Innovative strategies for measuring kinase activity to accelerate the next wave of novel kinase inhibitors

The development of protein kinase inhibitors (PKIs) has gained significance owing to their therapeutic potential for diseases like cancer. In addition, there has been a rise in refining kinase activity assays, each possessing unique biological and analytical characteristics crucial for PKI development. However, the PKI development pipeline experiences high attrition rates and approved PKIs exhibit unexploited potential because of variable patient responses. Enhancing PKI development efficiency involves addressing challenges related to understanding the PKI mechanism of action and employing biomarkers for precision medicine. Selecting appropriate kinase activity assays for these challenges can overcome these attrition rate issues. This review delves into the current obstacles in kinase inhibitor development and elucidates kinase activity assays that can provide solutions.

Phenotypic screening in Organ-on-a-Chip systems: a 1537 kinase inhibitor library screen on a 3D angiogenesis assay

Modern drug development increasingly requires comprehensive models that can be utilized in the earliest stages of compound and target discovery. Here we report a phenotypic screening exercise in a high-throughput Organ-on-a-Chip setup. We assessed the inhibitory effect of 1537 protein kinase inhibitors in an angiogenesis assay. Over 4000 micro-vessels were grown under perfusion flow in microfluidic chips, exposed to a cocktail of pro-angiogenic factors and subsequently exposed to the respective kinase inhibitors. Efficacy of compounds was evaluated by reduced angiogenic sprouting, whereas reduced integrity of the main micro-vessel was taken as a measure for toxicity. The screen yielded 53 hits with high anti-angiogenicity and low toxicity, of which 44 were previously unassociated with angiogenic pathways. This study demonstrates that Organ-on-a-Chip models can be screened in high numbers to identify novel compounds and targets. This will ultimately reduce bias in early-stage drug development and increases probability to identify first in class compounds and targets for today's intractable diseases.

Abstract 5876: Sorafenib and Lenvatinib induce vascular responses in patient derived HCC on-Chip models

Hepatocellular carcinoma (HCC) is the most common type of liver cancer. Its incidence is increasing, and is closely related to advanced liver disease. Interactions in the HCC microenvironment between tumor cells and the associated stroma actively regulate tumor initiation, progression, metastasis, and therapy response. In the present study, we used the OrganoPlate graft to establish a co-culture system consisting of dissociated HCC tumors (HCC 1-8) and cell lines, HCC derived fibroblasts and vasculature. Cultures were prepared and validated by assessing their response to Sorafenib and Lenvatinib (72 hours). Cultures had their viability (alamar blue assay), and chemokine/cytokine levels in the supernatant (Luminex) determined. In addition, the organization of the vasculature in the tumor compartment was studied through immunostainings, confocal imaging, and subsequent morphological analyses. HCC models were characterized by a range of specific markers, tumor (albumin), endothelial (CD31 and VE-Cadherin) and stromal (aSMA) cells. CD31 immunostained cultures were imaged, and morphology changes quantified. Sorafenib and Lenvatinib induced changes in the tumor vasculature area and organization. Hereby, we present vascularized patient-derived HCC models that include relevant cellular players of the HCC microenvironment. These co-cultures are highly suitable for studying specific cell types as well as patient-specific responses. We envision that this patient derived model will evolve to become a platform for understanding the interplay between angiogenesis, stroma and immune infiltrate in HCC.

Citation Format: Orsola Mocellin, Abbie Robinson, Aleksandra Olczyk, Stephane Treillard, Thomas Olivier, Chee Ng, Jeroen Heijmans, Désiréé Goubert, Arthur Stok, Gilles van Tienderen, Monique Verstegen, Sebastian Trietsch, Henriëtte Lanz, Paul Vulto, Jos Joore, Karla S. Queiroz. Sorafenib and Lenvatinib induce vascular responses in patient derived HCC on-Chip models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5876.

Abstract 3857: A novel microfluidic platform for understanding the role of PDAC stroma in immune response

Pancreatic Ductal Adenocarcinoma (PDAC), the most common pancreatic cancer type is estimated to become the second leading cause of cancer-related deaths by 2030 with mortality rates of up to 93%. PDAC is characterized by high-density stroma and an immunosuppressive tumor microenvironment that lead to a lack of efficacy of immunotherapeutic strategies. Those facts highlight the urgent need for more relevant PDAC in vitro models that support the discovery of novel (immuno-)therapies. Here, we describe the establishment of a multiple cell type culture in a microfluidic platform that will be applied for modeling immune and stroma cell interplay in PDAC. Microfluidic platforms such as the OrganoPlate® support 3D growth and inclusion of different cell types cultured under flow conditions. The aim of this project was to determine the involvement of stromal cells such as endothelial cells and pancreatic stellate cells in immune cell recruitment in pancreatic cancer. In order to generate a more relevant culture set up, supporting cells and PDAC organoids were used in the 3-lane OrganoPlate® to study immune cell recruitment. Migration of fluorescently labelled peripheral blood mononuclear cells from vasculature through the stromal compartment to the PDAC organoids was tracked for 72h using confocal microscopy. Migration of immune cells to the tumor cell compartment was significantly inhibited by the stromal compartment, thus confirming in vivo immune responses, as the stroma seems to form both a physical as well as a chemical barrier for immune cells to reach the active tumor site. Interestingly, PDAC organoid conditioned medium efficiently attracts immune cells into the tumor compartment, indicating that secreted factors play a relevant role in immune cell recruitment. Despite the positive effect on recruitment and immune-tumor cell interaction, a lack of tumor cell killing is observed. The co-culture of PDAC organoids with stromal and immune cells grown on-a-Chip as described in this study indicates the suitability of microfluidic platforms for generating complex models and its use for dissecting complex cellular interplay and processes involved in the lack of anti-tumor immune responses in PDAC.

Citation Format: Marlene Geyer, Sabrina D'Agosto, Henriëtte Lanz, Vincenzo Corbo, Jos Joore, Karla S. Queiroz. A novel microfluidic platform for understanding the role of PDAC stroma in immune response [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3857.

