Design, synthesis and antitumor activities of phthalazinone derivatives as PARP-1 inhibitors and PARP-1/HDAC-1 inhibitors

In recent years, poly(ADP-ribose)polymerase-1 (PARP-1) and histone deacetylase (HDAC) have emerged as significant targets in tumor therapy, garnering widespread attention. In this study, we designed and synthesized two novel phthalazinone PARP-1 inhibitors and dual PARP-1/HDAC-1 inhibitors, named DLC-1-46 containing dithiocarboxylate fragments and DLC-47-63 containing hydroxamic acid fragments, and evaluated their inhibitory activities on enzymes and cells. Among the PARP-1 inhibitors, most compounds exhibited high inhibitory activity against the PARP-1 enzyme, with DLC-1-6 being particularly notable, showing IC50 values <0.2 nM. Notably, DLC-1 demonstrated significant anti-proliferative activity, with IC50 values for inhibiting the proliferation of MDA-MB-436, MDA-MB-231, and MCF-7 cells reaching 0.08, 26.39, and 1.01 μM, respectively. Further investigation revealed that DLC-1 arrested MDA-MB-231 cells in the G1 phase and induced apoptosis in a dose-dependent manner. Among the designed dual PARP-1/HDAC-1 inhibitors, several compounds exhibited potent dual-target inhibitory activity, with DLC-49 displaying IC50 values of 0.53 nM and 17 nM for PARP-1 and HDAC-1, respectively. DLC-50 demonstrated the most potent anti-proliferative activity, with IC50 values for inhibiting the proliferation of MDA-MB-436, MDA-MB-231, and MCF-7 cells at 0.30, 2.70, and 2.41 μM, respectively. Cell cycle arrest and apoptosis assays indicated that DLC-50 arrested the cell cycle in the G2 phase and induced apoptosis in HCT-116 cells. Our findings present a novel avenue for further exploration of PARP-1 inhibitors and dual PARP-1/HDAC-1 inhibitors.

Inhibitors of PARP-1 exert inhibitory effects on the biological characteristics of hepatocellular carcinoma cells in vitro

It has been confirmed that the inhibitors of poly ADP-ribose polymerF(^9ase-1 (PARP-1) can inhibit the proliferation, apoptosis and invasion of tumor cells. However, the effects of inhibitors of PARP-1 on hepatocellular carcinoma remain to be elucidated. The aim of the present study was to investigate the effect of three types of PARP-1 inhibitor on the proliferation, apoptosis and migration of hepatocellular carcinoma in vitro. An MTT assay was performed to detect the proliferation of HepG2 cells following treatment with the PARP-1 inhibitors, AG014699, BSI-201 and AZD-2281. Flow cytometry was used to detect the apoptosis of HepG2 cells, Western blot analysis was used to detect the protein expression of Casepase-3, Casepase-8, B-cell lymphoma 2 (Bcl-2)-associated X protein (Bax), Bcl-2, phosphatase and tensin homolog (PTEN), tissue inhibitor of metalloproteinase (TIMP) 3 and matrix metalloprotease (MMP) 3. A Transwell assay was performed to detect the migration of HepG2 cells. The results showed that AG014699, BSI-201 and AZD-2281 had an inhibitory effect on the proliferation of HepG2 cells in a time- and concentration-dependent manner. AG014699 at concentrations of 10, 30 and 50 µmol/l, and BSI-201 at concentrations of 20, 40 and 60 µmol/l induced the apoptosis of HepG2 cells, and the apoptotic rates were particularly high at 48 h (31, vs. 0.01%; P<0.01 and 24.12, vs. 0.03%, respectively; P<0.01). The protein expression levels of Caspase 3, Caspase 8, Bax, PTEN and TIMP 3 increased with increasing drug concentrations, whereas the protein levels of Bcl-2 and MMP3 decreased with increasing drug concentrations, and were significantly different compared with those in the control group (P<0.01). In conclusion, AG014699, BSI-201 and AZD-2281 inhibitors of PARP-1 significantly inhibited the proliferation of HepG2 cells, however, AG014699 and BSI-201 demonstrated more sensitivity, induced apoptosis and inhibited migration of the hepatocellular carcinoma cells, which may be associated with alterations of the apoptosis signaling pathway and the expression of proteins associated with migration.

A new arylbenzofuran derivative functions as an anti-tumour agent by inducing DNA damage and inhibiting PARP activity

We previously reported that 7-hydroxy-5, 4'-dimethoxy-2-arylbenzofuran (HDAB) purified from Livistona chinensis is a key active agent. The present study investigated the function and molecular mechanism of HDAB. HDAB treatment of cervical cancer cells resulted in S phase arrest and apoptosis, together with cyclin A2 and CDK2 upregulation. Cyclin A2 siRNA and a CDK inhibitor efficiently relieved S phase arrest but increased the apoptosis rate. Mechanistic studies revealed that HDAB treatment significantly increased DNA strand breaks in an alkaline comet assay and induced ATM, CHK1, CHK2 and H2A.X phosphorylation. Wortmannin (a broad inhibitor of PIKKs) and CGK733 (a specific ATM inhibitor), but not LY294002 (a phosphatidylinositol 3-kinase inhibitor) or NU7026 (a DNA-PK specific inhibitor), prevented H2A.X phosphorylation and γH2A.X-positive foci formation in the nuclei, reversed S phase arrest and promoted the HDAB-induced apoptosis, suggesting that HDAB is a DNA damaging agent that can activate the ATM-dependent DNA repair response, thereby contributing to cell cycle arrest. In addition, molecular docking and in vitro activity assays revealed that HDAB can correctly dock into the hydrophobic pocket of PARP-1 and suppress PARP-1 ADP-ribosylation activity. Thus, the results indicated that HDAB can function as an anti-cancer agent by inducing DNA damage and inhibiting PARP activity.

Dual inhibition of EGFR at protein and activity level via combinatorial blocking of PI4KIIα as anti-tumor strategy

Our previous studies indicate that phosphatidylinositol 4-kinase IIα can promote the growth of multi-malignant tumors via HER-2/PI3K and MAPK pathways. However, the molecular mechanisms of this pathway and its potential for clinical application remain unknown. In this study, we found that PI4KIIα could be an ideal combinatorial target for EGFR treatment via regulating EGFR degradation. Results showed that PI4KIIα knockdown reduced EGFR protein level, and the expression of PI4KIIα shows a strong correlation with EGFR in human breast cancer tissues (r = 0.77, P < 0.01). PI4KIIα knockdown greatly prolonged the effects and decreased the effective dosage of AG-1478, a specific inhibitor of EGFR. In addition, it significantly enhanced AG1478-induced inhibition of tumor cell survival and strengthened the effect of the EGFR-targeting anti-cancer drug Iressa in xenograft tumor models. Mechanistically, we found that PI4KIIα suppression increased EGFR ligand-independent degradation. Quantitative proteomic analysis by stable isotope labeling with amino acids in cell culture (SILAC) and LC-MS/MS suggested that HSP90 mediated the effect of PI4KIIα on EGFR. Furthermore, we found that combined inhibition of PI4KIIα and EGFR suppressed both PI3K/AKT and MAPK/ERK pathways, and resulted in downregulation of multiple oncogenes like PRDX2, FASN, MTA2, ultimately leading to suppression of tumor growth. Therefore, we conclude that combined inhibition of PI4KIIα and EGFR exerts a multiple anti-tumor effect. Dual inhibition of EGFR at protein and activity level via combinatorial blocking of PI4KIIα presents a novel strategy to combat EGFR-dependent tumors.