Manuka honey enhanced sensitivity of HepG2, hepatocellular carcinoma cells, for Doxorubicin and induced apoptosis through inhibition of Wnt/β-catenin and ERK1/2

Background

Recently, there is increasing awareness focused on the identification of naturally occurring anticancer agents derived from natural products. Manuka honey (MH) has been recognized for its biological properties as antimicrobial, antioxidant, and anticancer properties. However, its antiproliferative mechanism in hepatocellular carcinoma is not investigated. The current study focused mainly on investigating the molecular mechanism and synergistic effect of anticancer properties of MH on Doxorubicin (DOX)-mediated apoptotic cell death, using two different p53 statuses (HepG2 and Hep3B) and one non-tumorigenic immortalized liver cell line.

Results

MH treatment showed a proliferative inhibitory effect on tested cells in a dose-dependent manner with IC₅₀ concentration of (6.92 ± 0.005%) and (18.62 ± 0.07%) for HepG2 and Hep3B cells, respectively, and induced dramatic morphological changes of Hep-G2 cells, which considered as characteristics feature of apoptosis induction after 48 h of treatment. Our results showed that MH or combined treatments induced higher cytotoxicity in p53-wild type, HepG2, than in p53-null, Hep3B, cells. Cytotoxicity was not observed in normal liver cells. Furthermore, the synergistic effect of MH and Dox on apoptosis was evidenced by increased annexin-V-positive cells and Sub-G1 cells in both tested cell lines with a significant increase in the percentage of Hep-G2 cells at late apoptosis as confirmed by the flow cytometric analysis. Consistently, the proteolytic activities of caspase-3 and the degradation of poly (ADP-ribose) polymerase were also higher in the combined treatment which in turn accompanied by significant inhibitory effects of pERK1/2, mTOR, S6K, oncogenic β-catenin, and cyclin D1 after 48 h. In contrast, the MH or combined treatment-induced apoptosis was accompanied by significantly upregulated expression of proapoptotic Bax protein and downregulated expression of anti-apoptotic Bcl-2 protein after 48 h.

Conclusions

Our data showed a synergistic inhibitory effect of MH on DOX-mediated apoptotic cell death in HCC cells. To our knowledge, the present study provides the first report on the anticancer activity of MH and its combined treatment with DOX on HCC cell lines, introducing MH as a promising natural and nontoxic anticancer compound.

Abstract 3553: Manuka honey induced apoptosis in hepatocellular carcinoma through inhibition of Wnt/b-catenin and ERK1/2

Hepatocellular carcinoma (HCC) is one of the most malignant tumors that affect individuals worldwide and most therapies are still badly guaranteed due to its potential toxicity. Nowadays, there is increasing awareness focused on identification of naturally occurring anticancer agents derived from food or natural products, as honey which possess a high content of polyphenols and flavonoids.

Manuka honey (MH) has been recognized by its biological properties as antimicrobial agent, anti-inflammatory activity, antioxidant efficacy and has a potent role in wound healing. Also Manuka honey possesses anticancer property in inhibiting proliferation of malignant tumor. However, its antiproliferative and apoptotic effect on human hepatocellular carcinoma cells (HepG2) remain unclear. Therefore, the current study focused mainly on investigating the anticancer properties of MH and its mechanism of action. Cell viability was evaluated by MTT assay, microscopic examination was undertaken to monitor the morphological alternation of HepG2 cells after treatment. Furthermore, the antiproliferative and apoptosis mechanism was estimated by the level of caspase-3 activity and a possible cross talk between protein expression of total ERK1/2, oncogenic β-catenin, cyclin D1, proapoptotic protein, Bax and poly (ADP-ribose) polymerase (PARP) is explained by observing their expression levels by western blot analysis. The combination effect of MH with doxorubicin (DOX) was also investigated.

Our results revealed that MH treatment for 48 h showed a substantially proliferation inhibition of HepG2 cells in a dose dependent manner with IC50 concentration of (6.92± 0.005%) and induces dramatic morphological changes of cells, which considered as characteristics of apoptosis. Consistently, MH or combined treatment showed a significant increase in caspase-3 activity in treated HepG2 cells when compared to untreated cells. In addition, the expression levels of total ERK1/2, oncogenic β-catenin and cyclin D1 were significantly downregulated with MH treatment, whereas the expression level of Bax and PARP cleavage were remarkably upregulated after 48h. In addition, a combination of MH and doxorubicin led to a significant synergistic effect.

Collectively, for our knowledge, the present study provides the first report on the anticancer activity of MH on HCC cells. Our study may provide a targeting therapy for HCC by inhibition of Wnt/ β-catenin and ERK1/2 signalling pathways and induction of apoptosis was detected by Bax up-regulation and PARP cleavage after 48h. Moreover, MH can be considered as a promising naturally occurring anticancer compound that can be used as an effective adjuvant therapeutic for treatment of HCC.

Citation Format: Heba R. Al Refaey, Ahmed S. Sultan. Manuka honey induced apoptosis in hepatocellular carcinoma through inhibition of Wnt/b-catenin and ERK1/2 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3553.