Atomic force microscopy (AFM) is a popular tool for evaluating the mechanical properties of biological materials (cells and tissues) at high resolution. This technique has become particularly attractive to cancer researchers seeking to bridge the gap between mechanobiology and cancer initiation, progression, and treatment resistance. The majority of AFM studies thus far have been extensively focused on the nanomechanical characterization of cells. However, these approaches fail to capture the complex and heterogeneous nature of a tumor and its host organ. Over the past decade, efforts have been made to characterize the mechanical properties of tumors and tumor-bearing tissues using AFM. This has led to novel insights regarding cancer mechanopathology at the tissue scale. In this Review, we first explain the principles of AFM nanoindentation for the general study of tissue mechanics. We next discuss key considerations when using this technique and preparing tissue samples for analysis. We then examine AFM application in characterizing the mechanical properties of cancer tissues. Finally, we provide an outlook on AFM in the field of cancer mechanobiology and its application in the clinic.

Immune evasion—a well-established cancer hallmark—is a major barrier to immunotherapy efficacy. While the molecular mechanisms and biological consequences underpinning immune evasion are largely known, the role of tissue mechanical stresses in these processes warrants further investigation. The tumor microenvironment (TME) features physical abnormalities (notably, increased fluid and solid pressures applied both inside and outside the TME) that drive cancer mechanopathologies. Strikingly, in response to these mechanical stresses, cancer cells upregulate canonical immune evasion mechanisms, including epithelial–mesenchymal transition (EMT) and autophagy. Consideration and characterization of the origins and consequences of tumor mechanical stresses in the TME may yield novel strategies to combat immunotherapy resistance. In this Perspective, we posit that tumor mechanical stresses—namely fluid shear and solid stresses—induce immune evasion by upregulating EMT and autophagy. In addition to exploring the basis for our hypothesis, we also identify explicit gaps in the field that need to be addressed in order to directly demonstrate the existence and importance of this biophysical relationship. Finally, we propose that reducing or neutralizing fluid shear stress and solid stress-induced cancer immune escape may improve immunotherapy outcomes.

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.

Polylactic acid (PLA) is widely used in tissue engineering and other biomedical applications. PLA can be modified with appropriate biocompatible ceramic materials since this would allow tailoring the mechanical properties of the tissues to be engineered. In this study, PLA-based non-woven fibrillar nanocomposites containing nanoparticles of hydroxyapatite (HA), a bioceramic commonly used in bone tissue engineering, were prepared via solution blow spinning (SBS). The compositions of the final materials were selected to study the influence of HA concentration on the structure, morphology, and thermal and mechanical properties. The resulting materials were highly porous and mainly constituted fibers. FTIR analysis did not reveal any specific interactions. The diameters of the fibers varied very little with the composition. For example, slightly thinner fibers were obtained for pure PLA and PLA + 10% HA, with fiber diameters of less than 400 nm, while the thicker fibers were found for PLA + 1% HA, with average diameters of 427 ± 170 nm. The crystallinity and stiffness of the PLA/HA composite increased with the HA content. Further, composites containing PLA fibers with slightly larger diameters were more ductile. Thus, with an appropriate balance between factors, such as the diameter of the solution-blow-spun PLA fibers, HA particle content, and degree of crystallinity, PLA/HA composites may be effectively used in tissue engineering applications.

Glioblastoma (GBM) is an incurable brain cancer characterized by its highly immunosuppressive tumor microenvironment and aggressive malignant features that resist treatment. To overcome limitations of Earth-based models (sedimentation and disaggregation) and leverage the unique biological effects of space (accelerated disease progression and immune dysregulation), we developed a panel of GBM-myeloid organoids for extended culture on the International Space Station. After 40 days, the spaceflight-grown organoids had more uniform and reproducible morphology compared to identical ground controls. Organoids containing GBM cells + monocytes had increased expression of chronic innate inflammation, adaptive immune activation, and tissue and vascular remodeling-associated genes. There was an increase in organization of gene expression patterns, with mesenchymal-related genes enriched in the core and inflammation-related genes enriched at the periphery, mimicking GBM tumor architecture. Secretomics confirmed the generation of more immunosuppressive organoids, with enrichment of proteins associated with more aggressive disease, including CXCL12 and LOX-1. GBM co-culture organoids thus had enhanced transcriptomic, proteomic, and architectural features when grown in microgravity that are associated with worse patient outcomes from retrospective data. Infrared laser scanning microscopy confirmed spatial chemical gradients for DNA, protein, and lipid species in both space- and terrestrially-grown organoids. In summary, we present not only a novel and superior model of glioblastoma for more relevant basic, mechanistic, and translational research, but also demonstrate methods to acquire high-quality and diverse data from organoids compatible with the unique experimental constraints of biological research in space to help establish a working model for orbital oncology.