Patient-derived Cell Cultures Research Articles

Establishment, characterization, and genetic profiling of patient-derived osteosarcoma cells from a patient with retinoblastoma

Osteosarcoma is the most common malignant bone cancer in pediatric patients. Patients who respond poorly to chemotherapy experience worse clinical outcomes with a high mortality rate. The major challenge is the lack of effective drugs for these patients. To introduce new drugs for clinical approval, preclinical studies based on in vitro models must demonstrate the potency of the tested drugs, enabling the drugs to enter phase 1 clinical trials. Patient-derived cell culture is a promising testing platform for in vitro studies, as they more accurately recapitulate cancer states and genetic profiles compared to cell lines. In the present study, we established patient-derived osteosarcoma cells (PDC) from a patient who had previously been diagnosed with retinoblastoma. We identified a new variant of a germline mutation in the RB1 gene in the tissue of the patient. The biological effects of this PDC were studied to observe whether the cryopreserved PDC retained a feature of fresh PDC. The cryopreserved PDC preserved the key biological effects, including cell growth, invasive capability, migration, and mineralization, that define the conserved phenotypes compared to fresh PDC. From whole genome sequencing analysis of osteosarcoma tissue and patient-derived cells, we found that cryopreserved PDC was a minor population in the origin tissue and was selectively grown under the culture conditions. The cryopreserved PDC has a high resistance to conventional chemotherapy. This study demonstrated that the established cryopreserved PDC has the aggressive characteristics of osteosarcoma, in particular the chemoresistance phenotype that might be used for further investigation in the chemoresistant mechanism of osteosarcoma. In conclusion, the approach we applied for primary cell culture might be a promising method to generate in vitro models for functional testing of osteosarcoma.

Methods for assessing and removing non-specific photoimmunotherapy damage in patient-derived tumor cell culture models.

Tumor-targeted, activatable photoimmunotherapy (taPIT) has been shown to selectively destroy tumor in a metastatic mouse model. However, the photoimmunoconjugate (PIC) used for taPIT includes a small fraction of non-covalently associated (free) benzoporphyrin derivative (BPD), which leads to non-specific killing invitro. Here, we report a new treatment protocol for patient-derived primary tumor cell cultures ultrasensitive to BPD photodynamic therapy (BPD-PDT). Based on free BPD efflux dynamics, the updated invitro taPIT protocol precludes non-specific BPD-PDT by silencing the effect of free BPD. Following incubation with PIC, incubating cells with PIC-free medium allows time for expulsion of free BPD whereas BPD covalently bound to PIC fragments is retained. Administration of the light dose after the intracellular free BPD drops below the threshold for inducing cell death helps to mitigate non-specific damage. In this study, we tested two primary ovarian tumor cell lines that are intrinsically chemoresistant, yet ultrasensitive to BPD-PDT such that small amounts of free BPD (afew percent of the total BPD dose) lead to potent induction of cell death upon irradiation. The modifications in the protocol suggested here improve invitro taPIT experiments that lack invivo mechanisms of free BPD clearance (i.e., lymph and blood flow).

The heterogeneous sensitivity of pediatric brain tumors to different oncolytic viruses is predicted by unique gene expression profiles

Despite decades of research, the prognosis of high-grade pediatric brain tumors (PBTs) remains dismal, however, recent cases of favorable clinical responses were documented in clinical trials using oncolytic viruses (OVs). In the current study, we employed four different species of OVs: adenovirus Delta24-RGD, herpes simplex virus rQNestin34.5v1, reovirus R124 and the non-virulent Newcastle Disease Virus rNDV-F0-GFP against three entities of PBTs (high-grade gliomas, atypical teratoid/rhabdoid tumors and ependymomas) to determine their in vitro efficacy. These four OVs were screened on 14 patient-derived PBT cell cultures and the degree of oncolysis was assessed using an ATP-based assay. Subsequently, the observed viral efficacies were correlated to whole transcriptome data and Gene Ontology analysis was performed. Although no significant tumor type-specific OV efficacy was observed, the analysis revealed the intrinsic biological processes that associated with OV efficacy. The predictive power of the identified expression profiles was further validated in vitro by screening additional PBTs. In summary, our results demonstrate OV susceptibility of multiple patient-derived PBT entities and the ability to predict in vitro responses to OVs using unique expression profiles. Such profiles may hold promise for future OV preselection with effective oncolytic potency in a specific tumor, therewith potentially improving OV responses.

