Titel Deelnemers "Korte inhoud" "Successful application of endoscopic ultrasound-guided fine needle biopsy to establish pancreatic patient-derived tumor xenografts" "Els Hermans, Schalk Van der Merwe, Jeroen Depreeuw, Jeroen Dekervel, Enrico Radaelli, Tania Roskams, Jos van Pelt, Baki Topal, Chris Verslype, Hans Prenen, Werner Van Steenbergen, Frederik Nevens, Diether Lambrechts, Frédéric Amant" "Background and study aim: Typically, pancreatic patient-derived tumor xenografts (PDXs) are established by transplanting large tumor biopsies obtained through invasive surgery approaches into immunocompromised mice. We aimed to develop pancreatic PDXs by transplanting tumor tissue acquired by endoscopic ultrasound (EUS)-guided fine needle biopsies (FNB), assess take rates compared to surgery-derived PDXs, and demonstrate the histological and genetic resemblance to the original tumor. Patients and methods: Biopsies of untreated pancreatic carcinoma were collected at surgery and during EUS and processed to generate PDXs. Results: By centrifugation of FNB-derived tissue prior to engraftment, we achieved an engraftment rate of 60 % (6/10). Despite a decrease in stromal tissue, the general morphology of FNB-derived PDXs was conserved as assessed by histopathology. At the genetic level, somatic mutation and copy number profiles were largely similar to the primary tumor. Conclusion: We show that it is technically feasible to establish pancreatic PDXs using a minimally invasive sampling technique, such as EUS-FNB. Although only a limited amount of tumor tissue was acquired, we obtained results similar to those from surgery-derived PDXs." "Enhanced Antitumor Efficacy of PhAc-ALGP-Dox, an Enzyme-Activated Doxorubicin Prodrug, in a Panel of THOP1-Expressing Patient-Derived Xenografts of Soft Tissue Sarcoma" "Britt Van Renterghem, Agnieszka Wozniak, Raf Sciot, Patrick Schöffski" "Despite poor response rates and dose-limiting cardiotoxicity, doxorubicin (doxo) remains the standard-of-care for patients with advanced soft tissue sarcoma. We evaluated the efficacy of two tetrapeptidic doxo prodrugs (PhAc-ALGP-Dox or CBR-049 and CBR-050) that are locally activated by enzymes expressed in the tumor environment, in ten sarcoma patient-derived xenografts. Xenograft models were selected based on expression of the main activating enzyme, i.e., thimet oligopeptidase (THOP1). Mice were either randomized to vehicle, doxo, CBR-049 and CBR-050 or control, doxo, aldoxorubicin (aldoxo) and CBR-049. Treatment efficacy was assessed by tumor volume measurement and histological assessment of ex-mouse tumors. CBR-049 showed significant tumor growth delay compared to control in all xenografts investigated and was superior compared to doxo in all but one. At the same time, CBR-049 showed comparable efficacy to aldoxo but the latter was found to have a complex safety profile in mice. CBR-050 demonstrated tumor growth delay compared to control in one xenograft but was not superior to doxo. For both experimental prodrugs, strong immunostaining for THOP1 was found to predict better antitumor efficacy. The prodrugs were well tolerated without any adverse events, even though molar doses were 17-fold higher than those administered and tolerated for doxo." "Assessment of the platelet-derived growth factor receptor alpha antibody olaratumab in a panel of patient-derived soft tissue sarcoma xenografts" "Agnieszka Wozniak, Britt Van Renterghem, Maria Debiec-Rychter, Raf Sciot, Daphne Hompes, Patrick Schöffski" "BACKGROUND: Soft tissue sarcoma (STS) comprises a family of rare, heterogeneous tumors of mesenchymal origin. Single-agent doxorubicin remains the first-line standard-of-care treatment for advanced and inoperable STS, but response rates are only around 15%. In 2016, phase Ib/II clinical trial results reported an overall survival benefit of 11.8 months when combining doxorubicin and the platelet-derived growth factor receptor alpha (PDGFRA)-directed antibody olaratumab compared to doxorubicin alone, without providing a scientific rationale for such unprecedented therapeutic effect. We decided to evaluate the efficacy of olaratumab in a panel of STS patient-derived xenografts (PDX). METHODS: NMRI nu/nu mice were bilaterally