Genetic and epigenetic alterations induced by the small-molecule panobinostat: A mechanistic study at the chromosome and gene levels

Dulaglutide reduces oxidative DNA damage and hypermethylation in the somatic cells of mice fed a high-energy diet by restoring redox balance, inflammatory responses, and DNA repair gene expressions

Obesity is an established risk factor for numerous malignancies, although it remains uncertain whether the disease itself or weight-loss drugs are responsible for a greater predisposition to cancer. The objective of the current study was to determine the impact of dulaglutide on genetic and epigenetic DNA damage caused by obesity, which is a crucial factor in the development of cancer. Mice were administered a low-fat or high-fat diet for 12 weeks, followed by a 5-week treatment with dulaglutide. Following that, modifications of the DNA bases were examined using the comet assay. To clarify the underlying molecular mechanisms, oxidized and methylated DNA bases, changes in the redox status, levels of inflammatory cytokines, and the expression levels of some DNA repair genes were evaluated. Animals fed a high-fat diet exhibited increased body weights, elevated DNA damage, oxidation of DNA bases, and DNA hypermethylation. In addition, obese mice showed altered inflammatory responses, redox imbalances, and repair gene expressions. The findings demonstrated that dulaglutide does not exhibit genotoxicity in the investigated conditions. Following dulaglutide administration, animals fed a high-fat diet demonstrated low DNA damage, less oxidation and methylation of DNA bases, restored redox balance, and improved inflammatory responses. In addition, dulaglutide treatment restored the upregulated DNMT1, Ogg1, and p53 gene expression. Overall, dulaglutide effectively maintains DNA integrity in obese animals. It reduces oxidative DNA damage and hypermethylation by restoring redox balance, modulating inflammatory responses, and recovering altered gene expressions. These findings demonstrate dulaglutide's expediency in treating obesity and its associated complications.

Dapagliflozin suppresses diabetes-induced oxidative DNA damage and hypermethylation in mouse somatic cells

Diabetes mellitus is a complex metabolic disorder resulting from the interplay of environmental, genetic, and epigenetic factors that increase the risk of cancer development. However, it is unclear whether the increased cancer risk is due to poor glycemic control or the use of some antidiabetic medications. Therefore, we investigated the genetic and epigenetic changes in somatic cells in a mouse model of diabetes and studied whether multiple exposures to the antidiabetic medication dapagliflozin influence these changes. We also elucidated the mechanism(s) of these ameliorations. The micronucleus test and modified comet assay were used to investigate bone marrow DNA damage and methylation changes. These assays revealed that dapagliflozin is non-genotoxic in the tested regimen, and oxidative DNA damage and hypermethylation were significantly higher in diabetic mice. Spectrophotometry also evaluated oxidative DNA damage and global DNA methylation, revealing similar significant alterations induced by diabetes. Conversely, the dapagliflozin-treated diabetic animals significantly reduced these changes. The expression of some genes involved in DNA repair and DNA methylation was disrupted considerably in the somatic cells of diabetic animals. In contrast, dapagliflozin treatment significantly restored these disruptions and enhanced DNA repair. The simultaneous effects of decreased oxidative DNA damage and hypermethylation levels suggest that dapagliflozin can be used as a safe antidiabetic drug to reduce DNA damage and hypermethylation in diabetes, demonstrating its usefulness in patients with diabetes to control hyperglycemia and decrease the development of its subsequent complications.

