DNA-PK is activated by SIRT2 deacetylation to promote DNA double-strand break repair by non-homologous end joining.

DNA-dependent protein kinase (DNA-PK) plays a critical role in non-homologous end joining (NHEJ), the predominant pathway that repairs DNA double-strand breaks (DSB) in response to ionizing radiation (IR) to govern genome integrity. The interaction of the catalytic subunit of DNA-PK (DNA-PKcs) with the Ku70/Ku80 heterodimer on DSBs leads to DNA-PK activation; however, it is not known if upstream signaling events govern this activation. Here, we reveal a regulatory step governing DNA-PK activation by SIRT2 deacetylation, which facilitates DNA-PKcs localization to DSBs and interaction with Ku, thereby promoting DSB repair by NHEJ. SIRT2 deacetylase activity governs cellular resistance to DSB-inducing agents and promotes NHEJ. SIRT2 furthermore interacts with and deacetylates DNA-PKcs in response to IR. SIRT2 deacetylase activity facilitates DNA-PKcs interaction with Ku and localization to DSBs and promotes DNA-PK activation and phosphorylation of downstream NHEJ substrates. Moreover, targeting SIRT2 with AGK2, a SIRT2-specific inhibitor, augments the efficacy of IR in cancer cells and tumors. Our findings define a regulatory step for DNA-PK activation by SIRT2-mediated deacetylation, elucidating a critical upstream signaling event initiating the repair of DSBs by NHEJ. Furthermore, our data suggest that SIRT2 inhibition may be a promising rationale-driven therapeutic strategy for increasing the effectiveness of radiation therapy.

Photocatalytic activity of biosynthesized silver nanoparticle fosters oxidative stress at nanoparticle interface resulting in antimicrobial and cytotoxic activities.

Inside the biological milieu, nanoparticles with photocatalytic activity have potential to trigger cell death non-specifically due to production of reactive oxygen species (ROS) upon reacting with biological entities. Silver nanoparticle (AgNP) possessing narrow band gap energy can exhibit high light absorption property and significant photocatalytic activity. This study intends to explore the effects of ROS generated due to photocatalytic activity of AgNP on antimicrobial and cytotoxic propensities. To this end, AgNP was synthesized using the principle of green chemistry from the peel extract of Punica granatum L., and was characterized using UV-Vis spectroscope, transmission electron microscope and x-ray diffraction, and so forth. The antimicrobial activity of AgNP against studied bacteria indicated that, ROS generated at AgNP interface develop stress on bacterial membrane leading to bacterial cell death, whereas Alamar Blue dye reduction assay indicated that increased cytotoxic activity with increasing concentrations of AgNP. The γH2AX activity assay revealed that increasing the concentrations of AgNP increased DNA damaging activity. The results altogether demonstrated that both antimicrobial and cytotoxic propensities are triggered primarily due interfacial ROS generation by photocatalytic AgNP, which caused membrane deformation in bacteria and DNA damage in HT1080 cells resulting in cell death.

Audit of the Prevalence of Noncorrelation of Immunofixation with Protein Electrophoresis and Serum Free Light Chain Assays in Multiple Myeloma in a Tertiary Cancer Care Center.

Multiple myeloma (MM) is diagnosed and monitored by correlating panel of test results including serum Protein electrophoresis (SPE), Immunofixation electrophoresis (IFE), serum Free Light chain (sFLC) measurements. This audit is aimed to evaluate the prevalence of non-correlation and discrepancies amongst the three investigations (SPE/IFE/sFLC) for assessment of MM. 106 MM patients were reviewed over 16 months in a tertiary cancer care center by the availability of 3 serum test results (SPE/IFE/sFLC). Patients were divided into 2 groups: group1, newly diagnosed MM patients who were yet to receive myeloma specific treatment (n = 48); and group2, already diagnosed MM patients on treatment and followup (n = 58). Treatment modalities included stem cell transplantation and standard chemotherapy regimens. Non-correlation between the three test results (IFE/SPE/sFLC) was observed (21% in group1 and 45% in group2). Three types of discrepancies were detected as follows: (a) IFE showing less number of restriction bands as compared to SPE (8.6% patients in group2); (b) SPE/IFE negative with an abnormal sFLC ratio (12.5% patients in group1 and 13.7% in group2); (c) SPE/IFE positive but normal sFLC ratio (8% in group1 and 22% in group2). To conclude, IFE may sometimes provide information that does not always correlate with either of the SPE or sFLC results due to different sensitivities, antigen-antibody interactions, or treatment. Hence, SPE plus sFLC may be more useful particularly for patients on follow-up while IFE plus sFLC may help screen the new patients. The judicious selection of the biochemical assays can effectively reduce the treatment cost in a developing country like India.