transplanted with tumor tissue of patient-derived xenograft models expressing PDGFRA, including models of leiomyosarcoma (UZLX-STS22), malignant peripheral nerve sheath tumor (UZLX-STS39), myxofibrosarcoma (UZLX-STS59) and undifferentiated pleomorphic sarcoma (UZLX-STS84). Mice were randomly divided into four different treatment groups: (1) control, (2) doxorubicin (3 mg/kg once weekly), (3) anti-PDGFRA [olaratumab (60 mg/kg twice weekly) + mouse anti-PDGFRA antibody 1E10 (20 mg/kg twice weekly)] and (4) the combination of doxorubicin and anti-PDGFRA (same dose/schedule as in the single treatment arms). Tumor volume, histopathology and Western blotting were used to assess treatment efficacy. RESULTS: Anti-PDGFRA treatment as a single agent did not reduce tumor growth and did not result in significant anti-proliferative or pro-apoptotic activity. Combining doxorubicin and anti-PDGFRA did not reduce tumor burden, though a mild inhibition of proliferation was observed in UZLX-STS39 and -STS59. A pro-apoptotic effect was observed in all models except UZLX-STS22. Antitumor effects on histology were not significantly different comparing doxorubicin and the combination treatment. Moreover, anti-PDGFRA treatment, both as a single agent as well as combined with doxorubicin, did not result in inhibition of the downstream MAPK and PI3K/AKT signaling pathways. CONCLUSIONS: We were not able to demonstrate significant antitumor effects of anti-PDGFRA treatment in selected STS PDX models, neither alone nor in combination with doxorubicin. This is in line with the very recent results of the phase III clinical trial NCT02451943 ANNOUNCE, which did not confirm the clinical benefit of olaratumab in combination with doxorubicin over single agent doxorubicin." "CYTOTOXIC THERAPY REVISED: EXPLORATION OF INNOVATIVE (PRO)DRUGS IN PATIENT-DERIVED XENOGRAFTS OF SOFT TISSUE SARCOMA" "Britt Van Renterghem" "Soft tissue sarcomas (STS) represent a heterogeneous group of rare, malignant tumors of mesenchymal origin, which comprises more than 80 histological subtypes. Despite their extensive histological and molecular variety, the majority of STS are treated in a rather uniform way, especially in advanced setting. For these patients, doxorubicin has remained the first-line standard-of-care ever since its first introduction in the 1970s. However, response rates to doxorubicin are only around 14% to 18% in unselected STS populations. Meanwhile, patients are put at risk of developing severe and irreversible anthracycline-related cardiotoxicity, not allowing to exceed a cumulative dose 550 mg/m2 over the lifetime of a patient. Consequently, first-line treatment is exhausted after administration of only 6-8 cycles and cannot be resumed in case of relapse, even in the few responding patients. Although over the past few decades multiple clinical trials have been performed to test alternative systemic therapies for these patients, none succeeded to surpass the limited activity of single-agent doxorubicin, nor replace it as a first-line standard-of-care. An explanation can be found in the way these clinical trials were designed, including relatively small numbers of patients with a variety of STS subtypes, instead of a more rational biomarker-driven patient selection. Consequently, proper preclinical testing of new potentially more active and less toxic therapies for these patients remains an important priority. In the course of this 4-year doctoral project, we established an additional 18 STS patient-derived xenograft (PDX) models by implantation of donor tissue from patients with STS. This brings our platform of STS PDX to 63 models of 16 different subtypes. All established models were thoroughly characterized by histological and/or molecular means and demonstrated the characteristics of the original donor tumor. To our knowledge, this platform is currently the most extensive academic platform of STS PDX available, and provides valuable preclinical research models to the sarcoma community. Using the established STS PDX models, we performed in vivo experiments with two tetrapeptidic prodrugs of doxorubicin that are activated by enzymes expressed in the tumor tissue and/or microenvironment. In this way, doxorubicin is released