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ABCB1 is a promising therapeutic target for overcoming multidrug resistance (MDR). In this work, we reported the structure-based design of triazolo[1,5- a ]pyrimidines as new ABCB1 modulators, of which WS-691 significantly increased sensitization of ABCB1-overexpressed SW620/Ad300 cells to paclitaxel (PTX) (IC 50 = 22.02 nM). Mechanistic studies indicated that WS-691 significantly increased the intracellular concentration of PTX and [ 3 H]-PTX while decreasing the efflux of [ 3 H]-PTX in SW620/Ad300 cells by inhibiting the efflux function of ABCB1. The cellular thermal shift assay suggested that WS-691 could stabilize ABCB1 by directly binding to ABCB1. WS-691 could stimulate the activity of ABCB1 ATPase but had almost no inhibitory activity against CYP3A4. Importantly, WS-691 increased the sensitivity of SW620/Ad300 cells to PTX in vivo without observed toxicity. Collectively, WS-691 is a highly potent and orally active ABCB1 modulator capable of overcoming MDR. The triazolo[1,5- a ]pyrimidine may be a promising scaffold for developing more potent ABCB1 modulators.

Aclarubicin (ACR), an anthracycline anti-tumor agent, is known to play important roles in cancer. Evidence has suggested that ACR has therapeutic effects on rats intracranially implanted with C6 glioma cells. However, the function and mechanism of ACR in glioma cells remain elusive. In this study, we examined the effects of ACR on glioma cell growth, apoptosis, and DNA damage. Our results showed that treatment with different concentrations of ACR (1, 2, and 5 μM) markedly impeded glioma cell survival, significantly decreased cell proliferation, and increased cell apoptosis and caspase-3 activity. Furthermore, ACR treatment promoted DNA damage through phosphorylation of ATM and CHK1 in U87 and U251 cells. Treatment with ACR also increased sirtuin 1 (SIRT1) expression and inhibited phosphatidylinositol 3'-kinase (PI3K)/AKT pathway activation. Interestingly, we found that AKT overexpression reversed the effects of ACR on glioma cell survival, proliferation, apoptosis, and DNA damage. Thus, our data suggest that ACR induces apoptosis and DNA damage in U87 and U251 cells through the SIRT1/PI3K/AKT signaling pathway., Competing Interests: There is no conflict of interest to be declared by the authors., (This journal is © The Royal Society of Chemistry.)