Hepatocellular carcinoma (HCC) is one of the greatest life threats for Chinese people, and the prognosis of this malignancy is poor due to the strong chemotherapy resistance in patients. Notch pathway components mediate cell survival and epithelial–mesenchymal transition (EMT), and also participate in the induction of multi-drug resistance (MDR). In the present study, we demonstrated the discovery of a novel inhibitor for Notch activating/cleaving enzyme ADAM-17, named ZLDI-8; it inhibited the cleavage of NOTCH protein, consequently decreased the expression of pro-survival/anti-apoptosis and EMT related proteins. ZLDI-8 treatment enhanced the susceptibility of HCC cells to a small molecular kinase inhibitor Sorafenib, and chemotherapy agents Etoposide and Paclitaxel. ZLDI-8 treatment enhanced the effect of Sorafenib on inhibiting tumor growth in nude HCC-bearing mice model. These results suggest that ZLDI-8 can be a promising therapeutic agent to enhance Sorafenib’s anti-tumor effect and to overcome the MDR of HCC patients.

The pregnane X receptor (PXR) mediates the resistance of sorafenib in hepatocellular carcinoma (HCC) by promoting the clearance or elimination of sorafenib via the drug resistance-related downstream genes of the PXR. Previously, we revealed that rhamnetin (a flavonoid functioning as an inhibitor of sirtuin (Sirt)1) could inhibit expression of the downstream gene of the PXR: multidrug resistance 1 (mdr-1). However, how rhamnetin regulates the PXR pathway in HCC cells is not known. Here, we demonstrated that rhamnetin decelerated elimination of the molecular-targeting agent sorafenib in HCC cells via the microRNA (miR)-148a/PXR axis. Rhamnetin treatment decreased expression of the drug resistance-related downstream genes of PXR (cyp3a4 [cytochrome P-450] or mdr-1 [multi-drug resistance 1]), which mediate the metabolism or elimination of sorafenib in HCC cells. Mechanistically, rhamnetin increased expression of miR-148a (which is tumor-suppressive) in a P53-dependent manner, leading to inhibition of PXR expression and decrease in expression of its downstream genes. Rhamnetin enhanced miRNA-148a transcription by repressing Sirt1 activation to enhance acetylation at residue-373 of P53. Rhamnetin treatment decelerated the metabolic clearance of sorafenib in HCC cells and enhanced the sensitivity of HCC cells to sorafenib. Our results suggest that rhamnetin could be a potential agent for overcoming sorafenib resistance in HCC treatment.

It is well known that estrogen receptor α (ERα) participates in the pathogenic progress of breast cancer, hepatocellular carcinoma and head and neck squamous cell carcinoma. In neuroblastoma cells and related cancer clinical specimens, moreover, the ectopic expression of ERα has been identified. However, the detailed function of ERα in the proliferation of neuroblastoma cell is yet unclear. The transcriptional activity of ETS-1 (E26 transformation specific sequence 1) was measured by luciferase analysis. Western blot assays and Real-time RT-PCR were used to examine the expression of ERα, ETS-1 and its targeted genes. The protein-protein interaction between ERα and ETS-1 was determined by co-IP and GST-Pull down assays. The accumulation of ETS-1 in nuclear was detected by western blot assays, and the recruitment of ETS-1 to its targeted gene’s promoter was tested by ChIP assays. Moreover, SH-SY5Y cells’ proliferation, anchor-independent growth, migration and invasion were quantified using the MTT, soft agar or Trans-well assay, respectively. The transcriptional activity of ETS-1 was significantly increased following estrogen treatment, and this effect was related to ligand-mediated activation of ERα. The interaction between the ERα and ETS-1 was identified, and enhancement of ERα activation would up-regulate the ETS-1 transcription factor activity via modulating its cytoplasm/nucleus translocation and the recruitment of ETS-1 to its target gene’s promoter. Furthermore, treatment of estrogen increased proliferation, migration and invasion of neuroblastoma cells, whereas the antagonist of ERα reduced those effects. In this study, we provided evidences that activation of ERα promoted neuroblastoma cells proliferation and up-regulated the transcriptional activity of ETS-1. By investigating the role of ERα in the ETS-1 activity regulation, we demonstrated that ERα may be a novel ETS-1 co-activator and thus a potential therapeutic target in human neuroblastoma treatment.