Abstract 4251: Establishment of hormone-dependent endometrial tumoroids in a conditioned-medium free, serum-free medium

Abstract Tumoroids, also known as cancer organoids, are self-assembled three-dimensional cultures of patient-derived tumor cells. Compared to traditional 2D cancer cell lines, tumoroids better maintain key characteristics of the original tumor including the genotype and transcriptome, which lead to better in vitro modeling of clinically relevant functional responses such as drug sensitivity. An under-studied aspect of tumoroid cultures has been their ability to recapitulate dependence on hormone signaling in vitro, with some reports indicating hormone dependence is lost over time in culture. To investigate this, we utilized Gibco™ OncoPro™ Tumoroid Culture Medium and defined tissue-specific supplements, FGF10 and beta-estradiol, that when added to the medium enabled the derivation of endometrial tumoroids from tumor resections. Derivation of tumoroid lines compatible with long-term growth depended on a variety of factors, including tissue quality and time from resection to culture initiation. Each of the 15 samples processed formed tumoroids when initially seeded into culture. 11/15 samples reformed tumoroids through multiple passages (typically 1-2 weeks per passage) over 1-3 months in culture. 7/15 samples met our high criteria for stable tumoroid line growth of >5 passages and reaching >5 cumulative population doublings (from initial number of cells seeded post-resection) in culture. Next-generation sequencing of the established tumoroids and the uncultured tumor material demonstrated a high degree of correlation (pearson’s r>0.9) of genomic mutations in a targeted panel; few differentially expressed genes were detected beyond down-regulation of immune-related genes, presumably because the medium is optimized for outgrowth of cancer epithelial cells, and immune cells do not persist during long-term culture. Endometrial tumoroids were capable of growing embedded in basement membrane extract (BME) or in suspension with dilute BME added and could be cryopreserved and recovered. Endometrial tumoroids retained gene expression levels (both presence and absence) of estrogen receptor and progesterone receptor for up to the 20 passages tested in vitro. A subset of the models was tested and showed increased growth rates in response to increased concentrations of beta-estradiol. Of those tested, 2/3 tumoroid cultures stopped growing within 1-2 weeks after removal of beta-estradiol from the medium, demonstrating dependence on this hormone for growth. Maintenance of hormone receptor expression and dependency should enable in vitro studies to understand the signaling mechanisms and potential ways to modulate them in the context of cancer. Overall, this method provides a toolset for studying endometrial cancer, particularly hormone dependency, and may be more broadly applicable to other gynecological or hormone dependent cancers. Citation Format: Chris Yankaskas, Brittany Balhouse, Colin Paul, Pradip Shahi Thakuri, Shyanne Salen, Mark Kennedy, Matt Dallas, David Kuninger. Establishment of hormone-dependent endometrial tumoroids in a conditioned-medium free, serum-free medium [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4251.

Abstract 6898: Cholangiocarcinoma patient-derived models in the NCI Patient-Derived Models Repository

Abstract Cholangiocarcinoma (CHOL) is an aggressive rare malignancy arising in the biliary tract with a 5-year relative survival rate of 10% and a 60-70% recurrence rate following surgical intervention. Advances in treatment strategies are hampered by the lack of well annotated and characterized preclinical models. The National Cancer Institute’s Patient-Derived Models Repository (NCI PDMR; https://pdmr.cancer.gov) has developed a national repository of Patient-Derived Models (PDMs) comprised of patient-derived xenografts (PDXs), in vitro patient-derived tumor cell cultures (PDCs) and cancer associated fibroblasts (CAFs) as well as patient-derived organoids (PDOrg). These PDMs are clinically annotated with molecular information available in an easily accessible database for the extramural community. To date, 94 patient CHOL tumor specimens (resections, biopsies, rapid autopsy) have been received from 55 unique patients with an overall PDX take rate of 36.3% (80 assessable specimens). There are currently 15 CHOL PDX models available for the research community to request with 14 more in final QC. Nine of the 15 public PDX models were generated from unique lesions in two rapid autopsy patients and while histo-morphologically consistent, some genomic heterogeneity is observed between the unique anatomical locations likely due to tumor evolution during metastasis. In addition, 27 in vitro PDOrgs, PDCs, and CAFs have been generated from patient or PDX material matched to most of the existing PDX models to allow for comparative translation research. The genetic landscape of the CHOL PDXs includes oncogenic drivers in NRAS, IDH1, ERBB2, TP53, KRAS and FGFR2 fusions; OncoKB likely oncogenic variants including ARID1A, AXIN1 and BAP1; and CDKN2A deep deletions representing most of the common alterations in CHOL. Early passage preclinical PDX and in vitro models for CHOL, and many other cancer types, with translational relevant features along with associated NextGen sequencing and patient treatment history are available from the NCI PDMR. Availability of preclinical models that can be used to study these cancers and improve preclinical drug screening is of high importance to better understand the biology of these cancers and prioritize novel therapeutics from bench to clinic. Funded by NCI Contract No. HHSN261200800001E Citation Format: Yvonne A. Evrard, Cindy R. Timme, Biswajit Das, Gareth Bliss, Carrie Bonomi, Carley Border, Ting-Chia Chang, Alice Chen, Li Chen, Michelle A. Crespo-Eugeni, Kevin Cooper, Natalie Czarra, Isabella Czernia, Kelly Dougherty, Marion Gibson, Tara Grinnage-Pulley, Shahanawaz Jiwani, Keegan Kalmbach, Chris A. Karlovich, Chelsea McGlynn, Michael Mullendore, Matthew Murphy, Rini Pauly, Kevin Plater, Jessica Steed, Luke Stockwin, Shannon Uzelac, Peter I-Fan Wu, Dianne L. Newton, P. Mickey Williams, Melinda G. Hollingshead, James H. Doroshow. Cholangiocarcinoma patient-derived models in the NCI Patient-Derived Models Repository [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6898.

