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BOC Sciences has developed various ADC cytotoxins for different targets and transferred them to cGMP-compliant production to meet specific requirements. Topoisomerase catalyzes DNA topological structure transformation by repeatedly breaking and connecting the phosphodiester bond of the DNA main chain through two continuous transesterification reactions. Topoisomerase directly participates in or affects life processes such as DNA replication and translation, transcription, recombination and mitosis. DNA topoisomerase II (Topo II) is closely associated with tumorigenesis, development, treatment, and prevention by regulating the dynamic changes of nucleic acid structure. Furthermore, a high expression level of Topo II is revealed in tumor cells that are not affected by other factors. Thus, so inhibiting the activity of Topo II can prevent the rapid proliferation of tumor cells.
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DNA topoisomerase II (Topo II) is an essential cellular enzyme. Functionally, it separates newly duplicated chromosome pairs, chromosome condensation, and changes in DNA supercoils. Structurally, Topo II is a homodimer consisting of two subtypes (Topo II α and Topo II β). It can be divided into three different domains: central domain, N-terminal domain and C-terminal domain. The C-terminal domain plays a significant role in the conformational recognition of DNA, while the N-terminal and main functional domains are the active domains of topoisomerase. The cleavage mechanisms between Topo II and DNA Topoisomerase I (Topo I) are not quite the same. Topo II produces a double-strand break on the DNA main chain, making another double-strand DNA pass through the gap. Which say, Topo II recognizes particular DNA sequences and binds to the DNA 5′-terminal phosphate group through a covalent bond to form dissociative complexes. Topo II is capable of changing the topological structure of DNA and catalyzing broken chains reconnection. In addition to performing all the functions of Topo I, Topo II can also separate sister chromatids that are cross-linked after DNA replication is complete.
J. Med. Chem. 2020, 63, 3, 884-904.
Topo II targeting drugs can be divided into two categories: Topo II poison and Topo II inhibitor. Topo II prison stabilizes Topo II-DNA complexes while Topo II inhibitor inhibits the catalytic activity of Topo II. Research has shown that the content of Topo II in S phase cells is higher than other cellular phases. Therefore, Topo II poison mainly causes irreversible double-strand breaks in S phase DNA, which eventually accumulates DNA cleavage complexes in the G2 phase. Topo II inhibitor, such as Doxorubicin, also mainly acts in the S phase. It slows down the relaxation of supercoiled DNA before DNA replication and affects the process from G1 to S, and eventually leads to cell cycle arrest at the G2 phase. Various anti-tumor clinical drugs applied to the topoisomerase II (Topo II) targeting mechanism, including Etoposide (VP-16), Teniposide (VM-26), Amrubicin, Doxorubicin (DOX) and Priarubicin (THP). Among these clinical drugs, Etoposide and Doxorubicin are the most commonly used anticancer drugs for malignant tumors such as small cell lung cancer and lymphatic cancer.
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