stilbenes and Retinoblastoma

For many cancers, the lack of potency and the toxicity of current drugs limits the dose achievable in patients and the efficacy of treatment. Among them, retinoblastoma is a rare cancer of the eye for which better chemotherapeutic options are needed. Combination therapy is a compelling approach to enhance the efficacy of current treatment, however clinical trials to test rationally designed combinations of approved drugs are slow and expensive, and limited by our lack of in-depth knowledge of drug specificity. Since many patients already turn to nutraceuticals in hopes of improving their condition, we hypothesized that certain approved drugs could potentially synergize with widely consumed supplements. Following this hypothesis, we devised an alternative screening strategy aimed at taking advantage of a bait compound such as a nutraceutical with potential therapeutic benefits but low potency, by screening chemical libraries for approved drugs that synergize with this companion effector. As a proof of concept, we sought to identify approved drugs with synergetic therapeutic effects toward retinoblastoma cells in combination with the antioxidant resveratrol, popular as a supplement. We systematically tested FDA-approved drugs and known bioactives seeking to identify such pairs, which led to uncovering only a few additive combinations; but to our surprise, we identified a class of anticancer drugs widely used in the clinic whose therapeutic effect is antagonized with resveratrol. Our observations could explain in part why some patients do not respond well to treatment. Our results validate this alternative approach, and we expect that our companion effector strategy could significantly impact both drug discovery and the nutraceutical industry.

Topics: Antineoplastic Agents; Cell Line, Tumor; Cell Survival; Dose-Response Relationship, Drug; Drug Screening Assays, Antitumor; Drug Synergism; High-Throughput Screening Assays; Humans; Inhibitory Concentration 50; Reproducibility of Results; Resveratrol; Retinal Neoplasms; Retinoblastoma; Small Molecule Libraries; Stilbenes

In this continuation of our research on derivatives containing the stilbene privileged structure or that are derived from it, we report the results of further studies carried out on the previously initiated collection of compounds. We used a parallel synthetic approach to rapidly obtain small sets of compounds and started the annotation of the library in progress by calculating some physicochemical properties to be eventually correlated with biological activities. A pharmacophore for the antiproliferative activity was also built to summarize the features of the library. We evaluated the antiproliferative and pro-apoptotic activities of all compounds as well as the cell-cycle effects of some representative compounds. After in-depth investigations, 3'-phenyl-[1,1';4',1'']terphenyl-4,3'',5''-triol showed the most interesting biological profile, as it interferes with cell-cycle progression at the G(1)-->S transition, acting on retinoblastoma phosphorylation and inducing cell differentiation.

Topics: Antineoplastic Agents; Apoptosis; Cell Differentiation; Cell Line, Tumor; Flow Cytometry; G1 Phase; HL-60 Cells; Humans; Inhibitory Concentration 50; K562 Cells; Phosphorylation; Retinoblastoma; S Phase; Small Molecule Libraries; Stilbenes

The aim of this study was to quantify tumor cell proliferation and growth, analyze tumor blood vessel development, and determine the efficacy of antiangiogenic and angiostatic therapy in targeting mature vessels in retinal tumors of the LH(BETA)T(AG) mouse model for retinoblastoma.. LH(BETA)T(AG) mouse retinas were analyzed at 4, 8, 12, and 16 weeks of age. Tumor burden was analyzed by histology; cell proliferation, vessel density, angiogenesis, and vessel maturation were detected by immunofluorescence. To assess the efficacy of mature vessel targeting, 16-week-old mice were treated with single subconjunctival injections of the selective vascular-targeting drug combretastatin A4 prodrug (CA4P) or anecortave acetate, and eyes were analyzed 1 day and 1 week after injection to determine microvessel density and the number of angiogenic and mature vessels.. Increased cell proliferation and angiogenesis were detected in the retinal inner nuclear layer (INL) before morphologic neoplastic changes were evident. As tumor size increased, angiogenesis diminished concomitantly with the appearance of mature vessels. Treatment with CA4P and anecortave acetate resulted in significant reductions in total vessel density. However, neither drug reduced the amount of alpha-smooth muscle actin (SMA)-positive, mature vessels.. Results of this study provide new insight into the relationship between tumor growth and blood vessel development in the LH(BETA)T(AG) mouse and establish the framework for defining the selective action of two vessel-targeting drugs against new blood vessels compared with mature blood vessels. These findings suggest a high potential value in targeting the process of angiogenesis in the treatment of children with retinoblastoma.

