Differential effects of c-myc and ABCB1 silencing on reversing drug resistance in HepG2/Dox cells

Anti-drug resistance, anti-inflammation, and anti-proliferation activities mediated by melatonin in doxorubicin-resistant hepatocellular carcinoma: in vitro investigations

Hepatocellular carcinoma (HCC) is the major life-threatening primary liver malignancy in both sexes all over the world. Unfortunately, the majority of patients are diagnosed at later stages because HCC does not elicit obvious symptoms during its early incidence. Consequently, most individuals escape the first-line HCC treatments and are treated with chemotherapy. Regrettably, the therapeutic outcomes for those patients are usually poor because of the development of multidrug resistance phenomena. Furthermore, most anti-HCC therapies cause severe undesired side effects that notably interfere with the life quality of such patients. Accordingly, there is an important need to search for an alternative therapeutic drug or adjuvant which is more efficient with safe or even minimal side effects for HCC treatment. Melatonin was recently reported to exert intrinsic antitumor activity in different cancers. However, the regulatory pathways underlying the antitumor activity of melatonin are poorly understood in resistant liver cells. Furthermore, a limited number of studies have addressed the therapeutic role of melatonin in HCC cells resistant to doxorubicin chemotherapy. In this study, we investigated the antitumor effects of melatonin in doxorubicin-resistant HepG2 cells and explored the regulatory pivotal targets underlying these effects. To achieve our aim, an MTT assay was used to calculate the 50% inhibitory concentration of melatonin and evaluate its antiproliferative effect on resistant cells. Additionally, qRT-PCR was used to quantify genes having a role in drug resistance phenotype (ABCB1, ABCC1, ABCC2, ABCC3, ABCC4, ABCC5, and ABCG2); apoptosis (caspases-3, and -7, Bcl2, Bax, and p53); anti-oxidation (NRF2); expression of melatonin receptors (MT1, MT2, and MT3); besides, programmed death receptor PD-1 gene. The active form of the caspase-3 enzyme was estimated by ELISA. A human inflammatory antibody membrane array was employed to quantify forty inflammatory factors expressed in treated cells. We observed that melatonin inhibited the proliferation of doxorubicin-resistant HepG2 cells in a dose-dependent manner after 24-h incubation time with a calculated IC₅₀ greater than 10 mM (13.4 mM), the expression levels of genes involved in drug resistance response (ABCB1, ABCC1, ABCC5, and ABCG2) were downregulated. Also, the expression of caspase-3, Caspase-7, NRF2, and p53 genes were expressed at higher levels as compared to control (DMSO-treated cells). An active form of caspase-3 was confirmed by ELISA. Moreover, the anti-inflammatory effect of melatonin was detected through the calculated fold change to control which was reduced for various mediators that have a role in the inflammation pathway. The current findings introduce melatonin as a promising anti-cancer treatment for human-resistant HCC which could be used in combination with current chemotherapeutic regimens to improve the outcome and reduce the developed multidrug resistance.

Development of prospective non-toxic inhibitors of ABCB1 activity and expression in a series of selenophenoquinolinones

Selenophenoquinolinone is a prospective scaffold for the development of ABCB1 inhibitors for the treatment of MDR cancers.

Could miR-34a Inhibition be Used as a Tool to Overcome Drug Resistance in MCF-7 Cells Treated with Synthesized Steroidal Heterocycles?

Background:

Progesterone derivatives have explored an improved effect on human cancer cells through combination of the explored heterocycles with progesterone moiety.miRNAs have an important role in moderating cancer cell survival, proliferation and drug resistance. The current study tested the hypothesis “whether miR-34a inhibitor has a negative impact on apoptosis and angiogenesis in MCF-7 cells treated with newly synthesized progesterone derivatives”.

Methods:

MCF-7 cells were treated with progesterone derivatives individually and in combination with miR-34a inhibitor. miR-34a expression levels were measured in MCF-7 cells treated with progesterone derivatives using QRT-PCR. MCF-7 cells treated with progesterone derivatives individually showed increased miR-34a expression levels. miR-34a deficient cells were treated with the newly synthesized progesterone derivatives, after that, apoptotic and angiogenic gene expression levels were determined using QRT-PCR. The studied genes were as follows: apoptotic (Bcl-2, survivin, CCND1, CDC2, P53 and P21) and angiogenic (VEGF, Hif-1α, MMP-2, Ang-1, Ang-2, and FGF-1).

Results:

The results showed that miR-34a deficient MCF-7 cells treated with the newly progesterone derivatives still have promising effects on apoptotic and angiogenic genes. Besides, results revealed that miRNA-34a deficient MCF-7 cells exhibited improved effect of tested compounds in some apoptotic and angiogenic genes such as CDC-2, MMP-2.

