Glioblastoma multiforme (GBM) are mortifying brain tumours that contain a subpopulation of tumour cells with stem-like properties, termed glioblastoma stem-like cells (GSCs). GSCs largely contribute to tumour initiation, propagation and resistance to current anti-cancer therapies. GSCs are situated in perivascular niches, closely associated with brain microvascular endothelial cells, thereby involved in bidirectional molecular and cellular interactions. Moreover, extracellular vesicles are suspected to carry essential information that can adapt the microenvironment to the tumour’s needs, including tumour-induced angiogenesis. In GBM, extracellular vesicles produced by differentiated tumour cells and GSCs were demonstrated to disseminate locally and at distance. Here, we report that the pro-angiogenic pro-permeability factor VEGF-A is carried in extracellular vesicles secreted from ex vivo cultured patient-derived GSCs. Of note, extracellular vesicle-derived VEGF-A contributes to the in vitro elevation of permeability and angiogenic potential in human brain endothelial cells. Indeed, VEGF-A silencing in GSCs compromised in vitro extracellular vesicle-mediated increase in permeability and angiogenesis. From a clinical standpoint, extracellular vesicles isolated from circulating blood of GBM patients present higher levels of VEGF-A, as compared to healthy donors. Overall, our results suggest that extracellular vesicle-harboured VEGF-A targets brain endothelial cells and might impact their ability to form new vessels. Thus, tumour-released EV cargo might emerge as an instrumental part of the tumour-induced angiogenesis and vascular permeability modus operandi in GBM.

SMARCA4-deficient thoracic sarcoma (SMARCA4-DTS) is a recently described entity with an aggressive clinical course and specific genetic alterations of the BAF chromatin remodeling complex. In the present study, we reviewed the clinical and pathologic features of 30 cases of SMARCA4-DTS, discussed its main differential diagnoses and the challenging diagnostic scenarios that the average pathologist may face. In addition, we tested the specificity of the “SMARCA4-DTS immunohistochemical signature” (co-loss of SMARCA4 and SMARCA2 with overexpression of SOX2) in a large cohort of intrathoracic malignancies. Patients ranged from 28 to 90 years of age (median: 48 y), with a marked male predominance (male:female=9:1) and they were usually smokers. Tumors were generally large compressive masses located in the mediastinum (n=13), pleura (n=5), lung (n=2) or in 2 or more of these topographies (n=10). Treatment strategies were varied, including 1 case treated with EZH2 inhibitors. Median overall survival was 6 months. Histologically, tumors were poorly differentiated frequently showing rhabdoid features. A subset of cases showed a focal myxoid stroma (7%, n=2/30) and rare cases displayed a previously unreported pattern simulating desmoplastic small round cell tumors (7%, n=2/30). Making a diagnosis was challenging when dealing with biopsy material from massively necrotic tumors and in this setting the expression of SOX2, CD34, and SALL4 proved useful. All tested cases displayed concomitant loss of SMARCA4 and SMARCA2 and most tumors expressed epithelial markers (Pan-keratin or EMA) (n=29/30), SOX2 (n=26/27), and CD34 (n=17/27). SMARCB1 expression was retained in all cases (23/23). SALL4 and Claudin-4 were expressed in a subset of cases (n=7/21 and 2/19, respectively). TTF-1 and P63 were focally expressed in 1 case each. P40 and NUT were not expressed (0/23 and 0/20, respectively) The SMARCA4-DTS immunohistochemical signature was both sensitive and specific, with only a subset of small cell carcinoma of the ovary hypercalcemic type showing overlapping phenotypes. Our study confirms and expands the specific features of SMARCA4-DTS, emphasizing the fact that they can be straightforwardly identified by pathologists.

Conclusion:We expand the current knowledge on PRDM10-STT and SCD34FT and provide additional evidence for considering them as overlapping entities.

