Benzo[a]pyrene-Induced Genotoxicity in Rats Is Affected by Co-Exposure to Sudan I by Altering the Expression of Biotransformation Enzymes.

The environmental pollutant benzo[a]pyrene (BaP) is a human carcinogen that reacts with DNA after metabolic activation catalysed by cytochromes P450 (CYP) 1A1 and 1B1 together with microsomal epoxide hydrolase. The azo dye Sudan I is a potent inducer of CYP1A1/2. Here, Wistar rats were either treated with single doses of BaP (150 mg/kg bw) or Sudan I (50 mg/kg bw) alone or with both compounds in combination to explore BaP-derived DNA adduct formation in vivo. Using 32P-postlabelling, DNA adducts generated by BaP-7,8-dihydrodiol-9,10-epoxide were found in livers of rats treated with BaP alone or co-exposed to Sudan I. During co-exposure to Sudan I prior to BaP treatment, BaP-DNA adduct levels increased 2.1-fold in comparison to BaP treatment alone. Similarly, hepatic microsomes isolated from rats exposed to Sudan I prior to BaP treatment were also the most effective in generating DNA adducts in vitro with the activated metabolites BaP-7,8-dihydrodiol or BaP-9-ol as intermediates. DNA adduct formation correlated with changes in the expression and/or enzyme activities of CYP1A1, 1A2 and 1B1 in hepatic microsomes. Thus, BaP genotoxicity in rats in vivo appears to be related to the enhanced expression and/or activity of hepatic CYP1A1/2 and 1B1 caused by exposure of rats to the studied compounds. Our results indicate that the industrially employed azo dye Sudan I potentiates the genotoxicity of the human carcinogen BaP, and exposure to both substances at the same time seems to be hazardous to humans.

Co-Exposure to Aristolochic Acids I and II Increases DNA Adduct Formation Responsible for Aristolochic Acid I-Mediated Carcinogenicity in Rats.

The plant extract aristolochic acid (AA), containing aristolochic acids I (AAI) and II (AAII) as major components, causes aristolochic acid nephropathy (AAN) and Balkan endemic nephropathy (BEN), unique renal diseases associated with upper urothelial cancer. Recently (Chemical Research in Toxicology 33(11), 2804-2818, 2020), we showed that the in vivo metabolism of AAI and AAII in Wistar rats is influenced by their co-exposure (i.e., AAI/AAII mixture). Using the same rat model, we investigated how exposure to the AAI/AAII mixture can influence AAI and AAII DNA adduct formation (i.e., AA-mediated genotoxicity). Using 32P-postlabelling, we found that AA-DNA adduct formation was increased in the livers and kidneys of rats treated with AAI/AAII mixture compared to rats treated with AAI or AAII alone. Measuring the activity of enzymes involved in AA metabolism, we showed that enhanced AA-DNA adduct formation might be caused partially by both decreased AAI detoxification as a result of hepatic CYP2C11 inhibition during treatment with AAI/AAII mixture and by hepatic or renal NQO1 induction, the key enzyme predominantly activating AA to DNA adducts. Moreover, our results indicate that AAII might act as an inhibitor of AAI detoxification in vivo. Consequently, higher amounts of AAI might remain in liver and kidney tissues, which can be reductively activated, resulting in enhanced AAI DNA adduct formation. Collectively, these results indicate that AAII present in the plant extract AA enhances the genotoxic properties of AAI (i.e., AAI DNA adduct formation). As patients suffering from AAN and BEN are always exposed to the plant extract (i.e., AAI/AAII mixture), our findings are crucial to better understanding host factors critical for AAN- and BEN-associated urothelial malignancy.

In Vivo Metabolism of Aristolochic Acid I and II in Rats Is Influenced by Their Coexposure.

