Hyperforin and Myrtucommulone Derivatives Act as Natural Modulators of Wnt/β-Catenin Signaling in HCT116 Colon Cancer Cells

The therapeutic activities of natural plant extracts have been well known for centuries. Many of them, in addition to antiviral and antibiotic effects, turned out to have anti-tumor activities by targeting different signaling pathways. The canonical Wnt pathway represents a major tumorigenic pathway deregulated in numerous tumor entities, including colon cancer. Here, we investigated the acylphloroglucinols hyperforin (HF) from St. John’s wort (Hypericum perforatum L.) and myrtucommulone A (MC A) from myrtle (Myrtus communis) and semi-synthetic derivatives thereof (HM 177, HM 297, HM298) for their effects on Wnt/β-catenin signaling. None of these substances revealed major cytotoxicity on STF293 embryonic kidney and HCT116 colon carcinoma cells at concentrations up to 10 μM. At this concentration, HF and HM 177 showed the strongest effect on cell proliferation, whereas MC A and HM 177 most prominently inhibited anchorage-independent growth of HCT116 cells. Western blot analyses of active β-catenin and β-catenin/TCF reporter gene assays in STF293 cells revealed inhibitory activities of HF, MC A and HM 177. In line with this, the expression of endogenous Wnt target genes, Axin and Sp5, in HCT116 cells was significantly reduced. Our data suggest that the acylphloroglucinols hyperforin, myrtucommulone A and its derivative HM 177 represent potential new therapeutic agents to inhibit Wnt/β-catenin signaling in colon cancer.     

Identification of estrogen regulated genes in Fe33 rat hepatoma cells by differential display polymerase chain reaction and their hormonal regulation in rat liver and uterus

We applied the differential display RT-PCR (ddRT-PCR) technology to identify estrogen-regulated hepatic genes in the estrogen receptor expressing rat hepatoma cell line Fe33. Three genes of known sequences were detected by the ddRT-PCR approach: IGF binding protein-1 (IGFBP-1), vitamin D-dependent calcium-binding protein (CaBP9k) and major acute phase protein (MAP). Effects of ethinyl estradiol on the mRNA levels of these genes were confirmed by "Northern-blot" analysis. If given in combination with dexamethasone and glucagon, ethinyl estradiol caused 40-, 15- and 11-fold increases in the mRNA steady state level of IGFBP-1, CaBP9k and MAP, respectively, in Fe33 cells 24 h after addition of hormone. Besides ethinyl estradiol, the partial estrogen agonist OH-tamoxifen caused dose dependent effects on expression of MAP and IGFBP-1. Estrogen regulation of the respective genes and the modulatory effects of progesterone (10 mg/animal/day) were studied in ovariectomized rats treated subcutaneously for 14 days with 1 microgram/animal/day estradiol. "Northern-blot" analysis of liver RNA revealed a 6-fold stimulation of IGFBP-1 mRNA levels in estradiol-treated compared to vehicle-treated rats and a weak but detectable increase of MAP mRNA steady state level (1.6-fold) upon estradiol administration. No effect of estradiol treatment could be monitored for CaBP9k in rat liver. Modulatory effects of progesterone on estradiol-stimulated expression in the liver could be monitored for IGFBP-1 only. In an extension of our investigation on the expression of the three genes in rat liver, we determined their expression and hormonal regulation in the uterus of the same animals. In the uterus, estradiol caused an increase in CaBP9k mRNA. In contrast, IGFBP-1 mRNA levels increased dramatically upon progesterone administration, whereas no effect of estradiol treatment could be detected. MAP mRNA levels increased only after coadministration of estradiol and progesterone. In conclusion, the ddRT-PCR proved to be a powerful method to identify estrogen-regulated genes. The study on the hormonal regulation of three genes stimulated by estrogen in Fe33 cells revealed similarities and differences in their regulation in vivo and in vitro.     

TiO2/WO3 hybrid structures produced through a sacrificial polymer layer technique for pollutant photo- and photoelectrooxidation under ultraviolet and visible light illumination

TiO₂/WO₃ hybrid structures were produced on graphite substrates following a three step procedure: (i) electrochemical deposition of WO₃ under potentiostatic conditions, (ii) electrochemical deposition of TiO₂–polyaniline (PANI) composite layers by potentiostatic polymerization of aniline in the presence of TiO₂ nanoparticles, (iii) high temperature (450 °C) treatment for decomposition of the PANI structure. Experiments on the photoelectrochemical response of the composite layers were carried out by cyclic voltammetry and chronoamperommetry in the dark and under illumination by using low power lamps emitting in the visible and UV spectrum ranges. The oxidation of three pollutants—oxalate ions, methanol and malachite green was used to evaluate the photoelectrocatalytic activity of the TiO₂/WO₃ structures. The photocurrents registered for the photooxidation of oxalate were higher than photocurrents measured at hybrid TiO₂/WO₃ electrodes obtained in conventional two-step electrodeposition of WO₃ and subsequently TiO₂ from corresponding salt solutions. The efficiency of the malachite green photodegradation in our experiments was also about two orders of magnitude higher than that obtained in TiO₂/WO₃ structures synthesized in a conventional way. These results are (very probably) due to the proposed synthetic approach involving PANI polymer layer as an immobilizing matrix and the opportunity to disperse homogeneously TiO₂ nanoparticles on the WO₃ surface provided.