Abnormal electrical properties in cancerous tumors have been observed for more than a century. Modern technological advances have enabled rapid improvements in our understanding of these electrical facets and our ability to leverage this information for diagnosis and treatment. Here, we outline the current knowledge of the electrical tumor microenvironment (eTME), including electrical abnormalities at the tissue, cell, and molecular scales. Of particular interest to solid tumors and immunotherapy, the innate immune system responds profoundly to these abnormalities with altered mobility and effector function. Improved understanding of the eTME has enabled new advances in disease detection, with techniques such as impedance spectroscopy showing promise as minimally invasive, sensitive, and specific methods that complement traditional approaches. Therapeutic strategies that use electrical stimulation via externally applied fields, electrically active nanomaterials and devices, and so-called electroceuticals have shown promise in augmenting cancer therapy efficacy, particularly via leveraging the immune system. This review summarizes the state of the field, highlighting the eTME as a foundational – yet often overlooked – feature of cancer and a rapidly-growing area of novel therapeutic development.

Supplementary Fig. S9: Expression levels of Cxcr3 and its ligands are increased in ICC tissues after GC/dual ICB treatment in murine 425-ICC.

Supplementary Fig. S8: Bulk tissue RNA sequencing analysis of ICC after GC/dual ICB combination therapy in orthotopic murine 425-ICC model.

The breast peritumor microenvironment (pTME) is increasingly recognized as a mediator of breast cancer progression and treatment resistance. However, how tumor compressive forces (i.e., solid stresses) influence it remains unclear. Using instant fluorescence lifetime imaging microscopy (FLIM), we show that in vitro compression metabolically reprograms stromal cells found in the breast pTME. Namely, compression shifts fibroblasts and differentiated adipocytes toward a more glycolytic state, but promotes increased oxidative phosphorylation in undifferentiated adipocytes. Through RNA-sequencing, we confirmed that compression downregulates oxidative phosphorylation and upregulates glycolysis in fibroblasts. Furthermore, we demonstrate that compression induces mitochondrial dysregulation in undifferentiated adipocytes, driven partly by upregulated mitophagy and disrupted fission/fusion dynamics. The analysis of human breast cancer samples confirms these stromal cell types recapitulate these distinct metabolic states, consistent with in vitro findings. By elucidating tumor-host mechano-metabolic interactions, these results will inform the development of innovative treatment strategies to improve survival.

Supplementary Fig. S12: Effect of ICB treatment scheduling on efficacy and toxicity.

Supplementary Table S1: Antibody list.

Supplementary Fig. S2: Standard chemotherapy converts ICB-resistant ICCs to ICB-responsive tumors, significantly delays tumor progression and increases survival in mice.

Mass effect, characterized by the compression and deformation of neural tissue from space-occupying lesions, can lead to debilitating neurological symptoms and poses a significant clinical challenge. In the primary brain tumor glioblastoma (GBM), we have shown previously that compressive solid stress originating from the growing tumor reduces cerebral blood flow, leading to neuronal loss, increased functional impairment, and poor clinical outcomes. However, the direct effects of compression on neurons and the underlying biophysical mechanisms are poorly understood. Here, using multiscale compression systems and physiologically relevant in vitro and in vivo models, we find that chronic mechanical compression induces neuronal apoptosis and loss of synaptic puncta, leading to disrupted neural network activity, as assessed by calcium imaging. This is accompanied by increased HIF-1 signaling and upregulation of downstream stress-adaptive genes in neurons. We further show that chronic compression triggers AP-1-driven gene expression in glial cells, promoting a neuroinflammatory response. Together, these findings reveal that solid stress directly contributes to neuronal dysfunction and inflammation caused by GBM by activating distinct pathways that can be targeted in future studies for neuroprotection.

Supplementary Fig. S10: Schematic of the animal experiment design.

