Mitochondrial-targeted curcuminoids: a strategy to enhance bioavailability and anticancer efficacy of curcumin.

Although the anti-cancer effects of curcumin has been shown in various cancer cell types, in vitro, pre-clinical and clinical studies showed only a limited efficacy, even at high doses. This is presumably due to low bioavailability in both plasma and tissues, particularly due to poor intracellular accumulation. A variety of methods have been developed to achieve the selective targeting of drugs to cells and mitochondrion. We used a novel approach by conjugation of curcumin to lipophilic triphenylphosphonium (TPP) cation to facilitate delivery of curcumin to mitochondria. TPP is selectively taken up by mitochondria driven by the membrane potential by several hundred folds. In this study, three mitocurcuminoids (mitocurcuminoids-1, 2, and 3) were successfully synthesized by tagging TPP to curcumin at different positions. ESI-MS analysis showed significantly higher uptake of the mitocurcuminoids in mitochondria as compared to curcumin in MCF-7 breast cancer cells. All three mitocurcuminoids exhibited significant cytotoxicity to MCF-7, MDA-MB-231, SKNSH, DU-145, and HeLa cancer cells with minimal effect on normal mammary epithelial cells (MCF-10A). The IC50 was much lower for mitocurcuminoids when compared to curcumin. The mitocurcuminoids induced significant ROS generation, a drop in ΔØm, cell-cycle arrest and apoptosis. They inhibited Akt and STAT3 phosphorylation and increased ERK phosphorylation. Mitocurcuminoids also showed upregulation of pro-apoptotic BNIP3 expression. In conclusion, the results of this study indicated that mitocurcuminoids show substantial promise for further development as a potential agent for the treatment of various cancers.

Impact of hyperhomocysteinemia on breast cancer initiation and progression: epigenetic perspective.

Our recent study showing association of hyperhomocysteinemia and hypomethioninemia in breast cancer and other studies indicating association of hyperhomocysteinemia with metastasis and development of drug resistance in breast cancer cells treated with homocysteine lead us to hypothesize that homocysteine might modulate the expression of certain tumor suppressors, i.e., RASSF1, RARß1, CNND1, BRCA1, and p21, and might influence prognostic markers such as BNIP3 by inducing epigenetic alteration. To demonstrate this hypothesis, we have treated MCF-7 and MDA-MB-231 cells with different doses of homocysteine and observed dose-dependent inhibition of BRCA1 and RASSF1, respectively. In breast cancer tissues, we observed the following expression pattern: BNIP3 > BRCA1 > RARß1 > CCND1 > p21 > RASSF1. Hyperhomocysteinemia was positively associated with BRAC1 hypermethylation both in breast cancer tissue and corresponding peripheral blood. Peripheral blood CpG island methylation of BRCA1 in all types of breast cancer and methylation of RASSF1 in ER/PR-negative breast cancers showed positive correlation with total plasma homocysteine. The methylation of RASSF1 and BRCA1 was associated with breast cancer initiation as well as progression, while BRCA1 methylation was associated with DNA damage. Vitamin B12 showed inverse association with the methylation at both the loci. RFC1 G80A and cSHMT C1420T variants showed positive association with methylation at both the loci. Genetic variants influencing remethylation step were associated positively with BRCA1 methylation and inversely with RASSF1 methylation. GCPII C1561T variant showed inverse association with BRCA1 methylation. We found good correlation of BRAC1 (r = 0.90) and RASSF1 (0.92) methylation pattern between the breast cancer tissue and the corresponding peripheral blood. To conclude, elevated homocysteine influences methionine dependency phenotype of breast cancer cells and is associated with breast cancer progression by epigenetic modulation of RASSF1 and BRCA1.

Oxidative stress in coronary artery disease: epigenetic perspective.

The association between oxidative stress and coronary artery disease (CAD) is well documented. However, the role of epigenetic factors contributing to oxidative stress is relatively unexplored. In this study, we aimed to explore the impact of DNA methylation profile in BCL2/E1B adenovirus interacting protein 3 (BNIP3), extracellular superoxide dismutase (EC-SOD) and glutathione-S-transferase P1 (GSTP1) on the oxidative stress in CAD. Further, the contribution of folate pathway genetic polymorphisms in regulating epigenome was elucidated. The expression of BNIP3, EC-SOD, and GSTP1 were studied by using Maxima@SYBR-green based real-time qPCR approach in peripheral blood samples. Combined bisulfite restriction analysis and methylation-specific PCR were used to study promoter CpG island methylation. Further, the effect of homocysteine on BNIP3 gene expression was studied in human aortic endothelial cells in vitro. CAD cases exhibited upregulation of BNIP3, downregulation of EC-SOD and GSTP1. Hypomethylation of BNIP3 and hypermethylation of EC-SOD were observed in CAD cases. The expression of BNIP3 was positively correlated with homocysteine, MDA, protein carbonyls, and methylene tetrahydrofolate reductase C677T, while showing inverse association with cytosolic serine hydroxymethyl transferase C1420T. The expressions of EC-SOD and GSTP1 showed positive association with thymidylate synthase (TYMS) 2R3R, while inverse association with MDA, protein carbonyls, and methionine synthase reductase (MTRR) A66G. In vitro analysis showed homocysteine-dependent upregulation of BNIP3. The results of this study suggest that the aberrations in one-carbon metabolism appear to induce altered gene expression of EC-SOD, GSTP1, and BNIP3, and thus contribute to the increased oxidative stress and increased susceptibility to CAD.

Cross-talk between one-carbon metabolism and xenobiotic metabolism: implications on oxidative DNA damage and susceptibility to breast cancer.

The aim of this case-control study is to explore the role of aberrations in xenobiotic metabolism in inducing oxidative DNA damage and altering the susceptibility to breast cancer. Cytochrome P4501A1 (CYP1A1) m1 (OR: 1.41, 95% CI 1.08-1.84), CYP1A1 m4 (OR: 5.13, 95% CI 2.68-9.81), Catecholamine-O-methyl transferase (COMT) H108L (OR: 1.49, 95% CI 1.16-1.92), and glutathione S-transferase (GST) T1 null (OR: 1.68, 95% CI 1.09-2.59) variants showed association with breast cancer risk. Reduced folate carrier 1 (RFC1) 80A/CYP1A1 m1/CYP1A1 m4 and RFC1 80A/thymidylate synthase (TYMS) 5'-UTR 2R/methionine synthase (MTR) 2756G/COMT 108L genetic combinations were found to inflate breast cancer risk under the conditions of low dietary folate (345 ± 110 vs. 379 ± 139 µg/day) and low plasma folate (6.81 ± 1.25 vs. 7.09 ± 1.26 ng/ml) by increasing plasma 8-oxo-2'-deoxyguanosine (8-oxodG). This increase in 8-oxodG is attributed to low methionine (49.38 ± 23.74 vs. 53.90 ± 23.85 µmol/l); low glutathione (378 ± 242 vs. 501 ± 126 µmol/l) and GSTT1 null variant; and hypermethylation of CpG island of extracellular-superoxide dismutase (EC-SOD) (92.78 ± 11.49 vs. 80.45 ± 9.86%), which impair O-methylation of catechol estrogens to methoxy estrogens, conjugation of glutathione to semiquinones/quinones and free radical scavenging respectively. Our results suggest cross-talk between one-carbon metabolism and xenobiotic metabolism influencing oxidative DNA damage and susceptibility to breast cancer.