Functionally-instructed modifiers of response to ATR inhibition in experimental glioma

BACKGROUND

The DNA damage response (DDR) is a physiological network preventing malignant transformation, e.g. by halting cell cycle progression upon DNA damage detection and promoting DNA repair. Glioblastoma are incurable primary tumors of the nervous system and DDR dysregulation contributes to acquired treatment resistance. Therefore, DDR targeting is a promising therapeutic anti-glioma strategy. Here, we investigated Ataxia telangiectasia and Rad3 related (ATR) inhibition (ATRi) and functionally-instructed combination therapies involving ATRi in experimental glioma.

METHODS

We used acute cytotoxicity to identify treatment efficacy as well as RNAseq and DigiWest protein profiling to characterize ATRi-induced modulations within the molecular network in glioma cells. Genome-wide CRISPR/Cas9 functional genomic screens and subsequent validation with functionally-instructed compounds and selected shRNA-based silencing were employed to discover and investigate molecular targets modifying response to ATRi in glioma cell lines in vitro, in primary cultures ex vivo and in zebrafish and murine models in vivo.

RESULTS

ATRi monotherapy displays anti-glioma efficacy in vitro and ex vivo and modulates the molecular network. We discovered molecular targets by genome-wide CRISPR/Cas9 loss-of-function and activation screens that enhance therapeutic ATRi effects. We validated selected druggable targets by a customized drug library and functional assays in vitro, ex vivo and in vivo.

CONCLUSION

In conclusion, our study leads to the identification of novel combination therapies involving ATRi that could inform future preclinical studies and early phase clinical trials.

Breast cancer patient-derived microtumors resemble tumor heterogeneity and enable protein-based stratification and functional validation of individualized drug treatment

Despite tremendous progress in deciphering breast cancer at the genomic level, the pronounced intra- and intertumoral heterogeneity remains a major obstacle to the advancement of novel and more effective treatment approaches. Frequent treatment failure and the development of treatment resistance highlight the need for patient-derived tumor models that reflect the individual tumors of breast cancer patients and allow a comprehensive analyses and parallel functional validation of individualized and therapeutically targetable vulnerabilities in protein signal transduction pathways. Here, we introduce the generation and application of breast cancer patient-derived 3D microtumors (BC-PDMs). Residual fresh tumor tissue specimens were collected from n = 102 patients diagnosed with breast cancer and subjected to BC-PDM isolation. BC-PDMs retained histopathological characteristics, and extracellular matrix (ECM) components together with key protein signaling pathway signatures of the corresponding primary tumor tissue. Accordingly, BC-PDMs reflect the inter- and intratumoral heterogeneity of breast cancer and its key signal transduction properties. DigiWest®-based protein expression profiling of identified treatment responder and non-responder BC-PDMs enabled the identification of potential resistance and sensitivity markers of individual drug treatments, including markers previously associated with treatment response and yet undescribed proteins. The combination of individualized drug testing with comprehensive protein profiling analyses of BC-PDMs may provide a valuable complement for personalized treatment stratification and response prediction for breast cancer.

Abstract 44: An in vivo platform of pre-characterized renal cell carcinoma (RCC) patient-derived xenograft models allows the preclinical evaluation of patient-tailored intervention strategies

Renal cell carcinoma (RCC), is the most common kidney cancer of adults, originating in the lining of the proximal convoluted tubule. Prognosis is poor in patients with advanced or metastasized RCC. Drug resistance towards Standard of Care (SoC, incl. everolimus, sorafenib, or sunitinib) drugs develops frequently within months. Therefore, development of novel options to target acquired TKI resistance mechanisms in advanced and metastatic RCC is still an urgent medical need. Preclinical models with high translational relevance can promote the implementation of novel personalized therapies. To evaluate novel targeted therapies and their combinations in preclinical settings, patient-derived xenograft (PDX) models represent valuable tools. Responsible local ethics committees approved usage of patient tissue and all animal procedures. In this study, RCC tissue from 167 patients was collected and xenotransplanted in mice. Partially, a multi-region approach, xenografting tissue from different regions of one tumor, was used. PDX models were characterized by immunohistochemistry (Ki-67, CD31, Pax2 and Pax8 antibodies), gene expression, copy number variations and mutational analyses. To evaluate in vivo drug response of RCC PDX models, mice transplanted with PDX tumors were treated with bevacizumab (i.p.), with everolimus, sorafenib, or sunitinib (p.o.). Adopted clinical response criteria for solid tumors (RECIST) were applied to classify the anti-tumor activity of the tested compounds in RCC PDX models. Next generation sequencing (NGS, panel) and transcriptome data were used to compare primary tumors and metastases. A comprehensive panel of subcutaneous RCC PDX models with well-conserved molecular and pathological features over multiple passages was established. The overall take for the RCC PDX in this study was 21%. Tumor growth characteristics were heterogeneous throughout the different models but were stable during in vivo passaging. Drug screening towards four SoC drugs, targeting the VEGF and PI3K/mTOR pathway, revealed individual and heterogeneous response profiles in the PDX, resembling the clinical situation. Intra-tumor heterogeneity can be assessed via PDX models from multi-tumor regions from one patient in our platform. Development of corresponding in vitro cell culture models from the PDX enables advanced high throughput drug screening in a personalized context. Analyzing novel targeted molecules is possible due to the pre-established molecular characterization of the PDX at the genomic and expression level. In conclusion, we established a new and molecularly characterized panel of RCC PDX models with high relevance for translational preclinical research.

