Identification of amentoflavone as a potent highly selective PARP-1 inhibitor and its potentiation on carboplatin in human non-small cell lung cancer

Background: Nuclear protein poly (ADP-ribose) polymerase-1 (PARP-1) is a key enzyme in the repair of DNA and is a promising target in the development of chemosensitizers. This study first investigated the inhibitory effects of amentoflavone (AMF) and its derivatives on PARP-1 and the potentiation of AMF on carboplatin (CBP) in nonsmall cell lung cancer (NSCLC). Purpose: This study aims to evaluate the inhibitory effect of AMF against PARP-1 and its potentiation on CBP in lung cancer both in vitro and in vivo. Study design: The inhibitory effect of AMF on PARP-1 was investigated using molecular docking and cell-free model of PARP-1 assay. Its potentiation on CBP in lung cancer was also evaluated. Methods: Fluorescence resonance energy transfer assay was used to detect the inhibitory effects of AMF and its analogues on PARP-1. Molecular docking was employed to predict the binding mode of AMF and PARP-1. MIT assay, isobologram analysis, Hoechst staining, and Annexin V-PI double staining were used to confirm the potentiation of AMF on CBP in vitro. siRNA (PARP-1)-A549 cells were used to reveal the action target of AMF. Western blot analysis, immunohistochemistry, and Tunnel assay were employed to evaluate the potentiation of AMF on CBP in A549 xenograft mice. Results: AMF and its analogues exerted excellent inhibitory effects on PARP-1 with IC 50 values ranging from 0.198 mu M to 0.409 mu M. Docking experiment showed that AMF can stably bind to PARP-1 with a comparable binding energy to olaparib. AMF can decrease the expression of PAR induced by H2O2 in vitro. AMF synergistically increased the CBP anti-proliferative effect in A549. However, its potentiation nearly disappeared when the cells were transfected with siRNAs against PARP-1. Oral administration of AMF (100 mg/kg), combined with CBP, remarkably inhibited A549 tumor growth and ki67 expression, and increased apoptosis compared with CBP-alone group. Conclusion: All results suggest that AMF can be a potential PARP-1 inhibitor and a candidate adjuvant agent to boost the anticancer effect of CBP in NSCLC.