Regulation of eukaryotic transcription initiation in response to cellular stress

Transcription initiation is a vital step in the regulation of eukaryotic gene expression. It can be dysregulated in response to various cellular stressors which is associated with numerous human diseases including cancer. Transcription initiation is facilitated via many gene-specific trans-regulatory elements such as transcription factors, activators, and coactivators through their interactions with transcription pre-initiation complex (PIC). These trans-regulatory elements can uniquely facilitate PIC formation (hence, transcription initiation) in response to cellular nutrient stress. Cellular nutrient stress also regulates the activity of other pathways such as target of rapamycin (TOR) pathway. TOR pathway exhibits distinct regulatory mechanisms of transcriptional activation in response to stress. Like TOR pathway, the cell cycle regulatory pathway is also found to be linked to transcriptional regulation in response to cellular stress. Several transcription factors such as p53, C/EBP Homologous Protein (CHOP), activating transcription factor 6 (ATF6α), E2F, transforming growth factor (TGF)-β, Adenomatous polyposis coli (APC), SMAD, and MYC have been implicated in regulation of transcription of target genes involved in cell cycle progression, apoptosis, and DNA damage repair pathways. Additionally, cellular metabolic and oxidative stressors have been found to regulate the activity of long non-coding RNAs (lncRNA). LncRNA regulates transcription by upregulating or downregulating the transcription regulatory proteins involved in metabolic and cell signaling pathways. Numerous human diseases, triggered by chronic cellular stressors, are associated with abnormal regulation of transcription. Hence, understanding these mechanisms would help unravel the molecular regulatory insights with potential therapeutic interventions. Therefore, here we emphasize the recent advances of regulation of eukaryotic transcription initiation in response to cellular stress.

Exploring CDKN1A Upregulation Mechanisms: Insights into Cell Cycle Arrest Induced by NC2603 Curcumin Analog in MCF-7 Breast Cancer Cells

Breast cancer stands out as one of the most prevalent malignancies worldwide, necessitating a nuanced understanding of its molecular underpinnings for effective treatment. Hormone receptors in breast cancer cells substantially influence treatment strategies, dictating therapeutic approaches in clinical settings, serving as a guide for drug development, and aiming to enhance treatment specificity and efficacy. Natural compounds, such as curcumin, offer a diverse array of chemical structures with promising therapeutic potential. Despite curcumin's benefits, challenges like poor solubility and rapid metabolism have spurred the exploration of analogs. Here, we evaluated the efficacy of the curcumin analog NC2603 to induce cell cycle arrest in MCF-7 breast cancer cells and explored its molecular mechanisms. Our findings reveal potent inhibition of cell viability (IC50 = 5.6 μM) and greater specificity than doxorubicin toward MCF-7 vs. non-cancer HaCaT cells. Transcriptome analysis identified 12,055 modulated genes, most notably upregulation of GADD45A and downregulation of ESR1, implicating CDKN1A-mediated regulation of proliferation and cell cycle genes. We hypothesize that the curcumin analog by inducing GADD45A expression and repressing ESR1, triggers the expression of CDKN1A, which in turn downregulates the expression of many important genes of proliferation and the cell cycle. These insights advance our understanding of curcumin analogs' therapeutic potential, highlighting not just their role in treatment, but also the molecular pathways involved in their activity toward breast cancer cells.

Targeting Cell Signaling Pathways in Lung Cancer by Bioactive Phytocompounds

Lung cancer is a heterogeneous group of malignancies with high incidence worldwide. It is the most frequently occurring cancer in men and the second most common in women. Due to its frequent diagnosis and variable response to treatment, lung cancer was reported as the top cause of cancer-related deaths worldwide in 2020. Many aberrant signaling cascades are implicated in the pathogenesis of lung cancer, including those involved in apoptosis (B cell lymphoma protein, Bcl-2-associated X protein, first apoptosis signal ligand), growth inhibition (tumor suppressor protein or gene and serine/threonine kinase 11), and growth promotion (epidermal growth factor receptor/proto-oncogenes/phosphatidylinositol-3 kinase). Accordingly, these pathways and their signaling molecules have become promising targets for chemopreventive and chemotherapeutic agents. Recent research provides compelling evidence for the use of plant-based compounds, known collectively as phytochemicals, as anticancer agents. This review discusses major contributing signaling pathways involved in the pathophysiology of lung cancer, as well as currently available treatments and prospective drug candidates. The anticancer potential of naturally occurring bioactive compounds in the context of lung cancer is also discussed, with critical analysis of their mechanistic actions presented by preclinical and clinical studies.

Exploring the Apoptotic-Induced Biochemical Mechanism of Traditional Thai Herb (Kerra™) Extract in HCT116 Cells Using a Label-Free Proteomics Approach

Background and Objectives: Natural products have proven to be a valuable source for the discovery of new candidate drugs for cancer treatment. This study aims to investigate the potential therapeutic effects of "Kerra™", a natural extract derived from a mixture of nine medicinal plants mentioned in the ancient Thai scripture named the Takxila Scripture, on HCT116 cells. Materials and Methods: In this study, the effect of the Kerra™ extract on cancer cells was assessed through cell viability assays. Apoptotic activity was evaluated by examining the apoptosis characteristic features. A proteomics analysis was conducted to identify proteins and pathways associated with the extract's mechanism of action. The expression levels of apoptotic protein markers were measured to validate the extract's efficacy. Results: The Kerra™ extract demonstrated a dose-dependent inhibitory effect on the cells, with higher concentrations leading to decreased cell viability. Treatment with the extract for 72 h induced characteristic features of early and late apoptosis, as well as cell death. An LC-MS/MS analysis identified a total of 3406 proteins. The pathway analysis revealed that the Kerra™ extract stimulated apoptosis and cell death in colorectal cancer cell lines and suppressed cell proliferation in adenocarcinoma cell lines through the EIF2 signaling pathway. Upstream regulatory proteins, including cyclin-dependent kinase inhibitor 1A (CDKN1A) and MYC proto-oncogene, bHLH transcription factor (MYC), were identified. The expressions of caspase-8 and caspase-9 were significantly elevated by the Kerra™ extract compared to the chemotherapy drug Doxorubicin (Dox). Conclusions: These findings provide strong evidence for the ability of the Kerra™ extract to induce apoptosis in HCT116 colon cancer cells. The extract's efficacy was demonstrated by its dose-dependent inhibitory effect, induction of apoptotic activity, and modulation of key proteins involved in cell death and proliferation pathways. This study highlights the potential of Kerra™ as a promising therapeutic agent in cancer treatment.