Citation Format: Dennis Kobelt, Dennis Gürgen, Michael Becker, Mathias Dahlmann, Susanne Flechsig, Elke Schaeffeler, Florian A. Büttner, Christian Schmees, Regina Bohnert, Jens Bedke, Matthias Schwab, Johann J. Wendler, Martin Schostak, Burkhard Jandrig, Wolfgang Walther, Jens Hoffmann. An in vivo platform of pre-characterized renal cell carcinoma (RCC) patient-derived xenograft models allows the preclinical evaluation of patient-tailored intervention strategies [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 44.

Generation and characterization of three induced pluripotent stem cells lines from an 86-year old female individual diagnosed with an invasive lobular mammary carcinoma

Invasive lobular carcinoma (ILC) is a distinct type of breast cancer and is accounting up to 10-15 % of all mammary carcinomas showing a pronounced increase in incidence rates over the last two decades. We generated three induced pluripotent stem cell (iPSC) lines from CD34+ progenitor cells isolated from a mammary carcinoma patient diagnosed with ILC. Here, we describe the characterization of the iPSCs by array-based comparative genomic hybridization (array CGH), immunocytochemistry, flow cytometry, reverse transcriptase polymerase chain reaction and directed in vitro differentiation. The iPSC lines will find application in the field of breast cancer research.

Protein Profiling of Breast Carcinomas Reveals Expression of Immune-Suppressive Factors and Signatures Relevant for Patient Outcome

In cancer, the complex interplay between tumor cells and the tumor microenvironment results in the modulation of signaling processes. By assessing the expression of a multitude of proteins and protein variants in cancer tissue, wide-ranging information on signaling pathway activation and the status of the immunological landscape is obtainable and may provide viable information on the treatment response. Archived breast cancer tissues from a cohort of 84 patients (no adjuvant therapy) were analyzed by high-throughput Western blotting, and the expression of 150 proteins covering central cancer pathways and immune cell markers was examined. By assessing CD8α, CD11c, CD16 and CD68 expression, immune cell infiltration was determined and revealed a strong correlation between event-free patient survival and the infiltration of immune cells. The presence of tumor-infiltrating lymphocytes was linked to the pronounced activation of the Jak/Stat signaling pathway and apoptotic processes. The elevated phosphorylation of PPARγ (pS112) in non-immune-infiltrated tumors suggests a novel immune evasion mechanism in breast cancer characterized by increased PPARγ phosphorylation. Multiplexed immune cell marker assessment and the protein profiling of tumor tissue provide functional signaling data facilitating breast cancer patient stratification.

Establishment of Four Induced Pluripotent Stem Cell Lines from CD34+ Hematopoietic Stem and Progenitor Cells from a Patient Diagnosed with an Invasive Lobular Mammary Carcinoma

CD34+ cells were isolated from peripheral blood of a breast cancer patient. By the introduction of five integration-free episomal vectors, the CD34+ cells were successfully reprogrammed and resulted in four iPSC clones. Flow Cytometry, reverse transcriptase PCR and immunocytochemistry confirm a robust expression of pluripotency factors and the concomitant loss of exogenous reprogramming plasmids. The maintenance of genomic integrity was confirmed by array-based comparative genomic hybridization and iPSCs harbored the capacity to differentiate into all three germ layers. Here, we present the generation and characterization of four iPSC lines that will find application in the field of breast cancer research.

[Patient-derived microtumors : Potential for therapeutic response prediction-a case study]

BACKGROUND

In view of continued development of new oncological approaches, there is a high demand for personalized tumor therapy. However, fast and effective functional platforms for the prediction of individual patient response to drug therapy are largely unavailable. Various promising approaches have already been described for three-dimensional cell culture models, which represent cellular complexity and almost identical structures of the original tumor tissue.

OBJECTIVES

Based on a case report, we show the capability and results of a novel test system using patient-derived microtumors (PDMs) and autologous tumor-infiltrating lymphocytes (TILs) for the prediction of response to cancer therapy.

METHODS

We established PDMs and TILs from primary tumor tissue of a renal cell carcinoma metastasis. Using immunohistochemistry and multiplex florescence-activated cell sorting (FACS ) analyses, the PDMs and TILs were characterized regarding to histology and immunophenotype. Tumor-specific cytotoxicity of standard of care and investigational compounds were assessed. The results were compared to the patient's individual in vivo response to therapy.

CONCLUSION

The cytotoxicity assay of PDMs and TILs showed a significant therapeutic response (p = 0.0004) to therapy with a programmed cell death protein 1 (PD-1) inhibitor and lenvatinib compared to the control. The in vitro results correlated positively with the in vivo data. In the future, patient-derived models could predict response to cancer therapy and may help to optimize treatment decision-making.