Conclusion:

These results revealed that miR-34a inhibitor did not have remarkable negative effect on apoptosis and angiogenesis. On contrary, it showed an improved effect on some genes. And consequently, miR-34a inhibitor could be used safely as a tool to tackle drug resistance in breast cancer cells.

Potentiation of Low-Dose Doxorubicin Cytotoxicity by Affecting P-Glycoprotein through Caryophyllane Sesquiterpenes in HepG2 Cells: an in Vitro and in Silico Study

Doxorubicin represents a valuable choice for different cancers, although the severe side effects occurring at the high effective dose limits its clinical use. In the present study, potential strategies to potentiate low-dose doxorubicin efficacy, including a metronomic schedule, characterized by a short and repeated exposure to the anticancer drug, and the combination with the natural chemosensitizing sesquiterpenes β-caryophyllene and β-caryophyllene oxide, were assessed in human hepatoma HepG2 cells. The involvement of P-glycoprotein (P-gp) in the HepG2-chemosensitization to doxorubicin was evaluated. Also, the direct interaction of caryophyllene sesquiterpenes with P-gp was characterized by molecular docking and dynamic simulation studies. A metronomic schedule allowed us to enhance the low-dose doxorubicin cytotoxicity and the combination with caryophyllane sesquiterpenes further potentiated this effect. Also, an increased intracellular accumulation of doxorubicin and rhodamine 123 induced by caryophyllane sesquiterpenes was found, thus suggesting their interference with P-gp function. A lowered expression of P-gp induced by the combinations, with respect to doxorubicin alone, was observed too. Docking studies found that the binding site of caryophyllane sesquiterpene was next to the ATP binding domain of P-gp and that β-caryophyllene possessed the stronger binding affinity and higher inhibition potential calculated by MM-PBSA. Present findings strengthen our hypothesis about the potential chemosensitizing power of caryophyllane sesquiterpenes and suggest that combining a chemosensitizer and a metronomic schedule can represent a suitable strategy to overcome drawbacks of doxorubicin chemotherapy while exploiting its powerful activity.

Possible Role of microRNA-122 in Modulating Multidrug Resistance of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a hypervascular primary liver cancer characterized by rapid progression, besides, resistance to traditional chemotherapeutic agents. It has been shown that microRNAs play critical roles in regulation of tumor cell sensitivity to drugs through modulating the expression of genes involved in drug transport. The present study investigated whether restoration of miR-122 in HCC cells could alter the cell cycle distribution and the expression of multidrug resistance (MDR)-related genes (ABCB1, ABCC1, ABCG2 and ABCF2). After overexpression of miR-122 in HepG2 cells treated or untreated with doxorubicin doses, total RNAs and protein extracts were isolated for application of QRT-PCR and western blotting techniques. Moreover, cell cycle distribution was monitored by flow cytometry. Our results revealed that, the over expression of miR-122 in HepG2 cells treated or untreated with doxorubicin could modulate the sensitivity of cells to chemotherapeutic drug through downregulation of MDR-related genes, ABCB1 and ABCF2. Interpretation of cell cycle distribution revealed that, the anti-proliferative effect of miR-122 is associated with the accumulation of cells in G₀/G1 phase. Moreover, treatment with miR-122 and doxorubicin resulted in high percentage of HCC cells in G₀/G1 phase. Taken together, our findings revealed that, overexpression of miR-122 inhibited HCC cell growth by inducing cell cycle arrest and this arrest is associated with down-regulation of MDR-related genes.

Long-Term Alteration of Reactive Oxygen Species Led to Multidrug Resistance in MCF-7 Cells

Reactive oxygen species (ROS) play an important role in multidrug resistance (MDR). This study aimed to investigate the effects of long-term ROS alteration on MDR in MCF-7 cells and to explore its underlying mechanism. Our study showed both long-term treatments of H₂O₂ and glutathione (GSH) led to MDR with suppressed iROS levels in MCF-7 cells. Moreover, the MDR cells induced by 0.1 μM H₂O₂ treatment for 20 weeks (MCF-7/ROS cells) had a higher viability and proliferative ability than the control MCF-7 cells. MCF-7/ROS cells also showed higher activity or content of intracellular antioxidants like glutathione peroxidase (GPx), GSH, superoxide dismutase (SOD), and catalase (CAT). Importantly, MCF-7/ROS cells were characterized by overexpression of MDR-related protein 1 (MRP1) and P-glycoprotein (P-gp), as well as their regulators NF-E2-related factor 2 (Nrf2), hypoxia-inducible factor 1 (HIF-1α), and the activation of PI3K/Akt pathway in upstream. Moreover, several typical MDR mediators, including glutathione S-transferase-π (GST-π) and c-Myc and Protein Kinase Cα (PKCα), were also found to be upregulated in MCF-7/ROS cells. Collectively, our results suggest that ROS may be critical in the generation of MDR, which may provide new insights into understanding of mechanisms of MDR.