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Year : 2019  |  Volume : 10  |  Issue : 1  |  Page : 27-43

Water-soluble version of SCR7-pyrazine inhibits DNA repair and abrogates tumor cell proliferation

1 Department of Biochemistry, Indian Institute of Science, Bengaluru, Karnataka, India
2 Department of Biochemistry, Indian Institute of Science; Institute of Bioinformatics and Applied Biotechnology, Electronic City, Bengaluru, Karnataka, India
3 Department of Studies in Chemistry, University of Mysore, Mysore, Karnataka, India
4 Department of Pharmaceutical Chemistry, KLE Academy of Higher Education and Research, KLE College of Pharmacy, Bengaluru, Karnataka, India
5 Institute of Bioinformatics and Applied Biotechnology, Electronic City, Bengaluru, Karnataka, India

Correspondence Address:
Dr. Sathees C Raghavan
Department of Biochemistry, Indian Institute of Science, Bengaluru, Karnataka
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jrcr.jrcr_24_18

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Aim: Mammalian DNA Ligases play pivotal role in processes such as DNA replication, recombination, and repair, which qualifies them as potent therapeutic targets to eradicate cancer cells. Recently, we have identified a small molecule inhibitor, SCR7 and its oxidized form SCR7-pyrazine (2-mercapto-6,7-diphenylpteridin-4-ol) (SCR7-P), which can inhibit nonhomologous end-joining (NHEJ) in a Ligase IV-dependent manner. In the present study, we describe a water-soluble version of ligase inhibitor, sodium salt of SCR7-P (Na-SCR7-P) and its anti-tumor effects. Materials and Methods: Water soluble version of SCR7-P was synthesised. To study the inhibitory effect of Na-SCR7-P on ligases, we did in vitro DNA end joining assays using double strand DNA substrates. For this, different concentrations of Na-SCR7-P was used along with purified ligases or cell-free extracts. Further, cytotoxicity induced by Na-SCR7-P was evaluated through trypan blue exclusion assay, JC-1 assay and cell cycle analysis. Anti-tumor activity of Na-SCR7-P was investigated in Swiss albino mice and its off-target effects were studied by conducting kidney and liver test and histological evaluation. Further, the anti-angiogenic effect of the compound was studied using in ovo chorioallantoic membrane assay. Results: Na-SCR7-P inhibited NHEJ in a Ligase IV-dependent manner. However, unlike SCR7 and SCR7-P, it blocked joining catalyzed by all three ligases in vitro, making it an ideal cancer therapeutic agent, as it may target multiple DNA transaction processes within the cancer cells. Na-SCR7-P decreased mitochondrial membrane potential (MMP) leading to cell death in cancer cells. Importantly, the administration of Na-SCR7-P led to a significant reduction in tumor growth from 12th day of treatment, and its impact was significantly higher than previously described SCR7, which targets Ligase IV within cells. Antitumor activity of Na-SCR7-P in mice resulted in enhanced lifespan, with minimal side effects. In addition, the in ovo chorioallantoic membrane assay revealed potent antiangiogenic property of Na-SCR7-P. Conclusion: Our results suggest that Na-SCR7-P can target NHEJ and other DNA repair pathways by disrupting Ligase mediated joining and can potentially be used as a strategy for cancer treatment, owing to its water solubility.

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