A Molecularly Characterized Preclinical Platform of Subcutaneous Renal Cell Carcinoma (RCC) Patient-Derived Xenograft Models to Evaluate Novel Treatment Strategies

Renal cell carcinoma (RCC) is a kidney cancer with an onset mainly during the sixth or seventh decade of the patient’s life. Patients with advanced, metastasized RCC have a poor prognosis. The majority of patients develop treatment resistance towards Standard of Care (SoC) drugs within months. Tyrosine kinase inhibitors (TKIs) are the backbone of first-line therapy and have been partnered with an immune checkpoint inhibitor (ICI) recently. Despite the most recent progress, the development of novel therapies targeting acquired TKI resistance mechanisms in advanced and metastatic RCC remains a high medical need. Preclinical models with high translational relevance can significantly support the development of novel personalized therapies. It has been demonstrated that patient-derived xenograft (PDX) models represent an essential tool for the preclinical evaluation of novel targeted therapies and their combinations. In the present project, we established and molecularly characterized a comprehensive panel of subcutaneous RCC PDX models with well-conserved molecular and pathological features over multiple passages. Drug screening towards four SoC drugs targeting the vascular endothelial growth factor (VEGF) and PI3K/mTOR pathway revealed individual and heterogeneous response profiles in those models, very similar to observations in patients. As unique features, our cohort includes PDX models from metastatic disease and multi-tumor regions from one patient, allowing extended studies on intra-tumor heterogeneity (ITH). The PDX models are further used as basis for developing corresponding in vitro cell culture models enabling advanced high-throughput drug screening in a personalized context. PDX models were subjected to next-generation sequencing (NGS). Characterization of cancer-relevant features including driver mutations or cellular processes was performed using mutational and gene expression data in order to identify potential biomarker or treatment targets in RCC. In summary, we report a newly established and molecularly characterized panel of RCC PDX models with high relevance for translational preclinical research.

Nicotinamide-N-methyltransferase is a promising metabolic drug target for primary and metastatic clear cell renal cell carcinoma

Background

The metabolic enzyme nicotinamide‐N‐methyltransferase (NNMT) is highly expressed in various cancer entities, suggesting tumour‐promoting functions. We systematically investigated NNMT expression and its metabolic interactions in clear cell renal cell carcinoma (ccRCC), a prominent RCC subtype with metabolic alterations, to elucidate its role as a drug target.

Methods

NNMT expression was assessed in primary ccRCC (n = 134), non‐tumour tissue and ccRCC‐derived metastases (n = 145) by microarray analysis and/or immunohistochemistry. Findings were validated in The Cancer Genome Atlas (kidney renal clear cell carcinoma [KIRC], n = 452) and by single‐cell analysis. Expression was correlated with clinicopathological data and survival. Metabolic alterations in NNMT‐depleted cells were assessed by nontargeted/targeted metabolomics and extracellular flux analysis. The NNMT inhibitor (NNMTi) alone and in combination with the inhibitor 2‐deoxy‐D‐glucose for glycolysis and BPTES (bis‐2‐(5‐phenylacetamido‐1,3,4‐thiadiazol‐2‐yl)ethyl‐sulfide) for glutamine metabolism was investigated in RCC cell lines (786‐O, A498) and in two 2D ccRCC‐derived primary cultures and three 3D ccRCC air–liquid interface models.

Results

NNMT protein was overexpressed in primary ccRCC (p = 1.32 × 10^–16) and ccRCC‐derived metastases (p = 3.92 × 10^–20), irrespective of metastatic location, versus non‐tumour tissue. Single‐cell data showed predominant NNMT expression in ccRCC and not in the tumour microenvironment. High NNMT expression in primary ccRCC correlated with worse survival in independent cohorts (primary RCC—hazard ratio [HR] = 4.3, 95% confidence interval [CI]: 1.5–12.4; KIRC—HR = 3.3, 95% CI: 2.0–5.4). NNMT depletion leads to intracellular glutamine accumulation, with negative effects on mitochondrial function and cell survival, while not affecting glycolysis or glutathione metabolism. At the gene level, NNMT‐depleted cells upregulate glycolysis, oxidative phosphorylation and apoptosis pathways. NNMTi alone or in combination with 2‐deoxy‐D‐glucose and BPTES resulted in inhibition of cell viability in ccRCC cell lines and primary tumour and metastasis‐derived models. In two out of three patient‐derived ccRCC air–liquid interface models, NNMTi treatment induced cytotoxicity.

Conclusions

Since efficient glutamine utilisation, which is essential for ccRCC tumours, depends on NNMT, small‐molecule NNMT inhibitors provide a novel therapeutic strategy for ccRCC and act as sensitizers for combination therapies.

