Reevesioside A, a cardenolide glycoside, induces anticancer activity against human hormone-refractory prostate cancers through suppression of c-myc expression and induction of G1 arrest of the cell cycle.
In the past decade, there has been a profound increase in the number of studies revealing that cardenolide glycosides display inhibitory activity on the growth of human cancer cells. The use of potential cardenolide glycosides may be a worthwhile approach in anticancer research. Reevesioside A, a cardenolide glycoside isolated from the root of Reevesia formosana, displayed potent anti-proliferative activity against human hormone-refractory prostate cancers. A good correlation (r² = 0.98) between the expression of Na⁺/K⁺-ATPase α₃ subunit and anti-proliferative activity suggested the critical role of the α₃ subunit. Reevesioside A induced G1 arrest of the cell cycle and subsequent apoptosis in a thymidine block-mediated synchronization model. The data were supported by the down-regulation of several related cell cycle regulators, including cyclin D1, cyclin E and CDC25A. Reevesioside A also caused a profound decrease of RB phosphorylation, leading to an increased association between RB and E2F1 and the subsequent suppression of E2F1 activity. The protein and mRNA levels of c-myc, which can activate expression of many downstream cell cycle regulators, were dramatically inhibited by reevesioside A. Transient transfection of c-myc inhibited the down-regulation of both cyclin D1 and cyclin E protein expression to reevesioside A action, suggesting that c-myc functioned as an upstream regulator. Flow cytometric analysis of JC-1 staining demonstrated that reevesioside A also induced the significant loss of mitochondrial membrane potential. In summary, the data suggest that reevesioside A inhibits c-myc expression and down-regulates the expression of CDC25A, cyclin D1 and cyclin E, leading to a profound decrease of RB phosphorylation. G1 arrest is, therefore, induced through E2F1 suppression. Consequently, reevesioside A causes mitochondrial damage and an ultimate apoptosis in human hormone-refractory prostate cancer cells.
School of Pharmacy, National Taiwan University, Taipei, Taiwan.
Wohn-Jenn
WJ
Leu
Graduate Institute of Natural Products, College of Pharmacy, Kaohsiung Medical University, Kaohsiung, Taiwan.
Hsun-Shuo
HS
Chang
School of Pharmacy, National Taiwan University, Taipei, Taiwan.
She-Hung
SH
Chan
School of Pharmacy, National Taiwan University, Taipei, Taiwan.
Jui-Ling
JL
Hsu
School of Pharmacy, National Taiwan University, Taipei, Taiwan.
Chia-Chun
CC
Yu
School of Pharmacy, National Taiwan University, Taipei, Taiwan.
Lih-Ching
LC
Hsu
Graduate Institute of Natural Products, College of Pharmacy, Kaohsiung Medical University, Kaohsiung, Taiwan.
Ih-Sheng
IS
Chen
School of Pharmacy, National Taiwan University, Taipei, Taiwan.
Jih-Hwa
JH
Guh
D000704:Analysis of Variance; D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D002298:Cardenolides / Q000494:pharmacology* / Q000627:therapeutic use; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D017931:DNA Primers / Q000235:genetics; D005434:Flow Cytometry; D059585:G1 Phase Cell Cycle Checkpoints / Q000187:drug effects*; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D008297:Male; D053078:Membrane Potential, Mitochondrial; D064129:Prostatic Neoplasms, Castration-Resistant / Q000188:drug therapy*; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D000970:Antineoplastic Agents; D002298:Cardenolides; D017931:DNA Primers; C489427:MYC protein, human; D016271:Proto-Oncogene Proteins c-myc; C000591895:reevesioside A; D002118:Calcium