The attenuated Mycoplasma bovis strain promotes apoptosis of bovine macrophages by upregulation of CHOP expression

Mycoplasma bovis (M. bovis) is one of the major pathogens in the bovine respiratory disease complex, which includes pneumonia, mastitis, and arthritis and causes a great economic loss in the cattle industry. In China, a live-attenuated vaccine strain M. bovis P150 was obtained by a continuous culture of the wild-type strain M. bovis HB0801 (P1) in vitro for 150 passages. Using the infected bovine macrophage cell line BoMac, this work attempted to investigate the mechanism of P150 attenuation and protective immune response. To begin, we show that M. bovis P150 effectively triggered cytotoxicity and apoptosis in BoMac, although with lower intracellular survival than P1. The transcriptomes of BoMac after infection with M. bovis strains P1 and P150 were sequenced, and bioinformatic analysis identified 233 differentially expressed genes (DEGs), with 185 upregulated and 48 downregulated. Further Gene Ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analyses revealed that the majority of the DEGs were linked to CHOP complex, MAP kinase phosphatase activity and were involved in the IL-17 signaling pathway in immune response, MAPK signaling pathway in signal transduction, and p53 signaling pathway in cell growth and death. Among them, the level of C/EBP homologous protein (CHOP) was significantly upregulated in P150-infected BoMac compared to P1-infected cells at different time points, along with its upstream and downstream genes phosphorylated-PERK, phosphorylated-EIF2α, ATF4, and GADD45A increased in the PERK-dependent ER stress response. The role of CHOP in apoptosis was further verified by M. bovis-induced siCHOP knockdown in BoMac cells. The results showed that CHOP knockdown enhanced P150-induced apoptosis and dramatically increased the M. bovis P1 and P150 intracellular survival, particularly for P150. These data suggest that P150 infection upregulates CHOP expression, which can increase apoptosis and mediate a crosstalk between ER stress and apoptosis during infection, and hence, contribute to high cytotoxicity and low intracellular survival.

Salinomycin induces cell cycle arrest and apoptosis and modulates hepatic cytochrome P450 mRNA expression in HepG2/C3a cells

Salinomycin (SAL) is a monocarboxylic polyether ionophore antibiotic isolated from Streptomyces albus. It exhibits an effective antitumor potential against numerous human cancer cells. This study aimed to assess the antiproliferative effects of SAL in human hepatocellular carcinoma HepG2/C3a cell line. We investigated the effects of SAL on cell growth, DNA damage induction, cell cycle changes and apoptosis; and relative changes in expression of cell cycle-related, apoptosis-related, and CYP450 genes. SAL induced cell cycle arrest in the G2/M phase, upregulation of CDKN1A and GADD45A and downregulation of cyclin genes including CCNB1 and CCNA2. SAL effectively suppressed mRNA levels of CTNNB1 gene, an important oncogene that promotes tumorigenesis. The decrease of HepG2/C3A cells' survival can also be due to downregulation of antiapoptotic BCL-2 expression, thus promoting the induction of apoptosis by SAL. This study also demonstrated the ability of SAL in modulating hepatic cytochrome P450 (CYP) mRNA expression, such that SAL caused the upregulation of CYP1A members and CYP3A5; and downregulation of CYP3A4. Taken together, these data contribute to the understanding of the mechanism of action of SAL, highlighting that metabolizing enzymes modulated by SAL can interfere with chemotherapy treatment and it must be considered in associated treatments.

Expression of Human Mutant Preproinsulins Induced Unfolded Protein Response, Gadd45 Expression, JAK-STAT Activation, and Growth Inhibition in Drosophila

Mutations in the insulin gene (INS) are frequently associated with human permanent neonatal diabetes mellitus. However, the mechanisms underlying the onset of this genetic disease is not sufficiently decoded. We induced expression of two types of human mutant INSs in Drosophila using its ectopic expression system and investigated the resultant responses in development. Expression of the wild-type preproinsulin in the insulin-producing cells (IPCs) throughout the larval stage led to a stimulation of the overall and wing growth. However, ectopic expression of human mutant preproinsulins, hINSC96Y and hINSLB15YB16delinsH, neither of which secreted from the β-cells, could not stimulate the Drosophila growth. Furthermore, neither of the mutant polypeptides induced caspase activation leading to apoptosis. Instead, they induced expression of several markers indicating the activation of unfolded protein response, such as ER stress-dependent Xbp1 mRNA splicing and ER chaperone induction. We newly found that the mutant polypeptides induced the expression of Growth arrest and DNA-damage-inducible 45 (Gadd45) in imaginal disc cells. ER stress induced by hINSC96Y also activated the JAK-STAT signaling, involved in inflammatory responses. Collectively, we speculate that the diabetes-like growth defects appeared as a consequence of the human mutant preproinsulin expression was involved in dysfunction of the IPCs, rather than apoptosis.

Diarylpentanoid (1,5-bis(4-hydroxy-3-methoxyphenyl)-1,4-pentadiene-3-one) (MS13) Exhibits Anti-proliferative, Apoptosis Induction and Anti-migration Properties on Androgen-independent Human Prostate Cancer by Targeting Cell Cycle-Apoptosis and PI3K Signalling Pathways

Diarylpentanoids exhibit a high degree of anti-cancer activity and stability in vitro over curcumin in prostate cancer cells. Hence, this study aims to investigate the effects of a diarylpentanoid, 1,5-bis(4-hydroxy-3-methoxyphenyl)-1,4-pentadiene-3-one (MS13) on cytotoxicity, anti-proliferative, apoptosis-inducing, anti-migration properties, and the underlying molecular mechanisms on treated androgen-independent prostate cancer cells, DU 145 and PC-3. A cell viability assay has shown greater cytotoxicity effects of MS13-treated DU 145 cells (EC₅₀ 7.57 ± 0.2 µM) and PC-3 cells (EC₅₀ 7.80 ± 0.7 µM) compared to curcumin (EC₅₀: DU 145; 34.25 ± 2.7 µM and PC-3; 27.77 ± 6.4 µM). In addition, MS13 exhibited significant anti-proliferative activity against AIPC cells compared to curcumin in a dose- and time-dependent manner. Morphological observation, increased caspase-3 activity, and reduced Bcl-2 protein levels in these cells indicated that MS13 induces apoptosis in a time- and dose-dependent. Moreover, MS13 effectively inhibited the migration of DU 145 and PC-3 cells. Our results suggest that cell cycle-apoptosis and PI3K pathways were the topmost significant pathways impacted by MS13 activity. Our findings suggest that MS13 may demonstrate the anti-cancer activity by modulating DEGs associated with the cell cycle-apoptosis and PI3K pathways, thus inhibiting cell proliferation and cell migration as well as inducing apoptosis in AIPC cells.

PB01 suppresses radio-resistance by regulating ATR signaling in human non-small-cell lung cancer cells

Despite the common usage of radiotherapy for the treatment of human non-small-cell lung cancer (NSCLC), cancer therapeutic efficacy and outcome with ionizing radiation remains a challenge. Here, we report the antitumor effects and mechanism of a novel benzothiazole derivative PB01 (4-methoxy-cyclohexane carboxylic acid [2-(3,5-dimethyl-isoxazole-4-yl) sulpanil-benzothiazole-6-yl]-amide) in radiation-resistant human NSCLC cells. PB01 treatment is cytotoxic because it induces reactive oxygen species, ER stress, Bax, cytochrome c expression, the ATR-p53-GADD45ɑ axis, and cleavage of caspase-3 and -9. Additionally, we found that radio-resistant A549 and H460 subclones, named A549R and H460R, respectively, show enhanced epithelial-to-mesenchymal transition (EMT), whereas PB01 treatment inhibits EMT and mediates cell death through ER stress and the ATR axis under radiation exposure in radio-resistant A549R and H460R cells. Together, these results suggest that PB01 treatment can overcome radio-resistance during radiotherapy of NSCLC.

