Plocabulin, a Novel Tubulin Inhibitor, Has Potent Antitumour Activity in Patient-Derived Xenograft Models of Soft Tissue Sarcoma

A clinically relevant subset of patients with soft tissue sarcoma presents with either locally advanced or upfront metastatic disease, or will develop distant metastases over time, despite successful treatment of their primary tumour. The currently available systemic agents to treat such advanced cases only provide modest disease control and are not active in all histological subtypes. Thus, there is an unmet need for novel and more efficacious agents to improve the outcome of this rare disease. In the current preclinical in vivo study, we evaluated plocabulin, a novel tubulin inhibitor, in five distinct histological subtypes of soft tissue sarcoma: dedifferentiated liposarcoma, leiomyosarcoma, undifferentiated sarcoma, intimal sarcoma and CIC-rearranged sarcoma. The efficacy was tested in seven patient-derived xenograft models, which were generated by the engraftment of tumour fragments from patients directly into nude mice. The treatment lasted 22 days, and the efficacy of the drug was assessed and compared to the doxorubicin and vehicle groups by volumetric analysis, histopathology and immunohistochemistry. We observed tumour volume control in all the tested histological subtypes. Additionally, in three sarcoma subtypes, extensive central necrosis, associated with significant tumour regression, was seen. This histological response is explained by the drug's vascular-disruptive properties, reflected by a decreased total vascular area in the xenografts. Our results demonstrate the in vivo efficacy of plocabulin in the preclinical models of soft tissue sarcoma and corroborate the findings of our previous study, which demonstrated similar vascular-disruptive effects in gastrointestinal stromal tumours-another subtype of soft tissue sarcoma. Our data provide a convincing rationale for further clinical exploration of plocabulin in soft tissue sarcomas.

Exploring stem cell biology in pituitary tumors and derived organoids

Pituitary tumorigenesis is highly prevalent and causes major endocrine disorders. Hardly anything is known on the behavior of the local stem cells in this pathology. Here, we explored the stem cells' biology in mouse and human pituitary tumors using transcriptomic, immunophenotyping and organoid approaches. In the prolactinoma-growing pituitary of dopamine receptor D2 knock-out mice, the stem cell population displays an activated state in terms of proliferative activity and distinct cytokine/chemokine phenotype. Organoids derived from the tumorous glands' stem cells recapitulated these aspects of the stem cells' activation nature. Upregulated cytokines, in particular interleukin-6, stimulated the stem cell-derived organoid development and growth process. In human pituitary tumors, cells typified by expression of stemness markers, in particular SOX2 and SOX9, were found present in a wide variety of clinical tumor types, also showing a pronounced proliferative status. Organoids efficiently developed from human tumor samples, displaying a stemness phenotype as well as tumor-specific expression fingerprints. Transcriptomic analysis revealed fading of cytokine pathways at organoid development and passaging, but their reactivation did not prove capable of rescuing early organoid expansion and passageability arrest. Taken together, our study revealed and underscored an activated phenotype of the pituitary-resident stem cells in tumorigenic glands and tumors. Our findings pave the way to defining the functional position of the local stem cells in pituitary tumor pathogenesis, at present barely known. Deeper insight can lead to more efficient and targeted clinical management, currently still not satisfactorily.

Abstract 2666: Anti-tumor effects of the novel KIT mutant inhibitor M4205 in patient-derived gastrointestinal stromal tumor (GIST) xenograft models

Background: The majority of GISTs are driven by constitutively activated KIT/PDGFRA kinases and susceptible to treatment with tyrosine kinase inhibitors such as imatinib, sunitinib and regorafenib. During treatment most tumors will develop heterogeneous secondary mutations in KIT or PDGFRA inducing drug resistance, so there is an unmet need for novel therapies. We tested the efficacy of M4205, a novel specific KIT inhibitor with high activity towards the most relevant KIT mutations, in patient-derived GIST xenograft models.

Methods: NMRI nu/nu mice (n=146) were transplanted with patient-derived GIST xenograft models UZLX-GIST9 (KIT:p.P577del;W557LfsX5;D820G) known to be resistant to both imatinib and sunitinib, with the dose-dependent imatinib-sensitive and sunitinib-sensitive models UZLX-GIST2B (KIT:p.A502_Y503dup), UZLX-GIST25 (KIT: p.K642E) and the cell-line derived model GIST882 (KIT: p.K642E)*. Mice were treated daily with vehicle (control), imatinib (100mg/kg), avapritinib (5mg/kg), sunitinib (20mg/kg), or M4205 (10mg/kg, 25mg/kg). Efficacy was assessed by tumor volume evolution, histopathology [hematoxilin & eosine staining (H&E)] and immunohistochemistry [Ki-67, phospho-Histone H3 (pHH3), cleaved PARP]. Histologic response (HR) was graded as previously described°. Mann Whitney U and Wilcoxon Matched Pairs tests were used for statistical analysis, with p<0.05 considered as significant.