Abstract 6911: Expanding reported molecular characteristics for the NCI Patient-Derived Models Repository

Abstract The National Cancer Institute’s Patient-Derived Models Repository (NCI PDMR; https://pdmr.cancer.gov) has developed a national repository of Patient-Derived Models (PDMs) comprised of patient-derived xenografts (PDXs), in vitro patient-derived tumor cell cultures (PDCs) and cancer associated fibroblasts (CAFs) as well as patient-derived organoids (PDOrg). These PDMs are clinically annotated with molecular information available in an easily accessible database for the extramural community. To ensure the data and models remains pertinent to current translational efforts, NCI actively reviews and adds new molecular features to the public database for researchers to use. While these data could be obtained through analysis of the available NextGen sequencing files in the PDMR database, many laboratories do not have the bioinformatics support to run these assessments for models that are of research interest. Therefore, new pipelines for an array of additional model and molecular characteristics present in PDX, PDOrg, and PDC models have been validated and are reported in the public database in a searchable format. Current model characteristics include addition of OncoTree Codes as a second histologic classifier, use of the PDXNet Consortium’s inferred ancestry caller to better represent Native/Latin American populations, human leukocyte antigen (HLA) typing, molecular classification of tumors (e.g. CMS subtyping of colorectal adenocarcinoma, PAM50 signature based subtyping of breast carcinoma), microsatellite instability (MSI) assessment, and identification of clinically relevant fusions. SOPs for the pipelines used are available on the public website to allow for independent validation and use by other laboratories. Funded by NCI Contract No. HHSN261200800001E Citation Format: Cindy R. Timme, Yvonne A. Evrard, Biswajit Das, Ting-Chia Chang, Alice Chen, Li Chen, Michelle A. Crespo-Eugeni, Shahanawaz Jiwani, Chris A. Karlovich, Rini Pauly, Peter I-Fan Wu, Dianne L. Newton, P. Mickey Williams, Melinda G. Hollingshead, James H. Doroshow. Expanding reported molecular characteristics for the NCI Patient-Derived Models Repository [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6911.

Abstract 1566: Cancer metastasis and stemness: The metastasis-inducer MACC1 regulates LGR5 to promote cancer stem cell-like properties in colorectal cancer

Abstract Colorectal cancer (CRC) is one of the leading causes of cancer-related deaths worldwide. The high mortality is directly associated with metastatic disease which is thought to be initiated by colon cancer stem cells according to cancer stem cell (CSC) model. Consequently, early identification of those patients who are at high risk for metastasis is crucial for improved treatment and patient outcome. Metastasis-associated in colon cancer 1 (MACC1) is a novel prognostic biomarker for tumor progression and metastasis formation independent of tumor stage. We previously showed an involvement of MACC1 in cancer stemness in the mouse intestine of our transgenic mouse models. However, the expression of MACC1 in human CSCs and possible implications remain elusive. Here, we explored the molecular mechanisms by which MACC1 regulates stemness and CSC-associated invasive phenotype based on patient-derived 3D cell culture models (PD3D), patient-derived xenografts (PDX) and human CRC cell lines. We showed that CD44-enriched CSCs from PD3D models express significantly higher levels of MACC1 and display higher tumorigenicity in immunocompromised mice. Similarly, RNA sequencing performed on PD3D and PDX models demonstrated significantly increased MACC1 expression in ALDH1(+) CSCs, highlighting its involvement in cancer stemness. We further showed the correlation of MACC1 with CSC markers CD44, NANOG and LGR5 in PD3D models as well as established cell lines. Additionally, MACC1 increased stem cell gene expression, clonogenicity and sphere formation. Strikingly, we showed that MACC1 binds as a transcription factor to the LGR5 gene promoter uncovering the long-known CSC marker LGR5 as novel essential signaling mediator used by MACC1 to induce CSC-like properties in human CRC patients. Our in vitro findings were further substantiated by significant positive correlation of MACC1 and LGR5 in CRC cell lines as well as CRC patient tumors. Taken together, this study indicates that the metastasis-inducer MACC1 act as a cancer stem cell-associated marker. Interventional approaches targeting MACC1 would potentially improve further targeted therapies for colorectal cancer patients to eradicate CSCs, prevent cancer recurrence and distant metastasis formation. Citation Format: Müge Erdem, Kyung Hwan Lee, Markus Hardt, Joseph Regan, Dennis Kobelt, Wolfgang Walther, Christian Regenbrecht, Ulrike S. Stein. Cancer metastasis and stemness: The metastasis-inducer MACC1 regulates LGR5 to promote cancer stem cell-like properties in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1566.

