Nadine Darwiche

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.

Molecular pathway for thymoquinone-induced cell-cycle arrest and apoptosis in neoplastic keratinocytes

Thymoquinone (TQ), the most abundant constituent in black seed, was shown to possess potent chemopreventive activities against DMBA-initiated TPA-promoted skin tumors in mice. Despite the potential interest in TQ as a skin antineoplastic agent, its mechanism of action has not been examined yet. Using primary mouse keratinocytes, papilloma (SP-1) and spindle (I7) carcinoma cells, we studied the cellular and molecular events involved in TQs antineoplastic activity. We show that non-cytotoxic concentrations of TQ reduce the proliferation of neoplastic keratinocytes by 50%. The sensitivity of cells to TQ treatment appears to be stage dependent such that papilloma cells are twice as sensitive to the growth inhibitory effects of TQ as the spindle cancer cells. TQ treatment of SP-1 cells induced G0/G1 cell-cycle arrest, which correlated with sharp increases in the expression of the cyclin-dependent kinase inhibitor p16 and a decrease in cyclin D1 protein expression. TQ-induced growth inhibition in I7 cells by inducing G2/M cell-cycle arrest, which was associated with an increase in the expression of the tumor suppressor protein p53 and a decrease in cyclin B1 protein. At longer times of incubation, TQ induced apoptosis in both cell lines by remarkably increasing the ratio of Bax/Bcl-2 protein expression and decreasing Bcl-xL protein. The apoptotic effects of TQ were more pronounced in SP-1 than in I7 cells. Collectively, these findings support a potential role for TQ as a chemopreventive agent, particularly at the early stages of skin tumorigenesis.

Characterization of the components of the putative mammalian sister chromatid cohesion complex.

Establishing and maintaining proper sister chromatid cohesion throughout the cell cycle are essential for maintaining genome integrity. To understand how sister chromatid cohesion occurs in mammals, we have cloned and characterized mouse orthologs of proteins known to be involved in sister chromatid cohesion in other organisms. The cDNAs for the mouse orthologs of SMC1S.c. and SMC3S.c. , mSMCB and mSMCD respectively, were cloned, and the corresponding transcripts and proteins were characterized. mSMCB and mSMCD are transcribed at similar levels in adult mouse tissues except in testis, which has an excess of mSMCD transcripts. The mSMCB and mSMCD proteins, as well as the PW29 protein, a mouse homolog of Mcd1pS.c./Rad21S.p., form a complex similar to cohesin in X. laevis. mSMCB, mSMCD and PW29 protein levels show no significant cell-cycle dependence. The bulk of the mSMCB, mSMCD and PW29 proteins undergo redistribution from the chromosome vicinity to the cytoplasm during prometaphase and back to the chromatin in telophase. This pattern of intracellular localization suggests a complex role for this group of SMC proteins in chromosome dynamics. The PW29 protein and PCNA, which have both been implicated in sister chromatid cohesion, do not colocalize, indicating that these proteins may not function in the same cohesion pathway. Overexpression of a PW29-GFP fusion protein in mouse fibroblasts leads to inhibition of proliferation, implicating this protein and its complex with SMC proteins in the control of mitotic cycle progression.

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.

Cell death mechanisms of plant-derived anticancer drugs: beyond apoptosis

Despite remarkable progress in the discovery and development of novel cancer therapeutics, cancer remains the second leading cause of death in the world. For many years, compounds derived from plants have been at the forefront as an important source of anticancer therapies and have played a vital role in the prevention and treatment of cancer because of their availability, and relatively low toxicity when compared with chemotherapy. More than 3000 plant species have been reported to treat cancer and about thirty plant-derived compounds have been isolated so far and have been tested in cancer clinical trials. The mechanisms of action of plant-derived anticancer drugs are numerous and most of them induce apoptotic cell death that may be intrinsic or extrinsic, and caspase and/or p53-dependent or independent mechanisms. Alternative modes of cell death by plant-derived anticancer drugs are emerging and include mainly autophagy, necrosis-like programmed cell death, mitotic catastrophe, and senescence leading to cell death. Considering that the non-apoptotic cell death mechanisms of plant-derived anticancer drugs are less reviewed than the apoptotic ones, this paper attempts to focus on such alternative cell death pathways for some representative anticancer plant natural compounds in clinical development. In particular, emphasis will be on some promising polyphenolics such as resveratrol, curcumin, and genistein; alkaloids namely berberine, noscapine, and colchicine; terpenoids such as parthenolide, triptolide, and betulinic acid; and the organosulfur compound sulforaphane. The understanding of non-apoptotic cell death mechanisms induced by these drugs would provide insights into the possibility of exploiting novel molecular pathways and targets of plant-derived compounds for future cancer therapeutics.

Expression of a binding protein for FGF is associated with epithelial development and skin carcinogenesis

Fibroblast growth factors (FGF)-1 and -2 are found in most embryonic and adult normal and tumor tissues, where they are immobilized in the extracellular matrix (EM). Mobilization of these FGFs is part of a tightly controlled process resulting in the activation of high-affinity receptors. Recently, we have shown that a novel human FGF-binding protein (FGF-BP) mediates the release of immobilized FGF-2 from the EM. Here we isolated genomic and cDNA clones of the mouse FGF-BP homologue and studied its expression during embryonic development and skin carcinogenesis. The murine gene contains two exons that generate a 1.2 kb mRNA and predicts an 18 kDa secreted protein that is 63% identical to its human homologue. FGF-BP mRNA expression during embryogenesis is restricted to skin, intestine and lung. In the developing skin, FGF-BP expression starts at embryonic day 9, reaches peak levels perinatally and is downregulated during postnatal development. Develepment regulation in the intestine is similar, but in lungs and ovaries high expression was also observed in the adult. FGF-BP mRNA expression in the adult skin is dramatically increased during early stages of carcinogen-induced transformation in vivo and by ras-activation in vitro. Finally, mouse FGF-BP binds to FGF-2 and can function as a modulator of FGF in FGF-responsive cells. Our results suggest a potential function of FGF-BP during development and tumorigenesis.