Results: M4205 (25mg/kg) caused tumor volume shrinkage in UZLX-GIST2B, -GIST25 and GIST882 with relative decrease to 45.6%, 35.1% and 57.3% on the last day as compared to baseline. In UZLX-GIST9 tumor growth to 132.4% was observed in M4205 (25mg/kg)-treated tumors as compared to baseline. In all models we observed significant smaller tumor volumes in M4205 (25mg/kg)-treated tumors compared to control, and this antitumor activity was superior to imatinib in UZLX-GIST9, -GIST2B and GIST882, and to sunitinib in -GIST25. Compared to controls, M4205 (25mg/kg) induced a significant decrease in mitosis (H&E) in all models, confirmed on pHH3 and Ki-67 immunostainings in three models. In -GIST25 and GIST882 grade 2-4 HR with myxoid degeneration was observed in all tumors. All treatments were well tolerated.

Conclusion: M4205 has significant antitumor activity in patient- and cell line-derived GIST xenograft models. The novel kinase inhibitor induces volumetric responses, decreases mitotic activity, has antiproliferative effects and in models with KIT exon 13 mutation leads to characteristic myxoid degeneration. * Cornillie et al. Mol Cancer Ther 2019; 18(6):1168-1178 ° Agaram et al. Clin Cancer Res 2007; 13:170-81

Citation Format: Luna De Sutter, Agnieszka Wozniak, Jasper Verreet, Ulla Vanleeuw, Lore De Cock, Nina Linde, Christine Drechsler, Christina Esdar, Raf Sciot, Patrick Schöffski. Anti-tumor effects of the novel KIT mutant inhibitor M4205 in patient-derived gastrointestinal stromal tumor (GIST) xenograft models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2666.

Abstract 3100: XenoSarc: patient-derived xenograft (PDX) models of soft tissue sarcoma (STS) and their histopathological and molecular characterization

STS constitutes a family of rare mesenchymal tumors with more than 70 subtypes described. The limited treatment options available for advanced STS patients underline the need for reliable preclinical models to test new therapeutic approaches. We established a panel of PDX models (XenoSarc) by subcutaneous implantation of fresh tumor specimens in athymic mice (nu/nu NRMI). Once tumor growth was observed, pieces of tumor were re-transplanted to next generations of animals. At each passage tumor fragments were collected for histopathological and molecular characterization. In an ongoing effort 493 STS samples from 414 consenting patients treated at the University Hospitals, Leuven (Belgium) have been transplanted. A total of 67 PDX models from 20 STS subtypes have been established, meaning they have stable morphological, immunohistochemical and genetic characteristics over at least 2 passages. The PDX platform includes more common STS subtypes such as myxofibrosarcoma (n=12 models), gastrointestinal stromal tumors (9), dedifferentiated liposarcoma (10), and leiomyosarcoma (8), as well as models from ultra-rare subtypes, e.g. pulmonary intimal sarcoma, extraskeletal osteosarcoma, mesenchymal chondrosarcoma, myxoinflammatory fibroblastic sarcoma and others. All relevant details about the donor patient and tumor characteristics, including sensitivity to the standard treatments, are known for every model. The models are well-characterized, with availability of molecular information on genomic profile (by low-coverage whole genome sequencing), and expression profile (by RNA sequencing). Xenografts are accompanied by ready to use tissue microarrays (TMA) from the models, which can be exploited for target identification and model selection for preclinical studies. Ex-mouse material can also be used to establish primary cell cultures and 3D organoids for in vitro screening purposes. The XenoSarc platform offers opportunities for studying the biology of various sarcoma subtypes including ultra-rare entities and was found to be a very reliable tool for early drug screening in STS in preparation of clinical testing of novel compounds. The platform is available for collaborative preclinical projects with academic and industrial partners.

Citation Format: Agnieszka Wozniak, Luna De Sutter, Lore De Cock, Britt Van Renterghem, Che-Jui Lee, Yannick Wang, Ulla Vanleeuw, Kimberly Verbeeck, Daphne Hompes, Friedl Sinnaeve, Hazem Wafa, Baki Topal, Joris Jaekers, Dirk Van Raemdonck, Maria Debiec-Rychter, Raf Sciot, Patrick Schöffski. XenoSarc: patient-derived xenograft (PDX) models of soft tissue sarcoma (STS) and their histopathological and molecular characterization [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3100.

HGG-56. Spatial mapping of the tumor micro-environment in pediatric glioma

High-grade glioma are the main cause of cancer-related death in children. The highly heterogeneous composition of the tumor cells and their interactions with the tumor micro-environment (TME), contribute substantially to the poor response to treatment and the high levels of morbidity and mortality. Here, we used high-dimensional, multiplexed immunohistochemistry to map the single-cell tissue architecture of 26 pediatric glioma samples covering 8 histologic diagnoses, allowing us to determine the spatial distribution of the various tumoral subtypes and how these interact with their local immune-microenvironment. Overall, this analysis showed that tumor grade anti-correlated with the amount of infiltrating cytotoxic T-lymphocytes (CTLs), which were typically more exhausted in the higher grade tumors. In addition, tumor associated macrophages were primarily infiltrating from the blood and presented an M2-like anti-inflammatory phenotype which became more extended with tumor grade. Using the spatial information, possible cell-cell interactions could be determined. In lower grade glioma, we observed an increased activation level of CTLs that were closely located to neighboring T-helper cells. In pediatric glioblastoma, on the other hand, CTLs, even though they were located close to a T-helper cell, could only minimally be activated, and showed more extended exhaustion when residing further away. Additionally, the activation of the CTLs was associated to the distance to the closest PD-L1 positive macrophage in pilocytic astrocytoma and desmoplastic infantile ganglioglioma. In conclusion, with the use of multiplex immunohistochemistry, we are able to study the tumor and TME of pediatric glioma in depth on a single-cell and spatial level, which allows us to further study the heterogeneous landscape of these tumors.