more selectively at the tumor site, which reduces doxorubicin-related side effects and allows to achieve higher local doses of active drug. In all STS PDX models investigated, PhAc-ALGP-Dox or CBR-049 demonstrated at least equal or superior antitumor activity than compared to standard-of-care doxorubicin. CBR-050 demonstrated antitumor efficacy only in one STS PDX and was not superior to doxorubicin. For both experimental prodrugs, strong immunostaining for THOP1, the main activating enzyme of both compounds, was found to predict better antitumor efficacy. These results warrant further clinical evaluation of PhAc-ALGP-Dox in patients with advanced STS, ideally selected for high THOP1-expressing tumors. Additionally, we explored the in vivo efficacy of enapotamab vedotin, an AXL-specific antibody drug conjugate (ADC). Despite the fact that two models responded with clinically relevant and complete tumor regressions, majority of models demonstrated only limited antitumor activity. These results are in line with the limited activity observed with enapotamab vedotin in the clinical trial performed in patients with solid tumors, which led to the discontinuation of the development of this compound. However, this trial did not select for patients with target expression, which raises concern about the interpretation of the efficacy signals. Lastly, we explored pixantrone, a non-cardiotoxic derivative of doxorubicin already approved for advanced non-Hodgkin lymphoma, in malignant peripheral nerve sheath tumor (MPNST) PDX models. We observed at least equal or superior responses as compared with standard-of-care doxorubicin in all four MPNST PDX investigated. These results warrant further evaluation of pixantrone as potentially better and safer alternative of doxorubicin in MPNST, a very aggressive STS subtype that is mostly occurring in young patients. In conclusion, we expanded our STS PDX platform and performed a rational selection of models for the early preclinical exploration of some novel treatments. We demonstrated promising in vivo efficacy of PhAc-ALGP-Dox, a cytotoxic doxorubicin prodrug, and pixantrone, a non-cardiotoxic derivative of doxorubicin. Based on these results, both drugs should be prioritized for clinical evaluation in patients with advanced STS." "Gemcitabine induces Epithelial-to-Mesenchymal Transition in patient-derived pancreatic ductal adenocarcinoma xenografts" "Ashenafi Shiferaw Bulle, Jeroen Dekervel, Louis Libbrecht, David Nittner, Eric Van Cutsem, Chris Verslype, Jos van Pelt" "There is a lack of well-characterized models for pancreatic ductal adenocarcinoma (PDAC). PDAC itself is unique because of its pronounced tumor microenvironment that influences tumor progression, behavior and therapeutic resistance. Here we investigated, in patient-derived tumor xenograft (PDTX) models developed from fine needle biopsies, the cancer cells behavior, Epithelial-to-Mesenchymal Transition (EMT) and drug response. For this, we studied two behaviorally distinct PDTX models. Tumor volume measurement, histology, immuno-histochemical staining, RT-qPCR, RNA sequencing and Western blotting were used to further characterize these models and investigate the effect of two classes of drugs (gemcitabine and acriflavine (HIF-inhibitor)). The models recapitulated the corresponding primary tumors. The growth-rate of the poorly differentiated tumor (PAC010) was faster than that of the moderately differentiated tumor (PAC006) (P" "Volatile organic compounds in gastrointestinal stromal tumour tissue originating from patient-derived xenografts" "Agnieszka Wozniak, Yemarshet Kelemework Gebreyohannes, Patrick Schöffski" "Gastrointestinal stromal tumours (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract and localize mainly in the stomach or small intestine. The metabolomic signatures of GISTs driven by different KIT gene mutations remain undiscovered and unexplored. The main aim of this pilot study was to determine and compare metabolomic profiles in GIST xenograft models with different genetic backgrounds. Metabolomic profiling using gas chromatography coupled with mass spectrometry followed by univariate and multivariate statistical analyses was applied to select metabolites that