Perspectives and controversies regarding the use of natural products for the treatment of lung cancer

Lung cancer is the leading cause of cancer‐related mortality both in men and women and accounts for 18.4% of all cancer‐related deaths. Although advanced therapy methods have been developed, the prognosis of lung cancer patients remains extremely poor. Over the past few decades, clinicians and researchers have found that chemical compounds extracted from natural products may be useful for treating lung cancer. Drug formulations derived from natural compounds, such as paclitaxel, doxorubicin, and camptothecin, have been successfully used as chemotherapeutics for lung cancer. In recent years, hundreds of new natural compounds that can be used to treat lung cancer have been found through basic and sub‐clinical research. However, there has not been a corresponding increase in the number of drugs that have been used in a clinical setting. The probable reasons may include low solubility, limited absorption, unfavorable metabolism, and severe side effects. In this review, we present a summary of the natural compounds that have been proven to be effective for the treatment of lung cancer, as well as an understanding of the mechanisms underlying their pharmacological effects. We have also highlighted current controversies and have attempted to provide solutions for the clinical translation of these compounds.

Zika virus infection induces endoplasmic reticulum stress and apoptosis in placental trophoblasts

Zika virus (ZIKV) infection to a pregnant woman can be vertically transmitted to the fetus via the placenta leading to Congenital Zika syndrome. This is characterized by microcephaly, retinal defects, and intrauterine growth retardation. ZIKV induces placental trophoblast apoptosis leading to severe abnormalities in the growth and development of the fetus. However, the molecular mechanism behind ZIKV-induced apoptosis in placental trophoblasts remains unclear. We hypothesize that ZIKV infection induces endoplasmic reticulum (ER) stress in the trophoblasts, and sustained ER stress results in apoptosis. HTR-8 (HTR-8/SVneo), a human normal immortalized trophoblast cell and human choriocarcinoma-derived cell lines (JEG-3 and JAR) were infected with ZIKV. Biochemical and structural markers of apoptosis like caspase 3/7 activity and percent apoptotic nuclear morphological changes, respectively were assessed. ZIKV infection in placental trophoblasts showed an increase in the levels of CHOP mRNA and protein expression, which is an inducer of apoptosis. Next, we also observed increased levels of ER stress markers such as phosphorylated forms of inositol-requiring transmembrane kinase/endoribonuclease 1α (P-IRE1α), and its downstream target, the spliced form of XBP1 mRNA, phosphorylated eukaryotic initiation factor 2α (P-eIF2α), and activation of cJun N-terminal Kinase (JNK) and p38 mitogen activated protein kinase (MAPK) after 16-24 h of ZIKV infection in trophoblasts. Inhibition of JNK or pan-caspases using small molecule inhibitors significantly prevented ZIKV-induced apoptosis in trophoblasts. Further, JNK inhibition also reduced XBP1 mRNA splicing and viral E protein staining in ZIKV infected cells. In conclusion, the mechanism of ZIKV-induced placental trophoblast apoptosis involves the activation of ER stress and JNK activation, and the inhibition of JNK dramatically prevents ZIKV-induced trophoblast apoptosis.

Rosmarinic acid-induced apoptosis and cell cycle arrest in triple-negative breast cancer cells

Rosmarinic acid (RA) is a polyphenolic compound with various pharmacological properties, including, anti-inflammatory, immunomodulatory, and neuroprotective, as well as having antioxidant and anticancer activities. This study evaluated the effects and mechanisms of RA in two racially different triple-negative breast cancer (TNBC) cell lines. Results obtained show that RA significantly caused cytotoxic and antiproliferative effects in both cell lines in a dose- and time-dependent manner. Remarkably, RA induced cell cycle arrest-related apoptosis and altered the expression of many apoptosis-involved genes differently. In MDA-MB-231 cells, RA arrested the cells in the G0/G1 phase. In contrast, the data suggest that RA causes S-phase arrest in MDA-MB-468 cells, leading to a 2-fold increase in the apoptotic effect compared to MDA-MB-231 cells. Further, in MDA-MB-231 cells, RA significantly upregulated the mRNA expression of three genes: harakiri (HRK), tumor necrosis factor receptor superfamily 25 (TNFRSF25), and BCL-2 interacting protein 3 (BNIP3). In contrast, in the MDA-MB-468 cell line, the compound induced a significant transcription activation in three genes, including TNF, growth arrest and DNA damage-inducible 45 alpha (GADD45A), and BNIP3. Furthermore, RA repressed the expression of TNF receptor superfamily 11B (TNFRSF11B) in MDA-MB-231 cells in comparison to the ligand TNF superfamily member 10 (TNFSF10) and baculoviral IAP repeat-containing 5 (BIRC5) in MDA-MB-468 cells. In conclusion, the data suggest that the polyphenol RA may have a potential role in TNBC therapies, particularly in MDA-MB-468 cells.

Therapeutic potentials of curcumin in the treatment of non-small-cell lung carcinoma

Non-small-cell lung carcinoma (NSCLC) is one of the most lethal malignancies that include more than 80% of lung cancer cases worldwide. During the past decades, plants and plant-derived products have attracted great interest in the treatment of various human diseases. Curcumin, the turmeric isolated natural phenolic compound, has shown a promising chemo-preventive and anticancer agent. Numerous studies have shown that curcumin delays the initiation and progression of NSCLC by affecting a wide range of molecular targets and cell signalling pathways including NF-kB, Akt, MAPKS, BCL-2, ROS and microRNAs (miRNAs). However, the poor oral bioavailability and low chemical stability of curcumin remain as major challenges in the utilisation of this compound as a therapeutic agent. Different analogs of curcumin and new delivery systems (e.g., micelles, nanoparticles and liposomes) provided promising solutions to overcome these obstacles and improve curcumin pharmacokinetic profile. The present review focuses on current reported studies about anti-NSCLC effects of curcumin. NSCLC involved miRNAs whose expression is regulated by curcumin has also been discussed. Furthermore, recent researches on the use of curcumin analogs and delivery systems to enhance the curcumin benefits in NSCLC are also described.

Molecular Insights into Potential Contributions of Natural Polyphenols to Lung Cancer Treatment

Naturally occurring polyphenols are believed to have beneficial effects in the prevention and treatment of a myriad of disorders due to their anti-inflammatory, antioxidant, antineoplastic, cytotoxic, and immunomodulatory activities documented in a large body of literature. In the era of molecular medicine and targeted therapy, there is a growing interest in characterizing the molecular mechanisms by which polyphenol compounds interact with multiple protein targets and signaling pathways that regulate key cellular processes under both normal and pathological conditions. Numerous studies suggest that natural polyphenols have chemopreventive and/or chemotherapeutic properties against different types of cancer by acting through different molecular mechanisms. The present review summarizes recent preclinical studies on the applications of bioactive polyphenols in lung cancer therapy, with an emphasis on the molecular mechanisms that underlie the therapeutic effects of major polyphenols on lung cancer. We also discuss the potential of the polyphenol-based combination therapy as an attractive therapeutic strategy against lung cancer.