The plant extract aristolochic acid (AA), containing aristolochic acid I (AAI) and II (AAII) as major components, causes aristolochic acid nephropathy and Balkan endemic nephropathy, unique renal diseases associated with upper urothelial cancer. Differences in the metabolic activation and detoxification of AAI and AAII and their effects on the metabolism of AAI/AAII mixture in the plant extract might be of great importance for an individual's susceptibility in the development of AA-mediated nephropathies and malignancies. Here, we investigated in vivo metabolism of AAI and AAII after ip administration to Wistar rats as individual compounds and as AAI/AAII mixture using high performance liquid chromatography/electrospray ionization mass spectrometry. Experimental findings were supported by theoretical calculations using density functional theory. We found that exposure to AAI/AAII mixture affected the generation of their oxidative and reductive metabolites formed during Phase I biotransformation and excreted in rat urine. Several Phase II metabolites of AAI and AAII found in the urine of exposed rats were also analyzed. Our results indicate that AAI is more efficiently metabolized in rats in vivo than AAII. Whereas AAI is predominantly oxidized during in vivo metabolism, its reduction is the minor metabolic pathway. In contrast, AAII is mainly metabolized by reduction. The oxidative reaction only occurs if aristolactam II, the major reductive metabolite of AAII, is enzymatically hydroxylated, forming aristolactam Ia. In AAI/AAII mixture, the metabolism of AAI and AAII is influenced by the presence of both AAs. For instance, the reductive metabolism of AAI is increased in the presence of AAII while the presence of AAI decreased the reductive metabolism of AAII. These results suggest that increased bioactivation of AAI in the presence of AAII also leads to increased AAI genotoxicity, which may critically impact AAI-mediated carcinogenesis. Future studies are needed to explain the underlying mechanism(s) for this phenomenon.

Application of hepatic cytochrome b5/P450 reductase null (HBRN) mice to study the role of cytochrome b5 in the cytochrome P450-mediated bioactivation of the anticancer drug ellipticine.

The anticancer drug ellipticine exerts its genotoxic effects after metabolic activation by cytochrome P450 (CYP) enzymes. The present study has examined the role of cytochrome P450 oxidoreductase (POR) and cytochrome b5 (Cyb5), electron donors to P450 enzymes, in the CYP-mediated metabolism and disposition of ellipticine in vivo. We used Hepatic Reductase Null (HRN) and Hepatic Cytochrome b5/P450 Reductase Null (HBRN) mice. HRN mice have POR deleted specifically in hepatocytes; HBRN mice also have Cyb5 deleted in the liver. Mice were treated once with 10 mg/kg body weight ellipticine (n = 4/group) for 24 h. Ellipticine-DNA adduct levels measured by 32P-postlabelling were significantly lower in HRN and HBRN livers than in wild-type (WT) livers; however no significant difference was observed between HRN and HBRN livers. Ellipticine-DNA adduct formation in WT, HRN and HBRN livers correlated with Cyp1a and Cyp3a enzyme activities measured in hepatic microsomes in the presence of NADPH confirming the importance of P450 enzymes in the bioactivation of ellipticine in vivo. Hepatic microsomal fractions were also utilised in incubations with ellipticine and DNA in the presence of NADPH, cofactor for POR, and NADH, cofactor for Cyb5 reductase (Cyb5R), to examine ellipticine-DNA adduct formation. With NADPH adduct formation decreased as electron donors were lost which correlated with the formation of the reactive metabolites 12- and 13-hydroxy-ellipticine in hepatic microsomes. No difference in adduct formation was observed in the presence of NADH. Our study demonstrates that Cyb5 contributes to the P450-mediated bioactivation of ellipticine in vitro, but not in vivo.

The impact of p53 on aristolochic acid I-induced nephrotoxicity and DNA damage in vivo and in vitro.

Exposure to aristolochic acid (AA) is associated with human nephropathy and urothelial cancer. The tumour suppressor TP53 is a critical gene in carcinogenesis and frequently mutated in AA-induced urothelial tumours. We investigated the impact of p53 on AAI-induced nephrotoxicity and DNA damage in vivo by treating Trp53(+/+), Trp53(+/-) and Trp53(-/-) mice with 3.5 mg/kg body weight (bw) AAI daily for 2 or 6 days. Renal histopathology showed a gradient of intensity in proximal tubular injury from Trp53(+/+) to Trp53(-/-) mice, especially after 6 days. The observed renal injury was supported by nuclear magnetic resonance (NMR)-based metabonomic measurements, where a consistent Trp53 genotype-dependent trend was observed for urinary metabolites that indicate aminoaciduria (i.e. alanine), lactic aciduria (i.e. lactate) and glycosuria (i.e. glucose). However, Trp53 genotype had no impact on AAI-DNA adduct levels, as measured by 32P-postlabelling, in either target (kidney and bladder) or non-target (liver) tissues, indicating that the underlying mechanisms of p53-related AAI-induced nephrotoxicity cannot be explained by differences in AAI genotoxicity. Performing gas chromatography-mass spectrometry (GC-MS) on kidney tissues showed metabolic pathways affected by AAI treatment, but again Trp53 status did not clearly impact on such metabolic profiles. We also cultured primary mouse embryonic fibroblasts (MEFs) derived from Trp53(+/+), Trp53(+/-) and Trp53(-/-) mice and exposed them to AAI in vitro (50 µM for up to 48 h). We found that Trp53 genotype impacted on the expression of NAD(P)H:quinone oxidoreductase (Nqo1), a key enzyme involved in AAI bioactivation. Nqo1 induction was highest in Trp53(+/+) MEFs and lowest in Trp53(-/-) MEFs; and it correlated with AAI-DNA adduct formation, with lowest adduct levels being observed in AAI-exposed Trp53(-/-) MEFs. Overall, our results clearly demonstrate that p53 status impacts on AAI-induced renal injury, but the underlying mechanism(s) involved remain to be further explored. Despite the impact of p53 on AAI bioactivation and DNA damage in vitro, such effects were not observed in vivo.