OTHR-39. Extraneural spreading of a diffuse leptomeningeal glioneuronal tumor in a child: patient-derived models show sensitivity to vinblastin and trametinib

Diffuse leptomeningeal glioneuronal tumors (DLGNT) are rare neoplasms of the central nervous system. We describe the generation of patient-derived models from a DLGNT that metastasized to the peritoneal cavity via a ventriculoperitoneal shunt in a child. The original tumor contained a KIAA1549:BRAF fusion with a chromosome 1p deletion and corresponded with methylation subclass DLGNT-MC-2 From a sample of ascitic fluid, metastatic tumoral cells could be extracted and expanded ex vivo into a long-term cell culture model. This patient-derived cell line (PDCL) showed mixed morphological phenotypes and expressed MAP2 and SYP. The KIAA1549:BRAF fusion was preserved and the PDCL still corresponded to the original methylation subclass DLGNT-MC-2. Whole-genome sequencing showed additional mutations potentially contributing to the malignant behavior of the tumor. Cytotoxic assays performed on the PDCL indicated high sensitivity to vinblastine and trametinib (MEK-inhibitor) and intermediate sensitivity to DRD/ClpP-modulators. The PDCL underwent viral transduction to induce GFP-fLux positivity and was intraperitoneally injected into immunocompromised mice. A mouse model could be generated, with the growth of a peritoneal tumor in a localized manner. The cells grown from the mouse tumor were again put into culture and were afterwards subjected to the same treatments as the PDCL. This confirmed a similar profile, with high sensitivity to vinblastin and trametinib and an intermediate sensitivity to the DRD/ClpP-modulators. In conclusion, we were able to generate patient-derived models from a metastatic DLGNT, which recapitulate the molecular characteristics of the original tumor. The models showed high sensitivity to vinblastin and targeted therapy with MEK-inhibition, but further studies are necessary to define the adequate treatment for this kind of tumor.

Correlation of Immunological and Molecular Profiles with Response to Crizotinib in Alveolar Soft Part Sarcoma: An Exploratory Study Related to the EORTC 90101 "CREATE" Trial

Alveolar soft part sarcoma (ASPS) is a rare subtype of soft tissue sarcoma characterized by an unbalanced translocation, resulting in ASPSCR1-TFE3 fusion that transcriptionally upregulates MET expression. The European Organization for Research and Treatment of Cancer (EORTC) 90101 “CREATE” phase II trial evaluated the MET inhibitor crizotinib in ASPS patients, achieving only limited antitumor activity. We performed a comprehensive molecular analysis of ASPS tissue samples collected in this trial to identify potential biomarkers correlating with treatment outcome. A tissue microarray containing 47 ASPS cases was used for the characterization of the tumor microenvironment using multiplex immunofluorescence. DNA isolated from 34 available tumor samples was analyzed to detect recurrent gene copy number alterations (CNAs) and mutations by low-coverage whole-genome sequencing and whole-exome sequencing. Pathway enrichment analysis was used to identify diseased-associated pathways in ASPS sarcomagenesis. Kaplan–Meier estimates, Cox regression, and the Fisher’s exact test were used to correlate histopathological and molecular findings with clinical data related to crizotinib treatment, aiming to identify potential factors associated with patient outcome. Tumor microenvironment characterization showed the presence of PD-L1 and CTLA-4 in 10 and 2 tumors, respectively, and the absence of PD-1 in all specimens. Apart from CD68, other immunological markers were rarely expressed, suggesting a low level of tumor-infiltrating lymphocytes in ASPS. By CNA analysis, we detected a number of broad and focal alterations. The most common alteration was the loss of chromosomal region 1p36.32 in 44% of cases. The loss of chromosomal regions 1p36.32, 1p33, 1p22.2, and 8p was associated with shorter progression-free survival. Using whole-exome sequencing, 13 cancer-associated genes were found to be mutated in at least three cases. Pathway enrichment analysis identified genetic alterations in NOTCH signaling, chromatin organization, and SUMOylation pathways. NOTCH4 intracellular domain dysregulation was associated with poor outcome, while inactivation of the beta-catenin/TCF complex correlated with improved outcome in patients receiving crizotinib. ASPS is characterized by molecular heterogeneity. We identify genetic aberrations potentially predictive of treatment outcome during crizotinib therapy and provide additional insights into the biology of ASPS, paving the way to improve treatment approaches for this extremely rare malignancy.

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

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.

Towards real-time intraoperative tissue interrogation for REIMS-guided glioma surgery

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REIMS can differentiate glioblastoma from normal brain with 99.2% sensitivity.

