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The epithelial-mesenchymal transition (EMT) is crucial for the invasion and metastasis of many epithelial tumors including colorectal carcinoma (CRC). In the present study, a scattering and fibroblastic morphology with reduced intercellular contacts was found in the SW480 colon cancer cells overexpressing the gene encoding thymosin beta4 (Tbeta4), which was accompanied by a loss of E-cadherin as well as a cytosolic accumulation of beta-catenin, two most prominent markers of EMT. Whereas E-cadherin downregulation was likely to be accounted by a ZEB1-mediated transcriptional repression, the accumulation of beta-catenin was a result of glycogen synthase kinase-3beta inactivation mediated by integrin-linked kinase (ILK) and/or its downstream effector, Akt. Intriguingly, ILK upregulation in Tbeta4-overexpressing SW480 cells seemed to be attributed mainly to a stabilization of this kinase by complexing with particularly interesting new Cys-His protein (PINCH) more efficiently. In the meantime, a strong correlation between the expression levels of Tbeta4, ILK and E-cadherin in CRC patients was also revealed by immunohistochemical analysis. Taken together, these data suggest a novel role of Tbeta4 in promoting CRC progression by inducing an EMT in tumor cells via upregulating ILK and consequentially its signal transduction.

Hypoxia-inducible factor (HIF) 1α and HIF2α and the inhibitor of apoptosis survivin represent prominent markers of many human cancers. They are also widely expressed in various embryonic tissues, including the central nervous system; however, little is known about their functions in embryos. Here, we show that zebrafish HIF2α protects neural progenitor cells and neural differentiation processes by upregulating the survivin orthologues birc5a and birc5b during embryogenesis. Morpholino-mediated knockdown of hif2α reduced the transcription of birc5a and birc5b, induced p53-independent apoptosis and abrogated neural cell differentiation. Depletion of birc5a and birc5b recaptured the neural development defects that were observed in the hif2α morphants. The phenotypes induced by HIF2α depletion were largely rescued by ectopic birc5a and birc5b mRNAs, indicating that Birc5a and Birc5b act downstream of HIF2α. Chromatin immunoprecipitation assay revealed that HIF2α binds to birc5a and birc5b promoters directly to modulate their transcriptions. Knockdown of hif2α, birc5a or birc5b reduced the expression of the cdk inhibitors p27/cdkn1b and p57/cdkn1c and increased ccnd1/cyclin D1 transcription in the surviving neural progenitor cells. The reduction in elavl3/HuC expression and enhanced pcna, nestin, ascl1b and sox3 expression indicate that the surviving neural progenitor cells in hif2α morphants maintain a high proliferation rate without terminally differentiating. We propose that a subset of developmental defects attributed to HIF2α depletion is due in part to the loss of survivin activity.

Cytochrome P450 1B1 (CYP1B1) is a heme-containing monooxygenase that metabolizes various polycyclic aromatic hydrocarbons and aryl amines, as well as retinoic acid and steroid hormones. Here we report the cloning of an ortholog of CYP1B1 from zebrafish and the demonstration that transcription of zebrafish CYP1B1 was modulated by two types of mechanisms during different developmental stage. First in late pharyngula stage before hatching, CYP1B1 was constitutively transcribed in retina, midbrain-hindbrain boundary and diencephalon regions through a close coordination between aryl hydrocarbon receptor 2 (AHR2)-dependent and AHR2-independent pathways. After hatching, the basal transcription was attenuated and it could not be elicited upon 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure. In contrast, TCDD exposure induced de novo CYP1B1 transcription in larval branchial arches and heart tissues via an AHR2-dependent pathway. Blocking AHR2 translation completely eliminated the TCDD-mediated CYP1B1 transcription. However, we did not detect any types of CYP1B1 transcription in liver and kidney tissues through the developmental stage. It suggests that the constitutive and TCDD-inducible types of CYP1B1 transcriptions are modulated by distinct pathways with different tissue specificities. Finally, we investigated the role of CYP1B1 in TCDD-mediated embryonic toxicity. Because knockdown of CYP1B1 did not prevent TCDD-induced pericardial edema and cranial defects, it suggests that CYP1B1 is not involved in the developmental toxicity of dioxin.

In digital microfluidics, droplet generation is a fundamental operation for quantitative liquid manipulation. The generation of well-defined micro-droplets on a chip with restricted device geometries has become a real obstacle...