Identification of Human Enzymes Oxidizing the Anti-Thyroid-Cancer Drug Vandetanib and Explanation of the High Efficiency of Cytochrome P450 3A4 in its Oxidation.

The metabolism of vandetanib, a tyrosine kinase inhibitor used for treatment of symptomatic/progressive medullary thyroid cancer, was studied using human hepatic microsomes, recombinant cytochromes P450 (CYPs) and flavin-containing monooxygenases (FMOs). The role of CYPs and FMOs in the microsomal metabolism of vandetanib to N-desmethylvandetanib and vandetanib-N-oxide was investigated by examining the effects of CYP/FMO inhibitors and by correlating CYP-/FMO-catalytic activities in each microsomal sample with the amounts of N-desmethylvandetanib/vandetanib-N-oxide formed by these samples. CYP3A4/FMO-activities significantly correlated with the formation of N-desmethylvandetanib/ vandetanib-N-oxide. Based on these studies, most of the vandetanib metabolism was attributed to N-desmethylvandetanib/vandetanib-N-oxide to CYP3A4/FMO3. Recombinant CYP3A4 was most efficient to form N-desmethylvandetanib, while FMO1/FMO3 generated N-oxide. Cytochrome b5 stimulated the CYP3A4-catalyzed formation of N-desmethylvandetanib, which is of great importance because CYP3A4 is not only most efficient in generating N-desmethylvandetanib, but also most significant due to its high expression in human liver. Molecular modeling indicated that binding of more than one molecule of vandetanib into the CYP3A4-active center can be responsible for the high efficiency of CYP3A4 N-demethylating vandetanib. Indeed, the CYP3A4-mediated reaction exhibits kinetics of positive cooperativity and this corresponded to the in silico model, where two vandetanib molecules were found in CYP3A4-active center.

Sarcosine influences apoptosis and growth of prostate cells via cell-type specific regulation of distinct sets of genes.

BACKGROUND: Sarcosine is a widely discussed oncometabolite of prostate cells. Although several reports described connections between sarcosine and various phenotypic changes of prostate cancer (PCa) cells, there is still a lack of insights on the complex phenomena of its effects on gene expression patterns, particularly in non-malignant and non-metastatic cells. METHODS: To shed more light on this phenomenon, we performed parallel microarray profiling of RNA isolated from non-malignant (PNT1A), malignant (22Rv1), and metastatic (PC-3) prostate cell lines treated with sarcosine. Microarray results were experimentally verified using semi-quantitative-RT-PCR, clonogenic assay, through testing of the susceptibility of cells pre-incubated with sarcosine to anticancer agents with different modes of actions (inhibitors of topoisomerase II, DNA cross-linking agent, antimicrotubule agent and inhibitor of histone deacetylases) and by evaluation of activation of executioner caspases 3/7. RESULTS: We identified that irrespective of the cell type, sarcosine stimulates up-regulation of distinct sets of genes involved in cell cycle and mitosis, while down-regulates expression of genes driving apoptosis. Moreover, it was found that in all cell types, sarcosine had pronounced stimulatory effects on clonogenicity. Except of an inhibitor of histone deacetylase valproic acid, efficiency of all agents was significantly (P < 0.05) decreased in sarcosine pre-incubated cells. CONCLUSIONS: Our comparative study brings evidence that sarcosine affects not only metastatic PCa cells, but also their malignant and non-malignant counterparts and induces very similar changes in cells behavior, but via distinct cell-type specific targets.

