Roberta Venè

Mechanisms of Inhibition of Tumor Angiogenesis and Vascular Tumor Growth by Epigallocatechin-3-Gallate

Purpose: Green tea consumption has been linked to a reduced occurrence of some tumor types. Current data indicate that the principal mediator of this chemopreventive effect is epigallocatechin-3-gallate (EGCG), the most abundant polyphenol found in dried tea leaves. Here, we examined the effects of this compound on the two key cell populations typically involved in tumor growth: tumor cells and endothelial cells. Experimental Design: The effects of green tea and EGCG were tested in a highly vascular Kaposi’s sarcoma (KS) tumor model and on endothelial cells in a panel of in vivo and in vitro assays. Results: EGCG inhibited KS-IMM cell growth and endothelial cell growth, chemotaxis, and invasion over a range of doses; high concentrations also induced tumor cell apoptosis. EGCG inhibited the metalloprotease-mediated gelatinolytic activity produced by endothelial cell supernatants and the formation of new capillary-like structures in vitro. Green tea or purified EGCG when administered to mice in the drinking water inhibited angiogenesis in vivo in the Matrigel sponge model and restrained KS tumor growth. Histological analysis of the tumors were consistent with an anti-angiogenic activity of EGCG and green tea. Conclusions: These data suggest that the green tea gallate or its derivatives may find use in the prevention and treatment of vascular tumors in a chemoprevention or adjuvant setting.

The chemopreventive polyphenol Curcumin prevents hematogenous breast cancer metastases in immunodeficient mice.

Dissemination of metastatic cells probably occurs long before diagnosis of the primary tumor. Metastasis during early phases of carcinogenesis in high risk patients is therefore a potential prevention target. The plant polyphenol Curcumin has been proposed for dietary prevention of cancer. We therefore examined its effects on the human breast cancer cell line MDA-MB-231 in vitroand in a mouse metastasis model. Curcumin strongly induces apoptosis in MDA-MB-231 cells in correlation with reduced activation of the survival pathway NFĸB, as a consequence of diminished ΙĸB and p65 phosphorylation. Curcumin also reduces the expression of major matrix metalloproteinases (MMPs) due to reduced NFĸ B activity and transcriptional downregulation of AP-1. NFĸ B/p65 silencing is sufficient to downregulate c-jun and MMP expression. Reduced NFĸ B/AP-1 activity and MMP expression lead to diminished invasion through a reconstituted basement membrane and to a significantly lower number of lung metastases in immunodeficient mice after intercardiac injection of 231 cells (p=0.0035). 68% of Curcumin treated but only 17% of untreated animals showed no or very few lung metastases, most likely as a consequence of down-regulation of NFĸ B/AP-1 dependent MMP expression and direct apoptotic effects on circulating tumor cells but not on established metastases. Dietary chemoprevention of metastases appears therefore feasible.

Mechanisms of the antiangiogenic activity by the hop flavonoid xanthohumol: NF-κB and Akt as targets

Xanthohumol (XN), the principal flavonoid of the hop plant (Humulus lupulus L.) and a constituent of beer, has been suggested to have potential cancer chemopreventive activities. We have observed that most cancer chemopreventive agents show antiangiogenic properties in vitro and in vivo, a concept we termed “angioprevention.” Here we show for the first time that XN can inhibit growth of a vascular tumor in vivo. Histopathology and in vivo angiogenesis assays indicated that tumor angiogenesis inhibition was involved. Further, we show the mechanisms for its inhibition of angiogenesis in vivo and related endothelial cell activities in vitro. XN repressed both the NF‐?B and Akt pathways in endothelial cells, indicating that components of these pathways are major targets in the molecular mechanism of XN. Moreover, using in vitro analyses, we show that XN interferes with several points in the angiogenic process, including inhibition of endothelial cell invasion and migration, growth, and formation of a network of tubular‐like structures. Our results suggest that XN can be added to the expanding list of antiangiogenic chemopreventive drugs whose potential in cancer prevention and therapy should be evaluated.

Anti-invasive effects of green tea polyphenol epigallocatechin-3-gallate (EGCG), a natural inhibitor of metallo and serine proteases.

Abstract Several reports have attributed to green tea chemopreventive and therapeutic properties. Epidemiological studies have linked the regular use of green tea to a reduced incidence of breast and colon carcinomas. Tea contains several antioxidants, including polyphenols of the catechin (green tea) and theaflavin (black tea) groups. Green tea derivatives have been shown to act in vitro and in vivo as antiinflammatory, antiviral and antitumor drugs. Despite the extensive body of data only few studies have investigated the molecular mechanisms underlying these effects. In this brief review we focus on the inhibitory activity of catechins derived from green tea toward proteases involved in tumor invasion.

