Homoharringtonine acts synergistically with SG235-TRAIL, a conditionally replicating adenovirus, in human leukemia cell lines.
OBJECTIVE
To investigate the synergistic effects of SG235-TRAIL, a novel oncolytic adenovirus expressing tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and homoharringtonine (HHT) in human leukemia cell lines.


METHODS
The combined effect of SG235-TRAIL and HHT was assessed using a crystal violet assay and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, followed by combination index analysis. Cell apoptosis was measured using flow cytometry combined with fluorescein-isothiocyanate-Annexin V staining. The activation of caspase pathway and the expression of Bcl-2 family proteins, TRAIL, and E1A were examined using Western blotting.


RESULTS
HHT synergized the cytotoxicity of SG235-TRAIL against leukemia cell lines Kasumi-1, KG-1, HL-60, and U937, concomitantly with increased apoptosis and enhanced activity of caspase-3 and -9. The combination therapy resulted in significantly lower levels of Bcl-2, Mcl-1, and Bid compared to treatment of cells with either HHT or SG235-TRAIL alone, suggesting that HHT sensitizes leukemia cells to SG235-TRAIL virus through alteration of anti-apoptotic signaling elements. Importantly, HHT combined with SG235-TRAIL did not show significant cytotoxicity to normal human mononuclear cells and mesenchymal stem cells.


CONCLUSIONS
Combining oncolytic adenovirus SG235-TRAIL and HHT synergistically enhances cytotoxicity in leukemia cells in vitro, suggesting that the combination therapy could represent a rational approach for the treatment of leukemia.
Meng
Hai-tao
HT
Institute of Hematology, the First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China.
Li
Lu
L
Liu
Hui
H
Wang
Ying
Y
Li
Gong-chu
GC
Qian
Wen-bin
WB
D000256:Adenoviridae / Q000378:metabolism; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology* / Q000633:toxicity; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D053148:Caspase 3 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D045744:Cell Line, Tumor; D003131:Combined Modality Therapy; D005434:Flow Cytometry; D006248:Harringtonines / Q000494:pharmacology* / Q000633:toxicity; D000077863:Homoharringtonine; D006801:Humans; D007938:Leukemia / Q000188:drug therapy*; D007963:Leukocytes, Mononuclear / Q000187:drug effects; D059630:Mesenchymal Stem Cells / Q000187:drug effects; D050130:Oncolytic Virotherapy / Q000379:methods*; D050504:Oncolytic Viruses / Q000378:metabolism; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000008:administration & dosage
D000972:Antineoplastic Agents, Phytogenic; D006248:Harringtonines; D053221:TNF-Related Apoptosis-Inducing Ligand; D000077863:Homoharringtonine; D053148:Caspase 3; D053453:Caspase 9