Abstract B011: Compression induces nuclear morphological irregularities in human astrocytes

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.