DNA methylation and not H3K4 trimethylation dictates the expression status of miR-152 gene which inhibits migration of breast cancer cells via DNMT1/CDH1 loop.

MicroRNAs (miRNA) are small non-coding RNAs which targets most protein-coding transcripts (mRNA) and destroy them. Thus miRNA controls the abundance of those specific proteins and impact on developmental, physiological and pathological processes. Dysregulation of miRNA function thus may lead to various clinicopathological complications, including breast cancer. Silencing of miR-152 gene due to promoter DNA methylation alter the expression pattern of several other genes. E-cadherin (CDH1) forms the core of adherent junctions between surrounding epithelial cells, link with actin cytoskeleton and affects cell signaling. CDH1 gene is down regulated by promoter DNA methylation during cancer progression. In this investigation, we attempt to elucidate the correlation of miR-152 and CDH1 function, as it is well known that the loss of CDH1 function is one of the major reasons for cancer metastasis and aggressiveness of spreading. For the first time we have shown that loss of CDH1 expression is directly proportional to the loss of miR-152 function in breast cancer cells. mRNA and protein expression profile of DNMT1 implicate that miR-152 targets DNMT1 mRNA and inhibits its protein expression. Tracing the molecular marks on DNA and histone 3 for understanding the mechanism of gene regulation by ChIP analyses leads to a paradoxical result that shows DNA methylation adjacent to active histone marking (enrichment of H3K4me3) silence miR-152 gene. Further experiments revealed that DNMT1 plays crucial role for regulation of miR-152 gene. When DNMT1 protein function is blocked miR-152 expression prevails and destroys the mRNA of DNMT1; this molecular regulatory mechanism is creating a cyclic feedback loop, which is now focused as DNMT1/miR-152 switch for on/off of DNMT1 target genes. We discovered modulation of CDH1 gene expression by DNMT1/miR-152 switches. We have demonstrated further that DNMT1 down regulation mediated upregulation of CDH1 (hereafter, DNMT1/CDH1 loop) in presence of ectopic-excess of miR-152 prevents migration of cancer cells. Our data provides novel insights into the regulation mechanism of miRNA and mRNA/protein coding genes and enhances the amplitude of cancer epigenome.

Clusterin gene is predominantly regulated by histone modifications in human colon cancer and ectopic expression of the nuclear isoform induces cell death.

Clusterin (CLU) is an important glycoprotein involved in various cellular functions. Different reports have mentioned that the two isoforms of CLU; secretary (sCLU) and nuclear (nCLU) have opposite (paradoxical) roles in cancer development. sCLU provides pro-survival signal, whereas nCLU is involved in pro-apoptotic signaling. However, the molecular mechanism of CLU gene regulation is not clear as of yet. We hypothesize that CLU gene is regulated by DNA methylation and histone modifications and clusterin plays an important role in colon cancer. To evaluate the hypothesis, we investigated CLU expression in colon cancer tissues and DNA methylation and histone modification status of CLU gene promoter. It is apparent from immonohistology data that both benign and cancerous (primary and metastasis) formalin fixed paraffin embedded (FFPE) tissue samples exhibit CLU expression. However and interestingly only noncancerous tissue samples show nCLU expression. Ectopic expression of nCLU either by epigenetic modulators or by nCLU transfection is responsible for colon cancer cell death. To clarify the molecular mechanisms for regulation of expression of CLU isoforms, we have analyzed DNA methylation and histone modifications, such as histone H3K9me3, H3K27me3, H3K4me3, and H3K9AcS10P patterns around the CLU promoter. There is no remarkable change in the DNA methylation status upon treatment of the cells by AZA, TSA and SAM. Our findings clearly show that promoter histone H3K9me3 and H3K27me3 marks are elevated in comparison to H3K4me3 and H3K9AcS10P marks in colon cancer cell lines.

Silencing of ZRF1 impedes survival of estrogen receptor positive MCF-7 cells and potentiates the effect of curcumin.

