SZ-685C, a marine anthraquinone, is a potent inducer of apoptosis with anticancer activity by suppression of the Akt/FOXO pathway.
OBJECTIVE
The aims of this study were to investigate the anti-cancer activity of SZ-685C, an anthracycline analogue isolated from marine-derived mangrove endophytic fungi, and to explore the molecular mechanisms underlying such activity.


METHODS
The effect of SZ-685C on the viability of cancer cell lines was investigated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. SZ-685C-induced apoptosis was assessed by Annexin V-fluorescein isothiocyanate/propidium iodide staining, terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling assay and analysis of caspase activation. The effect of SZ-685C on the Akt/FOXO pathway was studied using Western blotting analysis, and the in vivo anti-tumour efficacy was examined in an MDA-MB-435 breast cancer xenograft model.


RESULTS
SZ-685C suppressed the proliferation of six cancer cell lines derived from human breast cancer, prostate cancer, glioma and hepatoma (IC(50) values ranged from 3.0 to 9.6 microM) and the growth of breast cancer xenografts in mice. SZ-685C had a direct apoptosis-inducing effect through both the extrinsic and intrinsic apoptotic pathways, as shown by activation of caspase-8 and 9 as well as effector caspase-3 and poly (ADP-ribose) polymerase. Phosphorylation of Akt and its downstream effectors, forkhead box protein O1 and forkhead box protein O3a, was down-regulated in SZ-685C-treated cancer cells. Furthermore, the pro-apoptotic protein Bim was up-regulated by SZ-685C treatment consistent with FOXO dephosphorylation.


CONCLUSIONS
SZ-685C could induce apoptosis through the Akt/FOXO pathway, which consequently leads to the observed anti-tumour effect both in vitro and in vivo. Our data suggest that SZ-685C may be a potentially promising Akt inhibitor and anti-cancer drug candidate.
Key Laboratory of Tropical Disease Control (Sun Yat-sen University), Ministry of Education, Guangzhou, China.
Gui'e
G
Xie
Xun
X
Zhu
Qing
Q
Li
Minghui
M
Gu
Zhenjian
Z
He
Jueheng
J
Wu
Jun
J
Li
Yongcheng
Y
Lin
Mengfeng
M
Li
Zhigang
Z
She
Jie
J
Yuan
D000246:Adenosine Diphosphate Ribose / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D000880:Anthraquinones / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics / Q000502:physiology; D051017:Apoptosis Regulatory Proteins; D000072224:Bcl-2-Like Protein 11; D001943:Breast Neoplasms / Q000235:genetics / Q000473:pathology*; D006528:Carcinoma, Hepatocellular / Q000235:genetics; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism; D053181:Caspase 8 / Q000235:genetics / Q000378:metabolism; D005260:Female; D006801:Humans; D020287:In Situ Nick-End Labeling; D008113:Liver Neoplasms / Q000235:genetics; D008297:Male; D008565:Membrane Proteins; D051379:Mice; D008819:Mice, Nude; D010766:Phosphorylation / Q000187:drug effects; D011065:Poly(ADP-ribose) Polymerases / Q000235:genetics / Q000494:pharmacology; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D013778:Tetrazolium Salts; D013844:Thiazoles
D000880:Anthraquinones; D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; C000606775:BCL2L11 protein, human; D000072224:Bcl-2-Like Protein 11; C000606776:Bcl2l11 protein, mouse; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D013778:Tetrazolium Salts; D013844:Thiazoles; C042834:9,10-anthraquinone; D000246:Adenosine Diphosphate Ribose; D011065:Poly(ADP-ribose) Polymerases; D051057:Proto-Oncogene Proteins c-akt; D053148:Caspase 3; D053181:Caspase 8; C022616:thiazolyl blue