Continous, non-invasive monitoring of oxygen consumption in a parallelized microfluidic in vitro system provides novel insight into the response to nutrients and drugs of primary human hepatocytes

Oxygen plays a fundamental role in cellular energy metabolism, differentiation and cell biology in general. Consequently, in vitro oxygen sensing can be used to assess cell vitality and detect specific mechanisms of toxicity. In 2D in vitro models currently used, the oxygen supply provided by diffusion is generally too low, especially for cells having a high oxygen demand. In organ-on-chip systems, a more physiologic oxygen supply can be generated by establishing unidirectional perfusion. We established oxygen sensors in an easy-to-use and parallelized organ-on-chip system. We demonstrated the applicability of this system by analyzing the influence of fructose (40 mM, 80 mM), ammonium chloride (100 mM) and Na-diclofenac (50 µM, 150 µM, 450 µM, 1500 µM) on primary human hepatocytes (PHH). Fructose treatment for two hours showed an immediate drop of oxygen consumption (OC) with subsequent increase to nearly initial levels. Treatment with 80 mM glucose, 20 mM lactate or 20 mM glycerol did not result in any changes in OC which demonstrates a specific effect of fructose. Application of ammonium chloride for two hours did not show any immediate effects on OC, but qualitatively changed the cellular response to FCCP treatment. Na-diclofenac treatment for 24 hours led to a decrease of the maximal respiration and reserve capacity. We also demonstrated the stability of our system by repeatedly treating cells with 40 mM fructose, which led to similar cell responses on the same day as well as on subsequent days. In conclusion, our system enables in depth analysis of cellular respiration after substrate treatment in an unidirectional perfused organ-on-chip system.

EXTH-48. NOVEL COMBINATION THERAPY IN PRECLINICAL GLIOMA MODELS USING THE CELL CYCLE STABILIZING COMPOUND ARGYRIN F AND CHECKPOINT INHIBITION

Glioblastoma are incurable aggressive tumors and remain a therapeutic challenge. Glioblastoma frequently harbor alterations in the retinoblastoma pathway with subsequent cell cycle abnormalities. Here, we aimed to investigate the anti-glioma activity of the cell cycle-stabilizing compound Argyrin F and its potential treatment-induced vulnerabilities to exploit possibilities for novel combination therapies. We investigated cell viability, clonogenic survival, cell cycle status and immunoblots of human and murine glioma cells treated with Argyrin F. Moreover, we established an ex vivo glioma model using residual freshly resected tissue from patients, i.e. patient-derived microtumors (PDMs). Additionally, we extracted autologous tumor infiltrating lymphocytes (TILs) to perform co-culturing experiments. We performed mass spectrometry-based immunopeptidomics and used the orthotopic syngeneic SMA560/VM/Dk glioma mouse model. Argyrin F displayed anti-glioma efficacy in glioma cell lines in vitro and in PDM models ex vivo. Moreover, Argyrin F treatment induced cell cycle arrest, reduced clonogenic survival in vitro and prolonged survival in vivo. Argyrin F-treated SMA560 glioma displayed 4.6-fold more glioma-infiltrating CD8+ T cells. We discovered a distinctive treatment-induced immunopeptidome. Combination of Argyrin F plus PD-1 antibody increased cellular toxicity in PDM/TILs co-cultures ex vivo and prolonged overall survival compared with monotherapies in vivo. We conclude that our experimental data suggest a novel combination of Argyrin F plus PD-1 blockade and its clinical translation.

Targeting CSF1R Alone or in Combination with PD1 in Experimental Glioma

Glioblastoma is an aggressive primary tumor of the central nervous system. Targeting the immunosuppressive glioblastoma-associated microenvironment is an interesting therapeutic approach. Tumor-associated macrophages represent an abundant population of tumor-infiltrating host cells with tumor-promoting features. The colony stimulating factor-1/ colony stimulating factor-1 receptor (CSF-1/CSF1R) axis plays an important role for macrophage differentiation and survival. We thus aimed at investigating the antiglioma activity of CSF1R inhibition alone or in combination with blockade of programmed death (PD) 1. We investigated combination treatments of anti-CSF1R alone or in combination with anti-PD1 antibodies in an orthotopic syngeneic glioma mouse model, evaluated post-treatment effects and assessed treatment-induced cytotoxicity in a coculture model of patient-derived microtumors (PDM) and autologous tumor-infiltrating lymphocytes (TILs) ex vivo. Anti-CSF1R monotherapy increased the latency until the onset of neurological symptoms. Combinations of anti-CSF1R and anti-PD1 antibodies led to longterm survivors in vivo. Furthermore, we observed treatment-induced cytotoxicity of combined anti-CSF1R and anti-PD1 treatment in the PDM/TILs cocultures ex vivo. Our results identify CSF1R as a promising therapeutic target for glioblastoma, potentially in combination with PD1 inhibition.

