Regulation of multidrug resistance proteins by genistein in a hepatocarcinoma cell line: impact on sorafenib cytotoxicity

Arsenic trioxide reduces chemo-resistance to 5-fluorouracil and cisplatin in HBx-HepG2 cells via complex mechanisms

Background

Multidrug resistance is one of the major reasons chemotherapy-based treatments failed in hepatitis B virus (HBV) related hepatocellular carcinoma (HCC). Hypoxia is generally associated with tumor chemo-resistance. The aim of the study was to investigate the effect of Arsenic trioxide (As₂O₃) on the hypoxia-induced chemo-resistance to 5-FU or cisplatin and explored its underlying mechanism in the HBx-HepG2 cells.

Methods

MTT assay was used to examine the cell viability. Mitochondrial membrane potential (MMP) and cell cycle was examined by flow cytometry. qRT-PCR was employed to observe the mRNA expression level; and western blot assay was used to determine the protein expression level.

Results

Our results showed that transfection of HBx plasmid established the HBx-HepG2 cells expressing HBx, and the expression of HBx was confirmed by qRT-PCR and western blot. Exposure of HBx-HepG2 cells to hypoxia (5 % O₂, 3 % O₂, 1 % O₂) for 48 h increased the chemo-resistance to 5-fluorouracil (5-FU) (50–1600 µM) and cisplatin (25–800 µM), reduced MMP, and caused the cell cycle arrest at G₀/G₁ phase in a concentration-dependent manner. Hypoxia also concentration-dependently (5 % O₂, 3 % O₂, 1 % O₂) reduced mRNA expression level of P-glycoprotein (P-gp), multidrug resistance protein (MRP1), lung resistance protein (LRP), and decreased the protein expression level of hypoxia-inducible factor-1α (HIF-1α), P-gp MRP1, and LRP. Following pretreatment with As₂O₃ at a non-cytotoxic concentration re-sensitized the hypoxia (1 % O₂)-induced chemo-resistance to 5-FU and cisplatin in HBx-HepG2 cells. As₂O₃ pretreatment also prevented MMP reduction and G₀/G₁ arrest induced by hypoxia. Meanwhile, As₂O₃ antagonized increase of HIF-1α protein induced by hypoxia, and it also suppresses the increase in expression levels of P-gp, MRP1, and LRP mRNA and proteins. In addition, As₂O₃ in combination with 5-FU treatment caused up-regulation of DR5, caspase 3, caspase 8, and caspase 9, and down-regulation of BCL-2, but had no effect of DR4.

Conclusions

Our results may suggest that As₂O₃ re-sensitizes hypoxia-induced chemo-resistance in HBx-HepG2 via complex pathways, and As₂O₃ may be a potential agent that given in combination with other anti-drugs for the treatment of HBV related HCC, which is resistant to chemotherapy.

CSN5 silencing reverses sorafenib resistance of human hepatocellular carcinoma HepG2 cells

Hepatocellular carcinoma (HCC) is one of the most common tumor types, and is the third leading cause of cancer mortalities worldwide. A large number of patients with HCC are diagnosed at a late stage when the curative treatment of surgical resection and liver transplantation are no longer applicable. Sorafenib has been proved to improve overall survival in advanced HCC; however, drug resistance is common. The present study reported that the CSN5 is correlated with sorafenib resistance of the HCC cell line HepG2/S. Following silencing of CSN5, resistance to sorafenib was reversed, and multi-drug‑resistance proteins, including as adenosine triphosphate binding cassette (ABC)B1, ABCC2 and ABCG2 as well as CDK6, cyclin D1 and B‑cell lymphoma 2 were downregulated. In addition, it was demonstrated that the integrin beta-1, transforming growth factor‑β1 and nuclear factor‑κB pathways were modified by CSN5.

Modulators of the human ABCC2: hope from natural sources?

Human ABCC2 is an ATP-binding cassette transporter involved in the export of endobiotics and xenobiotics. It is involved in cisplatin resistance in cancer cells, particularly in ovarian cancer. The few known ABCC2 modulators are poorly efficient, so it is necessary to explore new ways to select and optimize efficient compounds ABCC2. Natural products offer an original scaffold for such a strategy and brings hope for this aim. This review covers basic knowledge about ABCC2, from distribution and topology aspects to physiological and pathological functions. It summarizes the effect of natural products as ABCC2 modulators. Certain plant metabolites act on different ABCC2 regulation levels and therefore are promising candidates to block the multidrug resistance mediated by ABCC2 in cancer cells.