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Starting from 5% glioblastoma, REIMS showed a 100% correct classification rate.

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Low-grade gliomas can be identified with a 97.5% sensitivity.

Introduction

Objectives

Methods

Results

Conclusion

Case Report: An Unusual Course of Angiosarcoma After Lung Transplantation

A 35-year-old woman underwent bilateral lung transplantation for primary ciliary dyskinesia and developed vascular tumors over a slow time course. Initial presentation of non-specific vascular tumors in the lungs and liver for up to 6 years after transplantation evolved toward bilateral ovarian angiosarcoma. Tumor analysis by haplotyping and human leukocyte antigen typing showed mixed donor chimerism, proving donor origin of the tumoral lesions. In retrospect, the donor became brain dead following neurosurgical complications for a previously biopsy-proven cerebral hemangioma, which is believed to have been a precursor lesion of the vascular malignancy in the recipient. Donor-transmitted tumors should always be suspected in solid organ transplant recipients in case of uncommon disease course or histology, and proper tissue-based diagnosis using sensitive techniques should be pursued.

ALK-positive histiocytosis: a new clinicopathologic spectrum highlighting neurologic involvement and responses to ALK inhibition

ALK-positive histiocytosis is a rare subtype of histiocytic neoplasm first described in 2008 in 3 infants with multisystemic disease involving the liver and hematopoietic system. This entity has subsequently been documented in case reports and series to occupy a wider clinicopathologic spectrum with recurrent KIF5B-ALK fusions. The full clinicopathologic and molecular spectra of ALK-positive histiocytosis remain, however, poorly characterized. Here, we describe the largest study of ALK-positive histiocytosis to date, with detailed clinicopathologic data of 39 cases, including 37 cases with confirmed ALK rearrangements. The clinical spectrum comprised distinct clinical phenotypic groups: infants with multisystemic disease with liver and hematopoietic involvement, as originally described (Group 1A: 6/39), other patients with multisystemic disease (Group 1B: 10/39), and patients with single-system disease (Group 2: 23/39). Nineteen patients of the entire cohort (49%) had neurologic involvement (7 and 12 from Groups 1B and 2, respectively). Histology included classic xanthogranuloma features in almost one-third of cases, whereas the majority displayed a more densely cellular, monomorphic appearance without lipidized histiocytes but sometimes more spindled or epithelioid morphology. Neoplastic histiocytes were positive for macrophage markers and often conferred strong expression of phosphorylated extracellular signal-regulated kinase, confirming MAPK pathway activation. KIF5B-ALK fusions were detected in 27 patients, whereas CLTC-ALK, TPM3-ALK, TFG-ALK, EML4-ALK, and DCTN1-ALK fusions were identified in single cases. Robust and durable responses were observed in 11/11 patients treated with ALK inhibition, 10 with neurologic involvement. This study presents the existing clinicopathologic and molecular landscape of ALK-positive histiocytosis and provides guidance for the clinical management of this emerging histiocytic entity.

Histopathological and Molecular Profiling of Clear Cell Sarcoma and Correlation with Response to Crizotinib: An Exploratory Study Related to EORTC 90101 "CREATE" Trial

Simple Summary

Clear cell sarcoma (CCSA) is a rare subtype of soft tissue sarcoma characterized by EWSR1 rearrangement and subsequent MET upregulation. The European Organisation for Research and Treatment of Cancer 90101 phase II trial evaluated the MET inhibitor crizotinib in CCSA but resulted in only sporadic responses. The aim of this exploratory study was to identify the molecular alterations potentially relevant for the treatment outcome by using archival CCSA samples and trial-related clinical data. We characterized MET signaling and revealed an infrequent activation of MET, which may explain the lack of response to crizotinib in the disease cohort. Based on sequencing analyses, we discovered copy number alterations, mutations and dysregulated pathways with potentially predictive or prognostic values for patients’ outcomes. This work describes the molecular heterogeneity in CCSA and provides deep insight into the biology of this ultra-rare malignancy, which may potentially lead to better therapeutic approaches.

Abstract

Clear cell sarcoma (CCSA) is characterized by a chromosomal translocation leading to EWSR1 rearrangement, resulting in aberrant transcription of multiple genes, including MET. The EORTC 90101 phase II trial evaluated the MET inhibitor crizotinib in CCSA but resulted in only sporadic responses. We performed an in-depth histopathological and molecular analysis of archival CCSA samples to identify alterations potentially relevant for the treatment outcome. Immunohistochemical characterization of MET signaling was performed using a tissue microarray constructed from 32 CCSA cases. The DNA from 24 available tumor specimens was analyzed by low-coverage whole-genome sequencing and whole-exome sequencing for the detection of recurrent copy number alterations (CNAs) and mutations. A pathway enrichment analysis was performed to identify the pathways relevant for CCSA tumorigenesis. Kaplan–Meier estimates and Fisher’s exact test were used to correlate the molecular findings with the clinical features related to crizotinib treatment, aiming to assess a potential association with the outcomes. The histopathological analysis showed the absence of a MET ligand and MET activation, with the presence of MET itself in most of cases. However, the expression/activation of MET downstream molecules was frequently observed, suggesting the role of other receptors in CCSA signal transduction. Using sequencing, we detected a number of CNAs at the chromosomal arm and region levels. The most common alteration was a gain of 8q24.21, observed in 83% of the cases. The loss of chromosomes 9q and 12q24 was associated with shorter survival. Based on exome sequencing, 40 cancer-associated genes were found to be mutated in more than one sample, with SRGAP3 and KMT2D as the most common alterations (each in four cases). The mutated genes encoded proteins were mainly involved in receptor tyrosine kinase signaling, polymerase-II transcription, DNA damage repair, SUMOylation and chromatin organization. Disruption in chromatin organization was correlated with longer progression-free survival in patients receiving crizotinib. Conclusions: The infrequent activation of MET may explain the lack of response to crizotinib observed in the majority of cases in the clinical trial. Our work describes the molecular heterogeneity in CCSA and provides further insight into the biology of this ultra-rare malignancy, which may potentially lead to better therapeutic approaches for CCSA.