The role and clinical implication of ZRF1 in breast cancer are poorly understood. So this study is aimed to explore the role of ZRF1 in breast cancer progression. With this context, we first assessed its expression pattern in FFPE primary and metastasis breast tissue samples as well as from publicly available databases. Moreover, we also explored the survival status of patients from the publicly available database and interestingly discover that high expression of ZRF1 decreases the survival of estrogen-positive breast cancer patients more than estrogen-negative status patients. In the perspective of this, we evaluated the role ZRF1 in MCF-7 breast cancer cells and found that it's silencing by knockdown results in decreased cell proliferation as well as cell viability. Results also show that expression of ZRF1 is down regulated in the presence of estrogen-depleted conditions but independent of RAS/MEK as well as AKT axes. Moreover, the decrease in viability of MCF-7 cells was accompanied by induction of apoptosis and DNA damage, well-marked with upregulation of cleaved PARP and downregulation of BCL2 and H2AUbK119 levels. Furthermore, we also explored that knockdown of ZRF1 sensitises the effect of curcumin, observed with decrease in cell viability and dropping of IC50 value from 25 to 15 µM. This investigation thus shed a new light on the role on ZRF1 in breast cancer cells and hence can be exploited to design better therapeutic intervention.

Chromatin dynamics: H3K4 methylation and H3 variant replacement during development and in cancer.

The dynamic nature of chromatin and its myriad modifications play a crucial role in gene regulation (expression and repression) during development, cellular survival, homeostasis, ageing, and apoptosis/death. Histone 3 lysine 4 methylation (H3K4 methylation) catalyzed by H3K4 specific histone methyltransferases is one of the more critical chromatin modifications that is generally associated with gene activation. Additionally, the deposition of H3 variant(s) in conjunction with H3K4 methylation generates an intricately reliable epigenetic regulatory circuit that guides transcriptional activity in normal development and homeostasis. Consequently, alterations in this epigenetic circuit may trigger disease development. The mechanistic relationship between H3 variant deposition and H3K4 methylation during normal development has remained foggy. However, recent investigations in the field of chromatin dynamics in various model organisms, tumors, cancer tissues, and cell lines cultured without and with therapeutic agents, as well as from model reconstituted chromatins reveal that there may be different subsets of chromatin assemblage with specific patterns of histone replacement executing similar functions. In this light, we attempt to explain the intricate control system that maintains chromatin structure and dynamics during normal development as well as during tumor development and cancer progression in this review. Our focus is to highlight the contribution of H3K4 methylation-histone variant crosstalk in regulating chromatin architecture and subsequently its function.

Epigenetic choreography of stem cells: the DNA demethylation episode of development.

Reversible DNA methylation is a fundamental epigenetic manipulator of the genomic information in eukaryotes. DNA demethylation plays a very significant role during embryonic development and stands out for its contribution in molecular reconfiguration during cellular differentiation for determining stem cell fate. DNA demethylation arbitrated extensive make-over of the genome via reprogramming in the early embryo results in stem cell plasticity followed by commitment to the principal cell lineages. This article attempts to highlight the sequential phases and hierarchical mode of DNA demethylation events during enactment of the molecular strategy for developmental transition. A comprehensive knowledge regarding the pattern of DNA demethylation during embryogenesis and organogenesis and study of the related lacunae will offer exciting avenues for future biomedical research and stem cell-based regenerative therapy.

Elucidation of caveolin 1 both as a tumor suppressor and metastasis promoter in light of epigenetic modulators.

Caveolin-1 (CAV1) is an integral part of plasma membrane protein playing a vital role in breast cancer initiation and progression. CAV1 acts both as a tumor suppressor as well as an oncogene, and its activity is thus highly dependent on cellular environment. Keeping this fact in mind, the recent work is designed to reveal the role of CAV1 in inhibiting cancer cell progression in presence of epigenetic modulators like 5-aza-2'-deoxycytidine (AZA), trichostatin A (TSA), S-adenosyl methionine (SAM) and sulforaphane (SFN). Forced expression of CAV1 by AZA, TSA, and SFN is correlated to induction of apoptosis and inhibition of cell migration in breast cancer. In breast cancer along with promoter DNA methylation, other epigenetic mechanisms are also involved in CAV1 expression. These observations clearly provide a new scenario regarding the role of CAV1 in cancer and as a possible therapeutic target in breast cancer.

Loss of tet methyl cytosine dioxygenase 3 (TET3) enhances cardiac fibrosis via modulating the DNA damage repair response.