Abstract 240: Mix and match - A comprehensive pipeline for matched patient-derived PDX and PD3D® modelsfor cancer research and preclinical drug development

Abstract Relevant in vivo and in vitro cancer models have been invaluable for our current understanding of cancer biology, as well as for therapy development. Using appropriate models in the drug development process significantly supports reliable and swift decision making in proceeding along the value chain. In parallel, animal experiments can be designed more specific to the scientific and regulatory needs, resulting in shorter development cycles and eventually the availability of better therapies for cancer patients. Patient-derived xenografts (PDX) are generated by implantation of cancerous tissue from a patient’s tumor either under the skin (ectopic) or into the organ of tumor origin (orthotopic) of an immunocompromised mouse and are the most used in vivo model for preclinical drug development. Patient-derived 3D cell culture models (PD3D®) are gaining increasing significance as relevant in vitro cancer models that recapitulate the original tumor tissue’s biology and are suitable for high-throughput drug screening. The combination of both platform’s increases the translational relevance of the development pipeline and offers the possibility to enlarge the respective panels of tumor models. Tackling an unmet medical need, we initially created matched mesothelioma PD3D® and PDX models. Mesothelioma is an aggressive cancer with poor prognosis and limited treatment options. Development of new therapies is hampered by shortage of available relevant tumor models. We created PD3D® models from PDX mesothelioma models and vice versa and generated drug sensitivity profiles with standard of care such as Gemcitabine, platinum derivates and a number of targeted agents to confirm their suitability as matched models for future projects. We were able to prove that models express stable histological, phenotypic features and drug sensitivity profiles across the two platforms. With this proof-of-concept study, the feasibility to combine the PD3D® biobank comprising more than 500 models from CELLphenomics with the PDX bank from CRL including 700 PDX models, has gained momentum. In consideration of the changing regulatory landscape, the combination of in vitro and in vivo platforms is a crucial step towards a drug development pipeline that incorporates the principles of 3R and increases its translational value due to fully human technologies being the corner stones of the drug development process. Citation Format: Jürgen Loskutov, Eva Oswald, Lena Wedeken, Christoph J. Reinhard, Julia Schueler, Christian R. Regenbrecht. Mix and match - A comprehensive pipeline for matched patient-derived PDX and PD3D® modelsfor cancer research and preclinical drug development [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 240.

Abstract 4235: PD3D®models as jacks-of-all-trades for cancer research and therapy response prediction

Abstract Physiologically relevant in vitro tumor models are crucial in any research setting from preclinical drug development to functional precision oncology. Patient-derived 3D cell culture models (PD3D®) are validated cancer models which recapitulate the biology of the original tumor tissue. PD3D® can be used to model intratumoral heterogeneity in medium and high throughput screens. Using a reverse clinical engineering approach, PD3D® models are already applied in personalized oncology to identify treatment for an individual patient. We successfully established a living biobank of more than 500 PD3D® models, spanning from common cancers like colorectal, breast (incl. TNBC), non-small cell lung and pancreatic carcinoma, to orphan indications including various subtypes of sarcomas. Not surprisingly, PD3D® model morphology and culture requirements differ between tumor entities. Treating PD3D® models with standard of care drugs in a semi-automated high-throughput assay, we observed heterogeneity in drug sensitivity between models of the same cancer type, recapitulating clinical response of patients. Combining drug sensitivity profiles with genomic and proteomic data of the same PD3D® models, we successfully identified a biomarker for predicting chemosensitivity towards MEK-targeting drugs. For application of PD3D® in truly personalized oncology, we developed a protocol that allows us to generate a PD3D® culture and perform a drug sensitivity assay for an individual patient within a therapy-relevant timeframe. Within 38 days we identified a systemic therapy for a young patient with a relapsed metastasized synovial sarcoma. After surgery and initiation of recommended chemotherapy, the patient is now under remission. To further expand the scope of PD3D® for therapy response prediction, we established a method for irradiation of PD3D® cultures with different dosages of photon and proton radiation. We observed significant, model specific differences in radiosensitivity between PD3D® sarcoma models which also reflect clinically heterogenous responses. Additionally, PD3D® models can be employed for a tumor organoid-on-chip platform (TumOC), delivering real-time information on physiological parameters like drug response-mediated oxygen consumption in a microfluidic system. In conclusion, PD3D® models act as jacks-of-all-trades in current and future cancer research, delivering robust and reliable data that not only is of academic value, but speeds up the drug development process, and are ready for prime time in functional precision oncology. Citation Format: Lena Wedeken, Samantha Forbrig, Katja Herrera-Glomm, Juergen Loskutov, Ulrike Pfohl, Irina Piven, Michael Poehle, Manuela J. Regenbrecht, Barbara Seller, Cynthia Yapto, Sabine Finkler, Larissa Ruhe, Quirin Graf Adelmann, Christoph Reinhard, Marie Flechner, Katja Uhlig, David Kaul, Siyer Roohani, Maya Niethard, Rica Sauer, Christian R. Regenbrecht. PD3D®models as jacks-of-all-trades for cancer research and therapy response prediction [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4235.