Topics: Actins; Angiogenesis Inhibitors; Animals; Antineoplastic Agents, Phytogenic; Bibenzyls; Biomarkers, Tumor; Cell Proliferation; Disease Models, Animal; Endoglin; Endothelium, Vascular; Intracellular Signaling Peptides and Proteins; Ki-67 Antigen; Mice; Mice, Transgenic; Microscopy, Fluorescence; Neovascularization, Pathologic; Pericytes; Pregnadienediols; Retinal Neoplasms; Retinoblastoma; Stilbenes

To evaluate the mechanism and timing of retinal tumor cell death in the LH(BETA)T(AG) mouse model of retinoblastoma after treatment with vascular targeting therapies and conventional therapies (focal chemotherapy and radiation).. For vascular targeting therapy, 12- or 16-week-old mice were treated with a single subconjunctival injection of either anecortave acetate (300 microg) or combretastatin A4 (1.5 mg). Eyes were analyzed at 1 day and 1 week after treatment. Tumor cell death was evaluated using TUNEL assays or immunofluorescence analysis of activated caspase 3 to detect apoptosis. Histopathologic analysis was performed to identify areas of necrosis. For conventional therapy, LH(BETA)T(AG) mice were treated with six serial subconjunctival injections of focally delivered carboplatin chemotherapy (100 microg/delivery) or hyperfractionated external beam radiotherapy (EBRT; 15 Gy total dose). Cell death was analyzed by TUNEL assay.. The highest levels of apoptotic cell death were seen 1 day after treatment in all treatment groups compared with vehicle controls. At 1 week after treatment, apoptotic cell death remained significantly elevated in the EBRT and carboplatin groups, but not after vessel targeting therapy. No significant necrosis was detected by histology in tumors of treated or of control eyes.. Conventional therapies (focal carboplatin chemotherapy and EBRT) and vascular targeting agents significantly increase cell death through apoptosis, while not having a significant effect on necrosis in this murine model of retinoblastoma. These studies will aid in the optimization of delivery schemes of combined treatment modalities.

Topics: Angiogenesis Inhibitors; Animals; Antineoplastic Agents; Apoptosis; Carboplatin; Caspase 3; Disease Models, Animal; Endothelium, Vascular; In Situ Nick-End Labeling; Mice; Mice, Transgenic; Neovascularization, Pathologic; Pregnadienediols; Radiotherapy, Conformal; Retinal Neoplasms; Retinoblastoma; Stilbenes; Time Factors

To determine the molecular mechanisms by which resveratrol induces retinoblastoma tumor cell death.. After resveratrol treatment, Y79 tumor cell viability was measured using a fluorescence-based assay, and proapoptotic and antiproliferative effects were characterized by Hoechst stain and flow cytometry, respectively. Mitochondrial transmembrane potential (DeltaPsim) was measured as a function of drug treatment using 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethyl-benzamidazolocarbocyanin iodide (JC-1), whereas the release of cytochrome c from mitochondria was assayed by immunoblotting and caspase activities were determined by monitoring the cleavage of fluorogenic peptide substrates.. Resveratrol induced a dose- and time-dependent decrease in Y79 tumor cell viability and inhibited proliferation by inducing S-phase growth arrest and apoptotic cell death. Preceding cell death, resveratrol evoked a rapid dissipation of DeltaPsim. This was followed by the release of cytochrome c into the cytoplasm and a substantial increase in the activities of caspase-9 and caspase-3. Additionally, in a cell-free system, resveratrol directly induced the depolarization of isolated mitochondria.. These results demonstrate that resveratrol, a nontoxic natural plant compound, inhibits Y79 cell proliferation and stimulates apoptosis through activation of the mitochondrial (intrinsic) apoptotic pathway and may warrant further exploration as an adjuvant to conventional anticancer therapies for retinoblastoma.

Topics: Antineoplastic Agents, Phytogenic; Apoptosis; Caspase 3; Caspase 9; Caspases; Cell Cycle; Cell Proliferation; Cytochromes c; Dose-Response Relationship, Drug; Flow Cytometry; Humans; Membrane Potentials; Mitochondria; Quinone Reductases; Resveratrol; Retinal Neoplasms; Retinoblastoma; Ribonucleotide Reductases; RNA, Messenger; Stilbenes; Time Factors; Tumor Cells, Cultured

To evaluate the effect of subconjunctival injections of combretastatin A-4 phosphate (CA-4P) prodrug treatment on tumor vasculature and growth in an animal model of hereditary retinoblastoma.. Twenty-four, 12-week-old simian virus-40 T-antigen-positive mice received six subconjunctival CA-4P injections at doses of 0.5, 1.0, 1.5, and 2.0 mg delivered at 72-hour intervals to the right eye only. Six control animals received placebo treatment. All animals underwent serial ophthalmic evaluations and were euthanatized at 16 weeks of age, and eyes were obtained for histopathologic examination. Eyes were graded for presence or absence of tumor, delay of tumor growth, and intratumoral vascularity.. The use of subconjunctivally injected CA-4P prodrug induced an extensive, dose-dependent decrease in microvessel density and led to significant tumor reduction in treated eyes compared with the placebo control (P <0.001). No evidence of corneal, lenticular, choroidal, or retinal toxicity was observed by histopathologic evaluation.. Subconjunctival delivery of CA-4P is associated with extensive dose-dependent reduction in blood vessel count in this murine model of retinoblastoma. A combination treatment of retinoblastoma incorporating CA-4P may allow enhanced tumor reduction enabling a decrease in standard treatment doses of both chemotherapy and external beam radiotherapy.

Topics: Animals; Antigens, Polyomavirus Transforming; Antineoplastic Agents; Conjunctiva; Disease Models, Animal; Dose-Response Relationship, Drug; Injections; Mice; Mice, Transgenic; Neovascularization, Pathologic; Prodrugs; Retinal Neoplasms; Retinoblastoma; Stilbenes