[Enhancement of FG020326 on sensitivity of MCF-7/ADR cells to taxotere via enhancing activation of caspase-8 and caspase-3].
OBJECTIVE
Multidrug resistance (MDR) is often characterized by over-expression of P-glycoprotein (P-gp) as drug efflux protein. Recent researches showed P-gp can inhibit caspase-dependent apoptosis, and protect MDR cells from apoptosis. This study was designed to investigate reversal effect of FG020326, a potent MDR modulator,on drug-resistance of MCF-7/ADR cells towards taxotere,and its mechanism.


METHODS
Drug-resistant MCF-7/ADR cells, over-expressed P-gp, were cultured with FG020326 and taxotere. The reversal effect of FG020326 was assayed by MTT method. Apoptotic morphology of MCF-7/ADR cells was observed under fluorescent microscope after Hoechst33258 staining, cell apoptosis was measured by flow cytometry (FCM). Activation of caspase-8 and caspase-3 was measured by Western blot and colorimetric assay.


RESULTS
FG020326 enhanced sensitivity of MCF-7/ADR cells to taxotere, and gave a 24-fold reversal of apoptosis-resistance with concentration of 10 micromol/L. Under effect of 10 micromol/L FG020326,chromatin condensation, apoptotic bodies, and sub-G1 peak were observed in MCF-7/ADR cells. Sensitivities of caspase-8 and caspase-3 were enhanced by demostrating cleavage of caspase-8, caspase-3,and PARP in MCF-7/ADR cells. Activities of caspase-3 and caspase-8 in MCF-7/ADR cells cultured with 10 micromol/L FG020326 and 0.1 micromol/L taxotere were increased in a time-dependent manner,and reached peak values at 48 h, which were significantly higher than those in cells cultured with taxotere alone.


CONCLUSIONS
FG020326 may reverse drug-resistance of MCF-7/ADR cells towards taxotere through enhancing activation of caspase-8 and caspase-3 induced by taxotere.
Wang
Xiu-Wen
XW
Research Department, Cancer Center, Sun Yat-sen University, Guangzhou, Guangdong, 510060, PR China.
Ding
Yan
Y
Liang
Yong-Ju
YJ
Chen
Li-Ming
LM
Shi
Zhi
Z
Yang
Xiao-Ping
XP
Gu
Lian-Quan
LQ
Fu
Li-Wu
LW
D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D001943:Breast Neoplasms / Q000473:pathology*; D053148:Caspase 3; D053181:Caspase 8; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D000077143:Docetaxel; D004317:Doxorubicin / Q000494:pharmacology; D018432:Drug Resistance, Multiple / Q000187:drug effects*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D005260:Female; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D043823:Taxoids / Q000494:pharmacology*
D000972:Antineoplastic Agents, Phytogenic; D007093:Imidazoles; D043823:Taxoids; D000077143:Docetaxel; D004317:Doxorubicin; C505407:CASP3 protein, human; C505530:CASP8 protein, human; D053148:Caspase 3; D053181:Caspase 8; D020169:Caspases