Akram Ghantous

What made sesquiterpene lactones reach cancer clinical trials

Sesquiterpene lactones (SLs) are plant-derived compounds often used in traditional medicine against inflammation and cancer. This review focuses on the chemical and biological properties of SLs that lead to enhanced anticancer and anti-inflammatory effects. The chemical properties comprise alkylating center reactivity, lipophilicity, and molecular geometry and electronic features. SLs in clinical trials are artemisinin, thapsigargin and parthenolide and many of their synthetic derivatives. These drugs are selective toward tumor and cancer stem cells by targeting specific signaling pathways, which make them lead compounds in cancer clinical trials.

Parthenolide: from plant shoots to cancer roots

Parthenolide (PTL), a sesquiterpene lactone (SL) originally purified from the shoots of feverfew (Tanacetum parthenium), has shown potent anticancer and anti-inflammatory activities. It is currently being tested in cancer clinical trials. Structure-activity relationship (SAR) studies of parthenolide revealed key chemical properties required for biological activities and epigenetic mechanisms, and led to the derivatization of an orally bioavailable analog, dimethylamino-parthenolide (DMAPT). Parthenolide is the first small molecule found to be selective against cancer stem cells (CSC), which it achieves by targeting specific signaling pathways and killing cancer from its roots. In this review, we highlight the exciting journey of parthenolide, from plant shoots to cancer roots.

Tobacco smoking-associated genome-wide DNA methylation changes in the EPIC study

AIM Epigenetic changes may occur in response to environmental stressors, and an altered epigenome pattern may represent a stable signature of environmental exposure. MATERIALS & METHODS Here, we examined the potential of DNA methylation changes in 910 prediagnostic peripheral blood samples as a marker of exposure to tobacco smoke in a large multinational cohort. RESULTS We identified 748 CpG sites that were differentially methylated between smokers and nonsmokers, among which we identified novel regionally clustered CpGs associated with active smoking. Importantly, we found a marked reversibility of methylation changes after smoking cessation, although specific genes remained differentially methylated up to 22 years after cessation. CONCLUSION Our study has comprehensively cataloged the smoking-associated DNA methylation alterations and showed that these alterations are reversible after smoking cessation.

Structure-activity relationship of seco-tanapartholides isolated from Achillea falcata for inhibition of HaCaT cell growth.

Four sesquiterpene lactones were isolated from Achillea falcata, through bioassay-guided fractionation, based on their differential ability to affect HaCaT cell growth. Identified seco-tanapartholides: 3-beta-methoxy-iso-seco-tanapartholide (1), tanaphillin (2), iso-seco-tanapartholide (3), and 8-hydroxy-3-methoxy-iso-seco-tanaparatholide (4) were found to differentially decrease keratinocyte cell viability. In addition, the stereoselectivity, lipophilicity, and number and position of hydroxyl groups present in these compounds were correlated with their biological activities for HaCaT cell growth inhibition. Statistical analyses confirmed an enhanced potency of the beta-OH iso-seco-tanapartholide over the alpha:beta-OH diastereoisomeric mixture. The highest potency, however, was mainly the function of the enhanced lipophilicity of the molecule.

Optimized DNA extraction from neonatal dried blood spots: application in methylome profiling

BackgroundNeonatal dried blood spots (DBS) represent an inexpensive method for long-term biobanking worldwide and are considered gold mines for research for several human diseases, including those of metabolic, infectious, genetic and epigenetic origin. However, the utility of DBS is restricted by the limited amount and quality of extractable biomolecules (including DNA), especially for genome wide profiling. Degradation of DNA in DBS often occurs during storage and extraction. Moreover, amplifying small quantities of DNA often leads to a bias in subsequent data, particularly in methylome profiles. Thus it is important to develop methodologies that maximize both the yield and quality of DNA from DBS for downstream analyses.ResultsUsing combinations of in-house-derived and modified commercial extraction kits, we developed a robust and efficient protocol, compatible with methylome studies, many of which require stringent bisulfite conversion steps. Several parameters were tested in a step-wise manner, including blood extraction, cell lysis, protein digestion, and DNA precipitation, purification and elution. DNA quality was assessed based on spectrophotometric measurements, DNA detectability by PCR, and DNA integrity by gel electrophoresis and bioanalyzer analyses. Genome scale Infinium HumanMethylation450 and locus-specific pyrosequencing data generated using the refined DBS extraction protocol were of high quality, reproducible and consistent.ConclusionsThis study may prove useful to meet the increased demand for research on prenatal, particularly epigenetic, origins of human diseases and for newborn screening programs, all of which are often based on DNA extracted from DBS.