In vitro grafting of hepatic spheroids and organoids on a microfluidic vascular bed

With recent progress in modeling liver organogenesis and regeneration, the lack of vasculature is becoming the bottleneck in progressing our ability to model human hepatic tissues in vitro. Here, we introduce a platform for routine grafting of liver and other tissues on an in vitro grown microvascular bed. The platform consists of 64 microfluidic chips patterned underneath a 384-well microtiter plate. Each chip allows the formation of a microvascular bed between two main lateral vessels by inducing angiogenesis. Chips consist of an open-top microfluidic chamber, which enables addition of a target tissue by manual or robotic pipetting. Upon grafting a liver microtissue, the microvascular bed undergoes anastomosis, resulting in a stable, perfusable vascular network. Interactions with vasculature were found in spheroids and organoids upon 7 days of co-culture with space of Disse-like architecture in between hepatocytes and endothelium. Veno-occlusive disease was induced by azathioprine exposure, leading to impeded perfusion of the vascularized spheroid. The platform holds the potential to replace animals with an in vitro alternative for routine grafting of spheroids, organoids, or (patient-derived) explants.

Abstract 2777: Modelling T Cell-Vasculature co-culture in a high-throughput microfluidic platform

Recent clinical success of immune checkpoint inhibitors and chimeric antigen receptor T cells has highly increased the attention for the field of immunotherapy. However, identifying responders to these therapies is challenging underscoring the necessity for translational models that increase understanding of tumor-immune responses. In the present study, a co-culture system containing immune cells and vasculature was established. Both are essential components of the tumor microenvironment and very often lacking in in vitro tumor models, highlighting the added value of our co-culture platform. We focused on optimizing endothelial and CD8+ T cell co-cultures and subsequently assessing T cell migration from the endothelial tubes via endothelial sprouts towards various chemoattractants. In order to generate stratified 3D co-cultures, the Mimetas OrganoPlate Graft containing 64 microfluidic culture units was used. The microfluidic units in this platform are composed of two parallel microfluidics channels and a central chamber. The two parallel microfluidic channels were used for generating parallel endothelial tubules, whilst angiogenic factors (S1P, VEGF, bFGF and PMA) were added to the central chamber of the culture unit resulting in a generation of a gradient and sprouting of the endothelial tubes towards the central chamber. Generated sprouts were stable and perfusable. The central chamber is designed for culturing complex microtissues such as spheroids, organoids and explants. Angiogenic endothelial tubules formed vascular beds in presence of added factors within 3-5 days. Once vascular beds were formed, activated and fluorescently labeled CD8+ T cells were loaded in the endothelial tubules and followed in culture for 48 hours. CD8+ T cell migration was observed both via the sprouts as well as by crossing the endothelial barrier, and increased in presence of gradients of CCL2, CCXl12 and CCL9. Highest CD8+ T cell numbers were observed in presence of a gradient generated with a mix of these three chemokines. Therefore, we present a high throughput co-culture system containing angiogenic endothelial tubules and CD8+ T cells. These co-cultures are highly suitable for studying T cell migration, event which precedes the detection and recognition of antigens at the surface of antigen-presenting cells and for interactions with other cells involved in the immune response. In addition, these co-cultures serve as a platform for understanding the interplay between T cell migration and angiogenesis in the tumor microenvironment. Furthermore, we envision that this model will evolve into an immunocompetent patient-derived tumor model that can be used to study immune responses to tumors.

Citation Format: Luuk de Haan, Sacha Spelier, Johnny Suijker, Erik Wallinga, Lenie van den Broek, Henriette Lanz, Jos Joore, Paul Vulto, Karla Queiroz. Modelling T Cell-Vasculature co-culture in a high-throughput microfluidic platform [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2777.

High throughput transepithelial electrical resistance (TEER) measurements on perfused membrane-free epithelia

Assessment of epithelial barrier function is critically important for studying healthy and diseased biological models. Here we introduce an instrument that measures transepithelial electrical resistance (TEER) of perfused epithelial tubes in the microfluidic OrganoPlate platform. The tubules are grown in microfluidic channels directly against an extracellular matrix, obviating the need for artificial filter membranes. We present TEER measurements on Caco-2 intestinal and renal proximal tubule epithelium. Forty tubules on one single plate were interrogated in less than a minute. We show that TEER measurement is significantly more sensitive than a fluorescent reporter leakage assay in response to staurosporine. We demonstrate a 40-channel time-lapse data acquisition over a 25 hour time period under flow conditions. We furthermore observed a 50% reduction in Caco-2 TEER values following exposure to a cocktail of inflammatory cytokines. To our best knowledge, this is the first instrument of its kind that allows routine TEER studies in perfused organ-on-a-chip systems without interference by artificial filter membranes. We believe the apparatus will contribute to accelerating routine adoption of perfused organ-on-a-chip systems in academic research and in industrial drug development.

Abstract 2794: A novel HNSCC organoid-on-a-chip platform for preclinical investigation and drug screening

Head and neck squamous cell carcinoma (HNSCC) cancer is a broad category of tumor types arising from the inner lining of various anatomic structures including the oral cavity, pharynx, larynx and salivary glands. Treatment often involves an intensive combination of surgery, radiotherapy and chemotherapy. Despite this, tumor recurrence rates remain high and survival rates are relatively poor. Here, we describe a novel high throughput drug screening platform combining the OrganoPlate®, a microfluidic based 3D-culture system, and HN cancer-derived organoids. MIMETAS develops Organ-on-a-Chip-based models for evaluation of new medicines. Our unique microfluidic technology enables testing of compounds on miniaturized 3D organ models in high-throughput. Hereby we show the establishment of HNSCC cancer-derived organoids in 2-lane OrganoPlate®, and its usefulness for phenotypic drug screenings. The aim of the study is to capture differential sensitivity of HN organoid lines to either a common platinum-based chemotherapy or to a targeted drug still not used in the clinic. Organoid lines (T1, T3 and T5) were embedded in the 2-lane OrganoPlate® as single cells in an extracellular matrix gel. At day 2, cultures were treated with cisplatin or PARP-inhibitor niraparib for 120 hours. Additionally, cultures exposed to high doses of cisplatin were evaluated after one week of recovery in order to determine treatment failure and recapitulate potential patient relapse.

Drug response was evaluated by assessment of morphology (phase contrast), cell viability (total nuclei count, alamar blue assay), proliferation (EdU incorporation) and DNA damage (phosphorylated histone H2AX). Organoid cultures grow well under medium perfusion in the 2-lane OrganoPlate® and selective sensitivity to cisplatin and niraparib is revealed by the used readouts. The high-throughput, microfluidic 2-lane OrganoPlate® platform offers an attractive method for growing HNSCC cancer-derived organoids, supporting development of individualized tumour models for phenotypic drug screenings.

Citation Format: Silvia Bonilla, Else Driehuis, Henriëtte Lanz, Hans Clevers, Jos Joore, Karla Queiroz, Paul Vulto. A novel HNSCC organoid-on-a-chip platform for preclinical investigation and drug screening [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2794.

