Triterpenoids as new promising anticancer drugs

Triterpenoids are structurally diverse organic compounds, characterized by a basic backbone modified in multiple ways, allowing the formation of more than 20 000 naturally occurring triterpenoid varieties. Several triterpenoids, including ursolic and oleanolic acid, betulinic acid, celastrol, pristimerin, lupeol, and avicins possess antitumor and anti-inflammatory properties. To improve antitumor activity, some synthetic triterpenoid derivatives have been synthesized, including cyano-3,12-dioxooleana-1,9 (11)-dien-28-oic (CDDO), its methyl ester (CDDO-Me), and imidazolide (CDDO-1m) derivatives. Of these, CDDO, CDDO-Me, and betulinic acid have shown promising antitumor activities and are presently under evaluation in phase I studies. Triterpenoids are highly multifunctional and the antitumor activity of these compounds is measured by their ability to block nuclear factor-kappa B activation, induce apoptosis, inhibit signal transducer, and activate transcription and angiogenesis. Anti-Cancer Drugs 20:880-892 (C) 2009 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins

Autocrine role of angiopoietins during megakaryocytic differentiation.

The tyrosine kinase Tie-2 and its ligands Angiopoietins (Angs) transduce critical signals for angiogenesis in endothelial cells. This receptor and Ang-1 are coexpressed in hematopoietic stem cells and in a subset of megakaryocytes, though a possible role of angiopoietins in megakaryocytic differentiation/proliferation remains to be demonstrated. To investigate a possible effect of Ang-1/Ang-2 on megakaryocytic proliferation/differentiation we have used both normal CD34(+) cells induced to megakaryocytic differentiation and the UT7 cells engineered to express the thrombopoietin receptor (TPOR, also known as c-mpl, UT7/mpl). Our results indicate that Ang-1/Ang-2 may have a role in megakaryopoiesis. Particularly, Ang-2 is predominantly produced and released by immature normal megakaryocytic cells and by undifferentiated UT7/mpl cells and slightly stimulated TPO-induced cell proliferation. Ang-1 production is markedly induced during megakaryocytic differentiation/maturation and potentiated TPO-driven megakaryocytic differentiation. Blocking endogenously released angiopoietins partially inhibited megakaryocytic differentiation, particularly for that concerns the process of polyploidization. According to these data it is suggested that an autocrine angiopoietin/Tie-2 loop controls megakaryocytic proliferation and differentiation

Proteasome inhibitors sensitize ovarian cancer cells to TRAIL induced apoptosis

In the present study we have explored the sensitivity of ovarian cancer cells to TRAIL and proteasome inhibitors. Particularly, we have explored the capacity of proteasome inhibitors to bypass TRAIL resistance of ovarian cancer cells. For these studies we have used the A2780 ovarian cancer cell line and its chemoresistant derivatives A2780/DDP and A2780/ADR, providing evidence that: (i) the three cell lines are either scarcely sensitive (A2780 and A2780/ADR) or moderately sensitive (A2780/DDP) to the cytotoxic effects of TRAIL; (ii) the elevated c-FLIP expression observed in ovarian cancer cells is a major determinant of TRAIL resistance of these cells; (iii) proteasome inhibitors (PS-341 or MG132) are able to exert a significant pro-apoptotic effect and to greatly enhance the sensitivity of both chemosensitive and chemoresistant A2780 cells to TRAIL; (iv) proteasome inhibitors damage mitochondria through stabilization of BH3-only proteins, Bax and caspase activation and significantly enhance TRAIL-R2 expression; (v) TRAIL-R2, but not TRAIL-R1, mediates the apoptotic effects of TRAIL on ovarian cancer cells. Importantly, studies on primary ovarian cancer cells have shown that these cells are completely resistant to TRAIL and proteasome inhibitors markedly enhance the sensitivity of these cells to TRAIL. Given the high susceptibility of ovarian cancer cells to proteasome inhibitors, our results further support the experimental use of these compounds in the treatment of ovarian cancer

A small molecule Smac mimic potentiates TRAIL-mediated cell death of ovarian cancer cells