BACKGROUND: Cardiac fibrosis is the hallmark of all forms of chronic heart disease. Activation and proliferation of cardiac fibroblasts are the prime mediators of cardiac fibrosis. Existing studies show that ROS and inflammatory cytokines produced during fibrosis not only signal proliferative stimuli but also contribute to DNA damage. Therefore, as a prerequisite to maintain sustained proliferation in fibroblasts, activation of distinct DNA repair mechanism is essential. RESULT: In this study, we report that TET3, a DNA demethylating enzyme, which has been shown to be reduced in cardiac fibrosis and to exert antifibrotic effects does so not only through its demethylating activity but also through maintaining genomic integrity by facilitating error-free homologous recombination (HR) repair of DNA damage. Using both in vitro and in vivo models of cardiac fibrosis as well as data from human heart tissue, we demonstrate that the loss of TET3 in cardiac fibroblasts leads to spontaneous DNA damage and in the presence of TGF-ß to a shift from HR to the fast but more error-prone non-homologous end joining repair pathway. This shift contributes to increased fibroblast proliferation in a fibrotic environment. In vitro experiments showed TET3's recruitment to H2O2-induced DNA double-strand breaks (DSBs) in mouse cardiac fibroblasts, promoting HR repair. Overexpressing TET3 counteracted TGF-ß-induced fibroblast proliferation and restored HR repair efficiency. Extending these findings to human cardiac fibrosis, we confirmed TET3 expression loss in fibrotic hearts and identified a negative correlation between TET3 levels, fibrosis markers, and DNA repair pathway alteration. CONCLUSION: Collectively, our findings demonstrate TET3's pivotal role in modulating DDR and fibroblast proliferation in cardiac fibrosis and further highlight TET3 as a potential therapeutic target.

Nanoparticle-mediated diagnosis, treatment, and prevention of breast cancer.

By virtue of their advanced physicochemical properties, nanoparticles have attracted significant attention from researchers for application in diverse fields of medical science. Breast cancer, presenting a high risk of morbidity and mortality, frequently occurs in women and is considered a malignant tumor. Globally, breast cancer is considered the second leading cause of death. Accordingly, its poor prognosis, invasive metastasis, and relapse have motivated oncologists and nano-medical researchers to develop highly potent nanotherapies to cure this deadly disease. In this case, nanoparticles have emerged as responsive platforms for breast cancer management, providing new approaches to improve the diagnostic accuracy, deliver targeted therapies, and limit the progression of this disease. Recently, smart nano-carriers encapsulating drugs, ligands, and tracking probes have been developed for the specific therapy of breast cancers. Further, efforts have been devoted to developing various nano-systems with minimal toxicity. The aim of this review is to present a background on novel nanotheranostic methods that can be employed to diagnose and treat breast cancers and encourage readers to focus on the development of novel nanomedicine for breast cancers and other deadly diseases. In this context, we discuss different methods for the diagnosis, treatment, and prevention of breast cancers using different metal and metal oxide nanoparticles.

SAMHD1 expression contributes to doxorubicin resistance and predicts survival outcomes in diffuse large B-cell lymphoma patients.

Diffuse large B-cell lymphoma (DLBCL) is a commonly diagnosed, aggressive non-Hodgkin's lymphoma. While R-CHOP chemoimmunotherapy is potentially curative, about 40% of DLBCL patients will fail, highlighting the need to identify biomarkers to optimize management. SAMHD1 has a dNTPase-independent role in promoting resection to facilitate DNA double-strand break (DSB) repair by homologous recombination. We evaluated the relationship of SAMHD1 levels with sensitivity to DSB-sensitizing agents in DLBCL cells and the association of SAMHD1 expression with clinical outcomes in 79 DLBCL patients treated with definitive therapy and an independent cohort dataset of 234 DLBCL patients. Low SAMHD1 expression, Vpx-mediated, or siRNA-mediated degradation/depletion in DLBCL cells was associated with greater sensitivity to doxorubicin and PARP inhibitors. On Kaplan-Meier log-rank survival analysis, low SAMHD1 expression was associated with improved overall survival (OS), which on subset analysis remained significant only in patients with advanced stage (III-IV) and moderate to high risk (2-5 International Prognostic Index (IPI)). The association of low SAMHD1 expression with improved OS remained significant on multivariate analysis independent of other adverse factors, including IPI, and was validated in an independent cohort. Our findings suggest that SAMHD1 expression mediates doxorubicin resistance and may be an important prognostic biomarker in advanced, higher-risk DLBCL patients.

miR-132-3p and KLF7 as novel regulators of aortic stiffening-associated EndMT in type 2 diabetes mellitus.