Fast-relaxing hydrogels with reversibly tunable mechanics for dynamic cancer cell culture

The mechanics of the tumor microenvironment (TME) significantly impact disease progression and the efficacy of anti-cancer therapeutics. While it is recognized that advanced in vitro cancer models will benefit cancer research, none of the current engineered extracellular matrices (ECM) adequately recapitulate the highly dynamic TME. Through integrating reversible boronate-ester bonding and dithiolane ring-opening polymerization, we fabricated synthetic polymer hydrogels with tumor-mimetic fast relaxation and reversibly tunable elastic moduli. Importantly, the crosslinking and dynamic stiffening of matrix mechanics were achieved in the absence of a photoinitiator, often the source of cytotoxicity. Central to this strategy was Poly(PEGA-co-LAA-co-AAPBA) (PELA), a highly defined polymer synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. PELA contains dithiolane for initiator-free gel crosslinking, stiffening, and softening, as well as boronic acid for complexation with diol-containing polymers to give rise to tunable viscoelasticity. PELA hydrogels were highly cytocompatible for dynamic culture of patient-derived pancreatic cancer cells. It was found that the fast-relaxing matrix induced mesenchymal phenotype of cancer cells, and dynamic matrix stiffening restricted tumor spheroid growth. Moreover, this new dynamic viscoelastic hydrogel system permitted sequential stiffening and softening to mimic the physical changes of TME.

Lentiviral expression of wild-type LAMA3A restores cell adhesion in airway basal cells from children with epidermolysis bullosa

The hallmark of epidermolysis bullosa (EB) is fragile attachment of epithelia due to genetic variants in cell adhesion genes. We describe 16 EB patients treated in the Ear, Nose and Throat department of a tertiary pediatric hospital linked to the United Kingdom’s National EB unit between 1992 and 2023. Patients suffered a high degree of morbidity and mortality from laryngotracheal stenosis. Variants in laminin subunit alpha-3 (LAMA3) were found in 10/15 patients where genotype was available. LAMA3 encodes a subunit of the laminin-332 heterotrimeric extracellular matrix protein complex and is expressed by airway epithelial basal stem cells. We investigated the benefit of restoring wildtype LAMA3 expression in primary EB patient-derived basal cell cultures. EB basal cells demonstrated weak adhesion to cell culture substrates, but could otherwise be expanded similarly to non-EB basal cells. In vitro lentiviral overexpression of LAMA3A in EB basal cells enabled them to differentiate in air-liquid interface cultures, producing cilia with normal ciliary beat frequency. Moreover, transduction restored cell adhesion to levels comparable to a non-EB donor culture. These data provide proof-of-concept for a combined cell and gene therapy approach to treat airway disease in LAMA3-affected EB.

Dielectrophoretic enrichment of live chemo-resistant circulating-like pancreatic cancer cells from media of drug-treated adherent cultures of solid tumors.