Differentiation-associated urothelial cytochrome P450 oxidoreductase predicates the xenobiotic-metabolizing activity of "luminal" muscle-invasive bladder cancers.

Extra-hepatic metabolism of xenobiotics by epithelial tissues has evolved as a self-defence mechanism but has potential to contribute to the local activation of carcinogens. Bladder epithelium (urothelium) is bathed in excreted urinary toxicants and pro-carcinogens. This study reveals how differentiation affects cytochrome P450 (CYP) activity and the role of NADPH:P450 oxidoreductase (POR). CYP1A1 and CYP1B1 transcripts were inducible in normal human urothelial (NHU) cells maintained in both undifferentiated and functional barrier-forming differentiated states in vitro. However, ethoxyresorufin O-deethylation (EROD) activity, the generation of reactive BaP metabolites and BaP-DNA adducts, were predominantly detected in differentiated NHU cell cultures. This gain-of-function was attributable to the expression of POR, an essential electron donor for all CYPs, which was significantly upregulated as part of urothelial differentiation. Immunohistology of muscle-invasive bladder cancer (MIBC) revealed significant overall suppression of POR expression. Stratification of MIBC biopsies into "luminal" and "basal" groups, based on GATA3 and cytokeratin 5/6 labeling, showed POR over-expression by a subgroup of the differentiated luminal tumors. In bladder cancer cell lines, CYP1-activity was undetectable/low in basal PORlo T24 and SCaBER cells and higher in the luminal POR over-expressing RT4 and RT112 cells than in differentiated NHU cells, indicating that CYP-function is related to differentiation status in bladder cancers. This study establishes POR as a predictive biomarker of metabolic potential. This has implications in bladder carcinogenesis for the hepatic versus local activation of carcinogens and as a functional predictor of the potential for MIBC to respond to prodrug therapies.

Cytochrome b 5 impacts on cytochrome P450-mediated metabolism of benzo[a]pyrene and its DNA adduct formation: studies in hepatic cytochrome b 5 /P450 reductase null (HBRN) mice.

Benzo[a]pyrene (BaP) is an environmental pollutant that, based on evidence largely from in vitro studies, exerts its genotoxic effects after metabolic activation by cytochrome P450s. In the present study, Hepatic Reductase Null (HRN) and Hepatic Cytochrome b 5 /P450 Reductase Null (HBRN) mice have been used to study the role of P450s in the metabolic activation of BaP in vivo. In HRN mice, cytochrome P450 oxidoreductase (POR), the electron donor to P450, is deleted specifically in hepatocytes. In HBRN mice the microsomal haemoprotein cytochrome b 5 , which can also act as an electron donor from cytochrome b 5 reductase to P450s, is also deleted in the liver. Wild-type (WT), HRN and HBRN mice were treated by i.p. injection with 125 mg/kg body weight BaP for 24 h. Hepatic microsomal fractions were isolated from BaP-treated and untreated mice. In vitro incubations carried out with BaP-pretreated microsomal fractions, BaP and DNA resulted in significantly higher BaP-DNA adduct formation with WT microsomal fractions compared to those from HRN or HBRN mice. Adduct formation (i.e. 10-(deoxyguanosin-N2-yl)-7,8,9-trihydroxy-7,8,9,10-tetrahydro-BaP [dG-N2-BPDE]) correlated with observed CYP1A activity and metabolite formation (i.e. BaP-7,8-dihydrodiol) when NADPH or NADH was used as enzymatic cofactors. BaP-DNA adduct levels (i.e. dG-N2-BPDE) in vivo were significantly higher (~ sevenfold) in liver of HRN mice than WT mice while no significant difference in adduct formation was observed in liver between HBRN and WT mice. Our results demonstrate that POR and cytochrome b 5 both modulate P450-mediated activation of BaP in vitro. However, hepatic P450 enzymes in vivo appear to be more important for BaP detoxification than its activation.

The Histone Deacetylase Inhibitor Valproic Acid Exerts a Synergistic Cytotoxicity with the DNA-Damaging Drug Ellipticine in Neuroblastoma Cells.

