The level of active DNA demethylation compounds in leukocytes and urine samples as potential epigenetic biomarkers in breast cancer patients

The active DNA demethylation process, which involves TET proteins, can affect DNA methylation pattern. TET dependent demethylation results in DNA hypomethylation by oxidation 5-methylcytosine (5-mC) to 5-hydroxymethylcytosine (5-hmC) and its derivatives. Moreover, TETs' activity may be upregulated by ascorbate. Given that aberrant DNA methylation of genes implicated in breast carcinogenesis may be involved in tumor progression, we wanted to determine whether breast cancer patients exert changes in the active DNA demethylation process. The study included blood samples from breast cancer patients (n = 74) and healthy subjects (n = 71). We analyzed the expression of genes involved in the active demethylation process (qRT-PCR), and 5-mC and its derivatives level (2D-UPLC MS/MS). The ascorbate level was determined using UPLC-MS. Breast cancer patients had significantly higher TET3 expression level, lower 5-mC and 5-hmC DNA levels. TET3 was significantly increased in luminal B breast cancer patients with expression of hormone receptors. Moreover, the ascorbate level in the plasma of breast cancer patients was decreased with the accompanying increase of sodium-dependent vitamin C transporters (SLC23A1 and SLC23A2). The presented study indicates the role of TET3 in DNA demethylation in breast carcinogenesis.

Melanogenesis Is Directly Affected by Metabolites of Melatonin in Human Melanoma Cells

Melatonin (N-acetyl-5-methoxytryptamine, MEL), its kynurenic (N1-acetyl-N2-formyl-5-methoxykynurenine, AFMK) and indolic derivatives (6-hydroxymelatonin, 6(OH)MEL and 5-methoxytryptamine, 5-MT) are endogenously produced in human epidermis. Melatonin, produced by the pineal gland, brain and peripheral organs, displays a diversity of physiological functions including anti-inflammatory, immunomodulatory, and anti-tumor capacities. Herein, we assessed their regulatory effect on melanogenesis using amelanotic (A375, Sk-Mel-28) and highly pigmented (MNT-1, melanotic) human melanoma cell lines. We discovered that subjected compounds decrease the downstream pathway of melanin synthesis by causing a significant drop of cyclic adenosine monophosphate (cAMP) level, the microphthalmia-associated transcription factor (MITF) and resultant collapse of tyrosinase (TYR) activity, and melanin content comparatively to N-phenylthiourea (PTU, a positive control). We observed a reduction in pigment in melanosomes visualized by the transmission electron microscopy. Finally, we assessed the role of G-protein-coupled seven-transmembrane-domain receptors. Obtained results revealed that nonselective MT1 and MT2 receptor antagonist (luzindole) or selective MT2 receptor antagonist (4-P-PDOT) did not affect dysregulation of the melanin pathway indicating a receptor-independent mechanism. Our findings, together with the current state of the art, provide a convenient experimental model to study the complex relationship between metabolites of melatonin and the control of pigmentation serving as a future and rationale strategy for targeted therapies of melanoma-affected patients.

Polystyrene nanoparticles: the mechanism of their genotoxicity in human peripheral blood mononuclear cells

Plastic nanoparticles are widely spread in the biosphere, but health risk associated with their effect on the human organism has not yet been assessed. The purpose of this study was to determine the genotoxic potential of non-functionalized polystyrene nanoparticles (PS-NPs) of different diameters of 29, 44, and 72 nm in human peripheral blood mononuclear cells (PBMCs) (in vitro). To select non-cytotoxic concentrations of tested PS-NPs, we analyzed metabolic activity of PBMCs incubated with these particles in concentrations ranging from 0.001 to 1000 µg/mL. Then, PS-NPs were used in concentrations from 0.0001 to 100 μg/mL and incubated with tested cells for 24 h. Physico-chemical properties of PS-NPs in media and suspension were analyzed using dynamic light scattering (DLS), atomic force microscopy (AFM), scanning electron microscopy (SEM) and zeta potential. For the first time, we investigated the mechanism of genotoxic action of PS-NPs based on detection of single/double DNA strand-breaks and 8-oxo-2'-deoxyguanosine (8-oxodG) formation, as well as determination of oxidative modification of purines and pyrimidines and repair efficiency of DNA damage. Obtained results have shown that PS-NPs caused a decrease in PBMCs metabolic activity, increased single/double-strand break formation, oxidized purines and pyrimidines and increased 8oxodG levels. The resulting damage was completely repaired in the case of the largest PS-NPs. It was also found that extent of genotoxic changes in PBMCs depended on the size of tested particles and their ζ-potential value.