Due to low numbers of circulating tumor cells (CTCs) in liquid biopsies, there is much interest in enrichment of alternative circulating-like mesenchymal cancer cell subpopulations from in vitro tumor cultures for utilization within molecular profiling and drug screening. Viable cancer cells that are released into the media of drug-treated adherent cancer cell cultures exhibit anoikis resistance or anchorage-independent survival away from their extracellular matrix with nutrient sources and waste sinks, which serves as a pre-requisite for metastasis. The enrichment of these cell subpopulations from tumor cultures can potentially serve as an in vitro source of circulating-like cancer cells with greater potential for scale-up in comparison with CTCs. However, these live circulating-like cancer cell subpopulations exhibit size overlaps with necrotic and apoptotic cells in the culture media, which makes it challenging to selectively enrich them, while maintaining them in their suspended state. We present optimization of a flowthrough high frequency (1 MHz) positive dielectrophoresis (pDEP) device with sequential 3D field non-uniformities that enables enrichment of the live chemo-resistant circulating cancer cell subpopulation from an in vitro culture of metastatic patient-derived pancreatic tumor cells. Central to this strategy is the utilization of single-cell impedance cytometry with gates set by supervised machine learning, to optimize the frequency for pDEP, so that live circulating cells are selected based on multiple biophysical metrics, including membrane physiology, cytoplasmic conductivity and cell size, which is not possible using deterministic lateral displacement that is solely based on cell size. Using typical drug-treated samples with low levels of live circulating cells (<3%), we present pDEP enrichment of the target subpopulation to ∼44% levels within 20 minutes, while rejecting >90% of dead cells. This strategy of utilizing single-cell impedance cytometry to guide the optimization of dielectrophoresis has implications for other complex biological samples.

Is it possible to detect surface antigen CD133 on patient-derived glioblastoma continuous cell cultures using fluorescent aptamers?

To detect CD133 in patient-derived glioblastoma continuous cell cultures using fluorescence microscopy and modified aptamers (molecular recognition elements) anti-CD133. To detect CD133, we used mousey fluorescence monoclonal antibodies anti-CD133 MA1-219, FAM-modified DNA aptamers anti-CD133 AP-1-M and Cs5. Non-aptamer DNA oligonucleotide NADO was used as a negative control. Detection was performed for three samples of patient-derived glioblastoma continuous cell cultures coded as 1548, 1721 and 1793. MA1-219 antibodies brightly stained cell culture 1548, to a lesser extent - 1721. There was diffuse staining of cell culture 1793. Cs5-FAM aptamer stained cells in a similar way, but much weaker. AP-1-M-FAM aptamer interacted with cells even weaker and diffusely stained only cell culture 1793. Non-aptamer NADO did not stain cell culture 1548 and very weakly diffusely stained cell culture 1793. For both molecular recognition elements (MA1-219 antibody and Cs5 aptamer), 3 cell culture samples can be arranged in the following order possibly reflecting CD133 status decrease: strong signal for cell culture 1548, much weaker for 1721, even weaker for 1793. Only cell culture 1548 can be considered CD133 positive with combination of Cs5+ and NADO signals. Cell culture 1793 is CD133 false positive with combination of Cs5+ and NADO+ signals.

Preclinical Evaluation of panobinostat and ONC201 for the treatment of diffuse intrinsic pontine glioma (DIPG)

Diffuse intrinsic pontine glioma (DIPG) also referred as paediatric high-grade glioma (pHGG) is a fast-growing and aggressive type of childhood brain cancer. Recent studies investigating the molecular pathogenesis of DIPG have identified new therapeutic targets, paving the way for a new line of drugs mainly HDAC inhibitors. However, despite long years of trials, no significant results have been generated yet. Panobinostat is a HDAC inhibitor that has shown promising preclinical cytotoxicity in DIPG but failed so far in clinical trials. This study aims to re-evaluate the efficacy of Panobinostat in DIPG in vitro using patient-derived DIPG cell cultures obtained directly from patients. ONC201 is another potentially effective drug in DIPG. This apoptotic agent has been considered in a few clinical trials in diffuse glioma including DIPG. Our results reveal a dose-dependent response to Panobinostat and ONC201 in DIPG cells. However, Panobinostat caused a significant reduction in the mean percentage cell viability at a lower concentration compared to ONC201. Panobinostat caused significant decreases in DIPG cell viability at concentrations greater than or equal to 0.002 μM (p<0.05), the response reached a plateau after 0.1 μM, which reduced cell viability to 32.81 % ± 0.25 % (p = 6.74E−06) when compared to control cells. ONC201 only significantly induced apoptosis at concentrations equal or higher than 0.01 μM (p<0.05), with its effect plateauing after 0.2 μM. This pre-clinical study supports the effectiveness of Panobinostat as a potential therapeutic agent for DIPG compared to ONC201, with no apparent synergistic effect observed in combination.