Neuroblastoma (NBL) originates from undifferentiated cells of the sympathetic nervous system. Chemotherapy is judged to be suitable for successful treatment of this disease. Here, the influence of histone deacetylase (HDAC) inhibitor valproate (VPA) combined with DNA-damaging chemotherapeutic, ellipticine, on UKF-NB-4 and SH-SY5Y neuroblastoma cells was investigated. Treatment of these cells with ellipticine in combination with VPA led to the synergism of their anticancer efficacy. The effect is more pronounced in the UKF-NB-4 cell line, the line with N-myc amplification, than in SH-SY5Y cells. This was associated with caspase-3-dependent induction of apoptosis in UKF-NB-4 cells. The increase in cytotoxicity of ellipticine in UKF-NB-4 by VPA is dictated by the sequence of drug administration; the increased cytotoxicity was seen only after either simultaneous exposure to these drugs or after pretreatment of cells with ellipticine before their treatment with VPA. The synergism of treatment of cells with VPA and ellipticine seems to be connected with increased acetylation of histones H3 and H4. Further, co-treatment of cells with ellipticine and VPA increased the formation of ellipticine-derived DNA adducts, which indicates an easier accessibility of ellipticine to DNA in cells by its co-treatment with VPA and also resulted in higher ellipticine cytotoxicity. The results are promising for in vivo studies and perhaps later for clinical studies of combined treatment of children suffering from high-risk NBL.

VPA does not enhance platinum binding to DNA in cisplatin-resistant neuroblastoma cancer cells.

Neuroblastoma represents a malignancy of the sympathetic nervous system characteristic by biological heterogeneity. Thus, chemotherapy exhibits only low effectivity in curing high-risk forms. Previous studies revealed the cytotoxic potential of valproate on neuroblastoma cells. Nevertheless, these studies omitted effects of hypoxia, despite its undeniable tumorigenic role. In this study, we addressed the question whether valproate promotes binding of platinum-based anti-cancer drugs (cisplatin, carboplatin and oxaliplatin) to DNA and role of hypoxia, cellular antioxidant capacity and cisplatin resistance in this process. Following parameters differed significantly when cells were exposed to treatment with platinum-based drugs: elevation of platinum content bound to DNA, elevation of total thiol content, GSH/GSSG ratio, glutathione reductase and peroxidase, superoxide dismutase and elevation of antioxidant capacity. Hypoxia caused a decrease in cytosine/adenine peak, and no changes in platinum-DNA binding properties were observed. After valproate co-treatment, oxidative stress-related parameters and cytosine/adenine peak were only elevated. The amount of platinum bound to DNA was not changed significantly. Valproate is not able to enhance platinum binding to DNA in neuroblastoma cells, neither in case of intrinsic resistance (UKF-NB-4) nor in case of acquired resistance (UKF-NB-4CDDP). Therefore, another mechanism different from increase in platinum binding to DNA should be considered as a synergistic effect of valproate by cisplatin treatment.

DNA interaction with platinum-based cytostatics revealed by DNA sequencing.

The main mechanism of action of platinum-based cytostatic drugs - cisplatin, oxaliplatin and carboplatin - is the formation of DNA cross-links, which restricts the transcription due to the disability of DNA to enter the active site of the polymerase. The polymerase chain reaction (PCR) was employed as a simplified model of the amplification process in the cell nucleus. PCR with fluorescently labelled dideoxynucleotides commonly employed for DNA sequencing was used to monitor the effect of platinum-based cytostatics on DNA in terms of decrease in labeling efficiency dependent on a presence of the DNA-drug cross-link. It was found that significantly different amounts of the drugs - cisplatin (0.21 µg/mL), oxaliplatin (5.23 µg/mL), and carboplatin (71.11 µg/mL) - were required to cause the same quenching effect (50%) on the fluorescent labelling of 50 µg/mL of DNA. Moreover, it was found that even though the amounts of the drugs was applied to the reaction mixture differing by several orders of magnitude, the amount of incorporated platinum, quantified by inductively coupled plasma mass spectrometry, was in all cases at the level of tenths of µg per 5 µg of DNA.

Impact of genetic modulation of SULT1A enzymes on DNA adduct formation by aristolochic acids and 3-nitrobenzanthrone.