BACKGROUND: The prevalence of diabetes mellitus has risen considerably and currently affects more than 422 million people worldwide. Cardiovascular diseases including myocardial infarction and heart failure represent the major cause of death in type 2 diabetes (T2D). Diabetes patients exhibit accelerated aortic stiffening which is an independent predictor of cardiovascular disease and mortality. We recently showed that aortic stiffness precedes hypertension in a mouse model of diabetes (db/db mice), making aortic stiffness an early contributor to cardiovascular disease development. Elucidating how aortic stiffening develops is a pressing need in order to halt the pathophysiological process at an early time point. METHODS: To assess EndMT occurrence, we performed co-immunofluorescence staining of an endothelial marker (CD31) with mesenchymal markers (α-SMA/S100A4) in aortic sections from db/db mice. Moreover, we performed qRT-PCR to analyze mRNA expression of EndMT transcription factors in aortic sections of db/db mice and diabetic patients. To identify the underlying mechanism by which EndMT contributes to aortic stiffening, we used aortas from db/db mice and diabetic patients in combination with high glucose-treated human umbilical vein endothelial cells (HUVECs) as an in vitro model of diabetes-associated EndMT. RESULTS: We demonstrate robust CD31/α-SMA and CD31/S100A4 co-localization in aortic sections of db/db mice which was almost absent in control mice. Moreover, we demonstrate a significant upregulation of EndMT transcription factors in aortic sections of db/db mice and diabetic patients. As underlying regulator, we identified miR-132-3p as the most significantly downregulated miR in the micronome of db/db mice and high glucose-treated HUVECs. Indeed, miR-132-3p was also significantly downregulated in aortic tissue from diabetic patients. We identified Kruppel-like factor 7 (KLF7) as a target of miR-132-3p and show a significant upregulation of KLF7 in aortic sections of db/db mice and diabetic patients as well as in high glucose-treated HUVECs. We further demonstrate that miR-132-3p overexpression and KLF7 downregulation ameliorates EndMT in high glucose-treated HUVECs. CONCLUSIONS: We demonstrate for the first time that EndMT contributes to aortic stiffening in T2D. We identified miR-132-3p and KLF7 as novel EndMT regulators in this context. Altogether, this gives us new insights in the development of aortic stiffening in T2D.

HELZ promotes R loop resolution to facilitate DNA double-strand break repair by homologous recombination.

R loops are RNA-DNA hybrid containing structures involved in diverse cellular processes, including DNA double-strand break (DSB) repair. R loop homeostasis involving the formation and resolution of R loops is critical for DSB repair, and its dysregulation leads to genome instability. Here we show that the HELZ helicase promotes R loop resolution to facilitate DSB repair by homologous recombination (HR). HELZ depletion causes hypersensitivity to DSB-inducing agents, and HELZ localizes and binds to DSBs. HELZ depletion further leads to genomic instability in a R loop dependent manner and the accumulation of R loops globally and at DSBs. HELZ binds to R loops in response to DSBs and promotes their resolution, thereby facilitating HR to promote genome integrity. Our findings thus define a role for HELZ in promoting the resolution of R loops critical for DSB repair by HR.

YB1 modulates the DNA damage response in medulloblastoma.

Y-box binding protein 1 (YBX1 or YB1) is a therapeutically relevant oncoprotein capable of RNA and DNA binding and mediating protein-protein interactions that drive proliferation, stemness, and resistance to platinum-based therapies. Given our previously published findings, the potential for YB1-driven cisplatin resistance in medulloblastoma (MB), and the limited studies exploring YB1-DNA repair protein interactions, we chose to investigate the role of YB1 in mediating radiation resistance in MB. MB, the most common pediatric malignant brain tumor, is treated with surgical resection, cranio-spinal radiation, and platinum-based chemotherapy, and could potentially benefit from YB1 inhibition. The role of YB1 in the response of MB to ionizing radiation (IR) has not yet been studied but remains relevant for determining potential anti-tumor synergy of YB1 inhibition with standard radiation therapy. We have previously shown that YB1 drives proliferation of cerebellar granular neural precursor cells (CGNPs) and murine Sonic Hedgehog (SHH) group MB cells. While others have demonstrated a link between YB1 and homologous recombination protein binding, functional and therapeutic implications remain unclear, particularly following IR-induced damage. Here we show that depleting YB1 in both SHH and Group 3 MB results not only in reduced proliferation but also synergizes with radiation due to differential response dynamics. YB1 silencing through shRNA followed by IR drives a predominantly NHEJ-dependent repair mechanism, leading to faster γH2AX resolution, premature cell cycle re-entry, checkpoint bypass, reduced proliferation, and increased senescence. These findings show that depleting YB1 in combination with radiation sensitizes SHH and Group 3 MB cells to radiation.

