated single nucleotide polymorphisms involved in radiation response, and to ultimately serve as a basis for using clinical datasets to identify new biomarkers. In step 1, we surveyed the literature on genetic and protein correlates to radiation response, in vivo or in vitro, across cellular, animal, and human studies. In step 2, we analyzed two publicly available microarray datasets and identified genes in which mRNA expression changed in response to radiation. Combining results from Step 1 and Step 2, we identified 20 genes that were common to all three sources. As a final step, a curated database of protein interactions was used to generate the most statistically reliable protein interaction network among any subset of the 20 genes resulting from Steps 1 and 2, resulting in identification of a small, tightly interacting network with 7 out of 20 input genes. We further ranked the genes in terms of likely importance, based on their location within the network using a graph-based scoring function. The resulting core interacting network provides an attractive set of genes likely to be important to radiation response.

Focal adhesion-chromatin linkage controls tumor cell resistance to radio- and chemotherapy

Cancer resistance to therapy presents an ongoing and unsolved obstacle, which has clear impact on patient's survival. In order to address this problem, novel in vitro models have been established and are currently developed that enable data generation in a more physiological context. For example, extracellular-matrix- (ECM-) based scaffolds lead to the identification of integrins and integrin-associated signaling molecules as key promoters of cancer cell resistance to radio- and chemotherapy as well as modern molecular agents. In this paper, we discuss the dynamic nature of the interplay between ECM, integrins, cytoskeleton, nuclear matrix, and chromatin organization and how this affects the response of tumor cells to various kinds of cytotoxic anticancer agents.

Integrin-linked kinase is dispensable for multiple myeloma cell survival

We investigated the utility of integrin-linked kinase (ILK) as a target for therapeutic intervention in multiple myeloma (MM). ILK (over-)expression was assessed in primary samples and MM cell lines, and the molecular and physiological consequences of siRNA-mediated ILK ablation were compared to treatment with the small molecule inhibitor QLT0267. Whereas ILK expression was ubiquitous, overexpression was only rarely observed in patient biopsies. ILK knockdown had no effect on the viability or survival pathway activity pattern of MM cells. Conversely, QLT0267 induced cell death in MM cell lines and most primary tumor samples via the intrinsic apoptotic pathway. Although this effect was largely tumor cell-specific it is unlikely to have been mediated via ILK. We conclude that ILK does not play a prominent role in the promotion or sustenance of established MM.

Genome-wide gene expression analysis in cancer cells reveals 3D growth to affect ECM and processes associated with cell adhesion but not DNA repair

Cell morphology determines cell behavior, signal transduction, protein-protein interaction, and responsiveness to external stimuli. In cancer, these functions profoundly contribute to resistance mechanisms to radio- and chemotherapy. With regard to this aspect, this study compared the genome wide gene expression in exponentially growing cell lines from different tumor entities, lung carcinoma and squamous cell carcinoma, under more physiological three-dimensional (3D) versus monolayer cell culture conditions. Whole genome cDNA microarray analysis was accomplished using the Affymetrix HG U133 Plus 2.0 gene chip. Significance analysis of microarray (SAM) and t-test analysis revealed significant changes in gene expression profiles of 3D relative to 2D cell culture conditions. These changes affected the extracellular matrix and were mainly associated with biological processes like tissue development, cell adhesion, immune system and defense response in contrast to terms related to DNA repair, which lacked significant alterations. Selected genes were verified by semi-quantitative RT-PCR and Western blotting. Additionally, we show that 3D growth mediates a significant increase in tumor cell radio- and chemoresistance relative to 2D. Our findings show significant gene expression differences between 3D and 2D cell culture systems and indicate that cellular responsiveness to external stress such as ionizing radiation and chemotherapeutics is essentially influenced by differential expression of genes involved in the regulation of integrin signaling, cell shape and cell-cell contact.