Carfilzomib Mitigates Lipopolysaccharide/D-Galactosamine/Dimethylsulfoxide-Induced Acute Liver Failure in Mice

Acute liver failure (ALF) is a disease accompanied by severe liver inflammation. No effective therapy is available yet apart from liver transplantation; therefore, developing novel treatments for ALF is urgently required. Inflammatory mediators released by NF-кB activation play an essential role in ALF. Proteasome inhibitors have many medical uses, such as reducing inflammation and NF-кB inhibition, which are believed to account for most of their repurposing effects. This study was undertaken to explore the possible protective effects and the underlying mechanisms of carfilzomib, a proteasome inhibitor, in a mouse model of ALF induced by lipopolysaccharide/D-galactosamine/dimethylsulfoxide (LPS/GalN/DMSO). Carfilzomib dose-dependently protected mice from LPS/GalN/DMSO-induced liver injury, as indicated by the decrease in serum alanine aminotransferase and aspartate aminotransferase levels. LPS/GalN/DMSO increased TNF-α, NF-кB, lipid peroxidation, NO, iNOS, cyclooxygenase-II, myeloperoxidase, and caspase-3 levels. Carfilzomib administration mitigated LPS/GalN/DMSO-induced liver damage by decreasing the elevated levels of TNF-α, NF-кB, lipid peroxidation, nitric oxide, iNOS, cyclooxygenase-II, myeloperoxidase, caspase-3, and histopathological changes. A restored glutathione level was also observed in the carfilzomib-treated LPS/GalN/DMSO mice. Our results demonstrate that carfilzomib protects against LPS/GalN/DMSO-induced ALF by inhibiting NF-кB, decreasing inflammatory mediators, oxidative/nitrosative stress, neutrophil recruitment, and apoptosis, suggesting that carfilzomib may be a potential therapeutic agent for ALF.

Saxagliptin, a selective dipeptidyl peptidase-4 inhibitor, alleviates somatic cell aneugenicity and clastogenicity in diabetic mice

Diabetes-related complications are becoming increasingly common as the global prevalence of diabetes increases. Diabetes is also linked to a high risk of developing cancer. This raises the question of whether cancer vulnerability is caused by diabetes itself or the use of antidiabetic drugs. Chromosomal instability, a source of genetic modification involving either an altered chromosomal number or structure, is a hallmark of cancer. Saxagliptin has been approved by the FDA for diabetes treatment. However, the detailed in vivo effects of prolonged saxagliptin treatment on chromosomal instability have not yet been reported. In this study, streptozotocin was used to induce diabetes in mice, and both diabetic and non-diabetic mice received saxagliptin for five weeks. Fluorescence in situ hybridization was conducted in combination with a bone marrow micronucleus test for measuring chromosomal instability. Our results indicated that saxagliptin is neither mutagenic nor cytotoxic, under the given treatment regimen. Diabetic mice had a much higher incidence of micronuclei formation, and a centromeric DNA probe was present inside the majority of the induced micronuclei, indicating that most of these were caused by chromosome nondisjunction. Conversely, diabetic mice treated with saxagliptin exhibited a significant decrease in micronuclei induction, which were centromeric-positive and centromeric-negative. Diabetes also causes significant biochemical changes indicative of oxidative stress, such as increased lipid peroxidation and decreased reduced/oxidized glutathione ratio, which was reversed by saxagliptin administration. Overall, saxagliptin, the non-mutagenic antidiabetic drug, maintains chromosomal integrity in diabetes and reduces micronuclei formation by restoring redox imbalance, further indicating its usefulness in diabetic patients.

Therapeutic targeting of DNA damage repair pathways guided by homologous recombination deficiency scoring in ovarian cancers

The susceptibility of cells to DNA damage and their DNA repair ability are crucial for cancer therapy. Homologous recombination is one of the major repairing mechanisms for DNA double-strand breaks. Approximately half of ovarian cancer (OvCa) cells harbor homologous recombination deficiency (HRD). Considering that HRD is a major hallmark of OvCas, scholars proposed HRD scoring to evaluate the HRD degree and guide the choice of therapeutic strategies for OvCas. In the last decade, synthetic lethal strategy by targeting poly (ADP-ribose) polymerase (PARP) in HR-deficient OvCas has attracted considerable attention in view of its favorable clinical effort. We therefore suggested that the uses of other DNA damage/repair-targeted drugs in HR-deficient OvCas might also offer better clinical outcome. Here, we reviewed the current small molecule compounds that targeted DNA damage/repair pathways and discussed the HRD scoring system to guide their clinical uses.