Objectives.: Ovarian cancer remains a leading cause of death in women and development of new therapies is essential. Second mitochondria derived activator of caspase (Smac) has been described to sensitize for apoptosis. We have explored the proapoptotic activity of a small molecule mimic of Smac/DIABLO on ovarian cancer cell lines (A2780 cells and its chemoresistant derivatives A2780/ADR and A2780/DDP), cancer cell lines and in primary ovarian cancer cells. Methods.: The effects of a small molecule mimic of Smac/DIABLO on ovarian cancer cell lines and primary ovarian cancer cells were determined by cell proliferation, apoptosis and biochemical assays. Results.: This compound added alone elicited only a weak proapoptotic effect; however, it strongly synergizes with tumor necrosis factor-related apoptosis inducing ligand (TRAIL) or agonistic TRAILR2 antibody (Lexatumumab) in inducing apoptosis of ovarian cancer cells. Conclusions.: These observations suggest that small molecule mimic of Smac/DIABLO could be useful for the development of experimental strategies aiming to treat ovarian cancer. Interestingly, in addition to its well known proapoptotic effects, Smac/DIABLO elicited a significant increase of pro-caspase-3 levels. © 2007 Elsevier Inc. All rights reserved

Additional file 1: Figures S1A, S1B, and S1C. of PML-RAR alpha induces the downmodulation of HHEX: a key event responsible for the induction of an angiogenetic response

Figure S1A Analysis of HHEX (top panel) and VEGF-A (middle panel) reported in 176 primary AMLs on the TCGA platform. The HHEX/VEGF-A ratio is reported in the bottom panel. Figure S1B Correlation between HHEX and VEGF-A levels observed in 18 primary APLs in the present study (p = 0.0484) and in 16 primary APLs in the TCGA data (p = 0.0284). Figure S1C Correlation between HHEX and VEGF-A levels observed in 18 primary APLs (p = 00484) and in 20 primary M5 AMLs in the TCGA data (p = 0.0174). (ZIP 689 kb

High sensitivity of ovarian cancer cells to the synthetic triterpenoid CDDO-Imidazolide

In the present study we have explored the sensitivity of ovarian cancer cells to the synthetic triterpenoid CDDO-Imidazolide (CDDO-Im). For these studies we have used the A2780 ovarian cancer cell line and its chemoresistant derivatives A2780/ADR and A2780/CISP, OVCAR3, SKOV3 and HEY cancer cell lines and primary ovarian cancer cells, providing evidence that: (i) the majority of these cell lines are highly sensitive to the pro-apoptotic effects induced by CDDO-Im: (ii) TRAIL, added alone exerted only a weak proapoptotic, but clearly potentiated the cytotoxic effect elicited by CDDO-Im; (iii) the apoptotic effect induced by CDDO-Im involves GSH depletion, c-FLIP downmodulation and caspase-8 activation: (iv) CDDO-Im inhibits STAT3 activation and CDDO-Im sensitivity is inversely related to the level of constitutive STAT3 activation. Importantly, studies on primary ovarian cancer cells have shown that these cells are sensitive to the pro-apoptotic effects of CDDO-Im. These observations support the experimental use of synthetic triterpenoids in the treatment of ovarian cancer. (C) 2009 Elsevier Ireland Ltd. All rights reserved

Angiopoietin and TPO-induced cell signaling in HUVEC cells.

<p>HUVEC cells, grown under standard endothelial cell culture conditions, have been starved overnight of growth factors and stimulated as indicated in panel B of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0039796#pone-0039796-g010" target="_blank">Fig.10</a>. <i>A –</i> Flow cytometry and Western Blot analysis of Tie-2 expression in HUVEC cells starved of growth factors and then stimulated for 15 min either in the absence (C ) or in the presence of either TPO or Ang-1 or Ang-2. <i>B and C</i> - WB and densitometric quantification (<i>top</i> and <i>bottom</i> panels, respectively).</p

Growth, differentiation, Tie-2 and Tie-1 expression in UT7/mpl cells. A:

