A novel series of compounds combining indolin-2-one and quinazolin-4（3H）-one moiety via a carbon-carbon double bond were synthesized by aldol-condensation of 2-methylquinazolin-4（3H）-one-6-carbaldehyde with various indolin-2-ones. The synthesized compounds were evaluated for their cytotoxic activity against five human cancer cell lines, namely, A549, MCF-7, HeLa, HT-29 and HCT-116. We found that compound 5e with two bromine atoms at the 5- and 7-positions of the indolin-2-one ring was most potent, which inhibited proliferation of five cancer cell lines in the range of 32.0%-62.3% at a concentration of 50 p,M. Our results further indicate that the connection of 5,7-dibromoindolin-2-one and 2-methylquinazolin- 4（3H）-one moiety with a carbon-carbon double bond is essential for compound 5e to exert cytotoxicity.
DNA double-strand break(DSB) is the most severe form of DNA damage,which is repaired mainly through high-fidelity homologous recombination(HR) or error-prone non-homologous end joining(NHEJ).Defects in the DNA damage response lead to genomic instability and ultimately predispose organs to cancer.Nicotinamide phosphoribosyltransferase(Nampt),which is involved in nicotinamide adenine dinucleotide metabolism,is overexpressed in a variety of tumors.In this report,we found that Nampt physically associated with CtIP and DNA-PKcs/Ku80,which are key factors in HR and NHEJ,respectively.Depletion of Nampt by small interfering RNA(siRNA) led to defective NHEJ-mediated DSB repair and enhanced HR-mediated repair.Furthermore,the inhibition of Nampt expression promoted proliferation of cancer cells and normal human fibroblasts and decreased β-galactosidase staining,indicating a delay in the onset of cellular senescence in normal human fibroblasts.Taken together,our results suggest that Nampt is a suppressor of HR-mediated DSB repair and an enhancer of NHEJ-mediated DSB repair,contributing to the acceleration of cellular senescence.
