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Potent antitumor activity of oncolytic adenovirus expressing Beclin-1 via induction of autophagic cell death in leukemia.

Tong Y, You L, Liu H, Li L, Meng H, Qian Q, Qian W - Oncotarget (2013)

Bottom Line: Here, we investigated whether a strategy that combines the oncolytic effects of an adenoviral vector with simultaneous expression of Beclin-1, an autophagy gene, offers a therapeutic advantage for leukemia.We also showed that SG511-BECN strongly inhibited the growth of leukemic progenitors in vitro.Our results suggest that infection of leukemia cells with an oncolytic adenovirus overexpressing Beclin-1 can induce significant autophagic cell death and provide a new strategy for the elimination of leukemic cells via a unique mechanism of action distinct from apoptosis.

View Article: PubMed Central - PubMed

Affiliation: Institute of Hematology, the First Affiliated Hospital, College of Medicine, Zhejiang University, P.R. China.

ABSTRACT
An attractive strategy among adenovirus-based oncolytic systems is to design adenoviral vectors to express pro-apoptotic genes, in which this gene-virotherapy approach significantly enhances tumor cell death by activating apoptotic pathways. However, the existence of cancer cells with apoptotic defects is one of the major obstacles in gene-virotherapy. Here, we investigated whether a strategy that combines the oncolytic effects of an adenoviral vector with simultaneous expression of Beclin-1, an autophagy gene, offers a therapeutic advantage for leukemia. A Beclin-1 cDNA was cloned in an oncolytic adenovirus with chimeric Ad5/11 fiber (SG511-BECN). SG511-BECN treatment induced significant autophagic cell death, and resulted in enhanced cell killing in a variety of leukemic cell lines and primary leukemic blasts. SG511-BECN effects were seen in chronic myeloid leukemia and acute myeloid leukemia with resistance to imatinib or chemotherapy, but exhibited much less cytotoxicity on normal cells. The SG511-BECN-induced autophagic cell death could be partially reversed by RNA interference knockdown of UVRAG, ATG5, and ATG7. We also showed that SG511-BECN strongly inhibited the growth of leukemic progenitors in vitro. In murine leukemia models, SG511-BECN prolonged the survival and decreased the xenograft tumor size by inducing autophagic cell death. Our results suggest that infection of leukemia cells with an oncolytic adenovirus overexpressing Beclin-1 can induce significant autophagic cell death and provide a new strategy for the elimination of leukemic cells via a unique mechanism of action distinct from apoptosis.

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Superior efficacy of SG511-BECN compared with the CRAd expressing TRAIL(A) Leukemic cells (2×104), human MNCs, and L02 cells were treated with Ad5-BECN, SG511, or SG511-BECN at an MOI of 50 for 72 h before analysis of cell viability (MTT assay). The results represent means ± SD of three independent experiments. *P<0.0001, vs SG511, # P=0.0007, vs SG511. (B) K562 cells were treated with the indicated viruses at 50 MOI and colonies were observed on day 7 under a light microscope. (C) K562, NB4, and THP-1 cells were infected with or without SG511, SG235-TRAIL, and SG511-BECN at an MOI of 50, respectively. The cells were then plated in methylcellulose medium. After incubation for 7 days, colonies (more than 50 cells) were scored. Data represent means ± SD for separate experiments. #SG511-BECN vs SG235-TRAIL, *SG511-BECN vs SG511.
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Figure 3: Superior efficacy of SG511-BECN compared with the CRAd expressing TRAIL(A) Leukemic cells (2×104), human MNCs, and L02 cells were treated with Ad5-BECN, SG511, or SG511-BECN at an MOI of 50 for 72 h before analysis of cell viability (MTT assay). The results represent means ± SD of three independent experiments. *P<0.0001, vs SG511, # P=0.0007, vs SG511. (B) K562 cells were treated with the indicated viruses at 50 MOI and colonies were observed on day 7 under a light microscope. (C) K562, NB4, and THP-1 cells were infected with or without SG511, SG235-TRAIL, and SG511-BECN at an MOI of 50, respectively. The cells were then plated in methylcellulose medium. After incubation for 7 days, colonies (more than 50 cells) were scored. Data represent means ± SD for separate experiments. #SG511-BECN vs SG235-TRAIL, *SG511-BECN vs SG511.

Mentions: To investigate the increased cytotoxic effect of SG511-BECN compared with SG511 and Ad-BECN, leukemia cells and human normal cells were infected with different vectors. At 72 h after viral infection, cell viability was determined by the MTT assay. Results showed that SG511-BECN had a remarkable cell killing effect compared with the other viruses in each leukemia cell line. The cell killing effect of SG511-BECN was about 2 times higher than that of SG511. In contrast, minimal cytotoxic effect was detected in normal cells (Fig. 3A). Importantly, CFU-L formation was almost completely eliminated when the SG511-BECN was used at an MOI of 50 (Fig. 3B). However, SG511 did not show a significant inhibitory effect on colony growth of K562 cells. Therefore, these findings suggest that the antileukemia activity of SG511-BECN is superior to that of SG511 vector in vitro.


