Effect of beta-Carotene on the development of the solid Ehrlich tumor in mice

Synthetic Diphenylacetylene-Based Retinoids Induce DNA Damage in Chinese Hamster Ovary Cells without Altering Viability

All-trans-retinoic acid (ATRA), the active metabolite of vitamin A, plays a pivotal role in cell differentiation, proliferation and embryonic development. It is an effective therapy for dermatological disorders and malignancies. ATRA is prone to isomerization and oxidation, which can affect its activity and selectivity. Novel diphenylacetylene-based ATRA analogues with increased stability can help to overcome these problems and may offer significant potential as therapeutics for a variety of cancers and neurodegenerative diseases, including amyotrophic lateral sclerosis. Here, we investigated the effects of these retinoids on cell viability and genotoxicity in the widely used model system of the rapidly proliferating Chinese hamster ovary cell line. DC360 is a fluorescent ATRA analogue and DC324 is a non-active derivative of DC360. EC23, DC525, DC540, DC645, and DC712 are promising analogues with increased bioactivity. The cytotoxic activity of the compounds was evaluated by ATP assay and DNA damage was tested by comet assay. No cytotoxicity was observed in the 10⁻⁶–10⁻⁵ M concentration range. All compounds induced DNA migration similar to ATRA, but DC324, DC360 and EC23 did so to a greater extent, particularly at higher concentrations. We believe that retinoid receptor-independent genotoxicity is a general characteristic of these compounds; however, further studies are needed to identify the molecular mechanisms and understand their complex biological functions.

Anticancer and Anti-Inflammatory Activities of a Standardized Dichloromethane Extract from Piper umbellatum L. Leaves

Despite the advances in anticancer drug discovery field, the worldwide cancer incidence is remarkable, highlighting the need for new therapies focusing on both cancer cell and its microenvironment. The tumor microenvironment offers multiple targets for cancer therapy, including inflammation. Nowadays, almost 75% of the anticancer agents used in chemotherapy are derived from natural products, and plants are an important source of new promising therapies. Continuing our research on Piper umbellatum species, here we describe the anticancer (in vitro antiproliferative activity and in vivo Ehrlich solid tumor model) and anti-inflammatory (carrageenan-induced paw edema and peritonitis models) activities of a standardized dichloromethane extract (SDE) from P. umbellatum leaves, containing 23.9% of 4-nerolidylcatechol. SDE showed in vitro and in vivo antiproliferative activity, reducing Ehrlich solid tumor growth by 38.7 and 52.2% when doses of 200 and 400 mg/kg, respectively, were administered daily by oral route. Daily treatments did not produce signals of toxicity. SDE also reduced paw edema and leukocyte migration on carrageenan-induced inflammation models, suggesting that the anticancer activity of SDE from Piper umbellatum leaves could involve antiproliferative and anti-inflammatory effects. These findings highlight P. umbellatum as a source of compounds against cancer and inflammation.

Design and synthesis of N-acylated aza-goniothalamin derivatives and evaluation of their in vitro and in vivo antitumor activity

Herein we describe the synthesis of a focused library of compounds based on the structure of goniothalamin (1) and the evaluation of the potential antitumor activity of the compounds. N-Acylation of aza-goniothalamin (2) restored the in vitro antiproliferative activity of this family of compounds. 1-(E)-But-2-enoyl-6-styryl-5,6-dihydropyridin-2(1H)-one (18) displayed enhanced antiproliferative activity. Both goniothalamin (1) and derivative 18 led to reactive oxygen species generation in PC-3 cells, which was probably a signal for caspase-dependent apoptosis. Treatment with derivative 18 promoted Annexin V/7-aminoactinomycin D double staining, which indicated apoptosis, and also led to G2 /M cell-cycle arrest. In vivo studies in Ehrlich ascitic and solid tumor models confirmed the antitumor activity of goniothalamin (1), without signs of toxicity. However, derivative 18 exhibited an unexpectedly lower in vivo antitumor activity, despite the treatments being administered at the same site of inoculation. Contrary to its in vitro profile, aza-goniothalamin (2) inhibited Ehrlich tumor growth, both on the ascitic and solid forms. Our findings highlight the importance of in vivo studies in the search for new candidates for cancer treatment.

Effect of goniothalamin on the development of Ehrlich solid tumor in mice

In this work the antiproliferative activity of goniothalamin (1), both in racemic and in its enantiomeric pure forms, in a solid tumor experimental model using laboratory animals is described. The antiedematogenic activity displayed by racemic 1 in the carrageenan edema model in mice together with the reduction of Ehrlich solid tumor model suggest a relationship between anticancer and antiinflammatory activities with the antiinflammatory activity favoring the antiproliferative activity itself.

