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Identification of 5-Iodotubercidin as a genotoxic drug with anti-cancer potential.

Zhang X, Jia D, Liu H, Zhu N, Zhang W, Feng J, Yin J, Hao B, Cui D, Deng Y, Xie D, He L, Li B - PLoS ONE (2013)

Bottom Line: We found that 5-Iodotubercidin could cause DNA damage, verified by induction of DNA breaks and nuclear foci positive for γH2AX and TopBP1, activation of Atm and Chk2, and S15 phosphorylation and up-regulation of p53.Moreover, 5-Iodotubercidin showed anti-tumor activity as it could reduce the tumor size in carcinoma xenograft mouse models in p53-dependent and -independent manners.These findings reveal 5-Iodotubercidin as a novel genotoxic drug that has chemotherapeutic potential.

View Article: PubMed Central - PubMed

Affiliation: Bio-X Institutes, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders, Ministry of Education, Shanghai Jiao Tong University, Shanghai, China.

ABSTRACT
Tumor suppressor p53, which is activated by various stress and oncogene activation, is a target for anti-cancer drug development. In this study, by screening panels of protein kinase inhibitors and protein phosphatase inhibitors, we identified 5-Iodotubercidin as a strong p53 activator. 5-Iodotubercidin is purine derivative and is used as an inhibitor for various kinases including adenosine kinase. We found that 5-Iodotubercidin could cause DNA damage, verified by induction of DNA breaks and nuclear foci positive for γH2AX and TopBP1, activation of Atm and Chk2, and S15 phosphorylation and up-regulation of p53. As such, 5-Iodotubercidin induces G2 cell cycle arrest in a p53-dependent manner. Itu also induces cell death in p53-dependent and -independent manners. DNA breaks were likely generated by incorporation of 5-Iodotubercidin metabolite into DNA. Moreover, 5-Iodotubercidin showed anti-tumor activity as it could reduce the tumor size in carcinoma xenograft mouse models in p53-dependent and -independent manners. These findings reveal 5-Iodotubercidin as a novel genotoxic drug that has chemotherapeutic potential.

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Related in: MedlinePlus

Itu treatment activates Atm and Chk2 and leads to p53 S15 phosphorylation.A. HCT116 cells were treated with 1 µM Itu for different periods of time and activation of Atm, Chk2, and p53 was assessed with western blot using specific phospho-antibodies. B. MEFs cells were treated with 1 µM Itu for different periods of time and activation of Atm, Chk2, and p53 was assessed with western blot using specific phospho-antibodies.
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pone-0062527-g004: Itu treatment activates Atm and Chk2 and leads to p53 S15 phosphorylation.A. HCT116 cells were treated with 1 µM Itu for different periods of time and activation of Atm, Chk2, and p53 was assessed with western blot using specific phospho-antibodies. B. MEFs cells were treated with 1 µM Itu for different periods of time and activation of Atm, Chk2, and p53 was assessed with western blot using specific phospho-antibodies.

Mentions: In addition to foci positive for γH2AX and TopBP1, Itu treatment also resulted in nuclear foci positive for p-Atm (10.13±2.88% for untreated cells vs. 85.84±4.63% for Itu treated cells) (S1981 phosphorylation, an indication of Atm activation) (Fig. 3A and 3B) [31], indicating that Itu causes DNA damage and activates Atm. Consistent with this observation, Itu-induced p-Atm and γH2AX foci formation in HCT116 cells could be diminished (down to 15.37±1.15% and 9.00±1.19% respectively) by treatment with caffeine, an inhibitor of Atm and Atr (Fig. 3A). To substantiate the finding that Itu activates Atm, we used western blot to analyze Atm S1981 phosphorylation, as well as Atm-mediated Chk2 phosphorylation. Although Atm is thought to be only activated by double stranded DNA breaks [7], [31], [32], recent studies showed that nucleoside analogs can also activate Atm as well as its downstream pathways [30], [33], [34]. Atm is found to be localized at the stalled replication forks and may help to prevent fork collapse in the cells [30], [33]. We found that Itu treatment led to a time-dependent phosphorylation on S1981 of Atm as well as Chk2 phosphorylation at Thr68 in HCT116 cells (Fig. 4A). Itu treatment also led to Ser15 phosphorylation on p53 (Fig. 4A), which is carried out by PIKKs as well. Similarly, Itu could stimulate p53 phosphorylation and Chk2 phosphorylation in MEFs (Fig. 4B). These results further support the conclusion that Itu causes DNA damage and activates Atm.


