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Youssef, O.

Publications and source records attributed to Youssef, O..

4 recordsLinked to original sources

A multimodal precision oncology platform integrating genomics,single-cell transcriptomics, and functional drug screening expandstherapeutic options in pediatric brain tumors

Precision oncology for pediatric brain tumors mainly relies on clinically validated, targetable genomic alterations, which are often sparse, yield few matched therapies, and do not guide chemotherapy selection. We developed a tiered framework in which deep whole-genome sequencing and single-cell RNA sequencing extend targeted-therapy selection, with ex vivo functional drug screening supporting selection of both targeted therapies and chemotherapies. We applied it to 17 children with malignant CNS tumors. The approach expanded recommendations beyond genomics: functional screening provided every patient with at least one high-confidence targeted-therapy or chemotherapy nomination, while single-cell RNA sequencing identified an average of 37 druggable gene targets per patient, producing a fourfold increase in high-confidence targeted-therapy recommendations. In an exploratory analysis, functional classifications were directionally consistent with outcomes in 8 of 10 evaluable cases, although combination treatments and radiation precluded causal attribution. Single-cell profiling also identified subclone-specific vulnerabilities, supporting prospective evaluation of the platform's feasibility and predictive utility.

cancer biology↗

Spatial transcriptomics reveals interferon pathway enrichment in early relapsing serous carcinoma

High-grade serous carcinoma (HGSC) is characterized by extensive inter and intra-patient heterogeneity, complicating the identification of reliable prognostic biomarkers and the prediction of treatment response. In clinical practice, the origin of diagnostic biopsies varies, from tubo-ovarian (adnexal) tissue to omental or peritoneal metastatic foci. Whether the different sites provide similar information for molecular characterization or treatment decisions remains unclear. Studies comparing site-specific molecular details and the spatial relationship of HGSC tissue from patients with different treatment outcomes could provide answers to the open questions. Here, we used spatial transcriptomics to profile matched treatment-naive adnexal and omental tumor samples from nine HGSC patients stratified by platinum-free interval (PFI). Pathway enrichment analysis revealed several differences between short and medium- and long PFI tumors, however most of these differences were site-agnostic. Most strikingly, tumor epithelium from short PFI patients showed an inflammatory phenotype driven by increased interferon response signaling, carried by effector interferon-stimulated gene expression at both tumor sites. Further, medium- and long PFI tumors were enriched for proliferative and cell cycle regulatory programs. Differential gene expression and copy-number analyses identified three genes, complement gene C3, and interferon-related genes IFI27 and BST2, consistently associated with short PFI across adnexal and omental sites. These were validated at the tissue level using RNA in-situ hybridization. A case study of copy-number-defined subclones further suggested that this phenotype can arise as a distinct subclonal population within a single tumor. Outcome analysis, using two publicly available ovarian cancer cohorts, showed that high C3 expression was significantly associated with shorter platinum-free survival. Together, these findings implicate complement and interferon signaling as concurrent features of treatment-naive HGSC tumors with early relapse in both adnexal and omental tissue, and nominate C3 as a candidate prognostic biomarker and potential therapeutic target.

cancer biology↗

Phosphodiesterase 3A modulators sensitize tumor cells to Bcl-xL and Bcl-2/Bcl-xL inhibitors

Phosphodiesterase 3A (PDE3A) modulators are emerging anticancer agents for tumors that co-express PDE3A and Schlafen 12 (SLFN12), promoting the formation of a cytotoxic PDE3A-SLFN12 complex. The effect correlates with PDE3A and SLFN12 expression levels. In this study, we conducted a high-throughput screening of 526 compounds in three sarcoma cell lines to identify synergistic or antagonistic interactions with PDE3A modulators. Synergistic mechanisms were further investigated in cell lines and in patient-derived xenograft models of leiomyosarcoma and myxofibrosarcoma in mice. Several drug classes showed potential synergy, and PDE3A modulators sensitized cells to otherwise ineffective Bcl-2/xL inhibitors. The combination of a PDE3A modulator and a Bcl-xL inhibitor induced tumor regression in a patient-derived leiomyosarcoma model in vivo. Our findings reveal that PDE3A modulators synergized with several inhibitors of key cancer pathways, offering promising potential for future treatments. With further research, PDE3A modulators and combination therapies could provide effective targeted treatment options for tumors expressing both PDE3A and SLFN12, paving the way for innovative and hopeful advancements in cancer treatment.

molecular biology↗

Transcriptional changes consistent with impaired neuronal differentiation, angiogenesis, and tumor plasticity induced in human subpallial telencephalic organoid-glioblastoma chimeras.

Glioblastoma multiforme (GBM) is one of the most aggressive and therapy-resistant brain tumors prevalent in both adults and children. Despite extensive research to understand GBM pathology, it remains unclear how neural cells in the human brain interact with GBM cells to support their brain propagation and therapy resistance and whether GBM cells exert any influence on the properties of human neural cells. In this study, we co-culture human stem cell-derived subpallial telencephalic organoids with patient-derived proneural or mesenchymal GBM spheroids to investigate their reciprocal interactions. We show that both proneural and mesenchymal GBM spheroids readily fuse and propagate with human organoids, forming organoid-GBM chimeras, without the need for exogenous growth factors. GBM cells within the chimeras adapt by modulating gene expression profiles consistent with diminished proliferation, heightened hypoxia, increased angiogenesis, and proneural-to-mesenchymal transition in proneural GBM. Both proneural or mesenchymal GBMs also exert an impact on the properties of neural cells in the chimeras, leading to the suppression of neuronal genes and an upregulation expression of genes associated with hypoxia and angiogenesis. Collectively, this study identifies specific genes and molecular pathways that can be altered in GBM and neural cells by reciprocal interactions in a human developing brain-like environment for an increased understanding of GBM pathology and future therapy development.

cancer biology↗