Potent antitumor activity of oncolytic adenovirus expressing Beclin-1 via induction of autophagic cell death in leukemia.

Tong Y, You L, Liu H, Li L, Meng H, Qian Q, Qian W - Oncotarget (2013)

Superior efficacy of SG511-BECN compared with the CRAd expressing TRAIL(A) Leukemic cells (2×104), human MNCs, and L02 cells were treated with Ad5-BECN, SG511, or SG511-BECN at an MOI of 50 for 72 h before analysis of cell viability (MTT assay). The results represent means ± SD of three independent experiments. *P<0.0001, vs SG511, # P=0.0007, vs SG511. (B) K562 cells were treated with the indicated viruses at 50 MOI and colonies were observed on day 7 under a light microscope. (C) K562, NB4, and THP-1 cells were infected with or without SG511, SG235-TRAIL, and SG511-BECN at an MOI of 50, respectively. The cells were then plated in methylcellulose medium. After incubation for 7 days, colonies (more than 50 cells) were scored. Data represent means ± SD for separate experiments. #SG511-BECN vs SG235-TRAIL, *SG511-BECN vs SG511.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3757243&req=5

Figure 3: Superior efficacy of SG511-BECN compared with the CRAd expressing TRAIL(A) Leukemic cells (2×104), human MNCs, and L02 cells were treated with Ad5-BECN, SG511, or SG511-BECN at an MOI of 50 for 72 h before analysis of cell viability (MTT assay). The results represent means ± SD of three independent experiments. *P<0.0001, vs SG511, # P=0.0007, vs SG511. (B) K562 cells were treated with the indicated viruses at 50 MOI and colonies were observed on day 7 under a light microscope. (C) K562, NB4, and THP-1 cells were infected with or without SG511, SG235-TRAIL, and SG511-BECN at an MOI of 50, respectively. The cells were then plated in methylcellulose medium. After incubation for 7 days, colonies (more than 50 cells) were scored. Data represent means ± SD for separate experiments. #SG511-BECN vs SG235-TRAIL, *SG511-BECN vs SG511.
Mentions: To investigate the increased cytotoxic effect of SG511-BECN compared with SG511 and Ad-BECN, leukemia cells and human normal cells were infected with different vectors. At 72 h after viral infection, cell viability was determined by the MTT assay. Results showed that SG511-BECN had a remarkable cell killing effect compared with the other viruses in each leukemia cell line. The cell killing effect of SG511-BECN was about 2 times higher than that of SG511. In contrast, minimal cytotoxic effect was detected in normal cells (Fig. 3A). Importantly, CFU-L formation was almost completely eliminated when the SG511-BECN was used at an MOI of 50 (Fig. 3B). However, SG511 did not show a significant inhibitory effect on colony growth of K562 cells. Therefore, these findings suggest that the antileukemia activity of SG511-BECN is superior to that of SG511 vector in vitro.

Bottom Line: Here, we investigated whether a strategy that combines the oncolytic effects of an adenoviral vector with simultaneous expression of Beclin-1, an autophagy gene, offers a therapeutic advantage for leukemia.We also showed that SG511-BECN strongly inhibited the growth of leukemic progenitors in vitro.Our results suggest that infection of leukemia cells with an oncolytic adenovirus overexpressing Beclin-1 can induce significant autophagic cell death and provide a new strategy for the elimination of leukemic cells via a unique mechanism of action distinct from apoptosis.

View Article: PubMed Central - PubMed

Affiliation: Institute of Hematology, the First Affiliated Hospital, College of Medicine, Zhejiang University, P.R. China.

ABSTRACT
An attractive strategy among adenovirus-based oncolytic systems is to design adenoviral vectors to express pro-apoptotic genes, in which this gene-virotherapy approach significantly enhances tumor cell death by activating apoptotic pathways. However, the existence of cancer cells with apoptotic defects is one of the major obstacles in gene-virotherapy. Here, we investigated whether a strategy that combines the oncolytic effects of an adenoviral vector with simultaneous expression of Beclin-1, an autophagy gene, offers a therapeutic advantage for leukemia. A Beclin-1 cDNA was cloned in an oncolytic adenovirus with chimeric Ad5/11 fiber (SG511-BECN). SG511-BECN treatment induced significant autophagic cell death, and resulted in enhanced cell killing in a variety of leukemic cell lines and primary leukemic blasts. SG511-BECN effects were seen in chronic myeloid leukemia and acute myeloid leukemia with resistance to imatinib or chemotherapy, but exhibited much less cytotoxicity on normal cells. The SG511-BECN-induced autophagic cell death could be partially reversed by RNA interference knockdown of UVRAG, ATG5, and ATG7. We also showed that SG511-BECN strongly inhibited the growth of leukemic progenitors in vitro. In murine leukemia models, SG511-BECN prolonged the survival and decreased the xenograft tumor size by inducing autophagic cell death. Our results suggest that infection of leukemia cells with an oncolytic adenovirus overexpressing Beclin-1 can induce significant autophagic cell death and provide a new strategy for the elimination of leukemic cells via a unique mechanism of action distinct from apoptosis.

Show MeSH
Related in: MedlinePlus