Cytotoxic evaluation of YSL-109 in a triple negative breast cancer cell line and toxicological evaluations

Breast cancer (BC) is the leading cause of cancer-related death in women worldwide. Triple negative breast cancer (TNBC) is the most aggressive form of BC being with the worst prognosis and the worst survival rates. There is no specific pharmacological target for the treatment of TNBC; conventional therapy includes the use of non-specific chemotherapy that generally has a poor prognosis. Therefore, the search of effective therapies against to TNBC continues at both preclinical and clinical level. In this sense, the exploration of different pharmacological targets is a continue task that pave the way to epigenetic modulation using novel small molecules. Lately, the inhibition of histone deacetylases (HDACs) has been explored to treat different BC, including TNBC. HDACs remove the acetyl groups from the ɛ-amino lysine resides on histone and non-histone proteins. In particular, the inhibition of HDAC6 has been suggested to be useful for the treatment of TNBC due to it is overexpressed in TNBC. Therefore, in this work, an HDAC6 selective inhibitor, the (S)-4-butyl-N-(1-(hydroxyamino)-3-(naphthalen-1-yl)-1-oxopropan-2-yl) benzamide (YSL-109), was assayed on TNBC cell line (MDA-MB231) showing an antiproliferative activity (IC₅₀ = 50.34 ± 1.11 µM), whereas on fibroblast, it was lesser toxic. After corroborating the in vitro antiproliferative activity of YSL-109 in TNBC, the toxicological profile was explored using combined approach with in silico tools and experimental assays. YSL-109 shows moderate mutagenic activity on TA-98 strain at 30 and 100 µM in the Ames test, whereas YSL-109 did not show in vivo genotoxicity and its oral acute toxicity (LD₅₀) in CD-1 female mice was higher than 2000 mg/kg, which is in agreement with our in silico predictions. According to these results, YSL-109 represents an interesting compound to be explored for the treatment of TNBC under preclinical in vivo models.

Crosstalk of TNF-α, IFN-γ, NF-kB, STAT1 and redox signaling in lipopolysaccharide/D-galactosamine/dimethylsulfoxide-induced fulminant hepatic failure in mice

Purpose

The clinical study of fulminant hepatic failure is challenging due to its high mortality and relative rarity, necessitating reliance on pre-clinical models to gain insight into its pathophysiology and develop potential therapies.

Methods and Results

In our study, the combination of the commonly used solvent dimethyl sulfoxide to the current-day model of lipopolysaccharide/d-galactosamine-caused fulminant hepatic failure was found to cause significantly greater hepatic damage, as indicated by alanine aminotransferase level. The effect was dose-dependent, with the maximum increase in alanine aminotransferase observed following 200 μl/kg dimethyl sulfoxide co-administration. Co-administration of 200 μl/kg dimethyl sulfoxide also remarkably increased histopathological changes induced by lipopolysaccharide/d-galactosamine. Importantly, alanine aminotransferase levels and survival rate in the 200 μl/kg dimethyl sulfoxide co-administration groups were both greater than those in the classical lipopolysaccharide/d-galactosamine model. We found that dimethyl sulfoxide co-administration aggravated lipopolysaccharide/d-galactosamine-caused liver damage by stimulating inflammatory signaling, as indicated by tumor necrosis factor alpha (TNF-α), interferon gamma (IFN-γ), inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) levels. Further, nuclear factor kappa B (NF-kB) and transcription factor activator 1 (STAT1) were upregulated, as was neutrophil recruitment, indicated by myeloperoxidase activity. Hepatocyte apoptosis was also increased, and greater nitro-oxidative stress was noted, as determined based on nitric oxide, malondialdehyde, and glutathione levels.