YAP1-TFE3-fused hemangioendothelioma: a multi-institutional clinicopathologic study of 24 genetically-confirmed cases

YAP1-TFE3-fused hemangioendothelioma is an extremely rare malignant vascular tumor. We present the largest multi-institutional clinicopathologic study of YAP1-TFE3-fused hemangioendothelioma to date. The 24 cases of YAP1-TFE3-fused hemangioendothelioma showed a female predominance (17 female, 7 male) across a wide age range (20-78 years old, median 44). Tumors were most commonly located in soft tissue (50%), followed by bone (29%), lung (13%), and liver (8%), ranging from 3 to 115 mm in size (median 40 mm). About two-thirds presented with multifocal disease, including 7 cases with distant organ metastasis. Histopathologically, we describe three dominant architectural patterns: solid sheets of coalescing nests, pseudoalveolar and (pseudo)vasoformative pattern, and discohesive strands and clusters of cells set in a myxoid to myxohyaline stroma. These patterns were present in variable proportions across different tumors and often coexisted within the same tumor. The dominant cytomorphology (88%) was large epithelioid cells with abundant, glassy eosinophilic to vacuolated cytoplasm, prominent nucleoli and well-demarcated cell borders. Multinucleated or binucleated cells, prominent admixed erythrocytic and lymphocytic infiltrates, and intratumoral fat were frequently present. Immunohistochemically, ERG, CD31, and TFE3 were consistently expressed, while expression of CD34 (83%) and cytokeratin AE1/AE3 (20%) was variable. CAMTA1 was negative in all but one case. All cases were confirmed by molecular testing to harbor YAP1-TFE3 gene fusions: majority with YAP1 exon 1 fused to TFE3 exon 4 (88%), or less commonly, TFE3 exon 6 (12%). Most patients (88%) were treated with primary surgical resection. Over a follow-up period of 4-360 months (median 36 months) in 17 cases, 35% of patients remained alive without disease, and 47% survived many years with stable, albeit multifocal and/or metastatic disease. Five-year progression-free survival probability was 88%. We propose categorizing YAP1-TFE3-fused hemangioendothelioma as a distinct disease entity given its unique clinical and histopathologic characteristics in comparison to conventional epithelioid hemangioendothelioma.

An egg in the leg: Case report of an osteochondrolipoma

Osteochondrolipomas, a very rare combination of chondroid and osseous differentiation within lipomas, are typically found in the neck and head area. We present the case of an osteochondrolipoma in the thigh of a 54-year-old female, with matching histological and cytological correlation. To the best of our knowledge, this atypical location has only been reported once in the literature.

TMOD-22. DIFFERENTIAL DRUG SENSITIVITY ANALYSIS IN PAIRED PATIENT-DERIVED CELL LINES OF GLIOBLASTOMA

Glioblastoma (GBM) remains the most aggressive adult brain tumour with dismal prognosis. Even when treated by the most optimal standard-of-care modalities, disease progression remains consistently inevitable. Understanding how tumours evolve from a newly diagnosed to a recurrent setting is therefore critical, but research models to functionally test how therapeutic interventions evolve accordingly remain scarce. Here, we describe our efforts to develop paired models including newly diagnosed and recurrent GBM cell lines derived from the same patients. Overall, we collected 50 tumour samples originating from 24 patients at different time points in their treatment scheme. This resulted in the generation of 27 models overall, from which 18 originated from 9 patients at different timepoints. The latter were subsequently investigated extensively. First, using genomic profiling, we consistently observed an increase in mutational burden and chromosomal aberrations in the recurrent samples, while transcriptomic profiling showed that tumour subtypes evolved in a very patient-specific way. A large fraction of the recurrent models showed resistance to temozolomide (TMZ), which coincided with a downregulation of DNA repair (MMR) pathways or mutations. Half of the tested models also acquired resistance to radiation therapy. Next to standard-of-care therapy, we investigated several small molecule inhibitors that are currently in clinical evaluation, which also showed differential sensitivity. Overall, the developed paired cell lines recapitulate the most important features related to tumour recurrence, and offer the opportunity for more elaborate dependency screening efforts.

