Page 35 - Read Online

Li et al. J Transl Genet Genom 2021;5:163-72 https://dx.doi.org/10.20517/jtgg.2021.22 Page 5

Figure 1. Dietary feeding of the KRE inhibits the occurence of HG-PIN and prostate adenocarcinoma in TRAMP mice. (A) A simple
illustration of prevention protocol by the KRE in the TRAMP model. (B) Percentages of HG-PIN or adenocarcinoma lesions in the
prostates of 12-week-old, vehicle control vs. 0.3% or 0.6% KRE conatining food administrated to TRAMP mice. The prostates were
from 8 mice in each group, and the total number of prostate acinus was counted. Fisher exact test show P < 0.05. (C) Prostates in 12-
weeks-old, vehicle control vs. 0.3% or 0.6% KRE containing food fed TRAMP mice were examined by H&E staining and histological
evaluation. 200× magnifications of images are shown. KRE: Kava root extract; HG-PIN: high-grade prostatic intraepithelial neoplasia;
TRAMP: transgenic adenocarcinoma of the mouse prostate. *P < 0.05 and **P < 0.01, respectively.

Kavalactones and KRE inhibit MAO-A activities in prostate cancer cell lines LNCaP and C4-2B cells
Several studies reported that MAO-A was associated with aggressive prostate cancer and promoted prostate
tumor growth and metastasis [20,21,24] . In addition, MAO-A is a key target for the treatment of
neuropsychiatric and neurodegenerative disorders . We therefore have examined whether the KRE and its
[19]
active components kavalacotones can inhibit cellular MAO-A activity in LNCaP and C4-2B cells. First, we
used the autodock program to dock kavalactones with MAO-A protein (PDB code: pdb 2bxs). Kawain and
methysticin have predicted IC values of 3.85 μM and 880.78 nM, respectively. Pymol program was used to
50
observe the superimposed binding of kawain and methysticin to the flavin adenosine dinucleotide (FAD)-
binding and the active site of MAO-A and the kavalactones were predicted to form hydrogen bonds
[Figure 3A and B].

In addition, the cellular MAO activities were examined by MAO-GLO assay after LNCaP and C4-2B cells
were treated with KRE and kavalactones for 24 h. Figure 3C and D show that kavalactones and KRE
significantly inhibited cellular MAO activities by about 25% to 51% (P < 0.05). These results suggest that
kavalactones and KRE are weak inhibitors of MAO activity in prostate cancer cells.

Kavalactones inhibit LSD1 activities in prostate cancer cells and dietary feeding of KRE is
associated with reduced LSD1 activities in prostate tumors
LSD1 is an epigenetic enzyme responsible for demethylation of H3K4 and H3K9 for reprogramming gene
expression profile and suggested to have a critical role in the progression of castration-resistant prostate
cancer via interacting with AR [25,26] . Given the catalytic activity of both MAO-A and LSD1 resides in the
amine oxidase domain and is dependent on its co-factor FAD , we therefore examined whether
[18]
kavalactones could also affect LSD1 activity in prostate cancer. Molecular docking analysis revealed that
kawain and methysticin superimpose FAD and binds to the FAD-binding domain of LSD1 and interacts
with important amino acids, methionine 332 and arginine 316, respectively [Figure 4A and B].