Alessio Papi

Cytotoxic and antioxidant activity of 4-methylthio-3-butenyl isothiocyanate from Raphanus sativus L. (Kaiware Daikon) sprouts.

There is high current interest in the chemopreventive potential of Brassica vegetables (cruciferae), particularly due to their content in glucosinolates (GL), which upon myrosinase hydrolysis release the corresponding isythiocyanates (ITC). Some ITCs, such as sulforaphane (SFN) from broccoli ( Brassica oleacea italica), have been found to possess anticancer activity through induction of apoptosis in selected cell lines, as well as indirect antioxidant activity through induction of phase II detoxifying enzymes. Japanese daikon ( Raphanus sativus L.) is possibly the vegetable with the highest per capita consumption within the Brassicaceae family. Thanks to a recently improved gram scale production process, it was possible to prepare sufficient amounts of the GL glucoraphasatin (GRH) as well as the corresponding ITC 4-methylthio-3-butenyl isothiocyanate (GRH-ITC) from its sprouts. This paper reports a study on the cytotoxic and apoptotic activities of GRH-ITC compared with the oxidized counterpart 4-methylsulfinyl-3-butenyl isothiocyanate (GRE-ITC) on three human colon carcinoma cell lines (LoVo, HCT-116, and HT-29) together with a detailed kinetic investigation of the direct antioxidant/radical scavenging ability of GRH and GRH-ITC. Both GRH-ITC and GRE-ITC reduced cell proliferation in a dose-dependent manner and induced apoptosis in the three cancer cell lines. The compounds significantly ( p < 0.05) increased Bax and decreased Bcl2 protein expression, as well as producing caspase-9 and PARP-1 cleavage after 3 days of exposure in the three cancer cell lines. GRH-ITC treatment was shown to have no toxicity with regard to normal human lymphocytes (-15 +/- 5%) in comparison with SFN (complete growth inhibition). GRH and GRH-ITC were able to quench the 2,2-diphenyl-1-picrylhydrazyl radical, with second-order rate constants of 14.0 +/- 2.8 and 43.1 +/- 9.5 M(-1) s(-1), respectively (at 298 K in methanol), whereas the corresponding value measured here for the reference antioxidant alpha-tocopherol was 425 +/- 40 M (-1) s (-1). GRH reacted with H2O2 and tert-butyl hydroperoxide in water (pH 7.4) at 37 degrees C, with rate constants of 1.9 +/- 0.3 x 10(-2) and 9.5 +/- 0.3 x 10(-4) M(-1) s (-1) (paralleling recently developed synthetic antioxidants) being quantitatively (>97%) converted to GRE. It is demonstrated that GRH-ITC has interesting antioxidant/radical scavenging properties, associated with a selective cytotoxic/apoptotic activity toward three human colon carcinoma cell lines, and very limited toxicity on normal human T-lymphocytes.

(-)-Epigallocatechin-3-gallate downregulates Pg-P and BCRP in a tamoxifen resistant MCF-7 cell line.

We investigated the anticancer effect of EGCG treatment on a breast carcinoma cell line resistant to tamoxifen (MCF-7Tam cells). As there are no reports about the molecular mechanisms implicated in EGCG treatment of tamoxifen resistant breast carcinoma cells, we studied the effects of EGCG treatment on three plasma membrane proteins that are involved in the mechanism of drug-resistance: Multidrug Resistance Protein (MRP1), P-glycoprotein (P-gp) and Breast Cancer Resistance Protein (BCRP). EGCG treatment (10-100 microg/ml for 24-72 hours) caused cell growth inhibition and dose-dependent apoptosis: after 100 microg/ml EGCG treatment for 24 hours, Bax expression increased and Bcl2 expression decreased (p<0.05). Coherently, Annexin V-FITC apoptosis assay detected a significant increase in labelled cells (p<0.05). EGCG did not affect MRP1: in contrast, 100 microg/ml EGCG administration caused P-gp decrease to 53% of control cells (p<0.001) and this effect was not due to downregulation of P-gp gene expression. EGCG induced P-gp decrease even when MG132, a strong proteasome inhibitor, was given together with EGCG to MCF-7Tam cells. EGCG treatment also inhibited BCRP activity: mRNA transcription and protein level did not change after treatment, but mitoxantrone test demonstrated a strong inhibition of BCRP activity (p<0.001). In conclusion, the present results showed that EGCG could down-regulate the activity of two molecules that play a key role in drug metabolism and transport and that are highly expressed in tamoxifen resistant breast carcinoma cells. The interaction of EGCG and drugs used in the therapy of estrogen sensitive breast carcinoma ought to be subject of studies and the potential use of EGCG in drug-resistant diseases ought to be better considered.

