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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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Antileukemic efficacy of SG511-BECN in established K562 tumors in vivoMice bearing subcutaneous K562 xenografts (n=8) were randomized to receive one of the following intratumoral injections on 5 consecutive days: PBS, Ad5, SG511, and SG511-BECN. (A) Time courses of changes in tumor volume in each group (n=7) are shown. (B) Survival curve analysis. The percentage of surviving mice was determined by monitoring the death of mice over a period of 25 days. Mice treated with SG511-BECN shows significant survival advantage over mice treated with other groups (P=0.0072). (C) Tumor tissues were obtained on day 5 after treatment with different viruses, and Beclin-1 expression and the level of LC3-II was determined by Western blotting. The expression of â-actin was used as loading control. (D) Electron microscopy images were taken of tumor tissues (3700×). Autophagic vacuoles are denoted by arrow.
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Figure 6: Antileukemic efficacy of SG511-BECN in established K562 tumors in vivoMice bearing subcutaneous K562 xenografts (n=8) were randomized to receive one of the following intratumoral injections on 5 consecutive days: PBS, Ad5, SG511, and SG511-BECN. (A) Time courses of changes in tumor volume in each group (n=7) are shown. (B) Survival curve analysis. The percentage of surviving mice was determined by monitoring the death of mice over a period of 25 days. Mice treated with SG511-BECN shows significant survival advantage over mice treated with other groups (P=0.0072). (C) Tumor tissues were obtained on day 5 after treatment with different viruses, and Beclin-1 expression and the level of LC3-II was determined by Western blotting. The expression of â-actin was used as loading control. (D) Electron microscopy images were taken of tumor tissues (3700×). Autophagic vacuoles are denoted by arrow.

Mentions: To assess the therapeutic efficacy of SG511 versus SG511-BECN against leukemic cells in vivo, K562 xenograft model was established. Figure 6A shows that CRAd-treated tumors were substantially delayed in their growth. Ad5 virus did not show any antileukemia activity. At 22 days post treatment, xenografts of mice treated with SG511 reached an average tumor volume of 1256 mm3. In contrast, mean tumor volume was 388 mm3 in the mice treated with SG511-BECN. Importantly, complete regression of the tumors was observed in two of seven mice treated with SG511-BECN, but not in SG511-treated mice. The Kaplan-Meier survival curve shows that all animals treated with SG511-BECN were still viable, while 85.7% of the SG511-treated mice survived. In comparison, only 57.1% of control mice and 28.6% of Ad5-treated mice were alive in the same time period (Fig. 6B), suggesting that CRAd expressing Beclin-1 confers significant survival benefits (P=0.0072). To verify induction of autophagy in vivo, the overexpression of Beclin-1 and LC3-I to LC3-II conversion in tumors were detected by Western blot on day 5 after viral injection. Notable overexpression of Beclin-1 protein and conversion of LC3-I to LC3-II were found in the SG511-BECN-treated tumor (Fig. 6C), confirming the role of autophagy in inhibiting tumor growth. Furthermore, TEM analyses of tumors showing the appearance of autophagic vesicles in SG511-BECN-treated group also supported this conclusion (Fig. 6D).


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)

Antileukemic efficacy of SG511-BECN in established K562 tumors in vivoMice bearing subcutaneous K562 xenografts (n=8) were randomized to receive one of the following intratumoral injections on 5 consecutive days: PBS, Ad5, SG511, and SG511-BECN. (A) Time courses of changes in tumor volume in each group (n=7) are shown. (B) Survival curve analysis. The percentage of surviving mice was determined by monitoring the death of mice over a period of 25 days. Mice treated with SG511-BECN shows significant survival advantage over mice treated with other groups (P=0.0072). (C) Tumor tissues were obtained on day 5 after treatment with different viruses, and Beclin-1 expression and the level of LC3-II was determined by Western blotting. The expression of â-actin was used as loading control. (D) Electron microscopy images were taken of tumor tissues (3700×). Autophagic vacuoles are denoted by arrow.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Figure 6: Antileukemic efficacy of SG511-BECN in established K562 tumors in vivoMice bearing subcutaneous K562 xenografts (n=8) were randomized to receive one of the following intratumoral injections on 5 consecutive days: PBS, Ad5, SG511, and SG511-BECN. (A) Time courses of changes in tumor volume in each group (n=7) are shown. (B) Survival curve analysis. The percentage of surviving mice was determined by monitoring the death of mice over a period of 25 days. Mice treated with SG511-BECN shows significant survival advantage over mice treated with other groups (P=0.0072). (C) Tumor tissues were obtained on day 5 after treatment with different viruses, and Beclin-1 expression and the level of LC3-II was determined by Western blotting. The expression of â-actin was used as loading control. (D) Electron microscopy images were taken of tumor tissues (3700×). Autophagic vacuoles are denoted by arrow.
Mentions: To assess the therapeutic efficacy of SG511 versus SG511-BECN against leukemic cells in vivo, K562 xenograft model was established. Figure 6A shows that CRAd-treated tumors were substantially delayed in their growth. Ad5 virus did not show any antileukemia activity. At 22 days post treatment, xenografts of mice treated with SG511 reached an average tumor volume of 1256 mm3. In contrast, mean tumor volume was 388 mm3 in the mice treated with SG511-BECN. Importantly, complete regression of the tumors was observed in two of seven mice treated with SG511-BECN, but not in SG511-treated mice. The Kaplan-Meier survival curve shows that all animals treated with SG511-BECN were still viable, while 85.7% of the SG511-treated mice survived. In comparison, only 57.1% of control mice and 28.6% of Ad5-treated mice were alive in the same time period (Fig. 6B), suggesting that CRAd expressing Beclin-1 confers significant survival benefits (P=0.0072). To verify induction of autophagy in vivo, the overexpression of Beclin-1 and LC3-I to LC3-II conversion in tumors were detected by Western blot on day 5 after viral injection. Notable overexpression of Beclin-1 protein and conversion of LC3-I to LC3-II were found in the SG511-BECN-treated tumor (Fig. 6C), confirming the role of autophagy in inhibiting tumor growth. Furthermore, TEM analyses of tumors showing the appearance of autophagic vesicles in SG511-BECN-treated group also supported this conclusion (Fig. 6D).

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