Abstract 2795: Ex vivo modelling of vascularized pdx-derived ovarian tumors

Predicting clinical response to anticancer drugs remains a major challenge in cancer therapy research. The current treatment of patients with ovarian cancer involves surgery and platinum-based chemotherapy, which still result in recurrence on advanced stages of the disease. During tumor progression, cancerous cells continuously accumulate mutations giving rise to a heterogeneous population of cells. Additionally, spatial distribution of stromal, endothelial and immune cells in the microenvironment affects tumor progression, cell morphology, and ultimately drug response. In order to predict clinical outcome of chemotherapy in vitro, tumor heterogeneity and microenvironment constituents must be conserved. Current models of tumor biology and microenvironment consist in xenografts of human tumors implanted in immunodeficient mice. These models allow studying systemic treatment response, but its application is limited to small developmental studies. Here, we present a high throughput in vitro 'grafting' platform where we co-culture blood vessels with tumor explants. Each unit in this platform is composed of two parallel microfluidic channels and a central chamber. Two endothelial tubules are generated in the microfluidic channels and cultured in presence of a gradient of angiogenic factors (S1P, VEGF, bFGF and PMA) added to the central chamber of the culture unit. Angiogenic tubules form vascular beds within 3-5 days, after which tumor explants are loaded to the central chamber on top of the vascular beds. The model shown in this study consists of ovarian serous papillary adenocarcinoma collected after xenograft growth in immunodeficient mice. This ovarian cancer explant was previously characterized as resistant to Paclitaxel. In this study, we observe how the vascular bed remodels in the presence of the explant and closely interacts with ovarian tumor tissue. Vessel perfusion and stabilization of vascular bed was monitored by real time imaging of 150 kDa FITC-Dextran. Cultures were evaluated by assessment of morphology and presence of endothelial and tumor cell biomarkers. Moreover, co-culture response to Sorafenib (anti-angiogenic), Palbociclib and Paclitaxel was detected by distinctive proliferation rates as compared to control conditions. The established ovary cancer-on-a-chip platform enables the study of fundamental aspects of tumor disease and progression. In addition, these co-cultures serve as a platform for understanding tumor-endothelial cell crosstalk and its consequences for tumor aggressiveness. Moreover, these models constitute a suitable platform for drug screenings of anti-cancer and anti-angiogenic compounds, making them a powerful translational tool for drug selection in personalized medicine applications.

Citation Format: Silvia Bonilla, Jean-François Mirjolet, Pauline Berger, Elodie Rajon, Erik Walinga, Remko van Vught, Henriëtte Lanz, Jos Joore, Paul Vulto, Fabrice Viviani, Karla Queiroz. Ex vivo modelling of vascularized pdx-derived ovarian tumors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2795.

An Intestine-on-a-Chip Model of Plug-and-Play Modularity to Study Inflammatory Processes

Development of efficient drugs and therapies for the treatment of inflammatory conditions in the intestine is often hampered by the lack of reliable, robust, and high-throughput in vitro and in vivo models. Current models generally fail to recapitulate key aspects of the intestine, resulting in low translatability to the human situation. Here, an immunocompetent 3D perfused intestine-on-a-chip platform was developed and characterized for studying intestinal inflammation. Forty independent polarized 3D perfused epithelial tubular structures were grown from cells of mixed epithelial origin, including enterocytes (Caco-2) and goblet cells (HT29-MTX-E12). Immune cells THP-1 and MUTZ-3, which can be activated, were added to the system and assessed for cytokine release. Intestinal inflammation was mimicked through exposure to tumor necrosis factor-α (TNFα) and interleukin (IL)-1β. The effects were quantified by measuring transepithelial electrical resistance (TEER) and proinflammatory cytokine secretion on the apical and basal sides. Cytokines induced an inflammatory state in the culture, as demonstrated by the impaired barrier function and increased IL-8 secretion. Exposure to the known anti-inflammatory drug TPCA-1 prevented the inflammatory state. The model provides biological modularity for key aspects of intestinal inflammation, making use of well-established cell lines. This allows robust assays that can be tailored in complexity to serve all preclinical stages in the drug discovery and development process.

Interstitial Flow Recapitulates Gemcitabine Chemoresistance in A 3D Microfluidic Pancreatic Ductal Adenocarcinoma Model by Induction of Multidrug Resistance Proteins

Pancreatic Ductal Adenocarcinoma (PDAC) is one of the most lethal cancers due to a high chemoresistance and poor vascularization, which results in an ineffective systemic therapy. PDAC is characterized by a high intratumoral pressure, which is not captured by current 2D and 3D in vitro models. Here, we demonstrated a 3D microfluidic interstitial flow model to mimic the intratumoral pressure in PDAC. We found that subjecting the S2-028 PDAC cell line to interstitial flow inhibits the proliferation, while maintaining a high viability. We observed increased gemcitabine chemoresistance, with an almost nine-fold higher EC50 as compared to a monolayer culture (31 nM versus 277 nM), and an alleviated expression and function of the multidrug resistance protein (MRP) family. In conclusion, we developed a 3D cell culture modality for studying intratissue pressure and flow that exhibits more predictive capabilities than conventional 2D cell culture and is less time-consuming, and more scalable and accessible than animal models. This increase in microphysiological relevance might support improved efficiency in the drug development pipeline.

3D human microvessel-on-a-chip model for studying monocyte-to-endothelium adhesion under flow - application in systems toxicology

Lifestyle and genetic factors can lead to the development of atherosclerosis and, ultimately, cardiovascular adverse events. Rodent models are commonly used to investigate mechanism(s) of atherogenesis. However, the 3Rs principles, aiming to limit animal testing, encourage the scientific community to develop new physiologically relevant in vitro alternatives. Leveraging the 96-chip OrganoPlate®, a microfluidic platform, we have established a three-dimensional (3D) model of endothelial microvessels-on-a-chip under flow using primary human coronary arterial endothelial cells. As functional readout, we have set up an assay to measure the adhesion of monocytes to the lumen of perfused microvessels. For monitoring molecular changes in microvessels, we have established the staining and quantification of specific protein markers of inflammation and oxidative stress using high content imaging, as well as analyzed transcriptome changes using microarrays. To demonstrate its usefulness in systems toxicology, we leveraged our 3D vasculature-on-a-chip model to assess the impact of the Tobacco Heating System (THS) 2.2, a candidate modified risk tobacco product, and the 3R4F reference cigarette on the adhesion of monocytic cells to endothelial microvessels. Our results show that THS 2.2 aerosol-conditioned medium had a reduced effect on monocyte-endothelium adhesion compared with 3R4F smoke-conditioned medium. In conclusion, we have established a relevant 3D vasculature-on-a-chip model for investigating leukocyte-endothelial microvessel adhesion. A case study illustrates how the model can be used for product testing in the context of systems toxicology-based risk assessment. The current model and its potential further development options also open perspectives of applications in vascular disease research and drug discovery.