Delivery of natural phenolic compounds for the potential treatment of lung cancer

The application of natural products to treat various diseases, such as cancer, has been an important area of research for many years. Several phytochemicals have demonstrated anticarcinogenic activity to prevent or reduce the progression of cancer by modulating various cellular mechanisms. However, poor bioavailability has hindered clinical success and the incorporation of these drugs into efficient drug delivery systems would be beneficial. For lung cancer, local delivery via the pulmonary route would also be more effective. In this article, recent in vitro scientific literature on phenolic compounds with anticancer activity towards lung cancer cell lines is reviewed and nanoparticulate delivery is mentioned as a possible solution to the problem of bioavailability. The first part of the review will explore the different classes of natural phenolic compounds and discuss recent reports on their activity on lung cancer cells. Then, the problem of the poor bioavailability of phenolic compounds will be explored, followed by a summary of recent advances in improving the efficacy of these phenolic compounds using nanoparticulate drug delivery systems. Graphical abstract The rationale for direct delivery of phenolic compounds loaded in microparticles to the lungs.

GADD45A and CDKN1A are involved in apoptosis and cell cycle modulatory effects of viscumTT with further inactivation of the STAT3 pathway

ViscumTT, a whole mistletoe preparation, has shown synergistic induction of apoptosis in several pediatric tumor entities. High therapeutic potential has previously been observed in Ewing's sarcoma, rhabdomyosarcoma, ALL and AML. In this study, we analyzed modulatory effects on the cell cycle by viscumTT in three osteosarcoma cell lines with various TP53 statuses. ViscumTT treatment induced G1 arrest in TP53 wild-type and null-mutant cells, but S arrest in TP53 mutant cells. Blockage of G1/S transition was accompanied by down-regulation of the key regulators CDK4, CCND1, CDK2, CCNE, CCNA. However, investigations on the transcriptional level revealed secondary TP53 participation. Cell cycle arrest was predominantly mediated by transcriptionally increased expression of GADD45A and CDKN1A and decreased SKP2 levels. Enhanced CDKN1A and GADD45A expression further played a role in viscumTT-induced apoptosis with involvement of stress-induced MAPK8 and inactivation of MAPK1/3. Furthermore, viscumTT inhibited the pro-survival pathway STAT3 by dephosphorylation of the two sites, Tyr705 and Ser727, by down-regulation of total STAT3 and its direct downstream targets BIRC5 and C-MYC. Moreover, tests of the efficacy of viscumTT in vivo showing reduction of tumor volume confirmed the high therapeutic potential as an anti-tumoral agent for osteosarcoma.

CHOP favors endoplasmic reticulum stress-induced apoptosis in hepatocellular carcinoma cells via inhibition of autophagy

C/EBP-homologous protein (CHOP) is an important component of the endoplasmic reticulum (ER) stress response. We demonstrated the induction of ER stress in response to tunicamycin stimulation, as evidenced by increased expression of chaperone proteins Grp78, Grp94, and enhanced eukaryotic initiation factor 2 subunit 1 (eIF2α) phosphorylation in hepatocellular carcinoma cells. Tunicamycin-induced ER stress resulted in apoptosis and autophagy simultaneously. While inhibition of autophagy mediated by 3-methyladenine pretreatment or direct knockdown of LC3B promoted cell apoptosis, activation of autophagy with rapamycin decreased tunicamycin- induced apoptosis in HCC cells. Furthermore, CHOP was shown to be significantly upregulated upon treatment with tunicamycin in HCC cells. Specific knockdown of CHOP not only enhanced tunicamycin-induced autophagy, but also significantly attenuated ER stress-induced apoptosis in HCC cells. Accordingly, simultaneous inhibition of autophagy in HCC cells with CHOP-knockdown could partially resensitize ER stress-induced apoptosis. Taken together, our data indicate that CHOP may favor ER stress-induced apoptosis in HCC cells via inhibition of autophagy in vitro.

Effects of novel brominated flame retardant TBPH and its metabolite TBMEHP on human vascular endothelial cells: Implication for human health risks

As a replacement for polybrominated diphenyl ethers, bis-(2-ethylhexyl) tetrabromophthalate (TBPH) is widely used as a novel flame retardant and has been detected in many environmental matrix including human blood. TBPH can be metabolized into mono-(2-ethyhexyl) tetrabromophthalate (TBMEHP) by carboxylesterase. However, their adverse effects on human vascular endothelium and their potential impacts on human cardiovascular disease are unknown. In this study, their adverse effects and associated molecular mechanisms on human vascular endothelial cells (HUVECs) were investigated. A concentration-dependent inhibition on HUVECs' viability and growth was observed for TBMEHP but not for TBPH. TBMEHP induced a marked G₀/G₁ cell cycle arrest and robust cell apoptosis at 1μg/mL by inducing expression of p53, GADD45α and cyclin dependent kinase (CDK) inhibitors (p21and p27) while suppressing the expression of cyclin D1, CDK2, CDK6, and Bcl-2. Unlike TBMEHP, TBPH caused early apoptosis after G₂/M phase arrest only at 10μg/mL via up-regulation of p21 and down-regulation of CDK2 and CDK4. TBMEHP decreased mitochondrial membrane potential and increased caspase-3 activity at 1μg/mL, suggesting that activation of p53 and mitochondrial pathway were involved in the cell apoptosis. The data showed that TBPH and TBMEHP induced different cell cycle arrest and apoptosis through different molecular mechanisms with much higher toxicity for TBMEHP. Our study implies that the metabolites of TBPH, possibly other novel brominated flame retardants, may be of potential concern for human cardiovascular disease.

Development of Certain Protein Kinase Inhibitors with the Components from Traditional Chinese Medicine

Traditional Chinese medicines (TCMs) have been used in China for more than two thousand years, and some of them have been confirmed to be effective in cancer treatment. Protein kinases play critical roles in control of cell growth, proliferation, migration, survival, and angiogenesis and mediate their biological effects through their catalytic activity. In recent years, numerous protein kinase inhibitors have been developed and are being used clinically. Anticancer TCMs represent a large class of bioactive substances, and some of them display anticancer activity via inhibiting protein kinases to affect the phosphoinositide 3-kinase, serine/threonine-specific protein kinases, pechanistic target of rapamycin (PI3K/AKT/mTOR), P38, mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinases (ERK) pathways. In the present article, we comprehensively reviewed several components isolated from anticancer TCMs that exhibited significantly inhibitory activity toward a range of protein kinases. These components, which belong to diverse structural classes, are reviewed herein, based upon the kinases that they inhibit. The prospects and problems in development of the anticancer TCMs are also discussed.