Abstract PS17-42: A fast and effective 3D preclinical assay system comprised of patient derived breast cancer microtumors combined with DigiWest protein signaling pathway analyses for therapeutic response prediction (Project PRIMO)

In the era of personalized medicine, the ability of pre-selecting individualized therapeutic options and pre-defining their suitability in advance of clinical treatment might facilitate decision making in breast cancer treatment and hence, improve patient outcome. In order to preclinically validate anti-cancer drug efficacy, it is crucial to design a model system that reveals the influence of cellular interactions of the tumor microenvironment and cellular heterogeneity on drug response. Within the PRIMO (Personalized Medicine for tailored cancer therapies) project, such a 3D preclinical model system comprised of patient-derived microtumors (PDM) and autologous tumor-infiltrating lymphocytes (TILs) isolated from fresh primary breast cancer tissue using limited digestion and subsequent culture in defined media in the absence of serum is established. Herein, the heterogeneous cellular composition of isolated PDM is analyzed by FFPE immunohistochemistry and compared to corresponding primary tumor tissue. The composition of autologous TILs influencing individual treatment responses is characterized by multi-color flow cytometry detecting different cell populations, such as tumor-specific CD8+ or regulatory CD4+ T-cells. By using the DigiWest technology, a proprietary high throughput immune assay screening tool, in-depth protein profiling of up to 200 analytes from low amounts of PDM material is performed. The generated protein profiles of PDM are compared to their corresponding primary tumor tissue as well as the pathological receptor grading. Furthermore, differences in activation of key signal transduction pathways are detected and related to treatment responses to small molecules, chemotherapeutics as well as immunotherapeutic agents within PDM and PDM-TIL co-cultures assessed by a functional viability assay in a microplate format. To expand this preclinical model system, we established PDM-co-cultures adding further immune cell types including natural killer (NK) cells or dendritic cells (DC).

In summary, immunohistochemical analyses combined with protein profiling of breast cancer PDM enables drug-mode-of-action analyses, biomarker identification together with personalized therapeutic sensitivity prediction. The platform presented here expands the preclinical repertoire of relevant test systems for efficacy testing of drugs and investigational compounds, pre-identified by protein pathways as well as genetic profiling in personalized medicine of breast cancer.

Citation Format: Nicole Anderle, Felix Ruoff, Simge Yuez, André Koch, Andreas Hartkopf, Sara Brucker, Michael Pawlak, Markus Templin, Christian Schmees. A fast and effective 3D preclinical assay system comprised of patient derived breast cancer microtumors combined with DigiWest protein signaling pathway analyses for therapeutic response prediction (Project PRIMO) [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS17-42.

HepaChip-MP - a twenty-four chamber microplate for a continuously perfused liver coculture model

HepaChip microplate (HepaChip-MP) is a microfluidic platform comprised of 24 independent culture chambers with continuous, unidirectional perfusion. In the HepaChip-MP, an automated dielectrophoresis process selectively assembles viable cells into elongated micro tissues. Freshly isolated primary human hepatocytes (PHH) and primary human liver endothelial cells (HuLEC) were successfully assembled as cocultures aiming to mimic the liver sinusoid. Minimal quantities of primary human cells are required to establish micro tissues in the HepaChip-MP. Metabolic function including induction of CYP enzymes in PHH was successfully measured demonstrating a high degree of metabolic activity of cells in HepaChip-MP cultures and sufficient sensitivity of LC-MS analysis even for the relatively small number of cells per chamber. Further, parallelization realized in HepaChip-MP enabled the acquisition of dose-response toxicity data of diclofenac with a single device. Several unique technical features should enable a widespread application of this in vitro model. We have demonstrated fully automated preparation of cell cultures in HepaChip-MP using a pipetting robot. The tubeless unidirectional perfusion system based on gravity-driven flow can be operated within a standard incubator system. Overall, the system readily integrates in workflows common in cell culture labs. Further research will be directed towards optimization of media composition to further extend culture lifetime and study oxygen gradients and their effect on zonation within the sinusoid-like microorgans. In summary, we have established a novel parallelized and scalable microfluidic in vitro liver model showing hepatocyte function and anticipate future in-depth studies of liver biology and applications in pre-clinical drug development.

Role of BCL9L in transforming growth factor-β (TGF-β)-induced epithelial-to-mesenchymal-transition (EMT) and metastasis of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) has a low overall survival rate, which is approximately 20% during the first year and decreases to less than 6% within five years of the disease. This is due to premature dissemination accompanied by a lack of disease-specific symptoms during the initial stages. Additionally, to date there are no biomarkers for an early prognosis available.A growing number of studies indicate that epithelial to mesenchymal transition (EMT), triggered by WNT-, TGF-β- and other signaling pathways is crucial for the initiation of the metastatic process in PDAC. Here we show, that BCL9L is up-regulated in PDAC cell lines and patient tissue compared to non-cancer controls. RNAi-induced BCL9L knockdown negatively affected proliferation, migration and invasion of pancreatic cancer cells. On a molecular basis, BCL9L depletion provoked an increment of E-cadherin protein levels, with concomitant increase of β-catenin retention at the plasma membrane. This is linked to the induction of a strong epithelial phenotype in pancreatic cancer cells upon BCL9L knockdown even in the presence of the EMT-inducer TGF-β. Finally, xenograft mouse models of pancreatic cancer revealed a highly significant reduction in the number of liver metastases upon BCL9L knockdown. Taken together, our findings underline the key importance of BCL9L for EMT and thus progression and metastasis of pancreatic cancer cells. Direct targeting of this protein might be a valuable approach to effectively antagonize invasion and metastasis of PDAC.