[Global DNA hipomethylation--the meaning in carcinogenesis]

DNA methylation plays an important role in the regulation of gene expression. Tumor cells are characterized by alterations of DNA methylation pattern, namely local CpG island hypermethylation and genome wide hypomethylation. The hypomethylation of the genome affects many repetitive sequences and transposable elements and is believed to results in chromosomal instability and increased mutations events. In this review we summarize the current knowledge concerning epigenetic mechanisms related to cancer, especially the relationship of DNA hypomethylation to carcinogenesis.

[Mechanism of DNA methylation and demethylation--its role in control of genes expression]

Cytosine methylation is a post-replicative DNA modification associated with transcriptional repression. This process consists in covalent addition of a methyl group to cytosine within the CpG dinucleotide. DNA methylation is catalyzed by DNA methyltransferases which transfer a methyl group from S-adenosyl-L-methionine to cytosine bases in DNA. Methylation patterns are determined by DNA methyltransferases, but also by the process of DNA demethylation. This review describes biochemical aspects of DNA methylation and demethylation and its role in regulation of genes expression, as well as shows cytosine methylation as promising target for anticancer therapy.

8-Oxo-7,8-dihydroguanine and 8-oxo-7,8-dihydro-2'-deoxyguanosine levels in human urine do not depend on diet

In the present study, we used the method involving HPLC pre-purification followed by gas chromatography with isotope dilution mass spectrometric detection for the determination of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) and 8-oxo-7,8-dihydroguanine (8-oxoGua) in human urine. The mean levels of 8-oxoGua and 8-oxodGuo in the urine samples of the subjects on unrestricted diet were respectively 1.87 nmol/kg 24 h (+/-0.90) and 0.83 nmol/kg 24 h (+/-0.49), and in the case of the groups studied, they did not depend on the applied diet. The sum of the amounts of both compounds in urine can give information about the formation rate of 8-oxoGua in cellular DNA. It is also likely that the levels of modified nucleo-base/side in urine sample are reflective of the involvement of different repair pathways responsible for the removal of 8-oxodGuo from DNA, namely base excision repair (BER) and nucleotide excision repair (NER).

Zinc and cadmium analysis in human prostate neoplasms

The objective of this study was to test the hypothesis that prostatic cancer is associated with the changes of zinc (Zn) and cadmium (Cd) concentration. Normal prostate, benign prostatic hyperplasia (BPH), and prostatic carcinoma (PCA) were analyzed for Zn and Cd by atomic absorption spectrometry. Cd level was measured using a graphite furnace and Zn level was measured by flame mode. Metal content was assessed in whole tissues and in nuclear, plasma membrane, and cytosolic fractions. An increase of Zn content in BPH, but a decrease in PCA as compared to normal tissue, was observed. Cd concentration appeared to be higher in BPH and PCA than in normal tissue. No correlation between Zn and Cd level was found in BPH specimens obtained from the same patients. Probability values of p < or = 0.05 were considered to indicate significant differences. Obtained results seem to support the hypothesis of Cd carcinogenicity and preventing function of Zn in prostatic cancer. Plasma membrane fraction corresponding to lysosomal, mitochondrial, and microsomal subcellular compartments are probably critical in Zn and Cd participation in human prostate neoplasms.