Unraveling the Anticancer Effect of Curcumin and Resveratrol

Resveratrol and curcumin are natural products with important therapeutic properties useful to treat several human diseases, including cancer. In the last years, the number of studies describing the effect of both polyphenols against cancer has increased; however, the mechanism of action in all of those cases is not completely comprehended. The unspecific effect and the ability to interfere in assays by both polyphenols make this challenge even more difficult. Herein, we analyzed the anticancer activity of resveratrol and curcumin reported in the literature in the last 11 years, in order to unravel the molecular mechanism of action of both compounds. Molecular targets and cellular pathways will be described. Furthermore, we also discussed the ability of these natural products act as chemopreventive and its use in association with other anticancer drugs.

Plant Polyphenols as Chemopreventive Agents for Lung Cancer

Lung cancer may be prevented by a diet rich in fruits and vegetables as they are enriched with dietary antioxidant polyphenols, such as flavonoids, proanthocyanidins, lignans, stilbenes, and phenolic acids. Dietary polyphenols exert a wide range of beneficial biological functions beyond their antioxidative properties and are involved in regulation of cell survival pathways leading to anticarcinogenic and antimutagenic functions. There are sufficient evidence from in vitro, in vivo, and epidemiological studies to suggest that the dietary intervention of polyphenols in cancer prevention, including the chemopreventive ability of dietary polyphenols, act against lung carcinogens. Cohort and epidemiological studies in selected risk populations have evaluated clinical effects of polyphenols. Polyphenols have demonstrated three major actions: antioxidative activity, regulation of phase I and II enzymes, and regulation of cell survival pathways against lung carcinogenesis. They have also shown an inverse association of lung cancer occurrences among high risk populations who consumed considerable amounts of fruits and vegetables in their daily diet. In in vitro cell culture experimental models, polyphenols bind with electrophilic metabolites from carcinogens, inactivate cellular oxygen radicals, prevent membrane lipid peroxidation and DNA oxidative damage, and adduct formation. Further, polyphenols enhance the detoxifying enzymes such as the phase II enzymes, glutathione transferases and glucuronosyl transferases.

GADD45α modulates curcumin sensitivity through c-Abl- and JNK-dependent signaling pathways in a mismatch repair-dependent manner

Colorectal cancer is a critical health concern because of its incidence as the third most prevalent cancer in the world. Currently, 5-fluorouracil (5-FU), 6-thioguanine, and certain other genotoxic agents are mainstays of treatment; however, patients often die due to emergence of resistant population. Curcumin, a bioactive compound derived from the dietary turmeric (Curcuma longa) is an effective anticancer, anti-inflammatory, and antioxidant agent. Previously, we reported that human colorectal cancer cell lines compromised for mismatch repair (MMR) function exhibit heightened sensitivity to curcumin due to sustained curcumin-induced unrepaired DNA damage compared to proficient population counterparts. In this report, we show that the protein levels of gadd45α, whose transcript levels are increased during DNA damage and stress signals, are upregulated following curcumin treatment in a dose- and time-dependent manner. We further observed that cells compromised for Mlh1 function (HCT116 + Ch2) displayed ~twofold increased GADD45α upregulation compared to similarly treated proficient counterparts (HCT116 + Ch3). Similarly, suppression of Mlh1 using ShRNA increased GADD45α upregulation upon curcumin treatment. On the other hand, suppression of GADD45α using SiRNA-blocked curcumin-induced cell death induction in Mlh1-deficient cells. Moreover, inhibition of Abl through ST571 treatment and its downstream effector JNK through SP600125 treatment blocked GADD45α upregulation and cell death triggered by curcumin. Collective results lead us to conclude that GADD45α modulates curcumin sensitivity through activation of c-Abl > JNK signaling in a mismatch repair-dependent manner.

Potential anti-cancer effect of curcumin in human lung squamous cell carcinoma

Background

To explore the molecular mechanisms of the anti-cancer effect of curcumin in human lung squamous cell carcinoma (LSQCC) SK-MES-1 cells.

Methods

Cell viability was determined using MTT assay. Ribonucleic acid sequencing was performed to measure expression levels of transcripts in LSQCC cells treated with 15 μmol/L curcumin (treatment groups) or an equal amount of dimethylsulfoxide (control). Cuffdiff software was used to identify differentially expressed genes (DEGs) in treatment groups, followed by enrichment analysis of DEGs using the Database for Annotation, Visualization and Integration Discovery. The protein-protein interaction (PPI) networks for up and downregulated DEGs were constructed by Cytoscape software using Search Tool for the Retrieval of Interacting Genes data to identify hub nodes.

Results

Curcumin significantly reduced cell viability in LSQCC cells. In total, 380 DEGs including 154 upregulated and 126 downregulated genes were found in the treatment groups. The upregulated genes were enriched in base excision repair (BER, such as PCNA, POLL, and MUTYH) and Janus kinase-signal transducer and activator of transcription (JAT-STAT) signaling pathways (such as AKT1 and STAT5A), while the downregulated genes were enriched in nine pathways, including the vascular endothelial growth factor (VEGF) signaling pathway (such as PTK2, VEGFA, MAPK1, and MAPK14) and mitogen-activated protein kinase (MAPK) signaling pathway (ARRB2, MAPK1, MAPK14, and NFKB1). PCNA and AKT1 were the hub nodes in the PPI network of upregulated genes while MAPK1, MAPK14, VEGFA, and NFKB1 were the hub nodes in the PPI network of downregulated genes.

Conclusions

Curcumin might exert anti-cancer effects on LSQCC via regulating BER, JAT-STAT, VEGF, and MAPK signaling pathways.

Curcumin a potent cancer preventive agent: Mechanisms of cancer cell killing

There is no doubt that diet could effectively improve health and halt cancers. Dietary phytochemical compounds and their derivatives represent a cornucopia of effectively anticancer compounds. This review discusses existing data on the anticancer activities of curcumin, and then offers possible explanations for and mechanisms of its cancer-preventive action. This review also offers insights into the molecular mechanism and targets through which curcumin modulates cell cycle, apoptotic signals, anti-apoptotic proteins, miRNAs, Wnt/beta-catenin signaling, protein kinases, nuclear factor-κB, proteasome activation, epigenetic regulation including DNA methylation and histone modification. Finally, this review provides explanations for how curcumin reverses the multi-drug resistance (MDR) of cancer cells.

Dual-drug delivery of curcumin and platinum drugs in polymeric micelles enhances the synergistic effects: a double act for the treatment of multidrug-resistant cancer

Combinational chemotherapy is often used to prevent drug induced resistance in cancer. The aim of this work is to test whether the co-delivery of drugs within one nanoparticle can result in increased synergistic effects of both drugs. Therefore, a micelle system with two different compartments, one for the drug curcumin and one for the conjugation of platinum drugs was designed. A triblock copolymer, based on the biodegradable polycaprolactone PCL, a PEG based shell and an amine bearing polymer as the interphase for the conjugation of platinum drugs was prepared by combination of ring-opening polymerization and RAFT polymerization. Curcumin was incorporated into the self-assembled onion-type micelle by physical encapsulation into the PCL core with an entrapment capacity of 6 wt%. The platinum(iv) drug oxoplatin was reacted with succinic anhydride to yield Pt(NH3)2Cl2[(COOH)2], which acted as the drug and as a crosslinker for the stabilisation of micelles. The size of the dual drug micelles was measured to be 38 nm by DLS, which was confirmed by TEM. The toxicity of the dual drug delivery system was tested against the A2780 human ovarian cancer cell line and compared with the IC50 value of micelles that deliver either curcumin or the platinum drug alone. The results were analysed using the CalcuSyn software. While curcumin and the platinum drug together without a carrier already showed synergy with a combination index ranging from 0.4 to 0.8, the combined delivery in one nanoparticle did enhance the synergistic effects resulting in a combination index of approximately 0.2-0.35. For comparison, a mixture of two nanoparticles, one with curcumin and the other with the platinum drug, was tested revealing a less noticeable synergistic effect compared to the co-delivery of both drugs in one drug carrier.