Abstract 1843: Intratumoral heterogeneity of renal cancer is related to differences in drug response and development of therapy resistance

Background:

Patients with advanced renal cell cancer (RCC) have a poor prognosis not least because of resistance towards standard drugs (SoC). Recently, pronounced intratumoral heterogeneity (ITH) in RCC was shown. We were interested whether this ITH is a potential cause for treatment failure. We developed a large panel of patient-derived xenograft (PDX) models from RCC, including subsets of models from different regions of one individual tumor. The PDX models were evaluated for response to SoC. To better understand correlations between inter- and intratumoral heterogeneity and treatment response, tumor models were panel sequenced and expression profiled.

Methods:

Specimens from primary and metastatic RCCs were collected from consenting patients and transplanted into mice. Tumor engraftment was monitored for up to 4 months. Tumor sections were examined histopathologically to assess concordance between patient tumor and model and were stained for RCC specific markers (Pax2, Pax8, CD31, and RCC). Stable growing PDX were treated with SoC (sunitinib, sorafenib, bevacizumab and everolimus). Global gene expression was analyzed in primary tumors and PDX models using microarrays (Affymetrix). In addition, sequence variations (Illumina NGS cancer panel) and MET and TERT gene copy numbers were analyzed in PDX models.

Results:

A panel of 34 RCC PDX models was established from more than 200 patient samples. Among these, 13 models were derived from different tumor regions of three advanced tumors.

Original patient tumor and PDX showed a very similar and characteristic RCC histopathology. Inter- and intratumoral heterogeneity was preserved for several passages.

We treated all PDX with standard targeted drugs and observed response rates comparable to results from clinical trials. One out of 8 regions obtained from one aggressive RCC clearly differentiated in regard to its response to bevacizumab and sunitinib. Genomic analysis revealed that this region has differences in global gene expression and sequence variation pattern. Besides a common MET mutation an additional variation in the HRAS gene was detected.

In the whole PDX set we found 34 sequence variations in 20 genes, e.g. ATM, MET, TP53 and VHL and copy number variations in the MET locus.

Conclusion:

We have shown that PDX derived from distinct regions within one individual tumor exhibit differences in targeted treatment response as well as in genetic profile. These differences and their correlation to their molecular heterogeneity is subject of ongoing investigations to explain failure in treatment response.

The available panel of renal cancer PDX provides an excellent source for translational research and for preclinical testing of new drug candidates.

Citation Format: Michael Becker, Burkhard Jandrig, Susanne Flechsig, Reiner Zeisig, Daniel Schindele, Martin Schostak, Christian Schmees, Annika Wulf-Goldenberg, Jörg Hennenlotter, Elke Schaeffeler, Matthias Schwab, Arnulf Stenzl, Jens Bedke, Jens Hoffmann. Intratumoral heterogeneity of renal cancer is related to differences in drug response and development of therapy resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1843. doi:10.1158/1538-7445.AM2017-1843

Live imaging of endogenous protein dynamics in zebrafish using chromobodies

Chromobodies are intracellular nanoprobes that combine the specificity of antibodies with the convenience of live fluorescence imaging in a flexible, DNA-encoded reagent. Here, we present the first application of this technique to an intact living vertebrate organism. We generated zebrafish lines expressing chromobodies that trace the major cytoskeletal component actin and the cell cycle marker PCNA with spatial and temporal specificity. Using these chromobodies, we captured full localization dynamics of the endogenous antigens in different cell types and at different stages of development. For the first time, the chromobody technology enables live imaging of endogenous subcellular structures in an animal, with the remarkable advantage of avoiding target protein overexpression or tagging. In combination with improved chromobody selection systems, we anticipate a rapid adaptation of this technique to new intracellular antigens and model organisms, allowing the faithful description of cellular and molecular processes in their dynamic state.

SUMMARY: Chromobodies - small, intracellular fluorescent antibodies - are used to trace endogenous antigens, without the need for direct protein tagging, in zebrafish embryos.

Abstract 1192: Establishment and characterization of a new patient-derived renal cell carcinoma xenograft panel

Objective:

Patients with advanced kidney cancer have a poor prognosis. The majority of patients develops treatment resistance towards Standard of Care (SoC) drugs within months. The successful development of novel personalized therapies depends on the availability of preclinical models with high clinical relevance. Our aim was to establish a panel of patient-derived renal cell carcinoma xenograft models for translational research.

Methods:

Specimens from primary and metastatic renal cell carcinoma tumors from consenting patients were collected after surgery and transplanted subcutaneously to immunodeficient mice within 24 hours. Tumor engraftment was followed for an initial period of up to 4 months. Successful engrafted patient-derived tumors were subsequently passaged to further mice. HE stained tumor sections were histopathologically examined to assess morphological concordance between patient tumor and PDX model. Renal cell carcinoma marker expression was determined by immunohistochemistry. Stably growing xenografts were tested for sensitivity towards SoC drugs, such as Avastin, Sunitinib, Sorafenib and Everolimus. Response to treatment was evaluated by comparing growth inhibition of treated in relation to untreated tumors. Primary tumors and the derived xenografts are currently under characterization for common oncogenic mutations using the Illumina TruSeq Amplicon Cancer Panel.