differentiated the GIST models studied. The significant differences observed in the metabolites were mainly derived from glycolysis, the citric acid cycle and glutamine and lipid metabolism. The obtained results may suggest variable metabolomic signatures of tumours, possibly related to the different underlying, specific KIT gene mutations and with potential implications for the biological behaviour and natural course of this rare disease. This study constitutes a proof of concept in GISTs and reveals the potential of the metabolomic approach in orphan malignancies." "A living biobank of patient-derived ductal carcinoma in situ mouse-intraductal xenografts identifies risk factors for invasive progression" "Colinda Scheele" "Ductal carcinoma in situ (DCIS) is a non-obligate precursor of invasive breast cancer (IBC). Due to a lack of biomarkers able to distinguish high- from low-risk cases, DCIS is treated similar to early IBC even though the minority of untreated cases eventually become invasive. Here, we characterized 115 patient-derived mouse-intraductal (MIND) DCIS models reflecting the full spectrum of DCIS observed in patients. Utilizing the possibility to follow the natural progression of DCIS combined with omics and imaging data, we reveal multiple prognostic factors for high-risk DCIS including high grade, HER2 amplification, expansive 3D growth, and high burden of copy number aberrations. In addition, sequential transplantation of xenografts showed minimal phenotypic and genotypic changes over time, indicating that invasive behavior is an intrinsic phenotype of DCIS and supporting a multiclonal evolution model. Moreover, this study provides a collection of 19 distributable DCIS-MIND models spanning all molecular subtypes." "Identification of novel therapeutic targets for fibrolamellar carcinoma using patient-derived xenografts and direct-from-patient screening" "Gadi Lalazar, David Requena, Lavoisier Ramos-Espiritu, Denise Ng, Patrick D. Bhola, Ype P de Jong, Ruisi Wang, Nicole J. C. Narayan, Bassem Shebl, Solomon Levin, Eleftherios Michailidis, Mohammad Kabbani, Koen Vercauteren, Arlene M. Hurley, Benjamin A. Farber, William J. Hammond, James A. Saltsman, Ethan M. Weinberg, J. Fraser Glickman, Barbara A. Lyons, Jessica Ellison, Erik Schadde, Martin Hertl, Jennifer L. Leiting, Mark J. Truty, Rory L. Smoot, Faith Tierney, Tomoaki Kato, Hans-Guido Wendel, Michael P. LaQuaglia, Charles M. Rice, Anthony Letai, Philip Coffino, Michael S. Torbenson, Michael Ortiz, Sanford M. Simon" "To repurpose therapeutics for fibrolamellar carcinoma (FLC), we developed and validated patient-derived xenografts (PDX) from surgical resections. Most agents used clinically and inhibitors of oncogenes overexpressed in FLC showed little efficacy on PDX. A high-throughput functional drug screen found primary and metastatic FLC were vulnerable to clinically available inhibitors of TOPO1 and HDAC and to napabucasin. Napabucasin's efficacy was mediated through reactive oxygen species and inhibition of translation initiation, and specific inhibition of eIF4A was effective. The sensitivity of each PDX line inversely correlated with expression of the antiapoptotic protein Bcl-xL, and inhibition of Bcl-xL synergized with other drugs. Screening directly on cells dissociated from patient resections validated these results. This demonstrates that a direct functional screen on patient tumors provides therapeutically informative data within a clinically useful time frame. Identifying these novel therapeutic targets and combination therapies is an urgent need, as effective therapeutics for FLC are currently unavailable.SIGNIFICANCE: Therapeutics informed by genomics have not yielded effective therapies for FLC. A functional screen identified TOPO1, HDAC inhibitors, and napabucasin as efficacious and synergistic with inhibition of Bcl-xL. Validation on cells dissociated directly from patient tumors demonstrates the ability for functional precision medicine in a solid tumor." "Conservation of copy number profiles during engraftment and passaging of patient-derived cancer xenografts." "Diether Lambrechts" "Interrogating open issues in cancer precision medicine with patient-derived xenografts" "Marine Jean Christophe"