Translating curcumin to the clinic for lung cancer prevention: evaluation of the preclinical evidence for its utility in primary, secondary, and tertiary prevention strategies

Lung cancer is responsible for over one million deaths worldwide each year. Smoking cessation for lung cancer prevention remains key, but it is increasingly acknowledged that prevention strategies also need to focus on high-risk groups, including ex-smokers, and patients who have undergone resection of a primary tumor. Models for chemoprevention of lung cancer often present conflicting results, making rational design of lung cancer chemoprevention trials challenging. There has been much focus on use of dietary bioactive compounds in lung cancer prevention strategies, primarily due to their favorable toxicity profile and long history of use within the human populace. One such compound is curcumin, derived from the spice turmeric. This review summarizes and stratifies preclinical evidence for chemopreventive efficacy of curcumin in models of lung cancer, and adjudges the weight of evidence for use of curcumin in lung cancer chemoprevention strategies.

The molecular basis for the pharmacokinetics and pharmacodynamics of curcumin and its metabolites in relation to cancer

This review addresses the oncopharmacological properties of curcumin at the molecular level. First, the interactions between curcumin and its molecular targets are addressed on the basis of curcumin's distinct chemical properties, which include H-bond donating and accepting capacity of the β-dicarbonyl moiety and the phenylic hydroxyl groups, H-bond accepting capacity of the methoxy ethers, multivalent metal and nonmetal cation binding properties, high partition coefficient, rotamerization around multiple C-C bonds, and the ability to act as a Michael acceptor. Next, the in vitro chemical stability of curcumin is elaborated in the context of its susceptibility to photochemical and chemical modification and degradation (e.g., alkaline hydrolysis). Specific modification and degradatory pathways are provided, which mainly entail radical-based intermediates, and the in vitro catabolites are identified. The implications of curcumin's (photo)chemical instability are addressed in light of pharmaceutical curcumin preparations, the use of curcumin analogues, and implementation of nanoparticulate drug delivery systems. Furthermore, the pharmacokinetics of curcumin and its most important degradation products are detailed in light of curcumin's poor bioavailability. Particular emphasis is placed on xenobiotic phase I and II metabolism as well as excretion of curcumin in the intestines (first pass), the liver (second pass), and other organs in addition to the pharmacokinetics of curcumin metabolites and their systemic clearance. Lastly, a summary is provided of the clinical pharmacodynamics of curcumin followed by a detailed account of curcumin's direct molecular targets, whereby the phenotypical/biological changes induced in cancer cells upon completion of the curcumin-triggered signaling cascade(s) are addressed in the framework of the hallmarks of cancer. The direct molecular targets include the ErbB family of receptors, protein kinase C, enzymes involved in prostaglandin synthesis, vitamin D receptor, and DNA.

Curcumin induces apoptosis in gallbladder carcinoma cell line GBC-SD cells

Background

Gallbladder carcinoma is a malignant tumor with a very low 5-year survival rate because of the difficulty with its early diagnosis and the very poor prognosis of the advanced cancer state. The aims of this study were to determine whether curcumin could induce the apoptosis of a gallbladder carcinoma cell line, GBC-SD, and to clarify its related mechanism.

Methods

First, the anti-proliferative activities of curcumin-treated and untreated GBC-SD cells were determined using the MTT and colony formation assays. Then, the early apoptosis of cells was detected by the annexin V/propidium iodide double-staining assay and Hoechst 33342 staining assay. Detection of mitochondrial membrane potential was used to validate the ability of curcumin on inducing apoptosis in GBC-SD cells. Cell cycle changes were detected by flow cytometric analysis. Finally, the expressions of the apoptosis-related proteins or genes caspase-3, PARP, Bcl-2, and Bax were analyzed by western blot and quantitative real time PCR assay. Statistical analyses were performed using the Student’s t-test for comparison of the results obtained from cells with or without curcumin treatment.

Results

The MTT assay revealed that curcumin had induced a dose- and a time-dependent decrease in cell viability. Colony counting indicated that curcumin had induced a dose-dependent decrease in the colony formation ability in GBC-SD cells. Cells treated with curcumin were arrested at the S phase, according to the flow cytometric analysis. A significant induction of both the early and late phases of apoptosis was shown by the annexin V-FITC and PI staining. Morphological changes in apoptotic cells were also found by the Hoechst 33342 staining. After treatment with curcumin fluorescence shifted from red to green as ΔΨm decreased. Furthermore, western blot and quantitative real time PCR assays demonstrated that the curcumin induced apoptosis in GBC-SD cells by regulating the ratio of Bcl-2/Bax and activating the expression of cleaved caspase-3.

Conclusions

Taken together, the results indicate that curcumin may be a potential agent for the treatment of gallbladder cancer.

Cytotoxic effects of curcumin in human retinal pigment epithelial cells

BACKGROUND

Curcumin from turmeric is an ingredient in curry powders. Due to its antiinflammatory, antioxidant and anticarcinogenic effects, curcumin is a promising drug for the treatment of cancer and retinal diseases. We investigated whether curcumin alters the viability and physiological properties of human retinal pigment epithelial (RPE) cells in vitro.

METHODOLOGY/PRINCIPAL FINDINGS

Cellular proliferation was investigated with a bromodeoxy-uridine immunoassay, and chemotaxis was investigated with a Boyden chamber assay. Cell viability was determined by trypan blue exclusion. Apoptosis and necrosis rates were determined with a DNA fragmentation ELISA. Gene expression was determined by real-time PCR, and secretion of VEGF and bFGF was examined with ELISA. The phosphorylation level of proteins was revealed by Western blotting. The proliferation of RPE cells was slightly increased by curcumin at 10 µM and strongly reduced by curcumin above 50 µM. Curcumin at 50 µM increased slightly the chemotaxis of the cells. Curcumin reduced the expression and secretion of VEGF under control conditions and abolished the VEGF secretion induced by PDGF and chemical hypoxia. Whereas low concentrations of curcumin stimulated the expression of bFGF and HGF, high concentrations caused downregulation of both factors. Curcumin decreased dose-dependently the viability of RPE cells via induction of early necrosis (above 10 µM) and delayed apoptosis (above 1 µM). The cytotoxic effect of curcumin involved activation of caspase-3 and calpain, intracellular calcium signaling, mitochondrial permeability, oxidative stress, increased phosphorylation of p38 MAPK and decreased phosphorylation of Akt protein.

