Involvement of membrane microdomains in oxidative stress-induced invasion of hepatoma cells

探讨了氧化应激诱导的肝癌细胞侵袭性改变中膜微区的可能参与。我已经报道了活性氧能促进肝癌细胞的侵袭，肝细胞生长因子（HGF）及其受体c-met之间的自分泌途径参与了这种促进作用。在本研究中，观察到在低氧培养条件下侵袭活性降低而不改变HGF基因表达，这表明在氧化应激诱导的肝癌细胞侵袭变化中存在新的调节途径。AH 109 A细胞在细胞膜上表达整合素α2、α5、α6、β1，并定位于细胞膜微区。甲基-β-环糊精影响AH 109 A的侵袭，提示膜微区参与了AH 109 A的侵袭。因此，氧化应激，特别是缺氧，对肝癌细胞侵袭的影响被广泛研究。低氧条件下培养的AH 109 A细胞侵袭能力降低，但对正常细胞单层的粘附能力和肝细胞生长因子的产生没有降低。在低氧培养条件下，AH 109 A细胞c-met的表达水平无明显变化。最近，c-met与整合素的关联被报道在通过HGF促进细胞运动中是重要的。这些结果表明，缺氧可能会影响c-met与AH 109 A细胞膜微区整合素的关联，从而改变其侵袭活性。虽然还需要进一步的研究，如c-met和整合素的免疫共沉淀分析，以阐明缺氧诱导的侵袭活动减少的确切机制，但本研究获得了一些证据，表明膜微区可能参与氧化应激诱导的肝癌侵袭变化。

The possible involvement of membrane microdomains in oxidative stress-induced change in invasion of hepatoma cells was investigated. I have already reported that reactive oxygen species could promote hepatoma cell invasion and that the autocrine pathway between hepatoyte growth factor (HGF) and its receptor, c-met, is involved in this promotion. In this research, the decrease in the invasive activity under the hypoxia culture condition without changing HGF gene expression was observed, suggesting the presence of the novel regulation pathway in oxidative stress-induced change in hepatoma cell invasion. AH109A cells expressed integrins α2, α5, α6, β1 on their cell membrane and these integrins were proved to be localized in their membrane microdomains. Moreover, methyl-β-cyclodextrin affected AH109A invasion, suggesting the involvement of membrane microdomain in their invasion. So, the effect of oxidative stress, especially hypoxia, on hepatoma cell invasion was extensively investigated. AH109A cells, when cultured under the hypoxia condition, showed decreased invasive activities, but they did not show decreased adhesive activities to the normal cell monolayer and decreased HGF production. The expression level of c-met in AH109A cells did not change under the hypoxia culture condition. Recently the association of c-met with integrins is reported to be important in the promotion of cell motility by HGF. These results suggest that hypoxia may affect the association of c-met with integrins in membrane microdomains of AH109A cells, thus changing their invasive activities. Although further studies, such as co-immunoprecipitation assay of c-met and integrins, are thought to be needed to clarify the precise mechanism for hypoxia-induced reduction in invasive activities, some evidences for the possible involvement of membrane microdomains in oxidative stress-induced change in hapatoma invasion were obtained by this research.