A novel patient-derived meningioma spheroid model as a tool to study and treat epithelial-to-mesenchymal transition (EMT) in meningiomas

Meningiomas are the most common intracranial brain tumours. These tumours are heterogeneous and encompass a wide spectrum of clinical aggressivity. Treatment options are limited to surgery and radiotherapy and have a risk of post-operative morbidities and radiation neurotoxicity, reflecting the need for new therapies. Three-dimensional (3D) patient-derived cell culture models have been shown to closely recapitulate in vivo tumour biology, including microenvironmental interactions and have emerged as a robust tool for drug development. Here, we established a novel easy-to-use 3D patient-derived meningioma spheroid model using a scaffold-free approach. Patient-derived meningioma spheroids were characterised and compared to patient tissues and traditional monolayer cultures by histology, genomics, and transcriptomics studies. Patient-derived meningioma spheroids closely recapitulated morphological and molecular features of matched patient tissues, including patient histology, genomic alterations, and components of the immune microenvironment, such as a CD68 + and CD163 + positive macrophage cell population. Comprehensive transcriptomic profiling revealed an increase in epithelial-to-mesenchymal transition (EMT) in meningioma spheroids compared to traditional monolayer cultures, confirming this model as a tool to elucidate EMT in meningioma. Therefore, as proof of concept study, we developed a treatment strategy to target EMT in meningioma. We found that combination therapy using the MER tyrosine kinase (MERTK) inhibitor UNC2025 and the histone deacetylase (HDAC) inhibitor Trichostatin A (TSA) effectively decreased meningioma spheroid viability and proliferation. Furthermore, we demonstrated this combination therapy significantly increased the expression of the epithelial marker E-cadherin and had a repressive effect on WHO grade 2-derived spheroid invasion, which is suggestive of a partial reversal of EMT in meningioma spheroids.

CSIG-06. CROSSTALK BETWEEN ONCOGENIC SIGNALING PATHWAYS AS DRIVERS OF THERAPY RESISTANCE AGAINST SMALL MOLECULE INHIBITORS IN GLIOBLASTOMA

Abstract Patients with glioblastoma multiforme (GBM) have a median survival of 15 months. Despite an intensive treatment schedule with resection, radio- and chemotherapy, recurrence is inevitable. An important challenge to overcome GBM treatment resistance involves intratumoral heterogeneity, characterized by molecularly, phenotypically, and clinically distinctive GBM subtypes. Different small molecule inhibitors have been designed to inhibit signaling proteins in oncogenic driver pathways, including the EGFR, PDGFR, MET, CDK4, and PI3K/Akt pathway, in GBM. However, these small molecule inhibitors have been unsuccessful in improving patient outcome. Here, we investigate if crosstalk and redundancy in signaling pathways is responsible for single-agent resistance using patient-derived glioblastoma 2D stem cell cultures (pdGBM). Eight brain-penetrable and clinically approved small molecule inhibitors (SMI) were used to target key GBM driver genes. We measured cell viability in triplicate with a CellTiter-Glo assay. The half-maximal inhibitory concentration (IC50) for each inhibitor was defined for six molecularly distinct pdGBM 2D cell cultures. Although inhibition of downstream effector proteins reduced cell viability more effectively (IC50 70nM-1µM), compared to inhibiting upstream membrane-bound tyrosine kinase receptors (IC50 1-15µM), remaining cell proliferation was seen in all pdGBM using the different SMIs as single agent. To identify resistance mechanisms, we investigated changes in phosphokinase activity after SMI monotherapy in the different pdGBM 2D cell cultures. Based upon these results, we could identify combinations of SMIs targeting compensatory pathways that drive treatment resistance. In conclusion, this study presents a mechanistically driven selection of tumor tailored combination treatment to overcome resistance to SMI monotherapy in pdGBM. The efficacy of these novel SMI combinations will be challenged next, moving from pdGBM 2D stem cell cultures towards pdGBM organoids.

DDDR-22. PREDICTING AND TARGETING CLONALLY EXPANDING, TMZ-RESISTANT TUMOR CELLS IN GLIOBLASTOMA

Abstract Emerging evidence supports the notion that phenotypic plasticity contributes to disease progression and drug resistance in malignant glioma. We have recently described a rare population of ALDH1A1+ tumor cells in newly diagnosed, treatment-naive glioblastoma that can adapt to the exposure of the standard chemotherapeutic temozolomide (TMZ). Their subclonal growth leads to AKT-driven, TMZ-resistant cellular hierarchies. Accumulation of ALDH1A1+/pAKT+ cells can therefore be noted subsequent to TMZ in patient relapse tissue and in PDX models of disease. We have also shown that this series of events requires a sequential targeting approach where these subclones are allowed to enrich under TMZ and, only in a second step, are treated with AKT inhibitors. This “enrich and kill” strategy doubles the TMZ-based survival benefit in preclinical PDX models (Kebir et al., Clin Cancer Res 2023). Here, we took advantage of short-term expanded patient-derived cell cultures, which allow the study of early stages of this type of adaptive plasticity in controlled conditions. Specifically, we characterized the human lysine-specific demethylase 5B (KDM5B) as a prospective indicator for subclonal expansion in rare cells under first-time exposure to TMZ. We used genetic reporters, pharmacological interference, CHIP-seq analysis and cellular barcoding to investigate the dynamics of KDM5B expression and the related intracellular cross-signaling. We monitored patient cell samples over prolonged periods of time, and we found that KDM5Bhigh treatment-naive glioblastoma cells preferentially contribute to the dynamics of ALDH1A1 subclones and drug resistance under the influence of TMZ. These findings may lay ground for the development of biomarker-assisted clinical trials. This work is supported by DFG/GRC-CRU337/2 (proj#405344257).