Conclusion

Co-treatment with low doses of dimethyl sulfoxide enhanced the lipopolysaccharide/d-galactosamine-caused hepatic failure in animals, with higher toxicity and greater survival rates. The current findings also highlight the potential danger of using dimethyl sulfoxide as a solvent in experiments involving the hepatic immune system, suggesting that the new lipopolysaccharide/d-galactosamine/dimethyl sulfoxide model described herein could be used for pharmacological screening with the goal to better understand hepatic failure and evaluate treatment approaches.

Multiple exposure to methylmercury aggravates DNA damage in the BTBR T + Itpr3 tf/J autistic mouse model: the role of DNA repair efficiency

Environmental and genetic factors have been recognized to play major roles in the pathogenesis of autism. Here we examined the BTBR T⁺Itpr3^tf/J (BTBR) mice's susceptibility, an autistic model, to the genotoxic effects and DNA repair dysregulation of methylmercury. Micronuclei formation and oxidative DNA damage were analyzed using the micronucleus/fluorescence in situ hybridization test and modified comet assay, respectively. The results showed higher centromeric-positive micronuclei and oxidative DNA damage in BTBR mice exposed to methylmercury than the unexposed mice, which indicates that mutagenesis aggravated in BTBR mice after methylmercury exposure. Lipid peroxides in BTBR mice were significantly elevated, with a decrease in reduced/oxidized glutathione ratio after methylmercury exposure, indicating an augmenting oxidant-antioxidant imbalance. The expression of several genes involved in DNA repair was markedly altered in BTBR mice after methylmercury exposure as evaluated via PCR array and RT-PCR analyses. Declining of the antioxidant defense and dysregulation in DNA repair process after methylmercury exposure may explain the aggravated genotoxic susceptibility of BTBR mice. Thus, autistic individuals exposed to methylmercury must be under regular medical follow-up through standard timetabled medical laboratory inquiry to allow for early recognition of any mutagenic changes. Additionally, strategies that elevate cellular antioxidants/DNA repair efficiency may counteract methylmercury-induced genotoxicity.

Epidemiology of Δ8THC-Related Carcinogenesis in USA: A Panel Regression and Causal Inferential Study

The use of Δ8THC is increasing at present across the USA in association with widespread cannabis legalization and the common notion that it is "legal weed". As genotoxic actions have been described for many cannabinoids, we studied the cancer epidemiology of Δ8THC. Data on 34 cancer types was from the Centers for Disease Control Atlanta Georgia, substance abuse data from the Substance Abuse and Mental Health Services Administration, ethnicity and income data from the U.S. Census Bureau, and cannabinoid concentration data from the Drug Enforcement Agency, were combined and processed in R. Eight cancers (corpus uteri, liver, gastric cardia, breast and post-menopausal breast, anorectum, pancreas, and thyroid) were related to Δ8THC exposure on bivariate testing, and 18 (additionally, stomach, Hodgkins, and Non-Hodgkins lymphomas, ovary, cervix uteri, gall bladder, oropharynx, bladder, lung, esophagus, colorectal cancer, and all cancers (excluding non-melanoma skin cancer)) demonstrated positive average marginal effects on fully adjusted inverse probability weighted interactive panel regression. Many minimum E-Values (mEVs) were infinite. p-values rose from 8.04 × 10-78. Marginal effect calculations revealed that 18 Δ8THC-related cancers are predicted to lead to a further 8.58 cases/100,000 compared to 7.93 for alcoholism and -8.48 for tobacco. Results indicate that between 8 and 20/34 cancer types were associated with Δ8THC exposure, with very high effect sizes (mEVs) and marginal effects after adjustment exceeding tobacco and alcohol, fulfilling the epidemiological criteria of causality and suggesting a cannabinoid class effect. The inclusion of pediatric leukemias and testicular cancer herein demonstrates heritable malignant teratogenesis.

The regulatory pattern of target gene expression by aberrant enhancer methylation in glioblastoma

Background

Glioblastoma multiforme (GBM) is the most common and aggressive primary malignant brain tumor with grim prognosis. Aberrant DNA methylation is an epigenetic mechanism that promotes GBM carcinogenesis, while the function of DNA methylation at enhancer regions in GBM remains poorly described.