Glycogen Synthase Kinase 3β Regulates Cell Death Induced by Synthetic Triterpenoids

The induction of programmed cell death in premalignant or malignant cancer cells by chemopreventive agents could be a valuable tool to control prostate cancer initiation and progression. In this work, we present evidence that the C-28 methyl ester of the synthetic oleanane triterpenoid 2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid (CDDO-Me) induces cell death in androgen-responsive and unresponsive human prostate cancer cell lines at nanomolar and low micromolar concentrations. CDDO-Me induced caspase-3, caspase-8, and caspase-9 activation; poly(ADP-ribose) polymerase cleavage; internucleosomal DNA fragmentation; and loss of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction in PC3 and DU145 cells. However, caspase-3 and caspase-8 inhibition by Z-DEVD-fmk and Z-IETD-fmk, respectively, or general caspase inhibition by BOC-D-fmk or Z-VAD-fmk did not rescue loss of cell viability induced by CDDO-Me, suggesting the activation of additional caspase-independent mechanisms. Interestingly, CDDO-Me induced inactivating phosphorylation at Ser(9) of glycogen synthase kinase 3beta (GSK3beta), a multifunctional kinase that mediates essential events promoting prostate cancer development and acquisition of androgen independence. The GSK3 inhibitor lithium chloride and, more effectively, GSK3 gene silencing sensitized PC3 and DU145 prostate cancer cells to CDDO-Me cytotoxicity. These data suggest that modulation of GSK3beta activation is involved in the cell death pathway engaged by CDDO-Me in prostate cancer cells.

The AKT/NF-κB inhibitor xanthohumol is a potent anti-lymphocytic leukemia drug overcoming chemoresistance and cell infiltration.

Although the vast majority of patients with acute lymphocytic leukemia (ALL) attain remission with modern therapies, relapsed leukemia will continue to be a common malignancy both in childhood and in adults, until new treatments are available. Therapeutic options for advanced B-cell acute lymphocytic leukemia are still limited and acquired drug resistance and extramedullary tissue infiltration are two major obstacles during treatment. The prenylflavonoid xanthohumol (XN) has shown in vitro and in vivo therapeutic potential against a range of tumors. In the present study we investigated the effects of XN on B-ALL cells in vitro and in an ALL-like xenograft mouse model. Treatment of ALL cell lines with XN resulted in growth arrest and apoptosis induction. XN retained its cytotoxicity when adriamycin resistant cells were examined while ALL cell clones adapted to long-term exposure to XN resulted highly responsive to cytotoxic drugs. Administration of 50μg XN/mouse (5 days/week) significantly increased animal life span by delaying the insurgence of neurological disorders due to leukemic cells dissemination. In agreement with a less invasive phenotype, cell migration and invasion were impaired by XN and basal levels of FAK, AKT and NF-κB signaling pathways were down-regulated in ALL cells upon XN exposure. Our data indicate that XN has significant antileukemic activity both in vitro and in vivo, which associates with impaired cell migration and invasion. Interestingly, this activity overcomes mechanisms leading to drug-resistance. XN represents a promising agent perspective for ALL therapy and recurrence prevention and would deserve clinical testing in the near future.

The chemopreventive retinoid 4HPR impairs prostate cancer cell migration and invasion by interfering with FAK/AKT/GSK3β pathway and β-catenin stability

BackgroundProstate cancer shows an extremely slow progression, appearing in its metastatic, hormone refractory phenotype mostly in elderly men. The chemopreventive targeting of this tumor could accordingly delay its malignancy over life expectancy. The cancer chemopreventive retinoid N-(4 hydroxyphenyl)retinamide (4HPR) has already been shown to restrain prostate cancer growth in vitro and in vivo, though its mechanisms of action are only partially explained.ResultsWe found that 4HPR impairs DU145 and PC3 prostate cancer cells migration and invasion by down-regulating FAK and AKT activation and by enhancing β-catenin degradation, causing the downregulation of target genes like cyclin D1, survivin and VEGF. This non-migratory phenotype was similarly produced in both cell lines by stable silencing of β-catenin. 4HPR was able to decrease AKT phosphorylation also when powerfully upregulated by IGF-1 and, consequently, to impair IGF-1-stimulated cell motility. Conversely, the expression of constitutively active AKT (myr-AKT) overcame the effects of 4HPR and β-catenin-silencing on cell migration. In addition, we found that BMP-2, a 4HPR target with antiangiogenic activity, decreased prostate cancer cell proliferation, migration and invasion by down-regulating the pathway described involving AKT phosphorylation, β-catenin stability and cyclin D1 expression.ConclusionThese data point to 4HPR as a negative regulator of AKT phosphorylation, effectively targeting the β-catenin pathway and inducing a relatively benign phenotype in prostate cancer cells, limiting neoangiogenesis and cell invasion.

Novel cell death pathways induced by N-(4-hydroxyphenyl)retinamide: therapeutic implications.