(-)-Epigallocatechin-3-gallate down-regulates EGFR, MMP-2, MMP-9 and EMMPRIN and inhibits the invasion of MCF-7 tamoxifen-resistant cells.

The activation of the EGFR (epidermal growth factor receptor) signalling pathway is one of the key mechanisms underlying the development of resistance to tamoxifen in breast cancer patients. As EGCG [(-)-epigallocatechin-3-gallate], the most active catechin present in green tea, has been shown to down-regulate EGFR, we studied the effects of 10-100 μg/ml EGCG treatment on growth and invasion in a breast carcinoma cell line resistant to tamoxifen [MCF-7Tam (MCF-7 breast carcinoma cell line resistant to tamoxifen) cells] and parental MCF-7. A dose-dependent down-regulation of EGFR mRNA expression and protein level occurred after 50 μg/ml EGCG treatment of MCF-7Tam cells. EGFR molecules on the plasma membrane surface of MCF-7Tam cells significantly decreased. EGFR phosphorylation (Tyr-992, Tyr-1045 and Tyr-1068) was higher in MCF-7Tam than in MCF-7 and it was reduced by EGCG treatment. ERK (extracellular regulated kinase) and phospho-ERK p42/44 were also down-regulated by EGCG treatment and in vitro cell growth and invasion decreased. MMP-2 (matrix metalloproteinase-2) and MMP-9, which are implicated in cell invasion and metastasis, and EMMPRIN (extracellular matrix metalloproteinase inducer), a glycoprotein able to activate MMPs, were significantly reduced after 50 μg/ml EGCG treatment. In keeping with this, TIMP-1 (tissue inhibitor of metalloproteinases-1) and TIMP-2, which down-regulate MMPs, increased after EGCG treatment. Altogether, the present data demonstrated that EGCG could attenuate the tamoxifen-resistant phenotype of MCF-7Tam cells. EGCG could stop MCF-7Tam cell growth and in vitro invasion through down-regulation of EGFR and other molecules implicated in aggressive biological behaviour. The present data support the hypothesis that EGCG is an interesting molecule to be investigated in tamoxifen-resistant breast carcinoma.

PPARγ and RXRγ ligands act synergistically as potent antineoplastic agents in vitro and in vivo glioma models

Glioblastoma represent the most common primary brain tumor in adults and are currently considered incurable. We investigated antiproliferative and anti‐invasive mechanisms of 6‐OH‐11‐O‐hydroxyfenantrene (IIF), a retinoid X receptor ligand, and pioglitazone (PGZ), a peroxisome proliferator‐activated receptor γ activator, in three different glioblastoma cell lines. A dose‐dependent reduction of tumor invasion and strong decrease of matrix metalloproteinases 2 and 9 expression was observed, especially when a combination therapy of IIF and PGZ was administered. Combined treatment also markedly reduced proliferation and induced apoptosis in all glioma cell lines tested. This was in particular accompanied by decrease of antiapoptotic proteins Bcl2 and p53, while simultaneously pro‐apoptotic cytochrome c, cleaved caspase 3, Bax and Bad levels increased. These in vitro findings were further substantiated in a murine glioma model in vivo, where oral administration of PGZ and IIF resulted in significantly reduced tumor volume and proliferation. Of note, treatment with nuclear receptor ligands was not only effective when the treatment was initiated shortly after the intraparenchymal seeding of the glioma cells, but even when initiated in the last third of the observation period. Collectively, our results demonstrate the effectiveness of a combined treatment of ligands of proliferator‐activated receptor and retinoid X receptor against glioblastoma.