Exposure to aristolochic acid (AA) causes aristolochic acid nephropathy (AAN) and Balkan endemic nephropathy (BEN). Conflicting results have been found for the role of human sulfotransferase 1A1 (SULT1A1) contributing to the metabolic activation of aristolochic acid I (AAI) in vitro. We evaluated the role of human SULT1A1 in AA bioactivation in vivo after treatment of transgenic mice carrying a functional human SULT1A1-SULT1A2 gene cluster (i.e. hSULT1A1/2 mice) and Sult1a1(-/-) mice with AAI and aristolochic acid II (AAII). Both compounds formed characteristic DNA adducts in the intact mouse and in cytosolic incubations in vitro. However, we did not find differences in AAI-/AAII-DNA adduct levels between hSULT1A1/2 and wild-type (WT) mice in all tissues analysed including kidney and liver despite strong enhancement of sulfotransferase activity in both kidney and liver of hSULT1A1/2 mice relative to WT, kidney and liver being major organs involved in AA metabolism. In contrast, DNA adduct formation was strongly increased in hSULT1A1/2 mice compared to WT after treatment with 3-nitrobenzanthrone (3-NBA), another carcinogenic aromatic nitro compound where human SULT1A1/2 is known to contribute to genotoxicity. We found no differences in AAI-/AAII-DNA adduct formation in Sult1a1(-/-) and WT mice in vivo. Using renal and hepatic cytosolic fractions of hSULT1A1/2, Sult1a1(-/-) and WT mice, we investigated AAI-DNA adduct formation in vitro but failed to find a contribution of human SULT1A1/2 or murine Sult1a1 to AAI bioactivation. Our results indicate that sulfo-conjugation catalysed by human SULT1A1 does not play a role in the activation pathways of AAI and AAII in vivo, but is important in 3-NBA bioactivation.

DNA Adducts Formed by Aristolochic Acid Are Unique Biomarkers of Exposure and Explain the Initiation Phase of Upper Urothelial Cancer.

Aristolochic acid (AA) is a plant alkaloid that causes aristolochic acid nephropathy (AAN) and Balkan endemic nephropathy (BEN), unique renal diseases frequently associated with upper urothelial cancer (UUC). This review summarizes the significance of AA-derived DNA adducts in the aetiology of UUC leading to specific A:T to T:A transversion mutations (mutational signature) in AAN/BEN-associated tumours, which are otherwise rare in individuals with UCC not exposed to AA. Therefore, such DNA damage produced by AA-DNA adducts is one rare example of the direct association of exposure and cancer development (UUC) in humans, confirming that the covalent binding of carcinogens to DNA is causally related to tumourigenesis. Although aristolochic acid I (AAI), the major component of the natural plant extract AA, might directly cause interstitial nephropathy, enzymatic activation of AAI to reactive intermediates capable of binding to DNA is a necessary step leading to the formation of AA-DNA adducts and subsequently AA-induced malignant transformation. Therefore, AA-DNA adducts can not only be utilized as biomarkers for the assessment of AA exposure and markers of AA-induced UUC, but also be used for the mechanistic evaluation of its enzymatic activation and detoxification. Differences in AA metabolism might be one of the reasons for an individual's susceptibility in the multi-step process of AA carcinogenesis and studying associations between activities and/or polymorphisms of the enzymes metabolising AA is an important determinant to identify individuals having a high risk of developing AA-mediated UUC.

Histone Deacetylase Inhibitors as Anticancer Drugs.

Carcinogenesis cannot be explained only by genetic alterations, but also involves epigenetic processes. Modification of histones by acetylation plays a key role in epigenetic regulation of gene expression and is controlled by the balance between histone deacetylases (HDAC) and histone acetyltransferases (HAT). HDAC inhibitors induce cancer cell cycle arrest, differentiation and cell death, reduce angiogenesis and modulate immune response. Mechanisms of anticancer effects of HDAC inhibitors are not uniform; they may be different and depend on the cancer type, HDAC inhibitors, doses, etc. HDAC inhibitors seem to be promising anti-cancer drugs particularly in the combination with other anti-cancer drugs and/or radiotherapy. HDAC inhibitors vorinostat, romidepsin and belinostat have been approved for some T-cell lymphoma and panobinostat for multiple myeloma. Other HDAC inhibitors are in clinical trials for the treatment of hematological and solid malignancies. The results of such studies are promising but further larger studies are needed. Because of the reversibility of epigenetic changes during cancer development, the potency of epigenetic therapies seems to be of great importance. Here, we summarize the data on different classes of HDAC inhibitors, mechanisms of their actions and discuss novel results of preclinical and clinical studies, including the combination with other therapeutic modalities.

