Comparison of the Impact of Xanthohumol and Phenethyl Isothiocyanate and Their Combination on Nrf2 and NF-κB Pathways in HepG2 Cells In Vitro and Tumor Burden In Vivo.

Marta Cykowiak,Robert Kleszcz,Violetta Krajka-Kuźniak,Wanda Baer-Dubowska,Małgorzata Kucińska,Hanna Piotrowska-Kempisty,Marek Murias,Hanna Szaefer,Adam Plewiński

doi:10.3390/nu13093000

Abstract

Background: Increasing evidence suggests that combinations of phytochemicals are more efficient than single components in the modulation of signaling pathways involved in cancer development. In this study, the impact of phenethyl isothiocyanate (PEITC), indole-3-carbinol (I3C), xanthohumol, (X), and resveratrol (RES) and their combinations on the activation and expression of Nrf2 and NF-κB in human hepatocytes and HCC cells were evaluated. Methods: THLE-2 and HepG2 cells were exposed to single phytochemicals and their combinations for 24 h. The activation of Nrf2 and NF-κB, expression of their target genes, and effect on cells survival were assessed. The tumor burden was evaluated in mice carrying xenografts. Results: All phytochemicals enhanced the activation and expression of Nrf2 and its target genes SOD and NQO1 in HepG2 cells. The increased expression of NQO1 (~90%) was associated with increased ROS generation. X + PEITC downregulated NF-κB activation reducing binding of its active subunits to DNA resulting in diminished COX-2 expression. In contrast to single phytochemicals, X + PEITC induced apoptosis. Moderate reduction of tumor burden in mice carrying xenografts following X and PEITC or their combination was observed. Conclusions: Since Nrf2 is overexpressed in HCC its reduced activation together with diminished level of NF-κB by X + PEITC may be considered as a strategy to support conventional HCC therapy.

Highlights

Hepatocellular carcinoma (HCC) is the leading primary liver tumor and an example of inflammation-driven malignancy [1]
IKK undergoes proteasomal degradation, while NF-κB is translocated to the nucleus, where it stimulates the expression of genes such as cyclooxygenase-2 (COX-2) [2]
The effect of tested compounds and their combinations on the viability of THLE-2 and HepG2 cell lines was estimated based on the MTT assay within the concentration range of 0.5–150 μM (Figure 2)

Summary

Introduction

Hepatocellular carcinoma (HCC) is the leading primary liver tumor and an example of inflammation-driven malignancy [1]. Several signaling pathways play a key role in the injury-inflammation-regeneration response. The classical NF-κB signaling is one of the most essential, activated especially during inflammation-related tumorigenesis. The presence of various stimulators leads to the activation of IκB kinase (IKK) responsible for phosphorylation of IκB. IKK undergoes proteasomal degradation, while NF-κB is translocated to the nucleus, where it stimulates the expression of genes such as cyclooxygenase-2 (COX-2) [2]. The overexpression of the latter is observed in human HCC and is linked with increased cell growth and invasiveness [1].

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Conclusion