Vitexin-2-O-xyloside, raphasatin and (-)-epigallocatechin-3-gallate synergistically affect cell growth and apoptosis of colon cancer cells.

Cytotoxic effects of the combination of the food components vitexin-2-O-xyloside (X), raphasatin (4-methylsulphanyl-3-butenyl isothiocyanates; G) and (-)-epigallocatechin-3-gallate (E) were investigated in colon (LoVo and CaCo-2) and breast (MDA-MB-231 and MCF-7) cancer cells. Breast cancer cells were more resistant than colon cells to X, G and E inhibition. On the contrary, marked synergistic effects among X, G and E on cell growth were found in both colon cancer cells. Further analysis revealed a G0/G1 arrest of the phase cell progression and apoptosis, linked to modulation of Bax, Bcl2, caspase-9 and poly(ADP-ribose) polymerase as well as Reactive Oxygen Species (ROS) generation in both colon cancer cells, whereas apoptosis and ROS were not significantly detected in normal human lymphocytes. We conclude that the X, G and E mixture might act by mitochondrial pathway activation of apoptosis, possibly elicited by ROS and the mixture may be effective in the chemoprevention of colon cancer.

PPARγ and RXR Ligands Disrupt the Inflammatory Cross‐talk in the Hypoxic Breast Cancer Stem Cells Niche

Cancer stem cells (CSCs) are affected by the local micro‐environment, the niche, in which inflammatory stimuli and hypoxia act as steering factors. Here, two nuclear receptors (NRs) agonists, i.e. pioglitazone (PGZ), a ligand of peroxisome proliferator activated receptor‐γ, and 6‐OH‐11‐O‐hydroxyphenanthrene (IIF), a ligand of retinoid X receptors, were investigated for their capability to interference with the cross‐talk between breast CSCs and the niche compartment. We found that IIF potentiates the ability of PGZ to hamper the mammospheres‐forming capability of human breast tumours and MCF7 cancer cells, reducing the expression of CSCs regulatory genes (Notch3, Jagged1, SLUG, Interleukin‐6, Apolipoprotein E, Hypoxia inducible factor‐1α and Carbonic anhydrase IX). Notably, these effects are not observed in normal‐MS obtained from human breast tissue. Importantly, NRs agonists abolish the capability of hypoxic MCF7 derived exosomes to induce a pro‐inflammatory phenotype in mammary glands fibroblasts. Moreover, NRs agonist also directly acts on breast tumour associated fibroblasts to downregulate nuclear factor‐κB pathway and metalloproteinases (MMP2 and MMP9) expression and activity. In conclusion, NRs agonists disrupt the inflammatory cross‐talk of the hypoxic breast CSCs niche. J. Cell. Physiol. 229: 1595–1606, 2014.

RXRγ and PPARγ ligands in combination to inhibit proliferation and invasiveness in colon cancer cells

Nuclear retinoid X receptors (RXRs) and peroxisome proliferator-activated receptors (PPARs are potential candidates as drug target for cancer prevention and treatment. We investigated if the rexinoid 6-OH-11-O-hydroxyphenantrene (IIF) potentiates the antitumoral properties of PPARgamma ligands as ciglitazone and pioglitazone, on two colon cancer cell lines: HCA-7 and HCT-116. Drugs inhibited cell growth and induced apoptosis synergistically. The combination resulted in a decrease of cyclooxigenase-2, metalloproteinases-2 and -9 expression level and activity while PPARgamma, RXRgamma and tissue inhibitors of metalloproteinase-1 and -2 expression were increased. Finally, IIF potentiated PPAR transcriptional activity by enhancement of peroxisome proliferator response elements transactivation.