Translocator protein (18 kDa) mediates the pro-growth effects of diazepam on Ehrlich tumor cells in vivo

The Translocator Protein (TSPO), previously known as the peripheral-type benzodiazepine receptor, is a ubiquitous drug- and cholesterol-binding protein that is up regulated in several types of cancer cells. TSPO drug ligands (e.g., diazepam) induce or inhibit tumor cell proliferation, depending on the dose and tissue origin. We have previously shown that TSPO is expressed in Ehrlich tumor cells and that diazepam increases proliferation of these cells in vitro. Here, we investigated the in vivo effects of diazepam on Ehrlich tumor growth and the role of TSPO in mediating this process. Oral administration of diazepam to mice (3.0mg/kg/day for 7 days) produced plasma and ascitic fluid drug concentrations of 83.83 and 54.12 nM, respectively. Diazepam increased Ehrlich tumor growth, likely due to its ability to increase tumor cell proliferation and Reactive Oxygen Species production. Radioligand binding assays and nucleotide sequencing revealed that Ehrlich tumor cell TSPO had the same pharmacological and biochemical properties as TSPO described in other tumor cells. The estimated K(d) for PK 11195 in Ehrlich tumor cells was 0.44 nM and 8.70 nM (low and high binding site, respectively). Structurally diverse TSPO drug ligands with exclusive affinity for TSPO (i.e., 4-chlordiazepam, Ro5-4864, and isoquinoline-carboxamide PK 11195) also increased Ehrlich tumor growth. However, clonazepam, a GABA(A)-specific ligand with no affinity for TSPO, failed to do so. Taken together, these data suggest that diazepam induces in vivo Ehrlich tumor growth in a TSPO-dependent manner.

Effects of peripheral-type benzodiazepine receptor ligands on Ehrlich tumor cell proliferation

Peripheral-type benzodiazepine receptors have been found throughout the body, and particularly, in high numbers, in neoplastic tissues such as the ovary, liver, colon, breast, prostate and brain cancer. Peripheral-type benzodiazepine receptor expression has been associated with tumor malignity, and its subcellular localization is important to define its function in tumor cells. We investigated the presence of peripheral-type benzodiazepine receptors in Ehrlich tumor cells, and the in vitro effects of peripheral-type benzodiazepine receptors ligands on tumor cell proliferation. Our results demonstrate the presence of peripheral-type benzodiazepine receptor in the nucleus of Ehrlich tumor cells (85.53+/-12.60%). They also show that diazepam and Ro5-4864 (peripheral-type benzodiazepine receptor agonists) but not clonazepam (a molecule with low affinity for the peripheral-type benzodiazepine receptor) decreased the percentage of tumor cells in G0-G1 phases and increased that of cells in S-G2-M phases. The effects of those agonists were prevented by PK11195 (a peripheral-type benzodiazepine receptor antagonist) that did not produce effects by itself. Altogether, these data suggest that the presence of peripheral-type benzodiazepine receptor within the nucleus of Ehrlich tumor cells is associated with tumor malignity and proliferation capacity.

[Effect of hypothyroidism on the solid form of Ehrlich tumor in intact or castrated adult female mice]

The effect of hypothyroidism on the solid form of the Ehrlich tumor in intact or castrated adult female mice was studied. Hypothyroidism was induced by treatment with propylthiouracil (PTU). Forty mice were divided into four groups: castrated hypothyroid, intact hypothyroid, castrated euthyroid, and intact euthyroid. The mice were inoculated with suspension cells into the left footpad. The tumor growth curve was determined by measuring the inoculated footpad during 12 days. At the end of the experimental period the mice were sacrificed. Hypothyroidism was associated with a reduction in size of the tumor only in the castrated animals. Although the neoplastic growth was lower, mean nuclear diameter, number of nucleolar organizer regions (NORs), and area of mitosis were higher. In conclusion, hypothyroidism resulted in a delayed growth of the tumor, but it did not affect the malignant features of the neoplastic cells. In addition, the isolated effect of castration caused only mild alterations, whereas hypothyroidism associated with castration resulted in a more prominent delay in the growth rate of the Ehrlich tumor.