Results:

Nearly 200 tumor samples were transplanted since 2011. To date, 30% were successfully engrafted in immunodeficient mice and further patient-derived tumors are presently under establishment. Engraftment rates of samples from pT3 and pT4 tumors were higher (34%) than those from pT1 and pT2 tumors (12%). Two tumor samples which were pre-treated before surgery engrafted so far (11%). We show that specific tumor histology and renal cell carcinoma marker expression remained preserved over the passages. The drug sensitivity testings revealed a heterogeneous response to SoC treatments with Sunitinib (79% significant growth inhibition) and Everolimus (64%) as most effective treatments in the PDX models. Avastin showed a significant growth inhibition in 57% whereas Sorafenib was effective in 36% of the RCC models. We are furthermore presenting the individual gene mutation status of each RCC model.

Conclusions:

Our newly established patient-derived renal cell carcinoma panel provides a novel tool for the investigation of mechanisms of drug resistance and sensitivity in kidney cancer, biomarker research and the development of new therapeutic approaches.

Citation Format: Susanne Flechsig, Annika Wulf-Goldenberg, Christian Schmees, Burkhard Jandrig, Jörg Hennenlotter, Jens Bedke, Martin Schostak, Andrew Crockford, Marco Gerlinger, James Larkin, Charles Swanton, Zoltan Szallasi, Iduna Fichtner, Jens Hoffmann. Establishment and characterization of a new patient-derived renal cell carcinoma xenograft panel. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1192. doi:10.1158/1538-7445.AM2014-1192

Macropinocytosis of the PDGF β-receptor promotes fibroblast transformation by H-RasG12V

Fibroblast transformation by H-RasG12V induces internalization of PDGFRβ by macropinocytosis, enhancing its signaling activity and increasing anchorage-independent proliferation. It is proposed that H-Ras transformation promotes tumor progression by enhancing growth factor receptor signaling through increased receptor macropinocytosis.

Receptor tyrosine kinase (RTK) signaling is frequently increased in tumor cells, sometimes as a result of decreased receptor down-regulation. The extent to which the endocytic trafficking routes can contribute to such RTK hyperactivation is unclear. Here, we show for the first time that fibroblast transformation by H-RasG12V induces the internalization of platelet-derived growth factor β-receptor (PDGFRβ) by macropinocytosis, enhancing its signaling activity and increasing anchorage-independent proliferation. H-RasG12V transformation and PDGFRβ activation were synergistic in stimulating phosphatidylinositol (PI) 3-kinase activity, leading to receptor macropinocytosis. PDGFRβ macropinocytosis was both necessary and sufficient for enhanced receptor activation. Blocking macropinocytosis by inhibition of PI 3-kinase prevented the increase in receptor activity in transformed cells. Conversely, increasing macropinocytosis by Rabankyrin-5 overexpression was sufficient to enhance PDGFRβ activation in nontransformed cells. Simultaneous stimulation with PDGF-BB and epidermal growth factor promoted macropinocytosis of both receptors and increased their activation in nontransformed cells. We propose that H-Ras transformation promotes tumor progression by enhancing growth factor receptor signaling as a result of increased receptor macropinocytosis.

Activation of protein kinase C alpha is necessary for sorting the PDGF beta-receptor to Rab4a-dependent recycling

Previous studies showed that loss of the T-cell protein tyrosine phosphatase (TC-PTP) induces Rab4a-dependent recycling of the platelet-derived growth factor (PDGF) beta-receptor in mouse embryonic fibroblasts (MEFs). Here we identify protein kinase C (PKC) alpha as the critical signaling component that regulates the sorting of the PDGF beta-receptor at the early endosomes. Down-regulation of PKC abrogated receptor recycling by preventing the sorting of the activated receptor into EGFP-Rab4a positive domains on the early endosomes. This effect was mimicked by inhibition of PKCalpha, using myristoylated inhibitory peptides or by knockdown of PKCalpha with shRNAi. In wt MEFs, short-term preactivation of PKC by PMA caused a ligand-induced PDGF beta-receptor recycling that was dependent on Rab4a function. Together, these observations demonstrate that PKC activity is necessary for recycling of ligand-stimulated PDGF beta-receptor to occur. The sorting also required Rab4a function as it was prevented by expression of EGFP-Rab4aS22N. Preventing receptor sorting into recycling endosomes increased the rate of receptor degradation, indicating that the sorting of activated receptors at early endosomes directly regulates the duration of receptor signaling. Activation of PKC through the LPA receptor also induced PDGF beta-receptor recycling and potentiated the chemotactic response to PDGF-BB. Taken together, our present findings indicate that sorting of PDGF beta-receptors on early endosomes is regulated by sequential activation of PKCalpha and Rab4a and that this sorting step could constitute a point of cross-talk with other receptors.