<p>Cell growth curve of UT7/mpl cells grown in the presence of GM-CSF or TPO. <b>B</b>: CD41 and CD61 (mean values ± SEM in three separate experiments) expression in UT7/mpl cells grown for 7 days either in the presence of GM-CSF or TPO. <b>C</b>: Proportion of cells with polylobated nuclei (mean values ± SEM in three separate experiments) at day 7 of either GM-CSF or TPO treatment. <b>D</b>: Flow cytometric analysis of Tie-2 expression in UT7/mpl cells grown either in the absence of growth factors (starved) or in the presence of either GM-CSF or TPO or Ang-1 or Ang-2 for 36 h. <b>E</b>: Mean Fluorescence Intensity (MFI) values of Tie-2 expression as evaluated by flow cytometry analysis. The data represent the mean values ± SEM observed in three separate experiments. <b>F</b>: Western blotting analysis of Tie-2 and TPO-R expression in UT7/mpl cells grown as above. <b>G</b>: Quantification of western blot results by band densitometry analysis (Mean Absorbance Units ± SEM from three separate experiments). <b>H</b>: Tie-1 expression in UT7/mpl cells. Flow cytometric analysis of Tie-1 expression in UT7/mpl cells deprived for 36 h of growth factors (starved) or grown for 36 h either in the presence of either GM-CSF, TPO, Ang-1, Ang-2, TPO+Ang-1 or TPO+Ang-2. In the first seven panels, from the top to the bottom a representative flow cytometry analysis of Tie-1 is shown. Mean Fluorescence Intensity (MFI) values (mean values ± SEM observed in three separate experiments) are reported in <b>I</b>. *, **, ***: p<0.05, p<0.01, p<0.001, respectively.</p

Angiopoietin and TPO-induced cell signaling in UT7/mpl cells and in normal megakaryocytes.

<p><i>A –</i> Flow cytometry and Western Blot analysis of Tie-2 expression in UT7/mpl cells starved for 16 h of growth factors and then stimulated for 15 min either in the absence (C ) or in the presence of either TPO or Ang-1 or Ang-2. <i>B</i> – UT7/mpl cells have been starved for 16 h of growth factors and then stimulated for various times (15, 90 and 180 min) with either TPO or Ang-1 or Ang-2 or TPO+Ang-1 or TPO+Ang-2. The cells were then harvested, lysed and analyzed by western blotting for the expression of p-ERK-1/−2, p-38, p-STAT-5A and p-AKT and their non-phosphorylated forms. Beta-actin was used to normalize for sample loading. A representative experiment out of three performed is shown. <i>C</i> – Day 7 megakaryocytes derived from unilineage cell cultures of normal CB CD34⁺ cells have been first starved for 6 h of exogenous growth factors and then stimulated for various times (15, 30 or 60 min) with either TPO or Ang-1 or Ang-2. Cells were then washed, lysed and processed as above. Beta-actin was used to normalize for sample loading. <i>D-E</i> Densitometric analysis of WB autoradiograms, performed on UT7/mpl (<i>panel D</i>) or d7 PB MKs (<i>panel E</i>) expressed as absorbance arbitrary units. The results represent the mean values observed in three separate experiments.</p

Tie-2 expression during Mk differentiation of cord blood or peripheral blood cord blood or peripheral blood CD34⁺ cells.

<p>Kinetics of Tie-2 expression during TPO-driven megakaryocytic differentiation of cord blood (CB, <i>Left Panels</i>) or cord blood (PB, <i>Right Panels</i>) CD34⁺ cells. Purified CB or PB CD34⁺ cells have been grown in serum-free medium in the presence of TPO and, at various days of culture, cell aliquots have been harvested and and analyzed for cell growth (<i>top panels</i>), for Tie-2 expression at mRNA and protein level (mean percentage of positive cells ± SEM observed in three separate experiments, <i>middle panels</i>) and for the expression of membrane differentiation markers CD34, CD41, CD61 and CD42b (<i>bottom panels</i>). In the <i>inset</i> the Tie-2 WB analysis on Mks grown from PB is reported. Mean values ± SEM observed in three separate experiments.</p