CONCLUSION

It is concluded that curcumin at concentrations described to be effective in the treatment of tumor cells and in inhibiting death of retinal neurons (∼10 µM) has adverse effects on RPE cells. It is suggested that, during the intake of curcumin as concomitant therapy of cancer or in the treatment of eye diseases, retinal function should be monitored carefully.

Effect of curcumin on dexamethasone-induced testicular toxicity in mice

CONTEXT

Curcumin is a yellow-orange polyphenol derived from turmeric [Curcuma longa L. (Zingiberaceaerhizomes)]. Turmeric is a main ingredient of Indian, Persian, and Thai dishes. Extensive studies within the last half a century have demonstrated the protective action of curcumin in many disorders of the body.

OBJECTIVE

This study evaluated the protective effect of curcumin on dexamethasone-induced spermatogenesis defects in mice.

MATERIALS AND METHODS

Thirty-two NMRI mice were randomly divided into 4 groups. The first (control) group received 1 mL/day of distilled water by intraperitoneal (i.p.) injection for 7 days. The second group received 200 mg/kg/day of curcumin (Cur) for 10 days. Third group received 7 mg/kg/day of dexamethasone (Dex) for 7 days. Forth group received 200 mg/kg of curcumin for 10 days after dexamethasone treatment. Testicular histopathology, morphometric analysis, head sperm counting, and immunohistochemistry assessments were performed for evaluation of the dexamethasone and curcumin effects.

RESULTS

Expression of Bcl-2 was significantly increased in the curcumin + dexamethasone group compared with dexamethasone-treated animals (p < 0.05). Dexamethasone induced spermatogenesis defects including epithelial vacuolizations, sloughing of germ cells, reduction of seminiferous tubule diameter, reduction in the number of sperm heads and significant maturation arrest (p < 0.001). Curcumin + dexamethasone treatment significantly prevented these changes (p < 0.05).

DISCUSSION AND CONCLUSION

The results of this study demonstrate that curcumin increases the expression of Bcl-2 protein, an important anti-apoptotic factor, and improves the spermatogenesis defects in dexamethasone treated mice. Curcumin has a potent protective effect against the testicular toxicity and might be clinically useful.

Molecular mechanisms of curcumin action: gene expression

Curcumin derived from the tropical plant Curcuma longa has a long history of use as a dietary agent, food preservative, and in traditional Asian medicine. It has been used for centuries to treat biliary disorders, anorexia, cough, diabetic wounds, hepatic disorders, rheumatism, and sinusitis. The preventive and therapeutic properties of curcumin are associated with its antioxidant, anti-inflammatory, and anticancer properties. Extensive research over several decades has attempted to identify the molecular mechanisms of curcumin action. Curcumin modulates numerous molecular targets by altering their gene expression, signaling pathways, or through direct interaction. Curcumin regulates the expression of inflammatory cytokines (e.g., TNF, IL-1), growth factors (e.g., VEGF, EGF, FGF), growth factor receptors (e.g., EGFR, HER-2, AR), enzymes (e.g., COX-2, LOX, MMP9, MAPK, mTOR, Akt), adhesion molecules (e.g., ELAM-1, ICAM-1, VCAM-1), apoptosis related proteins (e.g., Bcl-2, caspases, DR, Fas), and cell cycle proteins (e.g., cyclin D1). Curcumin modulates the activity of several transcription factors (e.g., NF-κB, AP-1, STAT) and their signaling pathways. Based on its ability to affect multiple targets, curcumin has the potential for the prevention and treatment of various diseases including cancers, arthritis, allergies, atherosclerosis, aging, neurodegenerative disease, hepatic disorders, obesity, diabetes, psoriasis, and autoimmune diseases. This review summarizes the molecular mechanisms of modulation of gene expression by curcumin.

Curcumin-cyclodextrin complexes potentiate gemcitabine effects in an orthotopic mouse model of lung cancer

Background:

Overall clinical outcome for advanced lung cancer remains very disappointing despite recent advances in treatment. Curcumin has been reported as potentially active against cancer.

Methods:

Owing to poor curcumin solubility, we have used cyclodextrins (CD) as an excipient allowing a considerable increase of aqueous solubility and bioavailability of curcumin. The effects of solubilised curcumin have been evaluated in cell cultures as well as in an in vivo orthotopic lung tumour mouse model.

Results:

Cell proliferation was reduced while apoptosis rates were increased when lung epithelial tumour cells were cultured in the presence of curcumin–CD complexes. For in vivo experiments, cells were grafted into lungs of C57Bl/6 mice treated by an oral administration of a non-soluble form of curcumin, CDs alone or curcumin–CD complexes, combined or not with gemcitabine. The size of orthotopically implanted lung tumours was reduced upon curcumin complex administration as compared with treatments with placebo or non-solubilised curcumin. Moreover, curcumin potentiated the gemcitabine-mediated antitumour effects.

Conclusion:

Our data demonstrate that curcumin, when given orally in a CD-solubilised form, reduces lung tumour size in vivo. In vitro experiments show impaired tumour cell proliferation and increased cell apoptosis. Moreover, our data underline a potential additive effect of curcumin with gemcitabine thus providing an efficient therapeutic option for antilung cancer therapy.

Induction of apoptosis and reduction of MMP gene expression in the U373 cell line by polyphenolics in Aronia melanocarpa and by curcumin

Malignant brain tumours are rare but are the most challenging types of cancers to treat. Despite conventional multimodality approaches available for their management, the outlook for most patients remains dismal due to the ability of the tumour cells to invade the normal brain. Attention has now focused on novel therapeutic interventions such as as the use of micronutrients. Both chokeberry extract (Aronia melanocarpa), which is rich in natural pigments such as anthocyanins and curcumin (diferuloylmethane) found in turmeric (Curcuma longa) have been reported to possess anticancer properties in other cancers. The aim of this study was to extend our previous research to evaluate the therapeutic potential of these two agents by testing their ability to induce apoptosis in an established glioblastoma cell line (U373). This was accomplished by treating the cells for 48 h with either chokeberry extract or curcumin, and using the Annexin-V assay. Gene profiles of 8 MMPs (2, 9, 14, 15, 16, 17, 24 and 25) and 4 TIMPs (1, 2, 3 and 4) were analysed for effects of mediators of invasion by quantitative real-time polymerase chain reaction (RT-PCR). The IC50 values determined for curcumin and chokeberry extract were 15 and 200 µg/ml, respectively. Our results also suggest that curcumin induces apoptosis but chokeberry extract is necrotic to this cell line. It is possible that chokeberry extract kills the cells by other non-apoptotic pathways. In addition, the RT-PCR results show downregulation of the gene expression of MMP-2, -14, -16 and -17 for both micronutrients. Taken together, the comparative data suggest that both curcumin and chokeberry extract may exhibit their anticancer potential by inducing apoptosis and inhibiting invasion by reducing MMP gene expression.

