Nano-scale physical properties characteristic to metastatic intestinal cancer cells identified by high-speed scanning ion conductance microscope

Exploration of individual colorectal cancer cell responses to H2O2 eustress using hopping probe scanning ion conductance microscopy

Colorectal cancer (CRC), a widespread malignancy, is closely associated with tumor microenvironmental hydrogen peroxide (H2O2) levels. Some clinical trials targeting H2O2 for cancer treatment have revealed its paradoxical role as a promoter of cancer progression. Investigating the dynamics of cancer cell H2O2 eustress at the single-cell level is crucial. In this study, non-contact hopping probe mode scanning ion conductance microscopy (HPICM) with high-sensitive Pt-functionalized nanoelectrodes was employed to measure dynamic extracellular to intracellular H2O2 gradients in individual colorectal cancer Caco-2 cells. We explored the relationship between cellular mechanical properties and H2O2 gradients. Exposure to 0.1 or 1 mmol/L H2O2 eustress increased the extracellular to intracellular H2O2 gradient from 0.3 to 1.91 or 3.04, respectively. Notably, cellular F-actin-dependent stiffness increased at 0.1 mmol/L but decreased at 1 mmol/L H2O2 eustress. This H2O2-induced stiffness modulated AKT activation positively and glutathione peroxidase 2 (GPX2) expression negatively. Our findings unveil the failure of some H2O2-targeted therapies due to their ineffectiveness in generating H2O2, which instead acts eustress to promote cancer cell survival. This research also reveals the complex interplay between physical properties and biochemical signaling in cancer cells' antioxidant defense, illuminating the exploitation of H2O2 eustress for survival at the single-cell level. Inhibiting GPX and/or catalase (CAT) enhances the cytotoxic activity of H2O2 eustress against CRC cells, which holds significant promise for developing innovative therapies targeting cancer and other H2O2-related inflammatory diseases.

Rapid scanning method for SICM based on autoencoder network

Scanning Ion Conductance Microscopy (SICM) enables non-destructive imaging of living cells, which makes it highly valuable in life sciences, medicine, pharmacology, and many other fields. However, because of the uncertainty retrace height of SICM hopping mode, the time resolution of SICM is relatively low, which makes the device fail to meet the demands of dynamic scanning. To address above issues, we propose a fast-scanning method for SICM based on an autoencoder network. Firstly, we cut under-sampled images into small image lists. Secondly, we feed them into a self-constructed primitive-autoencoder super-resolution network to compute high-resolution images. Finally, the inferred scanning path is determined using the computed images to reconstruct the real high-resolution scanning path. The results demonstrate that the proposed network can reconstruct higher-resolution images in various super-resolution tasks of low-resolution scanned images. Compared to existing traditional interpolation methods, the average peak signal-to-noise ratio improvement is greater than 7.5823 dB, and the average structural similarity index improvement is greater than 0.2372. At the same time, using the proposed method for high-resolution image scanning leads to a 156.25% speed improvement compared to traditional methods. It opens up possibilities for achieving high-time resolution imaging of dynamic samples in SICM and further promotes the widespread application of SICM in the future.

Mapping Nanomechanical Properties of Basal Surfaces in Metastatic Intestinal 3D Living Organoids with High-Speed Scanning Ion Conductance Microscopy

Studying mechanobiology is increasing of scientific interests in life science and nanotechnology since its impact on cell activities (e.g., adhesion, migration), physiology, and pathology. The role of apical surface (AS) and basal surface (BS) of cells played in mechanobiology is significant. The mechanical mapping and analysis of cells mainly focus on AS while little is known about BS. Here, high-speed scanning ion conductance microscope as a powerful tool is utilized to simultaneously reveal morphologies and local elastic modulus (E) of BS of genotype-defined metastatic intestinal organoids. A simple method is developed to prepare organoid samples allowing for long-term BS imaging. The multiple nano/microstructures, i.e., ridge-like, stress-fiber, and E distributions on BS are dynamically revealed. The statistic E analysis shows softness of BS derived from eight types of organoids following a ranking: malignant tumor cells > benign tumor cells > normal cells. Moreover, the correlation factor between morphology and E is demonstrated depending on cell types. This work as first example reveals the subcellular morphologies and E distributions of BS of cells. The results would provide a clue for correlating genotype of 3D cells to malignant phenotype reflected by E and offering a promising strategy for early-stage diagnosis of cancer.