We previously reported that N-(4-hydroxyphenyl)retinamide (4HPR) inhibits retinoblastoma tumor growth in a murine model in vivo and kills Y79 retinoblastoma cells in vitro. In this work, we assayed different cell death–related parameters, including mitochondrial damage and caspase activation, in Y79 cells exposed to 4HPR. 4HPR induced cytochrome c release from mitochondria, caspase-3 activation, and oligonucleosomal DNA fragmentation. However, pharmacologic inactivation of caspases by the pan-caspase inhibitor BOC-D-fmk, or specific caspase-3 inhibition by Z-DEVD-fmk, was not sufficient to prevent cell death, as assessed by loss of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction, lactate dehydrogenase release, disruption of mitochondrial transmembrane potential (Δψm), and ATP depletion. We found that 4HPR causes lysosomal membrane permeabilization and cytosolic relocation of cathepsin D. Pepstatin A partially rescued cell viability and reduced DNA fragmentation and cytosolic cytochrome c. The antioxidant N-acetylcysteine attenuated cathepsin D relocation into the cytosol, suggesting that lysosomal destabilization is dependent on elevation of reactive oxygen species and precedes mitochondrial dysfunction. Activation of AKT, which regulates energy level in the cell, by the retinal survival facto]r insulin-like growth factor I was impaired and insulin-like growth factor I was ineffective against ATP and Δψm loss in the presence of 4HPR. Lysosomal destabilization, associated with mitochondrial dysfunction, was induced by 4HPR also in other cancer cell lines, including PC3 prostate adenocarcinoma and the vascular tumor Kaposi sarcoma KS-Imm cells. The novel finding of a lysosome-mediated cell death pathway activated by 4HPR could have implications at clinical level for the development of combination chemoprevention and therapy of cancer. [Mol Cancer Ther 2007;6(1):286–98]

ADAM10 new selective inhibitors reduce NKG2D ligand release sensitizing Hodgkin lymphoma cells to NKG2D-mediated killing

ABSTRACT Hodgkin lymphoma (HL) resistant to conventional therapies is increasing, making of interest the search for new schemes of treatment. Members of the “A Disintegrin And Metalloproteases” (ADAMs) family, mainly ADAM10 or ADAM17, have been proposed as therapeutic targets in solid tumors and some ADAMs inhibitors have been shown to exert antitumor effects. We have previously described an overexpression of ADAM10 in HL, together with increased release of NKG2D ligands (NKG2D-L) and reduced activation of effector T lymphocytes with anti-lymphoma capacity. Aim of the present work was to verify whether inhibition of ADAM10 in HL cells could restore the triggering of NKG2D-dependent anti-lymphoma T cell response. As no selective ADAM10 blockers have been reported so far, we synthesized the two hydroxamate compounds LT4 and MN8 with selectivity for ADAM10 over metalloproteases (MMPs), LT4 showing higher specificity for ADAM10 over ADAM17. We show that (i) HL lymph nodes (LN) and cultured HL cells express high levels of the mature active membrane form of ADAM10; (ii) ADAM10 is the major sheddase for the NKG2D-L in HL cells; (iii) the new LT4 and MN8 compounds strongly reduce the shedding of NKG2D-L by HL cell lines and enhance the binding of NKG2D receptor; (iv) of note, these new ADAM10 inhibitors increase the sensitivity of HL cell lines to NKG2D-dependent cell killing exerted by natural killer and γδ T cells. Overall, the biologic activity of LT4 and MN8 appears to be more potent than that of the commercial inhibitor GI254023X.

Transient modulation of cytoplasmic and nuclear retinoid receptors expression in differentiating human teratocarcinoma NT2 cells.

Human embryonal carcinoma Ntera2/D1 (NT2) cells treated with retinoic acid (RA) differentiate into several cell types including post‐mitotic neurons. In this study we asked if RA‐induced differentiation alters the expression of RA and retinol (ROL) binding proteins. The regulation of the intracellular carrier proteins for ROL and RA, cellular retinol binding protein I (CRBP‐I), and cellular retinoic acid binding protein I and II (CRABP‐I, CRABP‐II) were studied along with the nuclear RA receptors RARα, RARβ and RARγ2. PCR analysis of total mRNA from RA‐treated cells showed a biphasic early induction of CRBP‐I, CRABP‐II, and RARγ2 genes. The immediate early gene Krox‐24, a zinc finger transcription factor which is up‐regulated during neuronal differentiation, was also induced, but after 1 week of treatment. The induction of CRBP‐I protein synthesis in differentiating NT2 cells was confirmed by western blotting and immunofluorescence experiments. Conversely, the synthetic retinoid N‐(4‐hydroxyphenyl)retinamide, which induces cell death, but not differentiation in different tumour cell types, did not produce the same modulation on gene expression in NT2 cells. These data suggest that the RA‐specific induction of CRBP‐I and CRABP‐II could be an early event in the process leading to neuronal differentiation of NT2 cells.