GADD45 proteins: central players in tumorigenesis

The Growth Arrest and DNA Damage-inducible 45 (GADD45) proteins have been implicated in regulation of many cellular functions including DNA repair, cell cycle control, senescence and genotoxic stress. However, the pro-apoptotic activities have also positioned GADD45 as an essential player in oncogenesis. Emerging functional evidence implies that GADD45 proteins serve as tumor suppressors in response to diverse stimuli, connecting multiple cell signaling modules. Defects in the GADD45 pathway can be related to the initiation and progression of malignancies. Moreover, induction of GADD45 expression is an essential step for mediating anti-cancer activity of multiple chemotherapeutic drugs and the absence of GADD45 might abrogate their effects in cancer cells. In this review, we present a comprehensive discussion of the functions of GADD45 proteins, linking their regulation to effectors of cell cycle arrest, DNA repair and apoptosis. The ramifications regarding their roles as essential and central players in tumor growth suppression are also examined. We also extensively review recent literature to clarify how different chemotherapeutic drugs induce GADD45 gene expression and how its up-regulation and interaction with different molecular partners may benefit cancer chemotherapy and facilitate novel drug discovery.

DNMT inhibitors and HDAC inhibitors regulate E-cadherin and Bcl-2 expression in endometrial carcinoma in vitro and in vivo

BACKGROUND

The effect of histone deacetylase inhibitors (HDACIs) and DNA methyltransferase inhibitors (DNMTIs) on proliferation of endometrial cancer (EC) cells in vitro and in vivo was investigated.

METHODS

Changes in methylation of the CDH1 promoter in HDACI- and DNMTI-treated HEC-1-B and RL-952 EC cells were detected. Nude mice with xenografted implants of human EC HEC-1-B cells were treated with valproic acid (VPA) and decitabine (DAC) and evaluated for tumor growth, CDH1 and Bcl-2 mRNA levels.

RESULTS

DAC, VPA and suberoylanilide hydroxamic acid (SAHA) inhibited proliferation, induced cell cycle arrest and enhanced the apoptotic index in both cell lines, DAC, VPA and SAHA upregulated E-cadherin mRNA and protein levels and downregulated Bcl-2 mRNA levels in vitro. DAC and VPA inhibited tumor growth, upregulated CDH1 mRNA and downregulated Bcl-2 mRNA levels in vivo.

CONCLUSIONS

A combination of HDACIs and DNMTIs suppresses the growth of EC, which is likely mediated by upregulation of E-cadherin and downregulation of Bcl-2.

Dietary phytochemicals, HDAC inhibition, and DNA damage/repair defects in cancer cells

Genomic instability is a common feature of cancer etiology. This provides an avenue for therapeutic intervention, since cancer cells are more susceptible than normal cells to DNA damaging agents. However, there is growing evidence that the epigenetic mechanisms that impact DNA methylation and histone status also contribute to genomic instability. The DNA damage response, for example, is modulated by the acetylation status of histone and non-histone proteins, and by the opposing activities of histone acetyltransferase and histone deacetylase (HDAC) enzymes. Many HDACs overexpressed in cancer cells have been implicated in protecting such cells from genotoxic insults. Thus, HDAC inhibitors, in addition to unsilencing tumor suppressor genes, also can silence DNA repair pathways, inactivate non-histone proteins that are required for DNA stability, and induce reactive oxygen species and DNA double-strand breaks. This review summarizes how dietary phytochemicals that affect the epigenome also can trigger DNA damage and repair mechanisms. Where such data is available, examples are cited from studies in vitro and in vivo of polyphenols, organosulfur/organoselenium compounds, indoles, sesquiterpene lactones, and miscellaneous agents such as anacardic acid. Finally, by virtue of their genetic and epigenetic mechanisms, cancer chemopreventive agents are being redefined as chemo- or radio-sensitizers. A sustained DNA damage response coupled with insufficient repair may be a pivotal mechanism for apoptosis induction in cancer cells exposed to dietary phytochemicals. Future research, including appropriate clinical investigation, should clarify these emerging concepts in the context of both genetic and epigenetic mechanisms dysregulated in cancer, and the pros and cons of specific dietary intervention strategies.

Antiproliferative effect of chrysin on anaplastic thyroid cancer

BACKGROUND

Anaplastic thyroid cancer (ATC) is an undifferentiated, aggressive malignancy, for which there are no effective therapies. Though ATCs only make up less than 2% of all thyroid cancer cases, they represent over half of the thyroid cancer-related deaths. Chrysin, a natural flavonoid, has recently been reported as a potential anti-cancer agent. However, the effect of this compound on ATC cells is not known. Thus, in this study, we evaluated the antiproliferative nature of chrysin in ATC cells.

METHODS

HTH7 and KAT18 cells, derived from patients with ATC, were treated with chrysin (25-50 μM) for up to 6 d. Cell proliferation was measured every 2 d using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). Western blot analysis for molecular makers of apoptosis was carried out to investigate the effect and mechanism of Chrysin on ATC.

RESULTS

Chrysin inhibited proliferation of HTH7 and KAT18 in a dose- and time-dependent manner. HTH7 and KAT18 cells with Chrysin treatment showed a significant increase in cleaved caspase-3, cleaved PolyADP Ribose Polymerase (PARP), along with a decrease in cyclin D1, Mcl-1, and XIAP. Furthermore, the ratio of Bax to Bcl-2 expression in ATC cells revealed an increase after the treatment.

CONCLUSIONS

Chrysin inhibits growth in ATC cells via apoptosis in vitro. Therefore, the natural flavonoid chrysin warrants further clinical investigation as a new potential drug for the treatment for ATC.

New cancer treatment strategy using combination of green tea catechins and anticancer drugs

Green tea is now recognized as the most effective cancer preventive beverage. In one study, 10 Japanese-size cups of green tea daily supplemented with tablets of green tea extract limited the recurrence of colorectal polyps in humans to 50%. Thus, cancer patients who consume green tea and take anticancer drugs will have double prevention. We studied the effects of combining (-)-epigallocatechin gallate (EGCG) and anticancer drugs, focusing on inhibition of cell growth and induction of apoptosis. Numerous anticancer drugs, such as tamoxifen, COX-2 inhibitors, and retinoids were used for the experiments, and the combination of EGCG and COX-2 inhibitors consistently induced the enhancement of apoptosis. To study the mechanism of the enhancement, we paid special attention to the enhanced expressions of DDIT3 (growth arrest and DNA damage-inducible 153, GADD153), GADD45A, and CDKN1A (p21/WAF1/CIP1) genes, based on our previous evidence that a combination of EGCG and sulindac specifically induced upregulated expression of GADD153 and p21 genes in PC-9 lung cancer cells. The synergistic enhancements of apoptosis and GADD153 gene expression in human non-small cell lung cancer cells by the combination of EGCG and celecoxib were mediated through the activation of the MAPK signaling pathway. This article reviews the synergistic enhancement of apoptosis, gene expression, and anticancer effects using various combinations of EGCG and anticancer drugs, including the combination of (-)-epicatechin (EC) and curcumin. Based on the evidence, we present a new concept: green tea catechins as synergists with anticancer drugs.