The mechanical responses and properties of breast epithelial cells are known to change during malignant transformation and progression due to the dynamics of their actin cytoskeleton network organization and the resulting viscoelastic deformability. Studying the viscoelastic creep behavior of breast cells may reveal new avenues for developing novel cancer diagnostic and therapeutic biomarkers and improving fundamental biophysical understanding of the disease. Here we present an approach that uses functional principal component analysis (fPCA) to distinguish between the viscoelastic responses of malignant and non-malignant live breast cells that are subjected to shear flow in microfluidic channels under in-situ observation with optical, fluorescence, and confocal microscopy. The fPCA method extracts critical features of cell viscoelasticity from the in-situ measured creep responses of non-tumorigenic breast cells (MCF-10A), less metastatic triple-negative breast cancer (TNBC) cells (MDA-MB-468), and highly metastatic breast cancer cells (MDA-MB-231). The results demonstrate distinguishable clustering patterns for the three types of cells in the first principal component (PC) and the second PC space. The first PC, indicative of the overall level of creep compliance, accounts for more than 98% of the total variance in the observed creep responses. The scores of the cells examined on the first PC axis increase with increasing cancer malignancy. They also correlate highly with the average moduli and viscosities extracted from viscoelastic models (-83% correlation with moduli and -85% correlation with viscosities). This suggests a direct link between the malignancy of cancer and the overall creep compliance level that is governed by cell viscoelastic properties. The implications of the results are discussed for the detection of non-tumorigenic and tumorigenic breast cells at different stages of cancer progression.

Supplementary Fig. S6: CTLA-4 blockade mediates the efficacy of GC/ICB therapy in ICC and increases CD8+CTL frequency in murine ICC.

Abstract Group 3 medulloblastomas (G3MB) carry the worst prognosis among medulloblastoma subtypes, yet molecularly targeted therapies remain elusive. Standard treatments cause severe long-term morbidity in survivors. Here, we identify tumor-derived sphingosine kinase 2 (SPHK2) as an essential driver of G3MB initiation and progression. SPHK2 exacerbates local immunosuppression by suppressing cytotoxic T-cell and NK-cell activity while promoting regulatory T-cell infiltration. Genetic or pharmacologic SPHK2 inhibition using Opaganib attenuates pro-survival tumor signaling and restores anti-tumor immunity, significantly improving survival in syngeneic G3MB mouse models. Combining Opaganib with fractionated low-dose radiation (f-LDRT) further enhances antigen presentation and reprograms tumor-associated myeloid cells toward an anti-tumor phenotype. This combination therapy markedly prolongs survival without inducing significant toxicity. Overall, our study establishes SPHK2 as a previously unrecognized therapeutic target and presents a safe, effective, microenvironment-reprogramming regimen for G3MB. One Sentence Summary Direct inhibition of tumor-derived SPHK2 overcomes local immunosuppression and downregulates pro-survival signaling in Group 3 medulloblastoma, while combination with fractionated low-dose radiation further enhances anti-tumor immunity and significantly improves survival.

Therapeutic resistance remains a major barrier to treating aggressive breast cancers, particularly triple-negative breast cancer (TNBC), in which hypoxia-associated stress adaptation within the tumor microenvironment limits treatment efficacy. Here, we investigated a multi-targeted therapeutic strategy combining histone deacetylase (HDAC) inhibition with blockade of hypoxia-associated chaperones HSP90β and mitochondrial TRAP1 in 3-D breast cancer models grown from TNBC human cells. HDAC inhibitors (HDACi; vorinostat [SAHA; pan-HDACi], valproic acid [VPA; HDAC1i], and CAY10603 [CAY; HDAC6i]; showed greater efficacy than paclitaxel at reducing viability and mammosphere formation in 3-D cultures, and induced apoptosis and G2/M cell cycle arrest in TNBC cells. Combined inhibition of HDACs with our novel agents targeting HSP90β (NDNB-25) or TRAP1 (NDNT-34) synergistically reduced mammosphere viability and disrupted spheroid architecture. Mechanistically, HSP90β and TRAP1 inhibition attenuated hypoxia-associated adaptive signaling by suppressing HIF-1α, VEGFA, HSP90β, and TRAP1 gene and protein expression. In co-cultures with HUVEC cells, these effects were accompanied by impaired endothelial network formation, tumor cell migration and invasion, mitotic progression, and clonogenic growth. Following Cleavage Under Targets and Release Using Nuclease (CUT&RUN) analysis, genome-wide HIF-1α occupancy analysis revealed extensive reprogramming of HIF-1α-associated regulatory programs under HDAC, HSP90β, and TRAP1 inhibition, including pathways linked to innate immunity, interferon signaling, redox balance, autophagy, mitochondrial function, and metabolic adaptation. Together, these findings identify hypoxia-associated stress adaptation as a therapeutically actionable vulnerability in aggressive breast cancer and support coordinated targeting of epigenetic regulation, proteostasis, and mitochondrial stress adaptation to enhance treatment response.

