Browsing by Author "Jan, Yi-Hua"

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Hypoxia-responsive miRNAs target argonaute 1 to promote angiogenesis
(2013-03-01)
Chen, Zhen
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Lai, Tsung-Ching
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Jan, Yi-Hua
;
Lin, Feng-Mao
;
Wang, Wei-Chi
Despite a general repression of translation under hypoxia, cells selectively upregulate a set of hypoxia-inducible genes. Results from deep sequencing revealed that Let-7 and miR-103/107 are hypoxia-responsive microRNAs (HRMs) that are strongly induced in vascular endothelial cells. In silico bioinformatics and in vitro validation showed that these HRMs are induced by HIF1 alpha and target argonaute 1 (AGO1), which anchors the microRNA-induced silencing complex (miRISC). HRM targeting of AGO1 resulted in the translational desuppression of VEGF mRNA. Inhibition of HRM or overexpression of AGO1 without the 3' untranslated region decreased hypoxia-induced angiogenesis. Conversely, AGO1 knockdown increased angiogenesis under normoxia in vivo. In addition, data from tumor xenografts and human cancer specimens indicate that AGO1-mediated translational desuppression of VEGF may be associated with tumor angiogenesis and poor prognosis. These fmdings provide evidence for an angiogenic pathway involving HRMs that target AGO1 and suggest that this pathway may be a suitable target for anti- or proangiogenesis strategies.
Targeting the XIAP/caspase-7 complex selectively kills caspase-3-deficient malignancies
(2013-09-01)
Lin, Yuan-Feng
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Lai, Tsung-Ching
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Chang, Chih-Kang
;
Chen, Chi-Long
;
Huang, Ming-Shyan
Caspase-3 downregulation (CASP3/DR) in tumors frequently confers resistance to cancer therapy and is significantly correlated with a poor prognosis in cancer patients. Because CASP3/DR cancer cells rely heavily on the activity of caspase-7 (CASP7) to initiate apoptosis, inhibition of activated CASP7 (p19/p12-CASP7) by X-linked inhibitor of apoptosis protein (XIAP) is a potential mechanism by which apoptosis is prevented in those cancer cells. Here, we identify the pocket surrounding the Cys(246) residue of p19/p12-CASP7 as a target for the development of a protein-protein interaction (PPI) inhibitor of the XIAP:p19/p12-CASP7 complex. Interrupting this PPI directly triggered CASP7-dependent apoptotic signaling that bypassed the activation of the apical caspases and selectively killed CASP3/DR malignancies in vitro and in vivo without adverse side effects in nontumor cells. Importantly, CASP3/DR combined with p19/p12-CASP7 accumulation correlated with the aggressive evolution of clinical malignancies and a poor prognosis in cancer patients. Moreover, targeting of this PPI effectively killed cancer cells with multidrug resistance due to microRNA let-7a-1-mediated CASP3/DR and resensitized cancer cells to chemotherapy-induced apoptosis. These findings not only provide an opportunity to treat CASP3/DR malignancies by targeting the XIAP:p19/p12-CASP7 complex, but also elucidate the molecular mechanism underlying CASP3/DR in cancers.