Constitutively active GSK3β as a means to bolster dendritic cell functionality in the face of tumour-mediated immune suppression

In patients with cancer, the functionality of Dendritic Cells (DC) is hampered by high levels of tumor-derived suppressive cytokines, which interfere with DC development and maturation. Poor DC development can limit the efficacy of immune checkpoint blockade and in vivo vaccination approaches. Interference in intracellular signaling cascades downstream from the receptors of major tumor-associated suppressive cytokines like IL-10 and IL-6, might improve DC development and activation, and thus enhance immunotherapy efficacy. We performed exploratory functional screens on arrays consisting of >1000 human kinase peptide substrates to identify pathways involved in DC development and its inhibition by IL-10 or IL-6. The resulting alterations in phosphorylation of the kinome substrate profile pointed to glycogen-synthase kinase-3β (GSK3β) as a pivotal kinase in both DC development and suppression. GSK3β inhibition blocked human DC differentiation in vitro, which was accompanied by decreased levels of IL-12p70 secretion, and a reduced capacity for T cell priming. More importantly, adenoviral transduction of monocytes with a constitutively active form of GSK3β induced resistance to the suppressive effects of IL-10 and melanoma-derived supernatants alike, resulting in improved DC development, accompanied by up-regulation of co-stimulatory markers, an increase in CD83 expression levels in mature DC, and diminished release of IL-10. Moreover, adenovirus-mediated intratumoral manipulation of this pathway in an in vivo melanoma model resulted in DC activation and recruitment, and in improved immune surveillance and tumor control. We propose the induction of constitutive GSK3β activity as a novel therapeutic means to bolster DC functionality in the tumor microenvironment.

Abstract 1173: A novel high throughput platform for head & neck cancer organoids drug screening

Head and neck (HN) cancer is a broad category of tumor types arising from various anatomic structures including the craniofacial bones, soft tissues, salivary glands, skin, and mucosal membranes. Treatment often involves an intensive combination of surgery, radiotherapy and chemotherapy. Despite this, tumour recurrence rates remain high and survival rates are relatively poor. Here, we describe a novel high throughput drug screening platform combining the OrganoPlate, a microfluidic based 3D culture plate, and HN cancer-derived organoids. MIMETAS develops Organ-on-a-Chip-based models for evaluation of new medicines. Our unique microfluidic technology enables testing of compounds on miniaturized 3D organ models in high-throughput. These models are expected to show better predictivity as compared to laboratory animals and conventional 2D cell culture models, without compromising throughput or ease of use. Hereby we show the establishment of HN cancer-derived organoids in 2-lane OrganoPlate, and its usefulness for phenotypic drug screenings. The aim of the study is to evaluate the 2-lane OrganoPlate as a platform for growing HN cancer organoids and drug screening. Organoid lines (T2, T3 and T4) were embedded in the 2-lane OrganoPlate as single cells in an Extracellular Matrix gel. At day 3, cultures were treated with Cisplatin or Carboplatin for 120 hours. Drug response was evaluated by assessment of morphology (phase contrast), Cell Viability (Alamar blue) and proliferation (EdU incorporation). Organoids cultures grow well under perfusion in the 2-lane OrganoPlate and different sensitivity to cisplatin is captured by the used readouts. The high-throughput, microfluidic 2-lane OrganoPlate platform offers an attractive method for growing HN cancer-derived organoids, supporting development of individualized tumour models for phenotypic drug screenings.

Citation Format: Karla Queiroz, Else Driehuis, Silvia Bonilla, Henriëtte Lanz, Hans Clevers, Jos Joore, Paul Vulto. A novel high throughput platform for head & neck cancer organoids drug screening [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1173.

Abstract 41: A novel high-throughput microfluidic drug screening platform using pancreatic ductal adenocarcinoma derived organoids

Pancreatic cancer is one of the deadliest tumors due to the limited treatment options and late diagnosis. Here, we describe a novel high throughput drug screening platform combining a microfluidic based 3D-culture plate, and the recently described pancreatic ductal adenocarcinoma (PDAC) derived organoids. The microfluidic plate is a high throughput microfluidic 3D cell culture platform, supporting physiologically relevant models with a minimal requirement of cell material and enabling a wide range of flow and co-culture options (e.g. with blood vessels). Organoids were derived from human PDAC xenografts and seeded in the microfluidic plate. The low amount of tissue material required (4000 cells per chip) and the high number of replicates on one plate (n=96 on a standard microtiter format plate) renders the microfluidic plate an efficient and cost-effective platform for drug screening and toxicity assays on complex, 3D models. Organoids were exposed to various chemotherapeutic drugs for 72 hours. The viability of the organoids before and after drug treatment is monitored with standard viability assays and subsequently used to generate dose response curves. In conclusion, we showed that the microfluidic plate can be used for high throughput drug screening assays and toxicity screening, and demonstrated its compatibility with human pancreatic PDAC derived organoids.

Citation Format: Bart Kramer, Wijnand van Paassen, Luuk de Haan, Henriette Lanz, Jos Joore. A novel high-throughput microfluidic drug screening platform using pancreatic ductal adenocarcinoma derived organoids [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 41.

Determination of Site-Specific Phosphorylation Ratios in Proteins with Targeted Mass Spectrometry

We show that parallel reaction monitoring (PRM) can be used for exact quantification of phosphorylation ratios of proteins using stable-isotope-labeled peptides. We have compared two different PRM approaches on a digest of a U87 cell culture, namely, direct-PRM (tryptic digest measured by PRM without any further sample preparation) and TiO₂-PRM (tryptic digest enriched with TiO₂ cartridges, followed by PRM measurement); these approaches are compared for the following phosphorylation sites: neuroblast differentiation-associated protein (AHNAK S5480-p), calcium/calmodulin-dependent protein kinase type II subunit delta (CAMK2D T337-p), and epidermal growth factor receptor (EGFR S1166-p). A reproducible percentage of phosphorylation could be determined (CV 6-13%) using direct-PRM or TiO₂-PRM. In addition, we tested the approaches in a cell culture experiment in which U87 cells were deprived of serum. As a "gold standard" we included immune precipitation of EGFR followed by PRM (IP-PRM). For EGFR (S1166) and AHNAK (S5480) a statistical significant change in the percentage of phosphorylation could be observed as a result of serum deprivation; for EGFR (S1166) this change was observed for both TiO₂-PRM and IP-PRM. The presented approach has the potential to multiplex and to quantify the ratio of phosphorylation in a single analysis.