The combination of arsenic, interferon-alpha, and zidovudine restores an “immunocompetent-like” cytokine expression profile in patients with adult T-cell leukemia lymphoma

BackgroundHTLV-I associated adult T-cell leukemia/lymphoma (ATL) carries a dismal prognosis due to chemo-resistance and immuno-compromised micro-environment. The combination of zidovudine and interferon-alpha (IFN) significantly improved survival in ATL. Promising results were reported by adding arsenic trioxide to zidovudine and IFN.ResultsHere we assessed Th1/Th2/Treg cytokine gene expression profiles in 16 ATL patients before and 30 days after treatment with arsenic/IFN/zidovudine, in comparison with HTLV-I healthy carriers and sero-negative blood donors. ATL patients at diagnosis displayed a Treg/Th2 cytokine profile with significantly elevated transcript levels of Foxp3, interleukin-10 (IL-10), and IL-4 and had a reduced Th1 profile evidenced by decreased transcript levels of interferon-γ (IFN-γ) and IL-2. Most patients (15/16) responded, with CD4+CD25+ cells significantly decreasing after therapy, paralleled by decreases in Foxp3 transcript. Importantly, arsenic/IFN/zidovudine therapy sharply diminished IL-10 transcript and serum levels concomittant with decrease in IL-4 and increases in IFN-γ and IL-2 mRNA, whether or not values were adjusted to the percentage of CD4+CD25+ cells. Finally, IL-10 transcript level negatively correlated with clinical response at Day 30.ConclusionsThe observed shift from a Treg/Th2 phenotype before treatment toward a Th1 phenotype after treatment with arsenic/IFN/zidovudine may play an important role in restoring an immuno-competent micro-environment, which enhances the eradication of ATL cells and the prevention of opportunistic infections.

Preclinical efficacy of the synthetic retinoid ST1926 for treating adult T-cell leukemia/lymphoma

Adult T-cell leukemia/lymphoma (ATL) is an aggressive neoplasm caused by human T-cell leukemia virus type 1 (HTLV-1). The HTLV-1 oncoprotein Tax plays an important role in ATL pathogenesis. ATL carries a poor prognosis due to chemotherapy resistance, stressing the need for alternative therapies. Here, we investigate the preclinical efficacy of the synthetic retinoid ST1926 in ATL and peripheral T-cell lymphomas. Clinically achievable concentrations of ST1926 induced a dramatic inhibition of cell proliferation in malignant T-cell lines and primary ATL cells with minimal effect on resting or activated normal lymphocytes. ST1926 induced apoptosis, DNA damage, and upregulation of p53 proteins in malignant T cells, whereas it caused an early downregulation of Tax proteins in HTLV-1-positive cells. In murine ATL, oral treatment with ST1926 prolonged survival and reduced leukemia cell infiltration, white blood cell counts, and spleen mass. In spleens of ST1926-treated animals, p53 and p21 proteins were upregulated, poly (ADP-ribose) polymerase was cleaved, and Tax transcripts were reduced. These results highlight the promising use of ST1926 as a targeted therapy for ATL.

Histone Acetyltransferase Cofactor Trrap Maintains Self-Renewal and Restricts Differentiation of Embryonic Stem Cells

Chromatin states are believed to play a key role in distinct patterns of gene expression essential for self‐renewal and pluripotency of embryonic stem cells (ESCs); however, the genes governing the establishment and propagation of the chromatin signature characteristic of pluripotent cells are poorly understood. Here, we show that conditional deletion of the histone acetyltransferase cofactor Trrap in mouse ESCs triggers unscheduled differentiation associated with loss of histone acetylation, condensation of chromatin into distinct foci (heterochromatization), and uncoupling of H3K4 dimethylation and H3K27 trimethylation. Trrap loss results in downregulation of stemness master genes Nanog, Oct4, and Sox2 and marked upregulation of specific differentiation markers from the three germ layers. Chromatin immunoprecipitation‐sequencing analysis of genome‐wide binding revealed a significant overlap between Oct4 and Trrap binding in ESCs but not in differentiated mouse embryonic fibroblasts, further supporting a functional interaction between Trrap and Oct4 in the maintenance of stemness. Remarkably, failure to downregulate Trrap prevents differentiation of ESCs, suggesting that downregulation of Trrap may be a critical step guiding transcriptional reprogramming and differentiation of ESCs. These findings establish Trrap as a critical part of the mechanism that restricts differentiation and promotes the maintenance of key features of ESCs. STEM CELLS 2013;31:979–991

