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

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 H₂O_2-related inflammatory diseases.