TP53 mutated glioblastoma stem-like cell cultures are sensitive to dual mTORC1/2 inhibition while resistance in TP53 wild type cultures can be overcome by combined inhibition of mTORC1/2 and Bcl-2

BACKGROUND

Glioblastoma is the most malignant tumor of the central nervous system and still lacks effective treatment. This study explores mutational biomarkers of 11 drugs targeting either the RTK/Ras/PI3K, the p53 or the Rb pathway using 25 patient-derived glioblastoma stem-like cell cultures (GSCs).

RESULTS

We found that TP53 mutated GSCs were approximately 3.5 fold more sensitive to dual inhibition of mammalian target of rapamycin complex 1 and 2 (mTORC1/2) compared to wild type GSCs. We identified that Bcl-2(Thr56/Ser70) phosphorylation contributed to the resistance of TP53 wild type GSCs against dual mTORC1/2 inhibition. The Bcl-2 inhibitor ABT-263 (navitoclax) increased sensitivity to the mTORC1/2 inhibitor AZD8055 in TP53 wild type GSCs, while sensitivity to AZD8055 in TP53 mutated GSCs remained unchanged.

CONCLUSION

Our data suggest that Bcl-2 confers resistance to mTORC1/2 inhibitors in TP53 wild type GSCs and that combined inhibition of both mTORC1/2 and Bcl-2 is worthwhile to explore further in TP53 wild type glioblastomas, whereas in TP53 mutated glioblastomas dual mTORC1/2 inhibitors should be explored.

Therapy response testing of breast cancer in a 3D high-throughput perfused microfluidic platform

BACKGROUND

Breast cancer is the most common invasive cancer among women. Currently, there are only a few models used for therapy selection, and they are often poor predictors of therapeutic response or take months to set up and assay. In this report, we introduce a microfluidic OrganoPlate® platform for extracellular matrix (ECM) embedded tumor culture under perfusion as an initial study designed to investigate the feasibility of adapting this technology for therapy selection.

METHODS

The triple negative breast cancer cell lines MDA-MB-453, MDA-MB-231 and HCC1937 were selected based on their different BRCA1 and P53 status, and were seeded in the platform. We evaluate seeding densities, ECM composition (Matrigel®, BME2rgf, collagen I) and biomechanical (perfusion vs static) conditions. We then exposed the cells to a series of anti-cancer drugs (paclitaxel, olaparib, cisplatin) and compared their responses to those in 2D cultures. Finally, we generated cisplatin dose responses in 3D cultures of breast cancer cells derived from 2 PDX models.

RESULTS

The microfluidic platform allows the simultaneous culture of 96 perfused micro tissues, using limited amounts of material, enabling drug screening of patient-derived material. 3D cell culture viability is improved by constant perfusion of the medium. Furthermore, the drug response of these triple negative breast cancer cells was attenuated by culture in 3D and differed from that observed in 2D substrates.

CONCLUSIONS

We have investigated the use of a high-throughput organ-on-a-chip platform to select therapies. Our results have raised the possibility to use this technology in personalized medicine to support selection of appropriate drugs and to predict response to therapy in a real time fashion.

High-throughput compound evaluation on 3D networks of neurons and glia in a microfluidic platform

With great advances in the field of in vitro brain modelling, the challenge is now to implement these technologies for development and evaluation of new drug candidates. Here we demonstrate a method for culturing three-dimensional networks of spontaneously active neurons and supporting glial cells in a microfluidic platform. The high-throughput nature of the platform in combination with its compatibility with all standard laboratory equipment allows for parallel evaluation of compound effects.

Improved intra-array and interarray normalization of peptide microarray phosphorylation for phosphorylome and kinome profiling by rational selection of relevant spots

Massive parallel analysis using array technology has become the mainstay for analysis of genomes and transcriptomes. Analogously, the predominance of phosphorylation as a regulator of cellular metabolism has fostered the development of peptide arrays of kinase consensus substrates that allow the charting of cellular phosphorylation events (often called kinome profiling). However, whereas the bioinformatical framework for expression array analysis is well-developed, no advanced analysis tools are yet available for kinome profiling. Especially intra-array and interarray normalization of peptide array phosphorylation remain problematic, due to the absence of “housekeeping” kinases and the obvious fallacy of the assumption that different experimental conditions should exhibit equal amounts of kinase activity. Here we describe the development of analysis tools that reliably quantify phosphorylation of peptide arrays and that allow normalization of the signals obtained. We provide a method for intraslide gradient correction and spot quality control. We describe a novel interarray normalization procedure, named repetitive signal enhancement, RSE, which provides a mathematical approach to limit the false negative results occuring with the use of other normalization procedures. Using in silico and biological experiments we show that employing such protocols yields superior insight into cellular physiology as compared to classical analysis tools for kinome profiling.

Kinome Profiling of Regulatory T Cells: A Closer Look into a Complex Intracellular Network

Regulatory T cells (Treg) are essential for T cell homeostasis and maintenance of peripheral tolerance. They prevent activation of auto-reactive T effector cells (Teff) in the context of autoimmunity and allergy. Otherwise, Treg also inhibit effective immune responses against tumors. Besides a number of Treg-associated molecules such as Foxp3, CTLA-4 or GARP, known to play critical roles in Treg differentiation, activation and function, the involvement of additional regulatory elements is suggested. Herein, kinase activities seem to play an important role in Treg fine tuning. Nevertheless, our knowledge regarding the complex intracellular signaling pathways controlling phenotype and function of Treg is still limited and based on single kinase cascades so far. To gain a more comprehensive insight into the pathways determining Treg function we performed kinome profiling using a phosphorylation-based kinome array in human Treg at different activation stages compared to Teff. Here we have determined intriguing quantitative differences in both populations. Resting and activated Treg showed an altered pattern of CD28-dependent kinases as well as of those involved in cell cycle progression. Additionally, significant up-regulation of distinct kinases such as EGFR or CK2 in activated Treg but not in Teff not only resemble data we obtained in previous studies in the murine system but also suggest that those specific molecular activation patterns can be used for definition of the activation and functional state of human Treg. Taken together, detailed investigation of kinome profiles opens the possibility to identify novel molecular mechanisms for a better understanding of Treg biology but also for development of effective immunotherapies against unwanted T cell responses in allergy, autoimmunity and cancer.

