利用探针跳跃式扫描离子电导显微镜技术揭示结直肠癌单细胞层面对H_(2)O_(2)良性应激的动态响应

Colorectal cancer(CRC),a widespread malignancy,is closely associated with tumor microenvironmental hydrogen peroxide(H_(2)O_(2))levels.Some clinical trials targeting H_(2)O_(2)for cancer treatment have revealed its paradoxical role as a promoter of cancer progression.Investigating the dynamics of cancer cell H_(2)O_(2)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 H_(2)O_(2)gradients in individual colorectal cancer Caco–2cells.We explored the relationship between cellular mechanical properties and H_(2)O_(2)gradients.Exposure to 0.1 or 1 mmol/L H_(2)O_(2)eustress increased the extracellular to intracellular H_(2)O_(2)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 H_(2)O_(2)eustress.This H_(2)O_(2)–induced stiffness modulated AKT activation positively and glutathione peroxidase 2(GPX2)expression negatively.Our findings unveil the failure of some H_(2)O_(2)-targeted therapies due to their ineffectiveness in generating H_(2)O_(2),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 H_(2)O_(2)eustress for survival at the single–cell level.Inhibiting GPX and/or catalase(CAT)enhances the cytotoxic activity of H_(2)O_(2)eustress against CRC cells,which holds significant promise for developing innovative therapies targeting cancer and other H_(2)O_(2)-related inflammatory diseases.

Mutant p53 in colon cancer

The accumulation of genetic alterations in driver genes is responsible for the development and malignant progression of colorectal cancer. Comprehensive genome analyses have revealed the driver genes, including APC, KRAS, TGFBR2, and TP53, whose mutations are frequently found in human colorectal cancers. Among them, the p53 mutation is found in ~60% of colorectal cancers, and a majority of mutations are missense-type at ‘hot spots’, suggesting an oncogenic role of mutant p53 by ‘gain-of-function’ mechanisms. Mouse model studies have shown that one of these missense-type mutations, p53 R270H (corresponding to human R273H), causes submucosal invasion of intestinal tumors, while the loss of wild-type p53 has a limited effect on the invasion process. Furthermore, the same mutant p53 promotes metastasis when combined with Kras activation and TGF-β suppression. Importantly, either missense-type p53 mutation or loss of wild-type p53 induces NF-κB activation by a variety of mechanisms, such as increasing promoter accessibility by chromatin remodeling, which may contribute to progression to epithelial–mesenchymal transition. These results indicate that missense-type p53 mutations together with loss of wild-type p53 accelerate the late stage of colorectal cancer progression through the activation of both oncogenic and inflammatory pathways. Accordingly, the suppression of the mutant p53 function via the inhibition of nuclear accumulation is expected to be an effective strategy against malignant progression of colorectal cancer.