Zinc Oxide Nanoparticle Synergizes Sorafenib Anticancer Efficacy with Minimizing Its Cytotoxicity

Abstract

Cancer, as a group, represents the most important cause of death worldwide. Unfortunately, the available therapeutic approaches of cancer including surgery, chemotherapy, radiotherapy, and immunotherapy are unsatisfactory and represent a great challenge as many patients have cancer recurrence and severe side effects. Methotrexate (MTX) is a well-established (antineoplastic or cytotoxic) chemotherapy and immunosuppressant drug used to treat different types of cancer, but its usage requires high doses causing severe side effects. Therefore, we need a novel drug with high antitumor efficacy in addition to safety. The aim of this study was the evaluation of the antitumor efficacy of zinc oxide nanoparticle (ZnO-NPs) and sorafenib alone or in combination on solid Ehrlich carcinoma (SEC) in mice. Sixty adult female Swiss-albino mice were divided equally into 6 groups as follows: control, SEC, MTX, ZnO-NPs, sorafenib, and ZnO-NPs+sorafenib; all treatments continued for 4 weeks. ZnO-NPs were characterized by TEM, zeta potential, and SEM mapping. Data showed that ZnO-NPs synergized with sorafenib as a combination therapy to execute more effective and safer anticancer activity compared to monotherapy as showed by a significant reduction (P < 0.001) in tumor weight, tumor cell viability, and cancer tissue glutathione amount as well as by significant increase (P < 0.001) in tumor growth inhibition rate, DNA fragmentation, reactive oxygen species generation, the release of cytochrome c, and expression of the apoptotic gene caspase-3 in the tumor tissues with minimal changes in the liver, renal, and hematological parameters. Therefore, we suggest that ZnO-NPs might be a safe candidate in combination with sorafenib as a more potent anticancer. The safety of this combined treatment may allow its use in clinical trials.

Figure 1

Characterization of ZnO-NPs: (a) TEM image of ZnO-NP average particle size = 37 nm; (b) SEM image of the synthesized ZnO-NPs; (c) zeta potential of ZnO-NPs.

Figure 2

Effect of the treatment with MTX (2.5 mg/kg/I.P.), ZnO-NPs (5 mg/kg/I.P.), sorafenib (30 mg/kg/orally), and the combination of ZnO-NPs+sorafenib on SEC weight for 4 weeks. Results showed significant reductions (P < 0.001) in tumor weight in all treated groups compared to nontreated SEC group, and the best reduction in tumor (1.07 ± 0.21 g) weight was observed in the group that received combination therapy as ZnO-NPs synergized with sorafenib to execute the antitumor activity.

Figure 3

Caspase-3 flow cytometry analysis indicates apoptotic cell population % in all groups. (a) SEC group. (b) MTX group. (c) ZnO-NP group. (d) Sorafenib group. (e) ZnO-NPs+sorafenib group. (f) Apoptotic cell population (%).

Figure 4

Schematic diagram of the probable mechanism of synergy between ZnO-NPs and sorafenib. Sorafenib has antagonist effect on vascular endothelial growth factor receptor (VEGFR-β), platelet-derived growth factor receptor (PDGFR), fibroblast growth factor receptor (FGFR), epidermal growth factor receptor (EGFR), protooncogene B-Raf, and protein kinase B-1 (AKT-1). However, ZnO-NPs are involved in reactive oxygen species (ROS) generation and increased cell wall lipid peroxidation (LPO) leading to cytotoxic and genotoxic effects. MEK: mitogen-activated protein kinase; ERK: extracellular signal-regulated kinase; PI3K: phosphatidylinositol-3-kinase; PDK1: pyruvate dehydrogenase lipoamide kinase isozyme 1; mTOR: mammalian target of rapamycin; p53: tumor protein p53; BAD: BCL-2-associated death promoter.