Morphological and oxidative alterations on Sertoli cells cytoskeleton due to retinol-induced reactive oxygen species

Retinol (vitamin A) is involved in several cellular processes, like cell division, differentiation, transformation and apoptosis. Although it has been shown that retinol is a limitant factor for all these processes, the precise mechanisms by which retinol acts are still unknown. In the present study we hypothesised that alterations in the cytoskeleton of Sertoli cells induced by retinol supplementation could indicate an adaptive maintenance of its functions, since it plays an important role in the transformation process that we observed. Previous results demonstrated that Sertoli cells treated with retinol showed an oxidative imbalance, that leads the cell to two phenotypes: apoptosis or transformation. Our group has identified characteristics of Sertoli cells transformed by retinol which results in normal cell functions modification. In the present study the actin filament fluorescence assay and the deformation coefficient showed a modification in the morphology induced by retinol. We also observed an oxidative alteration in isolated cytoskeleton proteins and did not show alterations when these proteins are analyzed by electrophoreses. Our results showed an increase in mitochondria superoxide production and a decrease in nitric oxide levels. All results were partially or completely reverted by co-treatment of the antioxidant Trolox. These findings suggest that the cytoskeleton components suffer individual alterations in different levels and that these alterations generate a global phenotype modification and that these processes are probably ROS dependent. We believe that the results from this study indicate an adaptation of the cytoskeleton to oxidative imbalance since there was not a loss of its function.

Low doses of beta-carotene and lutein inhibit AOM-induced rat colonic ACF formation but high doses augment ACF incidence

Epidemiological studies suggest that carotenoids such as beta-carotene and lutein play an important role in reducing the risk for several cancers. However, in colon cancer there is ambiguity with regard to the role of these compounds in that both preventive effects and tumor promotion have been observed. In the present study we observed that male F344 rats were able to tolerate up to 2,500 ppm of beta-carotene as well as of lutein. We have then assessed the chemopreventive efficacy of beta-carotene and lutein at dose levels of approximately 4 and 8% of the 2,500 ppm tolerated dose (TD) and also approximately 40 and 80% of the TD on azoxymethane (AOM)-induced colon carcinogenesis, using aberrant crypt foci (ACF) as a surrogate biomarker for colon cancer. Throughout the experiments, 5-week-old male F344 rats were fed the control diet (modified AIN-76A) or experimental diets containing 100 or 200 ppm (approximately 4 or 8% of the 2,500 ppm TD), or 1,000 or 2,000 ppm ( approximately 40 or 80% of the 2,500 ppm TD) of beta-carotene and lutein (n=10 rats/group). After 2 weeks on the experimental or control diets, all animals were injected with AOM (15 mg/kg body wt., once weekly for 2 weeks). At 14 weeks of age, all rats were killed, and their colons were evaluated for ACF. Administration of 100 or 200 ppm of beta-carotene inhibited AOM-induced total colonic ACF formation by 24% (p<0.01) and 36% (p<0.001), respectively, whereas lutein at 200 ppm produced a 27% inhibition (p<0.01) yet had no significant effect at the 100 ppm dose level. Surprisingly, administration of 1,000 or 2,000 ppm of beta-carotene and lutein increased colonic ACF formation in a dose-dependent manner, i.e., to 124% and 144% for the former and 110% and 159% for the latter. These results clearly suggest that further studies are warranted to determine whether the increase in ACF incidence by high doses of beta-carotene and lutein will also lead to an increase in tumor outcome. Taken together these data indicate that the chemopreventive activity of beta-carotene and lutein against colon carcinogenesis depends on the dose level.

Genotoxicity, recombinogenicity and cellular preneoplasic transformation induced by vitamin A supplementation

In spite of being one of the first vitamins to be discovered, the full range of biological activities of Vitamin A remains incomplete. A growing body of evidence has demonstrated an apparent enhancement of carcinogenesis, induced by dietary retinol. Since DNA damage is a well-recognized inducer of carcinogenesis, the aim of this study was to test the possible genotoxic effect of dietary retinol, using different types of bioassays. Retinol caused an increased recombinogenic activity in Drosophila melanogaster larvae as measured by the SMART test. In mammalian cell cultures, retinol supplementation-induced DNA double-strands breaks (DSB) and single-strands breaks (SSB), cell cycle progression and proliferative focus formation in terminal-differentiated rat Sertoli cells and increased DNA fragmentation in Chinese hamster lung fibroblasts (V79 cells), as measured by the comet assay. Altogether, our results suggest that retinol causes DNA damage and chromosomal rearrangements, which may disturbs key physiological processes and lead to cell cycle progression and preneoplasic transformation of terminal-differentiated mammalian cells.