Publications (2)2.84 Total impact
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Article: Reversal of mdr1-mediated multidrug resistance in human leukemia cells by a new spin-labeled derivative of podophyllotoxin.
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ABSTRACT: GP7 (4-[4"-(2", 2", 6", 6"-tetramethyl-l"-piperidinyloxy) amino]-4'-demethyl epipodophyllotoxin) is a promising anticancer drug of the podophyllotoxin class. However, little is known about its anti-multidrug resistance effects. In the present study, we investigated the effects of GP7 on P-glycoprotein (P-gp) overexpression multidrug-resistant human leukemia K562/ADM cells with the comparison of VP-16 and K562 cells. GP7 inhibited the proliferation of K562/ADM cells in a concentration- or time-dependent manner, and the inhibitory effect of GP7 on K562/ADM cells was 1.50-fold higher than that of VP-16. GP7 caused G2/M phase accumulation but VP-16 caused S phase accumulation in K562/ADM and K562 cells. GP7 could induce apoptosis of both K562/ADM and K562 cell lines, but there was no significant difference between GP7- and VP-16-induced apoptotic ratios. GP7 could also induce typical apoptotic morphological changes and internucleosomal DNA fragmentation of K562/ADM and K562 cells, but DNA fragmentation induced by GP7 in K562/ADM cells was weaker than that in K562 cells. When treated with GP7 or VP-16 for 48 h, 128-256 microM GP7 induced more DNA fragmentation than VP-16 did, but 32-64 microM GP7 induced less DNA fragmentation than VP-16 did. GP7 could down-regulate the expression of P-gp in K562/ADM cells but VP-16 could not. Our findings suggest that GP7 may reverse multidrug resistance in human leukemia K562/ADM cells via down-regulation of P-gp expression.Pharmazie 02/2010; 65(2):117-21. · 1.01 Impact Factor -
Article: GP7 induces internucleosomal DNA fragmentation independent of caspase activation and DNA fragmentation factor in NB4 cells.
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ABSTRACT: DNA fragmentation into internucleosomal fragments is the best recognized biochemical event of apoptosis. Two major caspase pathways have been identified in the signal transduction leading to DNA fragmentation: the receptor pathway and the mitochondrial pathway. DNA fragmentation factor (DFF) has been identified as a major apoptotic endonuclease in the internucleosomal DNA fragmentation process. However, the potential roles of caspases and DFF in internucleosomal DNA fragmentation induced by specific stimuli still need to be investigated since caspase-independent pathways and nuclease(s) other than DFF also play important roles during this process. In the present study, we investigated the activity of GP7 (4-[4"-(2",2",6",6"-tetramethyl-l"-piperidinyloxy) amino]-4'-demethyl epipodophyllotoxin), a new spin-labeled derivative of podophyllotoxin semi-synthesized by our university, to induce apoptosis of the human leukemia cell line NB4. GP7 induced the release of cytochrome-c from mitochondria, activations of caspase-3, -8, and -9, cleavage of DFF45/inhibitor of caspase-activated DNase, activation of DFF40/caspase-activated DNase, and apoptotic DNA fragmentation in NB4 cells. The broad-spectrum caspase inhibitor zVAD-fmk abrogated GP7-induced caspase-3, -8, and -9 activations but could not inhibit GP7-induced apoptotic DNA fragmentation in NB4 cells. Our findings suggest that GP7-induced apoptotic DNA fragmentation in NB4 cells is independent of caspase activation and DFF, although they are closely involved in this process.Oncology Reports 08/2007; 18(1):273-7. · 1.84 Impact Factor