Identification and characterization of a novel integrin-linked kinase inhibitor

Integrin-linked kinase (ILK) represents a relevant target for cancer therapy in light of its role in promoting oncogenesis and tumor progression. Through the screening of an in-house focused compound library, we identified N-methyl-3-(1-(4-(piperazin-1-yl)phenyl)-5-(4'-(trifluoromethyl)-[1,1'-biphenyl]-4-yl)-1H-pyrazol-3-yl)propanamide (22) as a novel ILK inhibitor (IC(50), 0.6 μM), which exhibited high in vitro potency against a panel of prostate and breast cancer cell lines (IC(50), 1-2.5 μM), while normal epithelial cells were unaffected. Compound 22 facilitated the dephosphorylation of Akt at Ser-473 and other ILK targets, including glycogen synthase kinase-3β and myosin light chain. Moreover, 22 suppressed the expression of the transcription/translation factor YB-1 and its targets HER2 and EGFR in PC-3 cells, which could be rescued by the stable expression of constitutively active ILK. Evidence indicates that 22 induced autophagy and apoptosis, both of which were integral to its antiproliferative activity. Together, this broad spectrum of mechanisms underlies the therapeutic potential of 22 in cancer treatment, which is manifested by its in vivo efficacy as a single oral agent in suppressing PC-3 xenograft tumor growth.

Dual targeting of EGFR and focal adhesion kinase in 3D grown HNSCC cell cultures

PURPOSE

Epidermal growth factor receptor (EGFR) and focal adhesion kinase (FAK) show frequent overexpression and hyperactivity in various human malignancies including head and neck squamous cell carcinomas (HNSCC). To examine effects of dual EGFR/FAK inhibition on cellular radiosensitivity of HNSCC cells in a more physiological environment, we employed a previously established laminin-rich extracellular matrix (lrECM) based three-dimensional (3D) cell culture model.

MATERIALS AND METHODS

UTSCC15 and SAS HNSCC cell lines stably transfected with EGFR-CFP or CFP were used. Single or combined EGFR (Cetuximab, siRNA) and FAK (TAE226, siRNA) inhibition were accomplished prior to measuring clonogenic survival and protein expression and phosphorylation. Immunofluorescence enabled visualization of EGFR-CFP and FAK.

RESULTS

Cetuximab resulted in higher radiosensitization in EGFR-CFP overexpressing cell lines than CFP controls. Single EGFR or FAK inhibition mediated radiosensitization, while dual EGFR/FAK targeting further augmented this effect. Despite signaling alterations upon Cetuximab and siRNA knockdown, analysis of protein expression and phosphorylation indicates EGFR and FAK signaling coexistence without obvious overlap.

CONCLUSIONS

Combined EGFR/FAK targeting yielded stronger radiosensitization than either approach alone, which might be based on non-overlapping downstream signaling. Whether dual targeting of EGFR and FAK can reasonably be combined with radiotherapy and chemotherapy needs clarification.

Small interfering RNA targeting integrin-linked kinase inhibited the growth and induced apoptosis in human bladder cancer cells

Integrin-linked kinase (ILK), an intracellular serine/threonine kinase, is implicated in cell growth and survival, cell-cycle progression, tumor angiogenesis, and cell apoptosis. Recent studies showed that the expression and activity of ILK increased significantly in many types of solid tumors. However, the exact molecular mechanism of ILK underlie tumor has not been fully ascertained. The purpose of our study was to determine whether knockdown of ILK would inhibit cell growth and induce apoptosis in bladder cancer cells using a plasmid vector based small interfering RNA (siRNA). The experiments showed that knockdown of ILK could remarkably inhibit cell proliferation and growth, regulate cell cycle and induce apoptosis of bladder cancer BIU-87 and EJ cells. We demonstrated that knockdown of ILK inhibited phosphorylation of downstream signaling targets protein kinase B/Akt, glycogen synthase kinase 3-beta (GSK-3β), and reduced expression of β-catenin in BIU-87 as well as EJ cells by Western blot and Immunofluorescence analysis. In addition, down-regulation of ILK also could increase expression of Ribonuclease inhibitor (RI), an important acidic cytoplasmic protein with many functions. BALB/C nude mice injected with the BIU-87 cells transfected ILK siRNA showed a significant inhibition of the tumor growth with lighter tumor weight, lower microvessels density and higher apoptosis rate than those in the other two control groups. In conclusion, these results suggest that ILK might be involved in the development of bladder cancer, and could be served as a novel potential therapy target for human bladder cancer. Our study may be of biological and clinical importance.