Results

We integrated multi-omics data to identify differential methylation enhancer region (DMER)-genes and revealed global enhancer hypomethylation in GBM. In addition, a DMER-mediated target genes regulatory network and functional enrichment analysis of target genes that might be regulated by hypomethylation enhancer regions showed that aberrant enhancer regions could contribute to tumorigenesis and progression in GBM. Further, we identified 22 modules in which lncRNAs and mRNAs synergistically competed with each other. Finally, through the construction of drug-target association networks, our study identified potential small-molecule drugs for GBM treatment.

Conclusions

Our study provides novel insights for understanding the regulation of aberrant enhancer region methylation and developing methylation-based biomarkers for the diagnosis and treatment of GBM.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12859-021-04345-8.

Epigenetic Mechanisms in DNA Double Strand Break Repair: A Clinical Review

Upon the induction of DNA damage, the chromatin structure unwinds to allow access to enzymes to catalyse the repair. The regulation of the winding and unwinding of chromatin occurs via epigenetic modifications, which can alter gene expression without changing the DNA sequence. Epigenetic mechanisms such as histone acetylation and DNA methylation are known to be reversible and have been indicated to play different roles in the repair of DNA. More importantly, the inhibition of such mechanisms has been reported to play a role in the repair of double strand breaks, the most detrimental type of DNA damage. This occurs by manipulating the chromatin structure and the expression of essential proteins that are critical for homologous recombination and non-homologous end joining repair pathways. Inhibitors of histone deacetylases and DNA methyltransferases have demonstrated efficacy in the clinic and represent a promising approach for cancer therapy. The aims of this review are to summarise the role of histone deacetylase and DNA methyltransferase inhibitors involved in DNA double strand break repair and explore their current and future independent use in combination with other DNA repair inhibitors or pre-existing therapies in the clinic.

Dual Targeting of Chromatin Stability By The Curaxin CBL0137 and Histone Deacetylase Inhibitor Panobinostat Shows Significant Preclinical Efficacy in Neuroblastoma

PURPOSE

We investigated whether targeting chromatin stability through a combination of the curaxin CBL0137 with the histone deacetylase (HDAC) inhibitor, panobinostat, constitutes an effective multimodal treatment for high-risk neuroblastoma.

EXPERIMENTAL DESIGN

The effects of the drug combination on cancer growth were examined in vitro and in animal models of MYCN-amplified neuroblastoma. The molecular mechanisms of action were analyzed by multiple techniques including whole transcriptome profiling, immune deconvolution analysis, immunofluorescence, flow cytometry, pulsed-field gel electrophoresis, assays to assess cell growth and apoptosis, and a range of cell-based reporter systems to examine histone eviction, heterochromatin transcription, and chromatin compaction.

RESULTS

The combination of CBL0137 and panobinostat enhanced nucleosome destabilization, induced an IFN response, inhibited DNA damage repair, and synergistically suppressed cancer cell growth. Similar synergistic effects were observed when combining CBL0137 with other HDAC inhibitors. The CBL0137/panobinostat combination significantly delayed cancer progression in xenograft models of poor outcome high-risk neuroblastoma. Complete tumor regression was achieved in the transgenic Th-MYCN neuroblastoma model which was accompanied by induction of a type I IFN and immune response. Tumor transplantation experiments further confirmed that the presence of a competent adaptive immune system component allowed the exploitation of the full potential of the drug combination.

CONCLUSIONS

The combination of CBL0137 and panobinostat is effective and well-tolerated in preclinical models of aggressive high-risk neuroblastoma, warranting further preclinical and clinical investigation in other pediatric cancers. On the basis of its potential to boost IFN and immune responses in cancer models, the drug combination holds promising potential for addition to immunotherapies.