EXTH-20. SINGLE-CELL DRUG ACTIVITY MAPPING IN GLIOBLASTOMA IDENTIFIES EXTENDED DRUG RESPONSE HETEROGENEITY AND THERAPY-INDUCED CELLULAR PLASTICITY

Glioblastoma (GBM) remains a highly malignant and incurable brain tumour. The inability to achieve clinical improvements in GBM treatment can be attributed to the excessive heterogeneity and plasticity of GBM cells, which is reflected by the presence of various cellular states within each tumour. How each of these tumour cell subtypes respond to therapy remains largely unknown. In this work, we developed a functional diagnostic analysis pipeline to measure therapeutic activity in GBM tumour cells at single-cell resolution using mass cytometry by time-of-flight (CyTOF). By applying an optimised GBM-specific and therapy-tailored antibody panel, we measured therapeutic activity upon exposure to ionising radiation (RT) or a small molecule MDM2 inhibitor (AMG232) in a cohort of patient-derived GBM cell lines (n=14). As such, extended heterogeneity in drug responsiveness was reflected by diverse degrees of alterations in cell cycle progression and apoptotic signalling, in addition to shifts in tumoral phenotypic states implying therapy-induced plasticity. A similar approach was used to measure drug activity in freshly resected tumour samples (n=18) harvested from different tumour regions (core or invasive front) within hours following surgery. Accordingly, we identified highly variable fractions of responsive tumour and microenvironmental cell populations in a patient-specific way. The ability to measure drug activity at single-cell resolution in a patient-tailored manner by applying a genotype-agnostic method, paves the way for advanced precision cancer medicine in GBM by offering a novel approach to more precisely select eligible patients for prospective clinical trials.

PATH-21. THE SINGLE-CELL PATHOLOGY LANDSCAPE OF PEDIATRIC GLIOMA

High-grade glioma are the main cause of cancer-related death in children. Despite extensive research, their prognosis remains poor with very few treatment options. This can be attributed to the highly heterogeneous and plastic nature of glioma tumor cells and their interactions with the microenvironment, although quantitative data are still largely missing. Here, we used high-dimensional, multiplexed immunohistochemistry to map the spatial, single-cell tissue architecture of 31 pediatric glioma samples covering 9 histologic diagnoses. This novel approach allowed us to map the spatial distribution of the various tumoral subtypes, which typically occur in specific tumoral niches, and how these interact with their local immune-microenvironment. Finally, by aligning these findings to the clinical data of the patients and comparing these to adult glioblastoma, we are now able to more precisely describe the heterogeneous landscape of pediatric glioma at single-cell resolution.

PATH-20. SPATIAL MAPPING OF THERAPY-INDUCED, PATHOLOGICAL CHANGES IN GLIOBLASTOMA AT SINGLE-CELL RESOLUTION

Glioblastoma (GBM) remains a highly malignant, intrinsically resistant and inevitably recurring brain tumor with dismal prognosis. The aggressiveness and lack of effective GBM treatments can be attributed to the highly heterogeneous and plastic nature of GBM tumor cells, which easily confer resistance to standard-of-care (SOC) therapy. While tumor progression has also been attributed to interactions with the tumor microenvironment, quantitative data describing these interactions are still largely missing. Here, we used high-dimensional, multiplexed immunohistochemistry to map evolutions in the spatial, single-cell tissue architecture of 120 paired adult GBM tumor samples derived from 60 patients at diagnosis (ND) and upon recurrence (REC) following SOC treatment. We mapped the spatial distribution of a multitude of GBM tumoral subtypes across this multicentric cohort, through which we identified a high level of heterogeneity defined by specific tumoral niches within and across patients and which evolved when subjected to SOC therapy. In addition, we describe the relationship of the various tumoral niches with their local immune-infiltrates, highlighting an even more immunosuppressive environment following SOC resistance. Finally, by aligning these findings to the observed genomic aberrations and the clinical data of the patients, we are now able to more precisely describe the heterogeneous landscape of glioblastoma and how it evolves under SOC treatment at spatial, single-cell resolution.

An uncommon presentation of a cutaneous angiosarcoma

Cutaneous angiosarcoma (cAS) is a rare and aggressive malignant vascular tumor, which mostly occurs in the head and neck region. The outcome of cAS is poor and timely diagnosis is paramount, but often delayed because of the slow onset and the variance in presentation. This paper reports on a case of an 88-year old woman who presented with a persisting "hematoma" in the left retro-auricular region. Although considered at initial differential diagnosis, no signs of malignancy were identified in histopathology and imaging in the diagnostic work-up. At first, short-term follow-up showed no progression of the lesion. But 3 months after the first presentation additional biopsies were taken, because of rapid expansion of the lesion. The initial histopathological findings were most consistent with a benign vascular lesion, with signs of hemorrhage and reactive inflammation. However, the additional immunohistochemical analysis showed the presence of MYC oncoprotein, which confirmed the clinical suspicion of angiosarcoma. Because size and location of the lesion rendered complete resection unattainable, radiotherapy was commenced, but no significant volume reduction could be achieved. Therefore, palliative irradiation was initiated. The patient passed away 1 month later. Clinical diagnosis is often difficult and little is known about imaging of cAS. Histology and immunohistochemistry can be misleading, as cAS are easily mistaken for other lesions. Most studies report that multimodality treatment with surgery and radiotherapy is preferable, but this can be challenging in the head & neck region.