SAMHD1 deacetylation by SIRT1 promotes DNA end resection by facilitating DNA binding at double-strand breaks.

Sterile alpha motif and HD domain-containing protein 1 (SAMHD1) has a dNTPase-independent function in promoting DNA end resection to facilitate DNA double-strand break (DSB) repair by homologous recombination (HR); however, it is not known if upstream signaling events govern this activity. Here, we show that SAMHD1 is deacetylated by the SIRT1 sirtuin deacetylase, facilitating its binding with ssDNA at DSBs, to promote DNA end resection and HR. SIRT1 complexes with and deacetylates SAMHD1 at conserved lysine 354 (K354) specifically in response to DSBs. K354 deacetylation by SIRT1 promotes DNA end resection and HR but not SAMHD1 tetramerization or dNTPase activity. Mechanistically, K354 deacetylation by SIRT1 promotes SAMHD1 recruitment to DSBs and binding to ssDNA at DSBs, which in turn facilitates CtIP ssDNA binding, leading to promotion of genome integrity. These findings define a mechanism governing the dNTPase-independent resection function of SAMHD1 by SIRT1 deacetylation in promoting HR and genome stability.

Causal Connections From Chronic Kidney Disease to Cardiac Fibrosis.

Cardiovascular disease and heart failure are the primary cause of morbidity and mortality in patients with chronic kidney disease. Because impairment of kidney function correlates with heart failure and cardiac fibrosis, a kidney-heart axis is suspected. Although our understanding of the underlying mechanisms still is evolving, the possibility that kidney-heart messengers could be intercepted offers ample reason to focus on this clinically highly relevant problem. Here, we review the current knowledge of how kidney injury causes heart failure and fibrosis.

Epigenetic drift towards histone modifications regulates CAV1 gene expression in colon cancer.

BACKGROUND: Caveolin-1 (CAV1) is an important structural component of cellular caveolae involved in cell signaling. CAV1 gene on/off regulatory mechanism in multiple diseases, including cancer is not clearly understood. The tumor suppressor versus oncogene paradox of CAV1 during tumor development tempted us to investigate the role for the epigenetic drift of CAV1 gene regulation. METHODS: We have analyzed CAV1 gene expression and associated epigenetic marks (DNA methylation and histone 3 modifications) in the CAV1 promoter in two colon cancer cell lines, under treatment with well established epigenetic modulators, AZA, SAM, TSA and SFN at varying concentrations. CAV1 gene promoter DNA methylation and histone modifications were analyzed by DNA methylation specific PCR, bisulphite modification of DNA and ChIP analyses following PCR respectively. RESULTS: Ectopic expression of CAV1 by epigenetic modulators inhibits colon cancer cell growth. CAV1 promoter DNA remains unmethylated before and after treatment with epigenetic modulators, which confirmed that DNA methylation is not the regulator of CAV1 expression in colon cancer. There was enrichment of H3K4me3 and H3K9AcS10P and depletion of H3K9me3 modifications around the CAV1 promoter. CONCLUSIONS: Our data provides novel insight into the regulation of CAV1 gene by histone H3 modifications and enhance the amplitude of the cancer epigenome.

Insights into the molecular interactions of thymoquinone with histone deacetylase: evaluation of the therapeutic intervention potential against breast cancer.

Many HDAC inhibitors have passed through the gateway of clinical trials. However, they have limited therapeutic implications due to their pleiotropic pharmaceutical properties and off-target effects. In view of this, dietary active phytochemicals were evaluated. Based upon the chemical and structural insights of HDAC active pockets, thymoquinone (TQ) was investigated to uncover its active participation in HDAC inhibition. The synergistic analysis of docking and molecular dynamics simulation disclosed the elementary interaction and stability of TQ with human HDACs. The in silico findings were corroborated with an in vitro analysis, demonstrating the efficient role of TQ in the attenuation of global HDAC activity. Furthermore, TQ also elicited downstream effects of HDAC inhibition: reactivation of HDAC target genes (p21 and Maspin), induction of the pro-apoptotic gene Bax, down regulation of the anti-apoptotic gene Bcl-2 and arrest of the cell cycle at the G2/M phase. Finally, the result of a higher cytotoxicity of TQ towards MCF-7 breast cancer cells in comparison to normal cells indicates the potential of TQ to be an anticancer drug.