A Targeted Approach for Evaluating DUX4-Regulated Proteins as Potential Serum Biomarkers for Facioscapulohumeral Muscular Dystrophy Using Immunoassay Proteomics.

Facioscapulohumeral muscular dystrophy (FSHD) is a progressive myopathy caused by misexpression of the double homeobox 4 (DUX4) embryonic transcription factor in skeletal muscle. Identifying quantitative and minimally invasive FSHD biomarkers to report on DUX4 activity will significantly accelerate therapeutic development. The goal of this study was to analyze secreted proteins known to be induced by DUX4 using the commercially available Olink Proteomics platform in order to identify potential blood-based molecular FSHD biomarkers. We used high-throughput, multiplex immunoassays from Olink Proteomics to measure the levels of several known DUX4-induced genes in a cellular myoblast model of FSHD, in FSHD patient-derived myotube cell cultures, and in serum from individuals with FSHD. Levels of other proteins on the Olink Proteomics panels containing these DUX4 targets were also examined in secondary exploratory analysis. Placental alkaline phosphatase (ALPP) levels correlated with DUX4 expression in both cell-based FSHD systems but did not distinguish FSHD patient serum from unaffected controls. ALPP, as measured with the Olink Proteomics platform, is not a promising FSHD serum biomarker candidate but could be utilized to evaluate DUX4 activity in discovery research efforts.

Identifying biomarkers and novel therapeutic targets in uveal melanoma.

Uveal melanoma (UM) is an orphan cancer despite being the most common eye tumor in adults. Patients often present to skin cancer centers for treatment of metastatic disease although there are significant genetic, biological, and clinical differences from cutaneous melanoma. The treatments most commonly used for metastatic UM are tebentafusp and combined immune checkpoint blockade, both of which yield low response rates and may be accompanied by high treatment costs and significant immune-related toxicities. Thus, it is of paramount importance to identify biomarkers and clinical profiles predictive of treatment response and to find novel therapeutic targets. The use of immune checkpoint blockade showed more favorable outcomes in patients with extrahepatic disease and normal levels of serum lactate dehydrogenase in a panel of retrospective studies, making its use more reasonable in this subgroup. To identify novel drug targets, we will analyze the expression and relevance of neural crest transcription factors in patient bio-specimens using next-generation nanopore sequencing. Computer algorithms and network-based analysis will facilitate the identification of druggable targets which will subsequently be validated in patient-derived short-term cell cultures. This approach will help to find novel and personalized treatments for UM.

Genomic Exploration of Distinct Molecular Phenotypes Steering Temozolomide Resistance Development in Patient-Derived Glioblastoma Cells

Chemotherapy using temozolomide is the standard treatment for patients with glioblastoma. Despite treatment, prognosis is still poor largely due to the emergence of temozolomide resistance. This resistance is closely linked to the widely recognized inter- and intra-tumoral heterogeneity in glioblastoma, although the underlying mechanisms are not yet fully understood. To induce temozolomide resistance, we subjected 21 patient-derived glioblastoma cell cultures to Temozolomide treatment for a period of up to 90 days. Prior to treatment, the cells’ molecular characteristics were analyzed using bulk RNA sequencing. Additionally, we performed single-cell RNA sequencing on four of the cell cultures to track the evolution of temozolomide resistance. The induced temozolomide resistance was associated with two distinct phenotypic behaviors, classified as “adaptive” (ADA) or “non-adaptive” (N-ADA) to temozolomide. The ADA phenotype displayed neurodevelopmental and metabolic gene signatures, whereas the N-ADA phenotype expressed genes related to cell cycle regulation, DNA repair, and protein synthesis. Single-cell RNA sequencing revealed that in ADA cell cultures, one or more subpopulations emerged as dominant in the resistant samples, whereas N-ADA cell cultures remained relatively stable. The adaptability and heterogeneity of glioblastoma cells play pivotal roles in temozolomide treatment and contribute to the tumor’s ability to survive. Depending on the tumor’s adaptability potential, subpopulations with acquired resistance mechanisms may arise.