Anticancer Therapy with HDAC Inhibitors: Mechanism-Based Combination Strategies and Future Perspectives

The increasing knowledge of molecular drivers of tumorigenesis has fueled targeted cancer therapies based on specific inhibitors. Beyond "classic" oncogene inhibitors, epigenetic therapy is an emerging field. Epigenetic alterations can occur at any time during cancer progression, altering the structure of the chromatin, the accessibility for transcription factors and thus the transcription of genes. They rely on post-translational histone modifications, particularly the acetylation of histone lysine residues, and are determined by the inverse action of histone acetyltransferases (HATs) and histone deacetylases (HDACs). Importantly, HDACs are often aberrantly overexpressed, predominantly leading to the transcriptional repression of tumor suppressor genes. Thus, histone deacetylase inhibitors (HDACis) are powerful drugs, with some already approved for certain hematological cancers. Albeit HDACis show activity in solid tumors as well, further refinement and the development of novel drugs are needed. This review describes the capability of HDACis to influence various pathways and, based on this knowledge, gives a comprehensive overview of various preclinical and clinical studies on solid tumors. A particular focus is placed on strategies for achieving higher efficacy by combination therapies, including phosphoinositide 3-kinase (PI3K)-EGFR inhibitors and hormone- or immunotherapy. This also includes new bifunctional inhibitors as well as novel approaches for HDAC degradation via PROteolysis-TArgeting Chimeras (PROTACs).

Specific epigenetic microenvironment and the regulation of tumor-related gene expression by trichloroethylene in human hepatocytes

Trichloroethylene (TCE), an important volatile organic solvent, causes a series of toxic damage to human. Conventional genetic mechanisms cannot fully explain its toxicity and carcinogenicity, indicative of the possible involvement of epigenetic mechanisms. Our study was intended to investigate the epigenetic toxicity and underlying mechanisms of TCE. Data showed that 0.3 mM TCE treatment for 24 h increased the growth of L-02 cells transiently. In contrast, subacute exposure to TCE inhibited cell growth and induced the genomic DNA hypomethylation and histone hyperacetylation. Further studies have revealed the TCE-induced DNA hypomethylation in the promoter regions of tumor-related genes, N-Ras, c-Jun, c-Myc, c-Fos and IGF-II, promoting their protein levels in a time-dependent manner. These results reveal there is a negative relationship existing between DNA hypomethylation and protein expression in tumor-related gene after TCE exposure under specific epigenetic microenvironment, serving as early biomarkers for TCE-associated diseases.

The MAP kinase inhibitor PD98059 reduces chromosomal instability in the autoimmune encephalomyelitis SJL/J-mouse model of multiple sclerosis

Multiple sclerosis (MS), a disease in which the immune system attacks nerve cells, has been associated with both genetic and environmental risk factors. We observed increased micronucleus (MN) formation in SJL/J mouse experimental autoimmune encephalomyelitis (EAE), an animal model of MS. Most of these MN were due to chromosomal loss. Increased activation of MAP kinases, which leads to disruption of the mitotic spindle and improper segregation of chromosomes, is associated with MS. MAP kinase inhibitors, such as PD98059, may therefore be beneficial for MS. In the EAE model, PD98059 treatment reduced adverse effects, including MN formation, lipid peroxidation, and GSH oxidation. Interventions that mitigate chromosomal instability may have therapeutic value in MS.

3-Aminobenzamide alleviates elevated DNA damage and DNA methylation in a BTBR T+Itpr3tf/J mouse model of autism by enhancing repair gene expression