Inhibition of Tumor Promotion by Parthenolide: Epigenetic Modulation of p21

The promotion stage in the multistep process of epidermal tumorigenesis is NF-кB–dependent, epigenetically regulated, and reversible, thus, a suitable target for chemoprevention. We investigated whether the NF-кB inhibitor, parthenolide, currently in cancer clinical trials, attenuates tumor promotion by modulating the epigenetically regulated NF-кB target genes, p21 and cyclin D1. Parthenolide selectively inhibited the growth of neoplastic keratinocytes while sparing normal ones. Specifically, in JB6P+ cells, a model of tumor promotion, noncytotoxic parthenolide concentrations abrogated tumor promoter–induced cell proliferation and anchorage-independent growth. Furthermore, parthenolide decreased tumor promoter–induced NF-кB activity, increased p21, and decreased cyclin D1 expression. In parthenolide-treated cells, p21 transcription correlated with relaxed chromatin and p65/NF-кB binding at the p21 promoter. However, cyclin D1 transcription correlated more with p65/NF-кB binding than with chromatin structure at the cyclin D1 promoter. Epigenetic regulation by parthenolide seemed specific, as parthenolide did not alter global histone acetylation and methylation and histone deacetylase activity. Because p21 expression by parthenolide was sustained, we used p21-siRNA and p21 −/− cancer cells and showed that the loss of p21 is cytoprotective against parthenolide. Low parthenolide concentrations (0.25 mg/kg) inhibited tumor growth of promoted JB6P+ cells in xenograft immunocompromised mice using two different chemoprevention protocols. Tissue microarray of mouse tumors showed that parthenolide decreased scores of the cell proliferation marker Ki67 and p65/NF-кB, whereas it increased p21 expression. These results show that low doses of parthenolide inhibit tumor promotion and epigenetically modulate p21 expression, highlighting the potential role of this drug as a chemopreventive agent and in epigenetic cancer therapy. Cancer Prev Res; 5(11); 1298–309. ©2012 AACR.

Maternal BMI at the start of pregnancy and offspring epigenome-wide DNA methylation: findings from the pregnancy and childhood epigenetics (PACE) consortium

&NA; Pre‐pregnancy maternal obesity is associated with adverse offspring outcomes at birth and later in life. Individual studies have shown that epigenetic modifications such as DNA methylation could contribute. Within the Pregnancy and Childhood Epigenetics (PACE) Consortium, we meta‐analysed the association between pre‐pregnancy maternal BMI and methylation at over 450,000 sites in newborn blood DNA, across 19 cohorts (9,340 mother‐newborn pairs). We attempted to infer causality by comparing the effects of maternal versus paternal BMI and incorporating genetic variation. In four additional cohorts (1,817 mother‐child pairs), we meta‐analysed the association between maternal BMI at the start of pregnancy and blood methylation in adolescents. In newborns, maternal BMI was associated with small (<0.2% per BMI unit (1 kg/m2), P < 1.06 × 10‐7) methylation variation at 9,044 sites throughout the genome. Adjustment for estimated cell proportions greatly attenuated the number of significant CpGs to 104, including 86 sites common to the unadjusted model. At 72/86 sites, the direction of the association was the same in newborns and adolescents, suggesting persistence of signals. However, we found evidence for acausal intrauterine effect of maternal BMI on newborn methylation at just 8/86 sites. In conclusion, this well‐powered analysis identified robust associations between maternal adiposity and variations in newborn blood DNA methylation, but these small effects may be better explained by genetic or lifestyle factors than a causal intrauterine mechanism. This highlights the need for large‐scale collaborative approaches and the application of causal inference techniques in epigenetic epidemiology.