Relation of exposure to amino acids involved in sarcosine metabolic pathway on behavior of non-tumor and malignant prostatic cell lines.

BACKGROUND: Sarcosine (N-methylglycine) was previously delineated as a substantial oncometabolite of prostate cancer (PCa) and its metabolism seems to be significantly involved in PCa development and behavior. METHODS: We focused on investigation whether the exposure of prostate cells (PNT1A, 22Rv1, and PC-3) to sarcosine-related amino acids (glycine, dimethylglycine, and sarcosine) affects their aggressiveness (cell mobility and division rates, using real-time cell based assay). The effect of supplementation on expression of glycine-N-methyltransferase (GNMT) mRNA was examined using qRT-PCR. Finally, post-treatment amino acids patterns were determined with consequent statistical processing using the Ward's method, factorial ANOVA and principal component analysis (P < 0.05). RESULTS: The highest migration induced sarcosine and glycine in metastatic PC-3 cells (a decrease in relative free area about 53% and 73%). The highest cell division was achieved after treatment of 22Rv1 and PC-3 cells with sarcosine (time required for division decreased by 65% or 45%, when compared to untreated cells). qRT-PCR revealed also significant effects on expression of GNMT. Finally, amino acid profiling shown specific amino acid patterns for each cell line. In both, treated and untreated PC-3 cells significantly higher levels of serine, glutamic acid, and aspartate, linked with prostate cancer progression were found. CONCLUSIONS: Sarcosine-related amino acids can exceptionally affect the behavior of benign and malignant prostate cells.

NADH:Cytochrome b5 Reductase and Cytochrome b5 Can Act as Sole Electron Donors to Human Cytochrome P450 1A1-Mediated Oxidation and DNA Adduct Formation by Benzo[a]pyrene.

Benzo[a]pyrene (BaP) is a human carcinogen that covalently binds to DNA after activation by cytochrome P450 (P450). Here, we investigated whether NADH:cytochrome b5 reductase (CBR) in the presence of cytochrome b5 can act as sole electron donor to human P450 1A1 during BaP oxidation and replace the canonical NADPH:cytochrome P450 reductase (POR) system. We also studied the efficiencies of the coenzymes of these reductases, NADPH as a coenzyme of POR, and NADH as a coenzyme of CBR, to mediate BaP oxidation. Two systems containing human P450 1A1 were utilized: human recombinant P450 1A1 expressed with POR, CBR, epoxide hydrolase, and cytochrome b5 in Supersomes and human recombinant P450 1A1 reconstituted with POR and/or with CBR and cytochrome b5 in liposomes. BaP-9,10-dihydrodiol, BaP-7,8-dihydrodiol, BaP-1,6-dione, BaP-3,6-dione, BaP-9-ol, BaP-3-ol, a metabolite of unknown structure, and two BaP-DNA adducts were generated by the P450 1A1-Supersomes system, both in the presence of NADPH and in the presence of NADH. The major BaP-DNA adduct detected by (32)P-postlabeling was characterized as 10-(deoxyguanosin-N(2)-yl)-7,8,9-trihydroxy-7,8,9,10-tetrahydro-BaP (assigned adduct 1), while the minor adduct is probably a guanine adduct derived from 9-hydroxy-BaP-4,5-epoxide (assigned adduct 2). BaP-3-ol as the major metabolite, BaP-9-ol, BaP-1,6-dione, BaP-3,6-dione, an unknown metabolite, and adduct 2 were observed in the system using P450 1A1 reconstituted with POR plus NADPH. When P450 1A1 was reconstituted with CBR and cytochrome b5 plus NADH, BaP-3-ol was the predominant metabolite too, and an adduct 2 was also generated. Our results demonstrate that the NADH/cytochrome b5/CBR system can act as the sole electron donor both for the first and second reduction of P450 1A1 during the oxidation of BaP in vitro. They suggest that NADH-dependent CBR can replace NADPH-dependent POR in the P450 1A1-catalyzed metabolism of BaP.

Electrochemical sensing of etoposide using carbon quantum dot modified glassy carbon electrode.