Inhibition of T-cell proliferation by Helicobacter pylori gamma-glutamyl transpeptidase

BACKGROUND & AIMS

Helicobacter pylori colonizes the human gastric mucosa of >50% of the world's population. Most of the patients have no overt clinical symptoms. However, the infection is invariably associated with the development of active chronic gastritis, leading in some cases to the development of peptic ulcer disease, distal gastric adenocarcinoma, and mucosa-associated lymphoid tissue lymphoma. In contrast to most other pathogens, infection with H pylori persists lifelong, but reasons for the persistence remain obscure. CD4-positive T cells are crucial for bacterial elimination but are inhibited by H pylori. We aimed to identify the factor responsible for suppression of T-cell response and characterize this inhibitory effect on a cellular and molecular level.

METHODS

Using size-exclusion chromatography, sodium dodecyl sulfate/polyacrylamide gel electrophoresis, and a spectrophotometric enzyme assay, we identified the secreted gamma-glutamyl transpeptidase of H pylori (HPGGT) as the factor responsible for inhibition of T-cell proliferation.

RESULTS

Mutagenesis of HPGGT in different H pylori strains completely abrogated this inhibitory effect. Recombinantly expressed HPGGT protein showed full antiproliferative activity. Site-directed mutagenesis and application of the GGT inhibitor acivicin revealed that inhibition of T cells depends on catalytic activity of HPGGT. Cell cycle analysis of human T cells indicated that HPGGT was necessary and sufficient to induce G(1) arrest. Reduced levels of c-Myc and phosphorylated c-Raf protein suggest the disruption of Ras-dependent signaling by HPGGT.

CONCLUSIONS

GGT is a novel immunosuppressive factor of H pylori inhibiting T-cell proliferation by induction of a cell cycle arrest in the G(1) phase.

VacA-associated inhibition of T-cell function: reviewed and reconsidered

Chronic Helicobacter pylori infection is characterized by dense infiltration of the mucosa with neutrophilic granulocytes, lymphocytes, and monocytes/macrophages. Among these different cell types, T-lymphocytes are the most intriguing and crucial cells for the elimination of the bacteria. Previous studies have elucidated possible mechanisms on how bacteria could interfere with the human immune response and claimed that especially the secreted vacuolating toxin VacA may be responsible for the chronic persistence of the bacteria. Some of these results have to be interpreted with caution and may just describe in vitro phenomena; others may reveal promising facts.

A secreted low-molecular-weight protein from Helicobacter pylori induces cell-cycle arrest of T cells

BACKGROUND & AIMS

Although Helicobacter pylori is recognized by the human immune system, the bacteria are not eliminated and lead to a chronic inflammation of the gastric mucosa.

METHODS

We investigated the interaction of H. pylori with human lymphocytes. T and B lymphocytes were isolated from H. pylori-infected patients and stimulated with anti-CD3/CD28 or interleukin-6.

RESULTS

Proliferation of lymphocytes was abolished on co-incubation with different H. pylori strains (1-5 bacteria/cell) or with protein extracts of culture supernatants. Inhibition of proliferation was independent of known virulence factors. The factor is a protein or protein complex with an apparent molecular weight between 30 and 60 kilodaltons, clearly distinct from VacA. Although antigen-specific activation of T cells (as shown by nuclear factor of activated T cells [NFAT]-activation, interferon-gamma production, and CD25 or CD69 up-regulation) remained intact, cell-cycle analysis showed that S-phase entry of T cells was inhibited completely by H. pylori. Consequently, stimulated T cells arrested in the G1 phase of the cell cycle. Western blot analysis showed markedly reduced phosphorylation of the retinoblastoma protein (pRb), suggesting inhibition of G1 cyclin-dependent kinase activity. In line with this, activities of cyclin D3 and cyclin E were down-regulated, and levels of the cyclin-dependent kinase inhibitor p27Kip1 were increased. Mouse embryonic fibroblasts deficient in p27 showed a decrease in H. pylori-induced inhibition of cell proliferation, suggesting a central role for p27 in mediating H. pylori-induced G1 arrest.

CONCLUSIONS

Induction of cell-cycle arrest in lymphocytes may be of major significance for the chronic persistence of bacteria in the human stomach.

Alterations of the nailfold capillary morphology associated with Raynaud phenomenon in patients with systemic lupus erythematosus

Quantitative analysis of nailfold capillary morphology was performed in age and sex matched groups of 29 patients with systemic lupus erythematosus (SLE) presenting Raynaud phenomenon (RP), 29 RP negative patients with SLE with the same duration of the disease, and 29 healthy controls. Percentages of tortuous, meandering and bushy capillaries were significantly increased in both groups of patients without influence of RP. Capillary density was lower, mean diameters of the capillary loops were higher in patients, especially when RP was present (at the venular branch in microns, mean +/- SD: controls: 15.0 +/- 2.0, RP negative patients with SLE: 17.6 +/- 3.6, RP positive patients with SLE: 20.5 +/- 6.3). In a subgroup of 13 patients with frequent Raynaud's attacks (more than 1/week), diameters were still higher (22.1 +/- 7.1, p to controls less than 0.0005; p to RP negative patients less than 0.05). In patients with SLE, the prevalence of RP seems not to be associated with the increased number of abnormal capillaries but with capillary enlargement, correlating with the frequency of attacks.