Identification of 5-Iodotubercidin as a genotoxic drug with anti-cancer potential.

Zhang X, Jia D, Liu H, Zhu N, Zhang W, Feng J, Yin J, Hao B, Cui D, Deng Y, Xie D, He L, Li B - PLoS ONE (2013)

Itu treatment activates Atm and Chk2 and leads to p53 S15 phosphorylation.A. HCT116 cells were treated with 1 µM Itu for different periods of time and activation of Atm, Chk2, and p53 was assessed with western blot using specific phospho-antibodies. B. MEFs cells were treated with 1 µM Itu for different periods of time and activation of Atm, Chk2, and p53 was assessed with western blot using specific phospho-antibodies.
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3646850&req=5

pone-0062527-g004: Itu treatment activates Atm and Chk2 and leads to p53 S15 phosphorylation.A. HCT116 cells were treated with 1 µM Itu for different periods of time and activation of Atm, Chk2, and p53 was assessed with western blot using specific phospho-antibodies. B. MEFs cells were treated with 1 µM Itu for different periods of time and activation of Atm, Chk2, and p53 was assessed with western blot using specific phospho-antibodies.
Mentions: In addition to foci positive for γH2AX and TopBP1, Itu treatment also resulted in nuclear foci positive for p-Atm (10.13±2.88% for untreated cells vs. 85.84±4.63% for Itu treated cells) (S1981 phosphorylation, an indication of Atm activation) (Fig. 3A and 3B) [31], indicating that Itu causes DNA damage and activates Atm. Consistent with this observation, Itu-induced p-Atm and γH2AX foci formation in HCT116 cells could be diminished (down to 15.37±1.15% and 9.00±1.19% respectively) by treatment with caffeine, an inhibitor of Atm and Atr (Fig. 3A). To substantiate the finding that Itu activates Atm, we used western blot to analyze Atm S1981 phosphorylation, as well as Atm-mediated Chk2 phosphorylation. Although Atm is thought to be only activated by double stranded DNA breaks [7], [31], [32], recent studies showed that nucleoside analogs can also activate Atm as well as its downstream pathways [30], [33], [34]. Atm is found to be localized at the stalled replication forks and may help to prevent fork collapse in the cells [30], [33]. We found that Itu treatment led to a time-dependent phosphorylation on S1981 of Atm as well as Chk2 phosphorylation at Thr68 in HCT116 cells (Fig. 4A). Itu treatment also led to Ser15 phosphorylation on p53 (Fig. 4A), which is carried out by PIKKs as well. Similarly, Itu could stimulate p53 phosphorylation and Chk2 phosphorylation in MEFs (Fig. 4B). These results further support the conclusion that Itu causes DNA damage and activates Atm.

Bottom Line: We found that 5-Iodotubercidin could cause DNA damage, verified by induction of DNA breaks and nuclear foci positive for γH2AX and TopBP1, activation of Atm and Chk2, and S15 phosphorylation and up-regulation of p53.Moreover, 5-Iodotubercidin showed anti-tumor activity as it could reduce the tumor size in carcinoma xenograft mouse models in p53-dependent and -independent manners.These findings reveal 5-Iodotubercidin as a novel genotoxic drug that has chemotherapeutic potential.

View Article: PubMed Central - PubMed

Affiliation: Bio-X Institutes, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders, Ministry of Education, Shanghai Jiao Tong University, Shanghai, China.

ABSTRACT
Tumor suppressor p53, which is activated by various stress and oncogene activation, is a target for anti-cancer drug development. In this study, by screening panels of protein kinase inhibitors and protein phosphatase inhibitors, we identified 5-Iodotubercidin as a strong p53 activator. 5-Iodotubercidin is purine derivative and is used as an inhibitor for various kinases including adenosine kinase. We found that 5-Iodotubercidin could cause DNA damage, verified by induction of DNA breaks and nuclear foci positive for γH2AX and TopBP1, activation of Atm and Chk2, and S15 phosphorylation and up-regulation of p53. As such, 5-Iodotubercidin induces G2 cell cycle arrest in a p53-dependent manner. Itu also induces cell death in p53-dependent and -independent manners. DNA breaks were likely generated by incorporation of 5-Iodotubercidin metabolite into DNA. Moreover, 5-Iodotubercidin showed anti-tumor activity as it could reduce the tumor size in carcinoma xenograft mouse models in p53-dependent and -independent manners. These findings reveal 5-Iodotubercidin as a novel genotoxic drug that has chemotherapeutic potential.

Show MeSH
Related in: MedlinePlus