Hourly or 3-hourly precipitation data from Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks (PERSIANN) and Tropical Rainfall Measuring Mission (TRMM) 3B42 satellite products and rain gauge records are used to characterize East Asian summer monsoon rainfall, including spatial patterns in June-August (JJA) mean precipitation amount, frequency, and intensity, as well as the diurnal and semidiurnal cycles. The results show that the satellite products are comparable to rain gauge data in revealing the spatial patterns of JJA precipitation amount, frequency, and intensity, with pattern correlation coefficients for five subregions ranging from 0.66 to 0.94. The pattern correlation of rainfall amount is higher than that of frequency and intensity. Relative to PERSIANN, the TRMM product has a better resemblance with rain gauge observations in terms of both the pattern correlation and rootmean-square error. The satellite products overestimate rainfall frequency but underestimate its intensity. The diurnal (24 h) harmonic dominates subdaily variations of precipitation over most of eastern China. A late-afternoon maximum over southeastern and northeastern China and a near-midnight maximum over the eastern periphery of the Tibetan Plateau are seen in the rain gauge data. The diurnal phases of precipitation frequency and intensity are similar to those of rainfall amount in most regions, except for the middle Yangtze River valley. Both frequency and intensity contribute to the diurnal variation of rainfall amount over most of eastern China. The contribution of frequency to the diurnal cycle of rainfall amount is generally overestimated in both satellite products. Both satellite products capture well the nocturnal peak over the eastern periphery of the Tibetan Plateau and the late-afternoon peak in southern and northeastern China. Rain gauge data over the region between the Yangtze and Yellow Rivers show two peaks, with one in the early morning and the other later in the afternoon. The satellite products only capture the major late-afternoon peak.
Cell migration is a critical step in cancer cell invasion. Recent studies have implicated the importance of the extracellular signal-regulated kinase (ERK) signaling pathway in cancer cell migration. However, the mechanism associated with ERK-regulated cell migration is poorly understood. Using a panel of breast cancer cell lines, we detected an excellent correlation between ERK activity and cell migration. Interestingly, we noticed that a 48-hour treatment with U0126 [specific mitogen-activated protein/ERK kinase (MEK)-1/2 inhibitor] was needed to significantly inhibit breast cancer cell migration, whereas this inhibitor blocked ERK activity within 1 hour. This observation suggests that ERK-dependent gene expression, rather than direct ERK signaling, is essential for cell migration. With further study, we found that ERK activity promoted the expression of the activator protein-1 (AP1) components Fra-1 and c-Jun, both of which were necessary for cell migration. Combination of U0126 treatment and Fra-1/c-Jun knockdown did not yield further reduction in cell migration than either alone, indicating that ERKs and Fra-1/c-Jun act by the same mechanism to facilitate cell migration. In an attempt to investigate the role of Fra-1/c-Jun in cell migration, we found that the ERK-Fra-1/c-Jun axis regulated slug expression in an AP1-dependent manner. Moreover, the occurrence of U0126-induced migratory inhibition coincided with slug reduction, and silencing slug expression abrogated breast cancer cell migration. These results suggest an association between ERK-regulated cell migration and slug expression. Indeed, cell migration was not significantly inhibited by U0126 treatment or Fra-1/c-Jun silencing in cells expressing slug transgene. Our study suggests that the ERK pathway regulates breast cancer cell migration by maintaining slug expression. [Cancer Res 2009;69(24):9228-35]
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