| The balance between the production and
elimination of reactive oxygen species (ROS) is essential
in determining whether cells survive or undergo apoptosis.
Nuclear factor erythroid 2-related factor 2 (Nrf2) may act as
a sensor for electrophilic stress, thus regulating the intracellular
antioxidant response. The present study investigated the
role of vitamin C (VC) and quercetin (Q) in the induction of
Nrf2-mediated oxidative stress in cancer cells. An MTT assay
was conducted to examine the anti-proliferative effects of VC
and Q. Reverse transcription-quantitative polymerase chain
reaction and western blot analysis were performed to determine
the messenger RNA (mRNA) and protein expression
of Nrf2, respectively. The activity of nicotinamide adenine
dinucleotide phosphate dehydrogenase quinone 1, heme
oxygenase 1, glutathione peroxidase, glutathione reductase
and reduced glutathione were measured by spectrophotometric
analysis. Intracellular generation of ROS was determined
using 2'‑7'‑dichlorodihydrofluorescein diacetate fluorescent
probes. The results demonstrated that the cytotoxicity (50%
inhibitory concentration) of VC and Q were 271.6-480.1
and 155.1-232.9 µM, respectively. Additionally, there was
a significant decrease in the expression of Nrf2 mRNA and
protein levels following the treatment of breast cancer cells
with VC and Q (P=0.024). Following treatment with VC and
Q, the nuclear/cytosolic Nrf2 ratio was reduced by 1.7-fold in
MDA-MB 231 cells, 2-fold in MDA-MB 468 cells, 1.4-fold in
MCF-7 cells and 1.2 fold in A549 cells. Sequential treatment
with VC and Q decreased endogenous production of ROS in a
dose-dependent manner (P=0.027). The results of the current
study suggest that VC and Q treatment may be developed as an
adjuvant for patients with cancer and overexpression of Nrf2. |