Supplementary Fig. S11: Cxcr3 in CD8 T cells mediates the benefit of GC/ICB combination therapy in orthotopic murine 425-ICC model.

Supplementary Fig. S4: IMC analysis of ICC after GC-based therapies in orthotopic murine 425-ICC model.

Supplementary Fig. S7: Immunophenotyping in murine 425-ICC and SS49-ICC.

Abstract Nodular brain tumors exert compressive forces on the surrounding host tissue over the course of tumor expansion. However, how these forces impact neighboring peritumoral cells remains poorly understood. In this study, we used an in vitro transwell compression device to evaluate the effect of brain tumor-mimicking compressive forces on immortalized human astrocytes, the most abundant stromal cell type in the brain peritumor. We utilized an unsupervised machine-learning clustering algorithm to determine the relative abundance of various nuclear geometries present in compressed and uncompressed cell groups. We found that compressed nuclei exhibited diverse morphologies, including circular, elongated, and crescent shapes. In contrast, uncompressed nuclei were morphologically homogeneous, with most maintaining a canonical circular or elliptical shape. We validated these observations using ImageJ, showing that compressed nuclei possessed significantly lower circularity, roundness, and solidity, while displaying significantly higher eccentricity. Additionally, we performed nuclear morphometric analysis to numerically characterize the relative irregularity of compressed nuclei based on the calculation of a nuclear irregularity index (NII). Our analysis revealed that the NII of compressed nuclei is significantly higher than their uncompressed counterparts while the nuclear area in both groups was similar. Among 7 morphological categories, uncompressed nuclei were classified as “normal” while compressed nuclei were classified as “irregular.” These findings suggest that compressed nuclei may either be undergoing mitotic catastrophe or another nuclear damaging event rather than acquire aberrant morphologies due to mechanically induced senescence or apoptosis. We also evaluated the impact of compressive stress on sub-nuclear components essential for nuclear integrity and mechanosensing. Through immunostaining, we discovered that compression markedly affects lamin and chromatin architecture, with compressed astrocytes exhibiting pronounced lamin wrinkling and reduced peripheral enrichment of the heterochromatin markers H3K9me3 and H3K27me3. Interestingly, both lamin wrinkling and loss of peripheral H3K27me3 appear to be independent of morphology as both irregularly and normally shaped nuclei of compressed cells exhibited similar phenotypes. We further demonstrated via gene set enrichment analysis and leading edge analysis that, relative to uncompressed cells, compressed cells upregulate transcripts encoding chromatin modifying enzymes associated with heterochromatin organization and methylation. Altogether, these results indicate that tumor compressive forces seemingly modulate gross nuclear shape and organization of sub-nuclear components in peritumoral astrocytes. Future studies aimed at confirming these changes in the intact peritumor are underway. Furthermore, how mechanically-induced nuclear changes in peritumoral astrocytes reciprocally regulate critical features of cancer (e.g., invasion, therapeutic resistance) remains to be investigated. Citation Format: Julian Najera, Bianca Batista, Meenal Datta. Compression induces nuclear morphological irregularities in human astrocytes [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Brain Cancer; 2026 Mar 23-25; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2026;86(6_Suppl):Abstract nr B011.