Evidence against a direct cytotoxic effect of alpha interferon and zidovudine in HTLV-I associated adult T cell leukemia/lymphoma

The combination of the anti-viral agents, zidovudine (AZT) and interferon-α (IFN), is a potent treatment of HTLV-I-associated adult T cell leukemia/lymphoma (ATL). In this study we investigate the possible mechanism of action of this combination by examining several cellular parameters including cell proliferation, cell cycle distribution and apoptosis. The ATL-derived T cell lines HuT-102 and MT-2 served as models. HTLV-I negative T cell lines (CEM and Jurkat) were used as controls. No significant modification of cell growth was observed except at suprapharmacological doses of AZT and IFN. Moreover, these effects were less pronounced in HTLV-I-infected cell lines compared to control cell lines. AZT and IFN treatment did not induce any significant modification of the expression of bcl-2 and p53. Interestingly no in vitrocytotoxic effect of AZT/IFN combination was observed on fresh leukemic cells derived from an acute ATL patient at diagnosis despite achievement of in vivo complete remission using the same therapy. These results suggest that the therapeutic effect of AZT and IFN is not through a direct cytotoxic effect of these drugs on the leukemic cells.

Protective Effect of Vitamin E on Ultraviolet B Light-Induced Damage in Keratinocytes

Ultraviolet (UV) B radiation is the most common environmental factor in the pathogenesis of skin cancer. Exposure of human skin to UVB radiation leads to the depletion of cutaneous antioxidants, the activation of nuclear factor kappa B (NF‐κB), and programmed cell death (apoptosis). Although antioxidant supplementation has been shown to prevent UVB‐induced photooxidative damage, its effect on components of cell signaling pathways leading to gene expression has not been clearly established. In the present study, the effect of the antioxidant vitamin, α‐tocopherol (α‐T), and its acetate analog, α‐tocopherol acetate (α‐TAc), on UVB‐induced damage in primary and neoplastic mouse keratinocytes was investigated. The ability of both vitamins to modulate UVB‐induced apoptosis and activation of the transcription factor NF‐κB were studied. Treatment of normal and neoplastic mouse epidermal keratinocytes (308 cells) with 30–60 mJ/cm2 UVB markedly decreased viable cell number and was accompanied by DNA fragmentation. When both vitamins were applied to cells at times before and after UVB radiation, a significant increase in the percentage of viable cells and concomitant decrease in the number of apoptotic cells was noted, with vitamin pretreatment providing a better protection than posttreatment. Simultaneous posttreatment of irradiated cells with α‐TAc abolished the cytotoxic effects of UVB and restored cell viability to control levels. In addition, simultaneous posttreatment of irradiated cells with α‐T reduced the number of apoptotic cells by half, indicating a synergistic effect of two such treatments compared with any single one. Flow cytometry analysis indicated that vitamin treatment suppressed both an increase in pre‐G0 cells and a decrease in cycling cells by UVB exposure. In addition, NF‐κB activation was detected 2 h after UV exposure and was maintained for up to 8 h. Pretreatment with vitamins significantly inhibited NF‐κB activation at 4 and 8 h. These results indicate that vitamin E and its acetate analog can modulate the cellular response to UVB partly through their action on NF‐κB activation. Thus, these antioxidant vitamins are potential drugs for the protection from or the reduction of UVB‐associated epidermal damage.

A journey under the sea: the quest for marine anti-cancer alkaloids.

The alarming increase in the global cancer death toll has fueled the quest for new effective anti-tumor drugs thorough biological screening of both terrestrial and marine organisms. Several plant-derived alkaloids are leading drugs in the treatment of different types of cancer and many are now being tested in various phases of clinical trials. Recently, marine-derived alkaloids, isolated from aquatic fungi, cyanobacteria, sponges, algae, and tunicates, have been found to also exhibit various anti-cancer activities including anti-angiogenic, anti-proliferative, inhibition of topoisomerase activities and tubulin polymerization, and induction of apoptosis and cytotoxicity. Two tunicate-derived alkaloids, aplidin and trabectedin, offer promising drug profiles, and are currently in phase II clinical trials against several solid and hematologic tumors. This review sheds light on the rich array of anti-cancer alkaloids in the marine ecosystem and introduces the most investigated compounds and their mechanisms of action.

Retinoic acid and arsenic trioxide trigger degradation of mutated NPM1, resulting in apoptosis of AML cells

Nucleophosmin-1 (NPM1) is the most frequently mutated gene in acute myeloid leukemia (AML). Addition of retinoic acid (RA) to chemotherapy was proposed to improve survival of some of these patients. Here, we found that RA or arsenic trioxide synergistically induce proteasomal degradation of mutant NPM1 in AML cell lines or primary samples, leading to differentiation and apoptosis. NPM1 mutation not only delocalizes NPM1 from the nucleolus, but it also disorganizes promyelocytic leukemia (PML) nuclear bodies. Combined RA/arsenic treatment significantly reduced bone marrow blasts in 3 patients and restored the subnuclear localization of both NPM1 and PML. These findings could explain the proposed benefit of adding RA to chemotherapy in NPM1 mutant AMLs, and warrant a broader clinical evaluation of regimen comprising a RA/arsenic combination.