Comprehensive Molecular Analysis of Inflammatory Myofibroblastic Tumors Reveals Diverse Genomic Landscape and Potential Predictive Markers for Response to Crizotinib

PURPOSE

The European Organization for Research and Treatment of Cancer (EORTC) clinical phase II trial 90101 "CREATE" showed high antitumor activity of crizotinib, an inhibitor of anaplastic lymphoma kinase (ALK)/ROS1, in patients with advanced inflammatory myofibroblastic tumor (IMFT). However, recent findings suggested that other molecular targets in addition to ALK/ROS1 might also contribute to the sensitivity of this kinase inhibitor. We therefore performed an in-depth molecular characterization of archival IMFT tissue, collected from patients enrolled in this trial, with the aim to identify other molecular alterations that could play a role in the response to crizotinib.

EXPERIMENTAL DESIGN

Twenty-four archival IMFT samples were used for histopathological assessment and DNA/RNA evaluation to identify gene fusions, copy-number alterations (CNA), and mutations in the tumor tissue. Results were correlated with clinical parameters to assess a potential association between molecular findings and clinical outcomes.

RESULTS

We found 12 ALK fusions with 11 different partners in ALK-positive IMFT cases by Archer analysis whereas we did not identify any ROS1-rearranged tumor. One ALK-negative patient responding to crizotinib was found to have an ETV6-NTRK fusion in the tumor specimen. The CNA profile and mutational landscape of IMFT revealed extensive molecular heterogeneity. Loss of chromosome 19 (25% of cases) and PIK3CA mutations (9% of cases) were associated with shorter progression-free survival in patients receiving crizotinib.

CONCLUSIONS

We identified multiple genetic alterations in archival IMFT material and provide further insight into the molecular profile of this ultra-rare, heterogeneous malignancy, which may potentially translate into novel treatment approaches for this orphan disease.

Investigation of tissue level tolerance for cerebral contusion in a controlled cortical impact porcine model

OBJECTIVE

Cerebral contusions (CC) represent a frequent lesion in traumatic brain injury, with potential morbidity from mass effect and tissue loss. Better understanding of the mechanical etiology will help to improve head protection. The goal of this study is to investigate the threshold for mechanical impact parameters to induce CC in an in vivo porcine controlled cortical impact model.

METHODS

Thirty-four adult male pigs underwent craniotomy and controlled cortical impact with a hemispherical tip on intact dura under general anesthesia. Peak impact depth varied between 1.1 and 12.6 mm, and impact velocity between 0.4 and 2.2 m/s while the dwell time was kept at 200 ms. Two days following impact, the animals underwent magnetic resonance (MR) imaging of the brain, and were subsequently sacrificed for brain extraction. CC damage was investigated by magnetic resonance imaging and histology.

RESULTS

All animals recovered from the impact without overt neurological deficit. Provoked injuries were histologically confirmed to be CC. Decreasing probability of cortical damage and white matter edema volume was observed with decreasing impact depth and velocity. No CC could be demonstrated below a product of impact depth and velocity of 0.8 mm*m/s, whereas the probability for CC was one third below 15 mm*m/s. The threshold for CC development as estimated from the current series of experiments, was situated at an impact depth of 2.0 mm and impact velocity of 0.4 m/s.

CONCLUSION

Mechanical thresholds for CC development could be explored in the current porcine controlled cortical impact model. Findings will be used to further refine a cerebral contusion porcine model with volumetric histology data in light of future finite element cerebral contusion validation studies.

Long-term efficacy update of crizotinib in patients with advanced, inoperable inflammatory myofibroblastic tumour from EORTC trial 90101 CREATE

PURPOSE

European Organisation for Research and Treatment of Cancer (EORTC) 90101 (CREATE) was a prospective, multicentric, non-randomised, open-label phase II basket trial to assess the efficacy and safety of crizotinib in patients with different types of cancers, including advanced inflammatory myofibroblastic tumour (IMT) with or without anaplastic lymphoma kinase (ALK) rearrangements. Here, we report updated results with long-term follow-up.

PATIENTS/METHODS

After central reference pathology, eligible ALK-positive and ALK-negative patients with advanced/metastatic IMT deemed incurable with surgery, radiotherapy or systemic therapy received oral crizotinib 250 mg twice daily. The ALK status was assessed centrally using immunohistochemistry and fluorescence in situ hybridisation. The primary end-point was the proportion of patients who achieved an objective response (i.e. complete or partial response). If ≥6 ALK-positive patients achieved a confirmed response, the trial would be deemed successful.