Integrin-linked kinase 1: role in hormonal cancer progression

Integrin-linked kinase 1 (ILK1) is a serine/threonine kinase that plays important roles in a variety of cellular functions including cell survival, migration and angiogenesis. ILK1 is normally expressed in numerous tissues and activated by growth factors, cytokines and hormones. Dysregulation of ILK1 expression or function is found in several hormonal tumors including breast, ovary and prostate. Emerging evidence suggests that ILK overexpression promotes cellular transformation, cell survival, epithelial mesenchymal transition (EMT), and metastasis of hormonal cancer cells while inhibition of ILK1 reduces tumor growth and progression. The recent development of ILK1 inhibitors has provided novel mechanisms for blocking ILK1 signaling to curb metastasis and therapy resistance of hormonal tumors. This review will focus on recent advances made towards understanding the role of ILK signaling axis in progression of hormonal cancer.

The role of the focal adhesion protein PINCH1 for the radiosensitivity of adhesion and suspension cell cultures

Focal adhesion (FA) signaling mediated by adhesion to extracellular matrix and growth factor receptors contributes to the regulation of the cellular stress response to external stimuli. Critical to focal adhesion assembly and signaling is the adapter protein PINCH1. To evaluate whether the prosurvival function of PINCH1 in radiation cell survival depends on cell adhesion, we examined PINCH1^fl/fl and PINCH1^−/− mouse embryonic fibroblasts and human cancer cell lines. Here, we found that the enhanced cellular radiosensitivity mediated by PINCH1 depletion observed under adhesion conditions is conserved when cells are irradiated under suspension conditions. This unsuspected finding could not be explained by the observed modification of adhesion and growth factor associated signaling involving FAK, Paxillin, p130^CAS, Src, AKT, GSK3β and ERK1/2 under suspension and serum withdrawal relative to adhesion conditions with serum. Our data suggest that the adapter protein PINCH1 critically participates in the regulation of the cellular radiosensitivity of normal and malignant cells similarly under adhesion and suspension conditions.

PINCH1 regulates Akt1 activation and enhances radioresistance by inhibiting PP1alpha

Tumor cell resistance to ionizing radiation and chemotherapy is a major obstacle in cancer therapy. One factor contributing to this is integrin-mediated adhesion to ECM. The adapter protein particularly interesting new cysteine-histidine-rich 1 (PINCH1) is recruited to integrin adhesion sites and promotes cell survival, but the mechanisms underlying this effect are not well understood. Here we have shown that PINCH1 is expressed at elevated levels in human tumors of diverse origins relative to normal tissue. Furthermore, PINCH1 promoted cell survival upon treatment with ionizing radiation in vitro and in vivo by perpetuating Akt1 phosphorylation and activity. Mechanistically, PINCH1 was found to directly bind to protein phosphatase 1alpha (PP1alpha) - an Akt1-regulating protein - and inhibit PP1alpha activity, resulting in increased Akt1 phosphorylation and enhanced radioresistance. Thus, our data suggest that targeting signaling molecules such as PINCH1 that function downstream of focal adhesions (the complexes that mediate tumor cell adhesion to ECM) may overcome radio- and chemoresistance, providing new therapeutic approaches for cancer.

Three-dimensional cell growth confers radioresistance by chromatin density modification

Cell shape and architecture are determined by cell-extracellular matrix interactions and have profound effects on cellular behavior, chromatin condensation, and tumor cell resistance to radiotherapy and chemotherapy. To evaluate the role of chromatin condensation for radiation cell survival, tumor cells grown in three-dimensional (3D) cell cultures as xenografts and monolayer cell cultures were compared. Here, we show that increased levels of heterochromatin in 3D cell cultures characterized by histone H3 deacetylation and induced heterochromatin protein 1alpha expression result in increased radiation survival and reduced numbers of DNA double strand breaks (DSB) and lethal chromosome aberrations. Intriguingly, euchromatin to heterochromatin-associated DSBs were equally distributed in irradiated 3D cell cultures and xenograft tumors, whereas irradiated monolayer cultures showed a 2:1 euchromatin to heterochromatin DSB distribution. Depletion of histone deacetylase (HDAC) 1/2/4 or application of the class I/II pharmacologic HDAC inhibitor LBH589 induced moderate or strong chromatin decondensation, respectively, which was translated into cell line-dependent radiosensitization and, in case of LBH589, into an increased number of DSBs. Neither growth conditions nor HDAC modifications significantly affected the radiation-induced phosphorylation of the important DNA repair protein ataxia telangiectasia mutated. Our data show an interrelation between cell morphology and cellular radiosensitivity essentially based on chromatin organization. Understanding the molecular mechanisms by which chromatin structure influences the processing of radiation-induced DNA lesions is of high relevance for normal tissue protection and optimization of cancer therapy.