In this study, enhancement of the electrochemical signals of etoposide (ETO) measured by differential pulse voltammetry (DPV) by modifying a glassy carbon electrode (GCE) with carbon quantum dots (CQDs) is demonstrated. In comparison with a bare GCE, the modified GCE exhibited a higher sensitivity towards electrochemical detection of ETO. The lowest limit of detection was observed to be 5 nM ETO. Furthermore, scanning electron microscopy (SEM), fluorescence microscopy (FM), and electrochemical impedance spectroscopy (EIS) were employed for the further study of the working electrode surface after the modification with CQDs. Finally, the GCE modified with CQDs under optimized conditions was used to analyse real samples of ETO in the prostate cancer cell line PC3. After different incubation times (1, 3, 6, 9, 12, 18 and 24 h), these samples were then prepared prior to electrochemical detection by the GCE modified with CQDs. High performance liquid chromatography with an electrochemical detection method was employed to verify the results from the GCE modified with CQDs.

Photo-initiated crosslinking extends mapping of the protein-protein interface to membrane-embedded portions of cytochromes P450 2B4 and b5.

Protein-protein interactions play a central role in the regulation of many biochemical processes (e.g. the system participating in enzyme catalysis). Therefore, a deeper understanding of protein-protein interactions may contribute to the elucidation of many biologically important mechanisms. For this purpose, it is necessary to establish the composition and stoichiometry of supramolecular complexes and to identify the crucial portions of the interacting molecules. This study is devoted to structure-functional relationships in the microsomal Mixed Function Oxidase (MFO) complex, which is responsible for biotransformation of many hydrophobic endogenous compounds and xenobiotics. In particular, the cytochrome b5 interaction with MFO terminal oxygenase cytochrome P-450 (P450) was studied. To create photolabile probes suitable for this purpose, we prepared cytochrome b5 which had a photolabile diazirine analog of methionine (pMet) incorporated into the protein sequence, employing recombinant expression in Escherichia coli. In addition to wild-type cytochrome b5, where three methionines (Met) are located at positions 96, 126, and 131, six mutants containing only one Met in the sequence were designed and expressed (see Table 1). In these mutants, a single Met was engineered into the catalytic domain (at positions 23, 41, or 46), into the linker between the protein domains (at position 96), or into the membrane region (at positions 126 or 131). These mutants should confirm or exclude these portions of cytochrome b5 which are involved in the interaction with P450. After UV irradiation, the pMet group(s) in the photolabile cytochrome b5 probe was(were) activated, producing covalent crosslinks with the interacting parts of P450 2B4 in the close vicinity. The covalent complexes were analyzed by the "bottom up" approach with high-accuracy mass spectrometry. The analysis provided an identification of the contacts in the supramolecular complex with low structural resolution. We found that all the above-mentioned cytochrome b5 Met residues can form intermolecular crosslinks and thus participate in the interaction. In addition, our results indicate the existence of at least two P450:cytochrome b5 complexes which differ in the orientation of individual proteins. The results demonstrate the advantages of the photo-initiated crosslinking technique which is able to map the protein-protein interfaces not only in the solvent exposed regions, but also in the membrane-embedded segments (compared to a typical crosslinking approach which generally only identifies crosslinks in solvent exposed regions).

Balkan endemic nephropathy: an update on its aetiology.

Balkan endemic nephropathy (BEN) is a unique, chronic renal disease frequently associated with upper urothelial cancer (UUC). It only affects residents of specific farming villages located along tributaries of the Danube River in Bosnia-Herzegovina, Croatia, Macedonia, Serbia, Bulgaria, and Romania where it is estimated that ~100,000 individuals are at risk of BEN, while ~25,000 have the disease. This review summarises current findings on the aetiology of BEN. Over the last 50 years, several hypotheses on the cause of BEN have been formulated, including mycotoxins, heavy metals, viruses, and trace-element insufficiencies. However, recent molecular epidemiological studies provide a strong case that chronic dietary exposure to aristolochic acid (AA) a principal component of Aristolochia clematitis which grows as a weed in the wheat fields of the endemic regions is the cause of BEN and associated UUC. One of the still enigmatic features of BEN that need to be resolved is why the prevalence of BEN is only 3-7 %. This suggests that individual genetic susceptibilities to AA exist in humans. In fact dietary ingestion of AA along with individual genetic susceptibility provides a scenario that plausibly can explain all the peculiarities of BEN such as geographical distribution and high risk of urothelial cancer. For the countries harbouring BEN implementing public health measures to avoid AA exposure is of the utmost importance because this seems to be the best way to eradicate this once mysterious disease to which the residents of BEN villages have been completely and utterly at mercy for so long.