In Situ Visualization of Dynamic Cellular Effects of Phospholipid Nanoparticles via High-Speed Scanning Ion Conductance Microscopy

Phospholipid nanoparticles have been actively employed for numerous biomedical applications. A key factor in ensuring effective and safe applications of these nanomaterials is the regulation of their interactions with target cells, which is significantly dependent on an in-depth understanding of the nanoparticle-cell interactions. To date, most studies investigating these nano-bio interactions have been performed under static conditions and may lack crucial real-time information. It is, however, noteworthy that the nanoparticle-cell interactions are highly dynamic. Consequently, to gain a deeper insight into the cellular effects of phospholipid nanoparticles, real-time observation of cellular dynamics after nanoparticle introduction is necessary. Herein, a proof-of-concept in situ visualization of the dynamic cellular effects of sub-100 nm phospholipid nanoparticles using high-speed scanning ion conductance microscopy (HS-SICM) is reported. It is revealed that upon introduction into the cellular environment, within a short timescale of hundreds of seconds, phospholipid nanoparticles can selectively modulate the edge motility and surface roughness of healthy fibroblast and cancerous epithelial cells. Furthermore, the dynamic deformation profiles of these cells can be selectively altered in the presence of phospholipid nanoparticles. This work is anticipated to further shed light on the real-time nanoparticle-cell interactions for improved formulation of phospholipid nanoparticles for numerous bioapplications.

Mechanical signatures of human colon cancers

Besides the standard parameters used for colorectal cancer (CRC) management, new features are needed in clinical practice to improve progression-free and overall survival. In some cancers, the microenvironment mechanical properties can contribute to cancer progression and metastasis formation, or constitute a physical barrier for drug penetration or immune cell infiltration. These mechanical properties remain poorly known for colon tissues. Using a multidisciplinary approach including clinical data, physics and geostatistics, we characterized the stiffness of healthy and malignant colon specimens. For this purpose, we analyzed a prospective cohort of 18 patients with untreated colon adenocarcinoma using atomic force microscopy to generate micrometer-scale mechanical maps. We characterized the stiffness of normal epithelium samples taken far away or close to the tumor area and selected tumor tissue areas. These data showed that normal epithelium was softer than tumors. In tumors, stroma areas were stiffer than malignant epithelial cell areas. Among the clinical parameters, tumor left location, higher stage, and RAS mutations were associated with increased tissue stiffness. Thus, in patients with CRC, measuring tumor tissue rigidity may have a translational value and an impact on patient care.

Genetic Alterations and Microenvironment that Drive Malignant Progression of Colorectal Cancer: Lessons from Mouse and Organoid Models

Comprehensive genome analyses have identified frequently mutated genes in human colorectal cancers (CRC). These include APC, KRAS, SMAD4, TP53, and FBXW7. The biological functions of the respective gene products in cell proliferation and homeostasis have been intensively examined by in vitro experiments. However, how each gene mutation or combinations of specific mutations drive malignant progression of CRC in vivo has not been fully understood. Based on the genomic information, we generated mouse models that carry multiple mutations of CRC driver genes in various combinations, and we performed comprehensive histological analyses to link genetic alteration(s) and tumor phenotypes, including liver metastasis. In this review article, we summarize the phenotypes of the respective genetic models carrying major driver mutations and discuss a possible mechanism of mutations underlying malignant progression.