Peroxisome Proliferator Activated Receptor-α/Hypoxia Inducible Factor-1α Interplay Sustains Carbonic Anhydrase IX and Apoliprotein E Expression in Breast Cancer Stem Cells

Aims Cancer stem cell biology is tightly connected to the regulation of the pro-inflammatory cytokine network. The concept of cancer stem cells “inflammatory addiction” leads to envisage the potential role of anti-inflammatory molecules as new anti-cancer targets. Here we report on the relationship between nuclear receptors activity and the modulation of the pro-inflammatory phenotype in breast cancer stem cells. Methods Breast cancer stem cells were expanded as mammospheres from normal and tumor human breast tissues and from tumorigenic (MCF7) and non tumorigenic (MCF10) human breast cell lines. Mammospheres were exposed to the supernatant of breast tumor and normal mammary gland tissue fibroblasts. Results In mammospheres exposed to the breast tumor fibroblasts supernatant, autocrine tumor necrosis factor-α signalling engenders the functional interplay between peroxisome proliferator activated receptor-α and hypoxia inducible factor-1α (PPARα/HIF1α). The two proteins promote mammospheres formation and enhance each other expression via miRNA130b/miRNA17-5p-dependent mechanism which is antagonized by PPARγ. Further, the PPARα/HIF1α interplay regulates the expression of the pro-inflammatory cytokine interleukin-6, the hypoxia survival factor carbonic anhydrase IX and the plasma lipid carrier apolipoprotein E. Conclusion Our data demonstrate the importance of exploring the role of nuclear receptors (PPARα/PPARγ) in the regulation of pro-inflammatory pathways, with the aim to thwart breast cancer stem cells functioning.

Betalains increase vitexin-2-O-xyloside cytotoxicity in CaCo-2 cancer cells

Vitexin-2-O-xyloside (XVX) from Beta vulgaris var. cicla L. (BVc) seeds, betaxanthin (R1) and betacyanin (R2) fractions from Beta vulgaris var. rubra L. (BVr) roots were combined and tested for cytotoxicity in CaCo-2 colon cancer cells. XVX was the most cytotoxic molecule, but the combination of XVX with R1 and R2 significantly prolonged its cytotoxicity. Cytotoxicity was mediated by the intrinsic apoptotic pathway, as shown by an increase in Bcl2-like protein 4, cleaved Poly ADP-Ribosyl Polymerase 1 and cleaved Caspase 3 levels with a parallel decrease in anti-apoptotic protein B-cell leukemia/lymphoma 2 levels. R1 and R2, used alone or in combination, reduced oxidative stress triggered by H2O2 in CaCo-2 cells. Betalains dampened cyclooxygenase-2 and interleukin-8 mRNA expression after lipopolysaccharide induction in CaCo-2, showing an anti-inflammatory action. Our results support the use of a cocktail of R1, R2 and XVX as a chemopreventive tool against colon cancer.

Drug delivery by polymeric micelles: an in vitro and in vivo study to deliver lipophilic substances to colonocytes and selectively target inflamed colon

UNLABELLED Colitis is the term used for chronic inflammatory bowel diseases at substantially increased risk of developing a form of colorectal cancer (CRC) known as colitis-associated cancer. In our study we synthesized core-shell polymeric micelles obtained by self-assembly of block copolymers for high efficiency delivery of anti-inflammatory and anti-cancer compounds to colonocytes and colon mucosa. We achieved an efficient intracellular delivery of these hydrophobic compounds (prednisone, retinoic acid and doxorubicin) to cultured colonocytes without cellular toxicity. The efficacy of retinoic acid and doxorubicin administration was significantly increased using these nanosized carriers. Moreover, these polymeric micelles have been shown to overcome the multidrug resistance efflux mechanism effectively delivering doxorubicin to multidrug-resistant colon cancer cells. These nanocarriers are also suitable for selective in vivo delivery of lipophilic drugs by enema administration to the inflamed colon tissue, specifically targeting the inflamed mucosa. FROM THE CLINICAL EDITOR This team of investigators studied polymeric micelles as highly efficient drug delivery systems enabling intracellular delivery of hydrophobic compounds (prednisone, retinoic acid, and doxorubicin) to cultured colonocytes without cellular toxicity, also demonstrating beneficial in vivo effects.