Curcumin inhibits PhIP induced cytotoxicity in breast epithelial cells through multiple molecular targets

Abstract

Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), found in cooked meat, is a known food carcinogen that causes several types of cancer, including breast cancer, as PhIP metabolites produce DNA adduct and DNA strand breaks. Curcumin, obtained from the rhizome of Curcuma longa, has potent anticancer activity. To date, no study has examined the interaction of PhIP with curcumin in breast epithelial cells. The present study demonstrates the mechanisms by which curcumin inhibits PhIP-induced cytotoxicity in normal breast epithelial cells (MCF-10A). Curcumin significantly inhibited PhIP-induced DNA adduct formation and DNA double stand breaks with a concomitant decrease in reactive oxygen species (ROS) production. The expression of Nrf2, FOXO targets; DNA repair genes BRCA-1, H2AFX and PARP-1; and tumor suppressor P16 was studied to evaluate the influence on these core signaling pathways. PhIP induced the expression of various antioxidant and DNA repair genes. However, co-treatment with curcumin inhibited this expression. PhIP suppressed the expression of the tumor suppressor P16 gene, whereas curcumin co-treatment increased its expression. Caspase-3 and -9 were slightly suppressed by curcumin with a consequent inhibition of cell death. These results suggest that curcumin appears to be an effective anti-PhIP food additive likely acting through multiple molecular targets.

Curcumin Inhibit PhIP-Induced Carcinogenicity by Regulating Expression of Nrf2 and FOXO Targets, and BRCA-1 and P16 Expression in Breast Epithelial Cells

“…Many studies demonstrate that an imbalance in the production and detoxification of ROS may lead to various cancers [13,14]. Our results show that curcumin reduced DNA adduct formation, decreased DNA double strand breaks and reduced ROS production to basal levels to result in an inhibition of PhIP-induced cell death [7]. Although PhIP induces antioxidant and DNA repair mechanisms through the Nrf2 and FOXO pathways, this response does not completely inhibit ROS or DNA adduct formation.…”

“…Both the Nrf2 and FOXO pathways are upregulated by PhIP to scavenge the elevated ROS and protect cells from DNA adduct formation and the resulting DNA damage. Increased expression of H2AFX and BRCA-1 in the PhIP-treated group as well as data from comet assays, ROS monitoring and immunofluorescence with anti-DNA adduct antibodies support this idea [7]. Previous studies have shown that BRCA-1, P-53 and other tumor suppressor genes are able to increase GADD-45 expression [16][17][18].…”

“…Bioactivated PhIP also causes the production of ROS; the effect of PhIP on both these processes has been established previously [12]. PhIPinduced DNA adducts and ROS lead to DNA double strand breaks [7]. The cumulative effect of these factors affects cells' normal behavior and is responsible for the decrease in cell viability.…”

“…DNA adducts accumulated in a dose-dependent manner in both 50 and 250 µM PhIP-treated breast epithelial MCF 10A cells. When MCF 10A cells were co-treated with curcumin, PhIP-induced DNA adduct formation was noticeably reduced [7].…”

“…Previously, Sato et al, [15] have shown that ROS production during the metabolism of heterocyclic amines including PhIP occurs through NADPH/P450, suggesting that production of ROS in PhIP-treated MCF-10A cells is due to the metabolism of PhIP to N-hydroxy-PhIP through p450 detoxification. Therefore, DNA double strand breaks in PhIP-treated cells are likely to arise through two mechanisms: (i) the ROS generated directly contribute to DSB; and (ii) PhIP-DNA adduct formation leads to DNA strand breaks [7].…”