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Background: LRRC15 is a member of the LRR (leucine-rich repeat) superfamily present on tumor-associated fibroblasts (CAFs) and stromal cells. The expression of LRRC15 is upregulated by the pro-inflammatory cytokine TGFβ. ABBV-085 is a monomethyl auristatin E (MMAE)-containing antibody-drug conjugate (ADC) designed to target LRRC15, and which has shown significant anti-tumor activity in several tumor models. This is the first focused examination of LRRC15 expression and ABBV-085 activity in soft-tissue sarcomas (STS). Methods: We analyzed the LRRC15 expression profile by immunohistochemistry in 711 STS cases, covering a broad spectrum of STS histologies and sub-classifications. In vivo experiments were carried out by using LRRC15-positive and LRRC15-negative patient-derived xenograft (PDX) models of STS. Results: In contrast to patterns observed in epithelial tumors, LRRC15 was expressed not only by stromal cells but also by cancer cells in multiple subsets of STS with significant variations noted between histological subtypes. Overexpression of LRRC15 is positively correlated with grade and independently associated with adverse outcome. ABBV-085 has robust preclinical efficacy against LRRC15 positive STS patient-derived xenograft (PDX) models. Conclusion: We provide the first preclinical evidence that LRRC15 targeting with an antibody-drug conjugate is a promising strategy in LRRC15-positive STS. ABBV-085 is being evaluated in an ongoing clinical trial in STS and other malignancies.

Background Undifferentiated pleomorphic sarcoma (UPS) is the most frequent, aggressive and less-characterized sarcoma subtype. This study aims to assess UPS molecular characteristics and identify specific therapeutic targets. Methods High-throughput technologies encompassing immunohistochemistry, RNA-sequencing, whole exome-sequencing, mass spectrometry, as well as radiomics were used to characterize three independent cohorts of 110, 25 and 41 UPS selected after histological review performed by an expert pathologist. Correlations were made with clinical outcome. Cell lines and xenografts were derived from human samples for functional experiments. Findings CD8 positive cell density was independently associated with metastatic behavior and prognosis. RNA-sequencing identified two main groups: the group A, enriched in genes involved in development and stemness, including FGFR2, and the group B, strongly enriched in genes involved in immunity. Immune infiltrate patterns on tumor samples were highly predictive of gene expression classification, leading to call the group B ‘ immune-high’ and the group A ‘ immune-low’. This molecular classification and its prognostic impact were confirmed on an independent cohort of UPS from TCGA. Copy numbers alterations were significantly more frequent in immune-low UPS. Proteomic analysis identified two main proteomic groups that highly correlated with the two main transcriptomic groups. A set of nine radiomic features from conventional MRI sequences provided the basis for a radiomics signature that could select immune-high UPS on their pre-therapeutic imaging. Finally, in vitro and in vivo anti-tumor activity of FGFR inhibitor JNJ-42756493 was selectively shown in cell lines and patient-derived xenograft models derived from immune-low UPS. Interpretation Two main disease entities of UPS, with distinct immune phenotypes, prognosis, molecular features and MRI textures, as well as differential sensitivity to specific anticancer agents were identified. Immune-high UPS may be the best candidates for immune checkpoint inhibitors, whereas this study provides rational for assessing FGFR inhibition in immune-low UPS. Funding This work was partly founded by a grant from La Ligue.

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A subset of benign peripheral nerve sheath tumors are "hybrid" combining several lines of differentiation, most often schwannian and perineurial features. The pathogenesis of these tumors was poorly described until the recent discovery of recurrent VGLL3 rearrangements in hybrid schwannoma/perineuriomas, supporting the hypothesis that this entity represents a distinct subgroup of tumors and not only a morphologic variation of other peripheral nerve sheath tumors. Following this finding, we investigated 10 cases of hybrid peripheral nerve sheath tumors with immunohistochemistry, RNA sequencing, and array comparative genomic hybridization. By light microscopy, 7 tumors were hybrid schwannoma/perineurioma tumors, and 3 were hybrid schwannoma/neurofibroma. Most cases of hybrid schwannoma/perineuriomas displayed VGLL3 rearrangements fused in 5′ either to CHD7 or CHD9 (n = 6/7) and had simple diploid genetic profiles with few copy number alterations. Compared with a control group composed of 28 tumors associated with varied neural phenotypes, all VGLL3-fused tumors clustered together by transcriptomic analysis. In contrast, 1 case of hybrid schwannoma/perineurioma tumor harbored a CDH9-ZFHX3 fusion, a prominent perineurial component identified by immunohistochemistry and clustered with perineuriomas. No recurrent genetic alteration was seen in the 3 hybrid schwannoma/neurofibromas. To summarize, this study confirms and expands the recent findings on hybrid schwannoma/ perineurioma, highlighting the predominance of VGLL3 fusions in these tumors.