Microfluidic 3D cell culture: from tools to tissue models

The transition from 2D to 3D cell culture techniques is an important step in a trend towards better biomimetic tissue models. Microfluidics allows spatial control over fluids in micrometer-sized channels has become a valuable tool to further increase the physiological relevance of 3D cell culture by enabling spatially controlled co-cultures, perfusion flow and spatial control over of signaling gradients. This paper reviews most important developments in microfluidic 3D culture since 2012. Most efforts were exerted in the field of vasculature, both as a tissue on its own and as part of cancer models. We observe that the focus is shifting from tool building to implementation of specific tissue models. The next big challenge for the field is the full validation of these models and subsequently the implementation of these models in drug development pipelines of the pharmaceutical industry and ultimately in personalized medicine applications.

Phaseguides as tunable passive microvalves for liquid routing in complex microfluidic networks

A microfluidic passive valving platform is introduced that has full control over the stability of each valve. The concept is based on phaseguides, which are small ridges at the bottom of a channel acting as pinning barriers. It is shown that the angle between the phaseguide and the channel sidewall is a measure of the stability of the phaseguide. The relationship between the phaseguide-wall angle and the stability is characterized numerically, analytically and experimentally. Liquid routing is enabled by using multiple phaseguide with different stability values. This is demonstrated by filling complex chamber matrices. As an ultimate demonstration of control, a 400-chamber network is used as a pixel array. It is the first time that differential stability is demonstrated in the realm of passive valving. It ultimately enables microfluidic devices for massive data generation in a low-cost disposable format.

Microfluidic titer plate for stratified 3D cell culture

Human tissues and organs are inherently heterogeneous. Their functionality is determined by the interplay between different cell types, their secondary architecture, vascular system and gradients of signaling molecules and metabolites. Here we propose a stratified 3D cell culture platform, in which adjacent lanes of gels and liquids are patterned by phaseguides to capture this tissue heterogeneity. We demonstrate 3D cell culture of HepG2 hepatocytes under continuous perfusion, a rifampicin toxicity assay and co-culture with fibroblasts. 4T1 breast cancer cells are used to demonstrate invasion and aggregation models. The platform is incorporated in a microtiter plate format that renders it fully compatible with automation and high-content screening equipment. The extended functionality, ease of handling and full compatibility to standard equipment is an important step towards adoption of Organ-on-a-Chip technology for screening in an industrial setting.

Kinome profiling of non-canonical TRAIL signaling reveals RIP1-Src-STAT3-dependent invasion in resistant non-small cell lung cancer cells

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) triggers apoptosis selectively in tumor cells through interaction with TRAIL-R1/DR4 or TRAIL-R2/DR5 and this process is considered a promising avenue for cancer treatment. TRAIL resistance, however, is frequently encountered and hampers anti-cancer activity. Here we show that whereas H460 non-small cell lung cancer (NSCLC) cells display canonical TRAIL-dependent apoptosis, A549 and SW1573 NSCLC cells are TRAIL resistant and display pro-tumorigenic activity, in particular invasion, following TRAIL treatment. We exploit this situation to contrast TRAIL effects on the kinome of apoptosis-sensitive cells to that of NSCLC cells in which non-canonical effects predominate, employing peptide arrays displaying 1024 different kinase pseudosubstrates more or less comprehensively covering the human kinome. We observed that failure of a therapeutic response to TRAIL coincides with the activation of a non-canonical TRAIL-induced signaling pathway involving, amongst others, Src, STAT3, FAK, ERK and Akt. The use of selective TRAIL variants against TRAIL-R1 or TRAIL-R2 subsequently showed that this non-canonical migration and invasion is mediated through TRAIL-R2. Short-hairpin-mediated silencing of RIP1 kinase prevented TRAIL-induced Src and STAT3 phosphorylation and reduced TRAIL-induced migration and invasion of A549 cells. Inhibition of Src or STAT3 by shRNA or chemical inhibitors including dasatinib and 5,15-diphenylporphyrin blocked TRAIL-induced invasion. FAK, AKT and ERK were activated in a RIP1-independent way and inhibition of AKT sensitized A549 cells to TRAIL-induced apoptosis. We thus identified RIP1-dependent and -independent non-canonical TRAIL kinase cascades in which Src and AKT are instrumental and could be exploited as co-targets in TRAIL therapy for NSCLC.

Roscovitine blocks leukocyte extravasation by inhibition of cyclin-dependent kinases 5 and 9

BACKGROUND AND PURPOSE

Roscovitine, a cyclin-dependent kinase (CDK) inhibitor that induces tumour cell death, is under evaluation as an anti-cancer drug. By triggering leukocyte apoptosis, roscovitine can also enhance the resolution of inflammation. Beyond death-inducing properties, we tested whether roscovitine affects leukocyte-endothelial cell interaction, a vital step in the onset of inflammation.

EXPERIMENTAL APPROACH

Leukocyte-endothelial cell interactions were evaluated in venules of mouse cremaster muscle, using intravital microscopy. In primary human endothelial cells, we studied the influence of roscovitine on adhesion molecules and on the nuclear factor-κB (NF-κB) pathway. A cellular kinome array, in vitro CDK profiling and RNAi methods were used to identify targets of roscovitine.

KEY RESULTS

In vivo, roscovitine attenuated the tumour necrosis factor-α (TNF-α)-induced leukocyte adherence to and transmigration through, the endothelium. In vitro, roscovitine strongly inhibited TNF-α-evoked expression of endothelial adhesion molecules (E-selectin, intercellular cell adhesion molecule, vascular cell adhesion molecule). Roscovitine blocked NF-κB-dependent gene transcription, but not the NF-κB activation cascade [inhibitor of κB (IκB) kinase activity, IκB-α degradation, p65 translocation]. Using a cellular kinome array and an in vitro CDK panel, we found that roscovitine inhibited protein kinase A, ribosomal S6 kinase and CDKs 2, 5, 7 and 9. Experiments using kinase inhibitors and siRNA showed that the decreased endothelial activation was due solely to blockade of CDK5 and CDK9 by roscovitine.

