The highly heterogeneous and invasive nature characteristic of high-grade gliomas (HGG) has historically limited the efficacy of standard-of-care approaches, resulting in poor prognosis and treatment outcomes. Novel immunotherapies have shown remarkable potential to promote antitumoral immune responses and allow for long-term tumor remission. However, the complexity of the HGG tumor microenvironment and the dynamic immunological changes associated with immunotherapy response can limit the diagnostic utility of conventional magnetic resonance imaging (MRI) and positron emission tomography (PET) approaches. Consequently, distinguishing true tumor progression from immunotherapy-related effects often requires prolonged clinical follow-up over several months. To address this, novel quantitative MRI and PET-based approaches are being evaluated in preclinical studies and clinical trials. These advanced imaging methods target key biological features of the tumor microenvironment, including vascularity, cellularity, intratumoral habitats, tracer pharmacokinetics and immune infiltration, and can provide metrics to stratify patient response at earlier timepoints to support clinical decision making and improve treatment outcomes. This review highlights key HGG biological characteristics, describes standard-of-care and emerging therapeutic strategies, and discusses both conventional and advanced imaging methods to characterize immunotherapeutic responses.

Wilms tumor (WT) is the most common renal malignancy of childhood. Despite improvements in the overall survival, relapse occurs in ~15% of patients with favorable histology WT (FHWT). Half of these patients will succumb to their disease. Identifying novel targeted therapies remains challenging in part due to the lack of faithful preclinical in vitro models. Here we establish twelve patient-derived WT cell lines and demonstrate that these models faithfully recapitulate WT biology using genomic and transcriptomic techniques. We then perform loss-of-function screens to identify the nuclear export gene, XPO1, as a vulnerability. We find that the FDA approved XPO1 inhibitor, KPT-330, suppresses TRIP13 expression, which is required for survival. We further identify synergy between KPT-330 and doxorubicin, a chemotherapy used in high-risk FHWT. Taken together, we identify XPO1 inhibition with KPT-330 as a potential therapeutic option to treat FHWTs and in combination with doxorubicin, leads to durable remissions in vivo.

Background/Objectives: Human epidermal growth factor receptor 2 (HER2)-positive breast cancer is linked to poorer overall survival and a higher risk of brain metastases compared to HER2-negative breast cancer. Current preclinical studies lack robust HER2+ metastatic syngeneic mouse models for investigating targeted and immunomodulatory therapies. This study aims to develop effective HER2+ mouse models to investigate response dynamics to HER2-targeted therapy and immunotherapy. Methods: The human HER2 gene (WT or mutant p.A775_G776insYVMA, GFP-tagged at the C-terminus) was introduced into triple-negative breast cancer (TNBC) mouse mammary carcinoma cells with known metastatic potential (4T1 and EO771) via lentiviral transduction. HER2 expression and phosphorylation were analyzed using Western blotting and immunohistochemistry. Tumors were treated with HER2-targeted therapy (trastuzumab and tucatinib), immune checkpoint blockade (anti-PD-1 and anti-CTLA-4), and anti-HER2 antibody–drug conjugate (ADC) to evaluate treatment efficacy. Metastatic potential was assessed with brain fluorescence imaging. Statistical analysis included ANOVA and Kaplan–Meier tests. Results: Newly established lines demonstrated expression of HER2+, with HER2^YVMA lines showing higher phosphorylation than HER2^WT lines. Cells were tumorigenic, demonstrating in vivo tumor take rates at 100% for 4T1-HER2 and 15–30% for EO771-HER2. HER2 overexpression led to a 30% increase in spontaneous brain metastasis in the 4T1-HER2 models. Trastuzumab alone did not reduce primary tumor size but significantly reduced brain GFP signal by 17% ± 8% and 26% ± 7% in the 4T1-HER2^WT and 4T1-HER2^YVMA models, respectively. Combinational therapies with anti-HER2 therapy and immune checkpoint blockade effectively suppressed primary tumor growth and prolonged survival in EO771-HER2^YVMA model. T-Dxd, but not T-DM1, demonstrated partial treatment response in the EO771-HER2^WT model. Conclusions: HER2+ syngeneic tumor models were developed that spontaneously metastasize to the brain and demonstrate variable responses to immunotherapies and ADCs. These models are valuable for advancing molecular imaging modalities for HER2+ brain metastasis, studying blood–brain barrier penetration of HER2-targeted drugs, and exploring the combination of therapies, including immunotherapy.

Chromatin remodeling complexes, such as the SWItch/Sucrose Non-Fermentable (SWI/SNF) complex, play key roles in regulating gene expression by modulating nucleosome positioning. The core subunit SMARCB1 is essential for these functions, as it anchors the complex to the nucleosome acidic patch, enabling effective chromatin remodeling. While biallelic inactivation of SMARCB1 is a hallmark of several aggressive pediatric malignancies, the functional implication of missense mutations is not fully understood. Current diagnostic approaches focus on detecting the presence or absence of SMARCB1 by immunohistochemistry often without consideration of mutation status. Here, we present a comprehensive deep mutational scanning of SMARCB1 , encompassing 8418 alterations, to assess their functional impact. We show that RPT2 missense mutations disrupt SMARCB1 antiproliferation function by destabilizing the SWI/SNF complex and impairing chromatin remodeling and transcriptional regulation comparable to nonsense mutations. These functional defects occur despite maintaining detectable protein expression thereby challenging current diagnostic reliance on IHC. These findings provide deeper understanding of the role of SMARCB1 in chromatin remodeling and cancer biology, highlighting limitations of mutation classification approaches.

Chromatin remodeling complexes, such as the SWItch/Sucrose Non-Fermentable (SWI/SNF) complex, play key roles in regulating gene expression by modulating nucleosome positioning. The core subunit SMARCB1 is essential for these functions, as it anchors the complex to the nucleosome acidic patch, enabling effective chromatin remodeling. While biallelic inactivation of SMARCB1 is a hallmark of several aggressive pediatric malignancies, the functional implication of missense mutations is not fully understood. Current diagnostic approaches focus on detecting the presence or absence of SMARCB1 by immunohistochemistry (IHC) often without consideration of mutation status as such data is lacking. Here, we present the first comprehensive deep mutational scanning (DMS) of SMARCB1, encompassing 8,418 amino acid substitutions, to systematically assess their functional impact. We show that missense mutations in the RPT2 domain of SMARCB1 disrupt SMARCB1 tumor suppressor function by destabilizing the SWI/SNF complex. Notably, we identify mutations in RPT2 that impair chromatin remodeling and transcriptional regulation to an extent comparable to nonsense mutations, despite maintaining detectable protein expression, thus challenging the conventional diagnostic reliance on IHC. Importantly, these mutations seem to act by disrupting winged-helix domain flexibility. These findings provide a deeper understanding of the role of SMARCB1 in chromatin remodeling and cancer biology, highlighting the limitations of current mutation classification approaches. By establishing a high-throughput functional framework, this study offers a critical resource for elucidating SMARCB1’s mutational landscape and its implications for cancer diagnostics.