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This study presents the design, synthesis, and characterization of bisindole molecules as anti-cancer agents against Tousled-like kinases (TLKs). We show that compound 2 composed of an indirubin-3′-oxime group linked with a (N -methylpiperidin-2-yl)ethyl moiety possessed inhibitory activity toward both TLK1 and TLK2 in vitro and diminished the phosphorylation level of the downstream substrate anti-silencing function 1 (ASF1) in replicating cells. The treatment of compound 2 impaired DNA replication, slowed S-phase progression, and triggered DNA damage response in replicating cells. Structure optimization further discovered six derivatives exhibiting potent TLK inhibitory activity and revealed the importance of the tertiary amine-containing moiety of the side chain. Moreover, the derivatives 6 , 17 , 19 , and 20 strongly suppressed the growth of triple-negative breast cancer MDA-MB-231 cells, non-small cell lung cancer A549 cells, and colorectal cancer HCT-116 cells, while normal lung fibroblast MRC5 and IMR90 cells showed a lower response to these compounds. Taken together, this study identifies tertiary amine-linked indirubin-3′-oximes as potent anticancer agents that inhibit TLK activity. [Display omitted] • Compound 2 is identified as a lead compound for development of TLK inhibitors. • The derivatives with a tertiary amine-containing side chain potently inhibit TLKs. • The derivatives impair chromatin replication and induce DNA damage response. • The derivatives are highly toxic to cancer cell lines. [ABSTRACT FROM AUTHOR]

A series of thiochromeno[2,3- c ]quinolin-12-one derivatives with various substitutions were synthesized and evaluated as topoisomerase (Topo) inhibitors. Six (8 , 10 , 12 , 14 , 19 , and 26) of 23 compounds showed strong inhibitory activities against Topo-mediated DNA relaxation and proliferation of five human cell lines including breast (MDA-MB-231, MDA-MB-468 and MCF7), colorectal (HCT116) and non-small cell lung (H1299) cancers. Among these, compounds 14 and 26 exhibited full inhibitory activities against Topo I at 3 μM and Topo IIα at 1 μM. Cancer cells treated with 26 accumulated DNA damage and were arrested at the G 2 /M phase. With time, cells proceeded to apoptosis, as revealed by increased amounts of cells with fragmented DNA and cleavage of caspase-8 and -9. In contrast, normal breast epithelial cells showed low sensitivity to 26. Taken together, our study identifies 26 as a potent Topo dual-inhibitor with low toxicity to normal cells, and elucidates that the terminal amino group of N -2-aminoethylamino or N -3-aminopropylamino at the 6th position and 8,10-di-halogen substituents on thiochromeno[2,3- c ]quinolin-12-one are critical for the Topo-inhibiting and cancer-killing activities. Image 1 • Six compounds identified as dual Topo inhibitors. • 26 exhibits the highest toxicity in five cancer cell lines but is less toxic in normal breast epithelial cells. • 26 traps Topo I and IIα on chromatin and suppresses their activities. • 26 triggers DNA damage, cell-cycle arrest at the G 2 /M phase, followed by apoptosis. [ABSTRACT FROM AUTHOR]