CONCLUSIONS AND IMPLICATIONS

Our study highlights a novel mode of action for roscovitine, preventing endothelial activation and leukocyte-endothelial cell interaction by inhibition of CDK5 and 9. This might expand its usage as a promising anti-inflammatory compound.

Monitoring selectivity in kinase-promoted phosphorylation of densely packed peptide monolayers using label-free electrochemical detection

This paper describes remarkably high sensitivities in the label-free detection of kinase-promoted phosphorylation for 14 different peptide substrates on electrode-immobilized monolayers (gold or nitride) using serine/threonine kinases PKA, PKC, and CaMK2. Peptide substrates were preselected using (33)P-labeling in a microarray of 1024 substrates. The three most active peptides (A1-A3, C1-C3, and M1-M3) were investigated using electrochemical impedance spectroscopy (EIS) and ion-sensitive field effect transistors (ISFETs). Some of the peptide substrates, for example, the PKC-specific substrate PPRRSSIRNAH (C1), showed a remarkably high sensitivity in the EIS-based sensor measurements. Our studies revealed that this high sensitivity is primarily due to the monolayer's packing density. Nanoscopic studies demonstrated a distinct disordering of the C1-monolayer upon phosphorylation, while phosphatase-promoted dephosphorylation regenerated the highly ordered peptide monolayer. As a matter of fact, the initial surface packing of the peptide monolayer mainly determined the level of sensitivity, whereas electrostatic repulsion of the redox-active species was found to be much less important.

Abstract 1941: TRAIL-induced kinase activation in Non small cell lung cancer cells

Non-small cell lung cancer (NSCLC) is a disease with poor prognosis and novel therapeutic approaches are greatly needed. Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is an interesting agent that is able to trigger apoptosis through interactions with TRAIL receptors. An important feature of TRAIL is its ability to induce apoptosis in a wide variety of tumors without harming normal cells, making it an attractive anti-cancer therapeutic compared to conventional anti-cancer agents. However, TRAIL is also able to activate signaling pathways that are involved in survival, proliferation and migration of tumor cells. Thus, TRAIL-based therapies combined with inhibitors of such pathways are expected to enhance therapeutic benefit.

In this study, we aimed to identify and characterize kinases that are activated by recombinant TRAIL in NSCLC cells. We monitored the activation of a number of kinases known to be involved in TRAIL signaling by Western blotting, including p38 MAPK, JNK, ERK and Akt. In addition we employed PepChip kinase arrays. With these arrays 1024 peptide kinase substrates can be screened in one experiment, whereby a comparison of kinase patterns between untreated and treated cells can be obtained.

NSCLC, H460 and A549 cell lines, which are sensitive and resistant for TRAIL, respectively, were exposed to 50 ng/ml TRAIL for different periods of time (5 to 240 minutes) to evaluate the kinetics of kinase activation. In H460 cells, TRAIL induced the phosphorylation of p38 MAPK after 2 hours and JNK1/2 after 3 hours. As the activation of these kinases can be both anti- and pro-apoptotic, kinase inhibitors were used to explore this further. In H460 cells the activation of JNK, ERK and Akt had anti-apoptotic activity. Inhibition of these kinases with SP600125, PD098059, and LY294002, respectively, showed a 2-fold increase in apoptosis when combined with TRAIL. The activation of MAPK p38 on the other hand was pro-apoptotic, since its inhibition with SB203580 resulted in a reduction of TRAIL-induced apoptosis in H460 cells. In resistant A549 cells, however, Akt, ERK, p38 MAPK, and JNK1/2 activation appeared to have anti-apoptotic activity. Furthermore, in these cells an increase in IκBα phosphorylation was observed that was not seen in H460 cells, where levels of phosphorylated IκBα decreased after 1 hour that correlated with cleavage of RIP. Thus suppression of NFκB activation could be associated with TRAIL sensitivity. PepChip kinase arrays, revealed the activation of kinases that are involved in cell migration, such as Rho/Rock in A549 cells, and further investigations are ongoing. In conclusion, we observed differential TRAIL-dependent activation of p38 MAPK, JNK1/2, ERK, Akt and IκBα in sensitive and resistant NSCLC cells as well as in pathways that regulate migration. The relationship with TRAIL antitumor activity is currently further explored.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1941. doi:10.1158/1538-7445.AM2011-1941

Multiple reaction monitoring assay for pre-eclampsia related calcyclin peptides in formalin fixed paraffin embedded placenta

Although the cause of pre-eclampsia during pregnancy has not been elucidated yet, it is evident that placental and maternal endothelial dysfunction is involved. We previously demonstrated that in early onset pre-eclampsia placental calcyclin (S100A6) expression is significantly higher compared to controls ( De Groot , C. J. ; Clin. Proteomics 2007 , 1 , 325 ). In the current study, the results were confirmed and relatively quantified by using multiple reaction monitoring (MRM) on two peptide fragments of calcyclin. Cells were obtained from control (n = 5) and pre-eclamptic placental (n = 5) tissue collected by laser capture microdissection from formalin-fixed paraffin-embedded (FFPE) material treated with a solution to reverse formalin fixation. Two calcyclin peptides with an extra glycine inserted in the middle of the amino acid sequence were synthesized and used as an internal reference. Data presented show that MRM on laser microdissected material from FFPE tissue material is possible. The developed MRM assay to study quantitative levels of proteins in FFPE laser microdissected cells using nonisotopic-labeled chemical analogs of mass tagged internal references showed that in pre-eclamptic patients elevated levels of calcyclin is observed in placental trophoblast cells compared to normal trophoblast cells. By immunohistochemistry, we were able to confirm this observation in a qualitative manner.

Identification of Novel Phosphorylation Motifs Through an Integrative Computational and Experimental Analysis of the Human Phosphoproteome

Protein phosphorylation occurs in certain sequence/structural contexts that are still incompletely understood. The amino acids surrounding the phosphorylated residues are important in determining the binding of the kinase to the protein sequence. Upon phosphorylation these sequences also determine the binding of certain domains that specifically bind to phosphorylated sequences. Thus far, such 'motifs' have been identified through alignment of a limited number of well identified kinase substrates. RESULTS: Experimentally determined phosphorylation sites from Human Protein Reference Database were used to identify 1,167 novel serine/threonine or tyrosine phosphorylation motifs using a computational approach. We were able to statistically validate a number of these novel motifs based on their enrichment in known phosphopeptides datasets over phosphoserine/threonine/tyrosine peptides in the human proteome. There were 299 novel serine/threonine or tyrosine phosphorylation motifs that were found to be statistically significant. Several of the novel motifs that we identified computationally have subsequently appeared in large datasets of experimentally determined phosphorylation sites since we initiated our analysis. Using a peptide microarray platform, we have experimentally evaluated the ability of casein kinase I to phosphorylate a subset of the novel motifs discovered in this study. Our results demonstrate that it is feasible to identify novel phosphorylation motifs through large phosphorylation datasets. Our study also establishes peptide microarrays as a novel platform for high throughput kinase assays and for the validation of consensus motifs. Finally, this extended catalog of phosphorylation motifs should assist in a systematic study of phosphorylation networks in signal transduction pathways.