Little is known about genetic and epigenetic alterations in autism spectrum disorder. Moreover, the efficiency of DNA repair in autism must be improved to correct these alterations. We examined whether 3-aminobenzamide (3-AB) could reverse these alterations. We conducted experiments to clarify the molecular mechanism underlying these ameliorations. An assessment of genetic and epigenetic alterations by a modified comet assay showed elevated levels of oxidative DNA strand breaks and DNA hypermethylation in BTBR T⁺Itpr3^tf/J (BTBR) mice used as a model of autism. Oxidative DNA strand breaks and DNA methylation were further quantified fluorometrically, and the results showed similar changes. Conversely, 3-AB treated BTBR mice showed a significant reduction in these alterations compared with untreated mice. The expressions of 43 genes involved in DNA repair were altered in BTBR mice. RT² Profiler PCR Array revealed significantly altered expression of seven genes, which was confirmed by RT-PCR analyses. 3-AB treatment relieved these disturbances and significantly improved Ogg1 and Rad1 up-regulation. Moreover, autism-like behaviors were also mitigated in BTBR animals by 3-AB treatment without alterations in locomotor activities. The simultaneous effects of reduced DNA damage and DNA methylation levels as well as the regulation of repair gene expression indicate the potential of 3-AB as a therapeutic agent to decrease the levels of DNA damage and DNA methylation in autistic patients. The current data may help in the development of therapies that ultimately provide a better quality of life for individuals suffering from autism.

Vorinostat is genotoxic and epigenotoxic in the mouse bone marrow cells at the human equivalent doses

Vorinostat was approved as the first histone deacetylase inhibitor for the management of cutaneous T cell lymphoma. However, it's in vivo genetic and epigenetic effects on non-cancerous cells remain poorly understood. As genetic and epigenetic changes play a critical role in the pathogenesis of carcinogenesis, we investigated whether vorinostat induces genetic and epigenetic alterations in mouse bone marrow cells. Bone marrow cells were isolated 24 h following the last oral administration of vorinostat at the doses of 25, 50, or 100 mg/kg/day for five days (approximately equal to the recommended human doses). The cells were then used to assess clastogenicity and aneugenicity by the micronucleus test complemented by fluorescence in situ hybridization assay; DNA strand breaks, oxidative DNA strand breaks, and DNA methylation by the modified comet assay; apoptosis by annexin V/PI staining analysis and the occurrence of the hypodiploid DNA content; and DNA damage/repair gene expression by polymerase chain reaction (PCR) Array. The expression of the mRNA transcripts were also confirmed by real-time PCR and western blot analysis. Vorinostat caused structural chromosomal damage, numerical chromosomal abnormalities, DNA strand breaks, oxidative DNA strand breaks, DNA hypomethylation, and programed cell death in a dose-dependent manner. Furthermore, the expression of numerous genes implicated in DNA damage/repair were altered after vorinostat treatment. Accordingly, the genetic/epigenetic mechanism(s) of action of vorinostat may play a role in its carcinogenicity and support the continued study and development of new compounds with lower toxicity.

Evaluation of DNA repair efficiency in autistic children by molecular cytogenetic analysis and transcriptome profiling

Data regarding DNA repair perturbations in autism, which might increase the risk of malignancy, are scarce. To evaluate whether DNA repair may be disrupted in autistic children, we assessed the incidence of endogenous basal DNA strand breaks as well as the efficiency of repairing DNA damage caused by γ-ray in lymphocytes isolated from autistic and healthy children. The incidence of DNA damage and the kinetics of DNA repair were determined by comet assay, while the incidence of residual DNA damage was evaluated by structural chromosomal aberration analysis. Transcriptome profiling of 84 genes associated with DNA damage and repair-signaling pathways was performed by RT² Profiler PCR Array. The array data were confirmed by RT-PCR and western blot studies. Our data indicate that the incidence of basal oxidative DNA strand breaks in autistic children was greater than that in nonautistic controls. Lymphocytes from autistic children displayed higher susceptibility to damage by γ-irradiation and slower repair rate than those from nonautistic children. Although the total unstable chromosomal aberrations were unaffected, lymphocytes from autistic children were more susceptible to chromosomal damage caused by γ-ray than those from nonautistic children. Transcriptomic analysis revealed that several genes associated with repair were downregulated in lymphocytes from autistic individuals and in those exposed to γ-irradiation. This may explain the increased oxidative DNA damage and reduced repair rate in lymphocytes from autistic individuals. These features may be related to the possible correlation between autism and the elevated risk of cancer and may explain the role of the disruption of the DNA repair process in the pathogenesis of autism.