RESULTS

At data cut-off on 28th January 2021, we performed the final analysis of this trial. Of the 20 eligible and treated patients (19 of whom were evaluable for efficacy), with a median follow-up of 50 months, five were still on crizotinib treatment (4/12 ALK-positive and 1/8 ALK-negative patients). The updated objective response rate (ORR) was 66.7% (95% confidence interval [CI] 34.9-90.1%) in ALK-positive patients and 14.3% (95% CI 0.0-57.9%) in ALK-negative patients. In the ALK-positive and ALK-negative patients, the median progression-free survival was 18.0 months (95% CI 4.0-NE) and 14.3 months (95% CI 1.2-31.1), respectively; 3-year overall survival rates were 83.3% (95% CI 48.2-95.6) and 34.3% (95% CI 4.8-68.5). Safety results were consistent with previously reported data.

CONCLUSION

These updated results confirm previous findings that crizotinib is effective, with durable responses, in patients with locally advanced or metastatic ALK-positive IMT. With further follow-up after the original primary analysis, the ORR increased, as patients derived long-term benefit and some responses converted from stable disease to partial responses.

CLINICAL TRIAL NUMBER

EORTC 90101, NCT01524926.

Retrospective Analysis of the Clinical Presentation, Treatment and Outcome of Angiosarcoma in a Sarcoma Referral Center

INTRODUCTION

Angiosarcoma (AS) is a rare subtype of soft tissue sarcoma. We performed a retrospective analysis of patient characteristics, treatments and prognostic factors in patients treated in a single sarcoma center.

METHODS

We reviewed records of patients treated between 1987 and 2018, categorized in 7 different subtypes according to tissue of origin and underlying risk factors. The Kaplan-Meier method was used to estimate overall survival (OS); the Cox proportional hazards model was used to study prognostic variables.

RESULTS

Among 134 patients, 30% had radiation-induced, 31% primary soft tissue, 24% cutaneous, 5% breast, 4% bone, 2% lymphedema-associated and 4% unknown primary AS. Key patient/disease characteristics varied between subgroups. The median OS was 22.0 months for the entire cohort, with 28.9% with a 5-year survival. Metastasis at diagnosis was seen in 23% of patients; 38% developed metachronous metastasis. Sixty-six (49%) patients received systemic therapy; common first-line treatments were doxorubicin (48%) and paclitaxel (39%), without a significant difference in OS between agents. Younger age, breast/radiation-induced AS, primary surgery and palliative chemotherapy were associated with better OS. Synchronous metastasis, soft tissue/unknown primary location correlated with poor survival.

CONCLUSION

AS is a very heterogeneous sarcoma subtype, with substantial variability in clinical presentation and survival among patient subsets. Prognosis is poor, and there is no difference in outcome comparing the 2 most frequently used chemotherapy agents in the first line, paclitaxel and doxorubicin.

DNA methylation based glioblastoma subclassification is related to tumoral T-cell infiltration and patient survival

BACKGROUND

Histologically classified glioblastomas (GBM) can have different clinical behavior and response to therapy, for which molecular subclassifications have been proposed. We evaluated the relationship of epigenetic GBM subgroups with immune cell infiltrations, systemic immune changes during radiochemotherapy, and clinical outcome.

METHODS

450K genome-wide DNA methylation was assessed on tumor tissue from 93 patients with newly diagnosed GBM, treated with standard radiochemotherapy and experimental immunotherapy. Tumor infiltration of T cells, myeloid cells, and Programmed cell death protein 1 (PD-1) expression were evaluated. Circulating immune cell populations and selected cytokines were assessed on blood samples taken before and after radiochemotherapy.

RESULTS

Forty-two tumors had a mesenchymal, 27 a receptor tyrosine kinase (RTK) II, 17 RTK I, and 7 an isocitrate dehydrogenase (IDH) DNA methylation pattern. Mesenchymal tumors had the highest amount of tumor-infiltrating CD3+ and CD8+ T cells and IDH tumors the lowest. There were no significant differences for CD68+ cells, FoxP3+ cells, and PD-1 expression between groups. Systemically, there was a relative increase of CD8+ T cells and CD8+ PD-1 expression and a relative decrease of CD4+ T cells after radiochemotherapy in all subgroups except IDH tumors. Overall survival was the longest in the IDH group (median 36 mo), intermediate in RTK II tumors (27 mo), and significantly lower in mesenchymal and RTK I groups (15.5 and 16 mo, respectively).

CONCLUSIONS

Methylation based stratification of GBM is related to T-cell infiltration and survival, with IDH and mesenchymal tumors representing both ends of a spectrum. DNA methylation profiles could be useful in stratifying patients for immunotherapy trials.

Curative, Organ-Sparing, Multimodal, Perioperative Treatment of a Young Patient with a Rectoanal Inflammatory Myofibroblastic Tumor

INTRODUCTION

We report the case of a young female patient with a technically resectable, nonmetastatic, rectoanal, anaplastic lymphoma kinase gene (ALK)-translocated inflammatory myofibroblastic tumor (IMFT).

CASE PRESENTATION

The patient was successfully treated preoperatively with the tyrosine kinase inhibitor (TKI) crizotinib, to downsize the primary tumor, followed by sphincter-sparing surgery, and adjuvant radiotherapy and crizotinib. She is now in follow-up with good sphincter function and with no evidence of active disease.

CONCLUSION

Pre- and postoperative treatment administration of crizotinib can be given with curative intent to patients with locally advanced, nonmetastatic IMFTs to avoid mutilating surgery.