Flavopiridol protects against inflammation by attenuating leukocyte-endothelial interaction via inhibition of cyclin-dependent kinase 9

OBJECTIVE

The cyclin-dependent kinase (CDK) inhibitor flavopiridol is currently being tested in clinical trials as anticancer drug. Beyond its cell death-inducing action, we hypothesized that flavopiridol affects inflammatory processes. Therefore, we elucidated the action of flavopiridol on leukocyte-endothelial cell interaction and endothelial activation in vivo and in vitro and studied the underlying molecular mechanisms.

METHODS AND RESULTS

Flavopiridol suppressed concanavalin A-induced hepatitis and neutrophil infiltration into liver tissue. Flavopiridol also inhibited tumor necrosis factor-α-induced leukocyte-endothelial cell interaction in the mouse cremaster muscle. Endothelial cells were found to be the major target of flavopiridol, which blocked the expression of endothelial cell adhesion molecules (intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and E-selectin), as well as NF-κB-dependent transcription. Flavopiridol did not affect inhibitor of κB (IκB) kinase, the degradation and phosphorylation of IκBα, nuclear translocation of p65, or nuclear factor-κB (NF-κB) DNA-binding activity. By performing a cellular kinome array and a kinase activity panel, we found LIM domain kinase-1 (LIMK1), casein kinase 2, c-Jun N-terminal kinase (JNK), protein kinase C (PKC), CDK4, CDK6, CDK8, and CDK9 to be influenced by flavopiridol. Using specific inhibitors, as well as RNA interference (RNAi), we revealed that only CDK9 is responsible for the action of flavopiridol.

CONCLUSIONS

Our study highlights flavopiridol as a promising antiinflammatory compound and inhibition of CDK9 as a novel approach for the treatment of inflammation-associated diseases.

Abstract 1261: TRAIL-induced pro- and antiapoptotic kinase activation in non-small cell lung cancer cells

Non-small cell lung cancer (NSCLC) is a disease with poor prognosis and novel therapeutic approaches are greatly needed. Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) belongs to the TNF gene superfamily and it mediates its apoptotic function through interaction with the death receptors, DR4 and DR5. An important feature of TRAIL is its ability to induce apoptosis in a wide variety of tumors without harming normal cells, making it an attractive anti-cancer therapeutic compared to conventional anti-cancer agents. However, TRAIL is also able to activate signaling pathways that are implicated in cell survival and cell proliferation, counteracting its death-inducing effects. Thus, TRAIL-based therapies combined with inhibitors of pro-survival signals are expected to have beneficial therapeutic effects.

In this study, we examined the pro-survival signaling induced by recombinant TRAIL in NSCLC cells. We monitored the activation of a number of kinases known to be involved in TRAIL signaling by Western blotting, including p38 MAPK, JNK, ERK and Akt. In addition we employed PepChip kinase arrays. With these arrays 1024 peptide kinase substrates can be screened in one experiment, whereby a comparison of kinase patterns between untreated and treated cells can be obtained.

H460 and A549 NSCLC cell lines, which are sensitive and resistant for TRAIL, respectively, were exposed to 50 ng/ml TRAIL for different periods of time (5, 10, 15, 30, 60, 120, 180, 240 minutes) to evaluate the kinetics of the kinases. In H460 cells, TRAIL phosphorylated p38 MAPK after 2 hours and JNK1/2 after 3 hours. As the activation of these kinases can be both anti- and pro-apoptotic, kinase inhibitors were used to explore this further. In H460 cells the activation of JNK, ERK and Akt had anti-apoptotic activity. Inhibition of these kinases with SP600125, PD098059, and LY294002, respectively, showed a 2 fold increase in apoptosis when combined with TRAIL. The activation of MAPK p38 on the other hand was pro-apoptotic, since its inhibition with SB203580 resulted in a reduction of TRAIL-induced apoptosis in H460 cells. In resistant A549 cells, however, Akt, ERK, p38 MAPK, and JNK1/2 activation appeared to have anti-apoptotic activity. Furthermore, in these cells an increase in IκBα phosphorylation was observed that was not seen in H460 cells, where levels of phosphorylated IκBα decreased after 1 hour that correlated with cleavage of RIP. Thus reduction of NFκB activation could be associated with TRAIL sensitivity. Additional experiments, including the PepChip kinase arrays, are ongoing to further examine the involvement of these and other kinases in TRAIL sensitivity and for possible use in sensitization strategies. In conclusion, we observed differential TRAIL-dependent activation of p38 MAPK, JNK1/2, ERK, Akt and IκBα in sensitive and resistant NSCLC cells and the relationship with TRAIL sensitivity is currently further explored.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1261.

Comparison of peptide array substrate phosphorylation of c-Raf and mitogen activated protein kinase kinase kinase 8

Kinases are pivotal regulators of cellular physiology. The human genome contains more than 500 putative kinases, which exert their action via the phosphorylation of specific substrates. The determinants of this specificity are still only partly understood and as a consequence it is difficult to predict kinase substrate preferences from the primary structure, hampering the understanding of kinase function in physiology and prompting the development of technologies that allow easy assessment of kinase substrate consensus sequences. Hence, we decided to explore the usefulness of phosphorylation of peptide arrays comprising of 1176 different peptide substrates with recombinant kinases for determining kinase substrate preferences, based on the contribution of individual amino acids to total array phosphorylation. Employing this technology, we were able to determine the consensus peptide sequences for substrates of both c-Raf and Mitogen Activated Protein Kinase Kinase Kinase 8, two highly homologous kinases with distinct signalling roles in cellular physiology. The results show that although consensus sequences for these two kinases identified through our analysis share important chemical similarities, there is still some sequence specificity that could explain the different biological action of the two enzymes. Thus peptide arrays are a useful instrument for deducing substrate consensus sequences and highly homologous kinases can differ in their requirement for phosphorylation events.