An isolated swarm of small earthquakes occurred in 1992, near Dongfang on Hainan Island, southern China. The Institute of Geophysics, State Seismological Bureau of China, monitored the swarm with five DCS‐302 digital accelerometers for three months from 1992 June 1. 18 earthquakes, with magnitudes ML ranging from 1.8 to 3.6, were well located by five stations, and shear‐wave splitting varying azimuthally was analysed on 27 seismic records from these events. The mean polarization azimuth of the faster shear wave was WNW. Time delays between the split shear waves at two stations varied with time and space. The time delays at one station fell abruptly after earthquakes of magnitudes 3.1 and 3.6, but did not change significantly at the second station. This behaviour is consistent with the delay‐time changes being caused by changes in the aspect ratio of vertical liquid‐filled (EDA) cracks. Thus, the variation in shear‐wave‐splitting time delay could be due to changes in crustal stress related to nearby small‐magnitude earthquake activity. The connection between earthquake activity and crustal stress variation measured by shear‐wave splitting leaves the door open for possible observations of crustal stress transients related to the onset of an earthquake; however, our data cannot be considered as definite evidence for such precursors.
Nuclear factor erythroid 2-related factor (NRF2) is an important transcription factor in oxidative stress regulation. Overexpression of NRF2 is associated with human breast carcinogenesis, and increased NRF2 mRNA levels predict poor patient outcome for breast cancer. However, the mechanisms linking gain of NRF2 expression and poor prognosis in breast cancer are still unclear. Here, we provide evidence that NRF2 deletion inhibits proliferation and metastasis of breast cancer cells by down-regulating RhoA. Restoration of RhoA in MCF7 and MDA-MB-231 cells induced NRF2 knockdown-suppressed cell growth and metastasis in vitro, and NRF2 silencing suppressed stress fiber and focal adhesion formation leading to decreased cell migration and invasion. Mechanistic studies showed that NRF2 binds to the promoter region of estrogen-related receptor α (ERR1) and may function as a silencer. This may enhance RhoA protein stability and lead to RhoA overexpression in breast cancer cell. Our findings indicate that NRF2 silencing-mediated reduction of RhoA expression contributes, at least in part, to the poor outcome of breast cancer patients with high NRF2 expression.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.