γ-H2AX kinetics as a novel approach to high content screening for small molecule radiosensitizers.

BACKGROUND: Persistence of γ-H2AX after ionizing radiation (IR) or drug therapy is a robust reporter of unrepaired DNA double strand breaks in treated cells. METHODS: DU-145 prostate cancer cells were treated with a chemical library ±IR and assayed for persistence of γ-H2AX using an automated 96-well immunocytochemistry assay at 4 hours after treatment. Hits that resulted in persistence of γ-H2AX foci were tested for effects on cell survival. The molecular targets of hits were validated by molecular, genetic and biochemical assays and in vivo activity was tested in a validated Drosophila cancer model. RESULTS: We identified 2 compounds, MS0019266 and MS0017509, which markedly increased persistence of γ-H2AX, apoptosis and radiosensitization in DU-145 cells. Chemical evaluation demonstrated that both compounds exhibited structurally similar and biochemical assays confirmed that these compounds inhibit ribonucleotide reductase. DNA microarray analysis and immunoblotting demonstrates that MS0019266 significantly decreased polo-like kinase 1 gene and protein expression. MS0019266 demonstrated in vivo antitumor activity without significant whole organism toxicity. CONCLUSIONS: MS0019266 and MS0017509 are promising compounds that may be candidates for further development as radiosensitizing compounds as inhibitors of ribonucleotide reductase.

Pharmacokinetic study of a novel sonosensitizer chlorin-e6 and its sonodynamic anti-cancer activity in hepatoma-22 tumor-bearing mice.

PURPOSE: The sonodynamically induced anti-tumor effect of chlorin-e6 (Ce6) was studied in mice bearing hepatoma-22 solid tumors. METHODS: In order to determine the optimum timing of ultrasound exposure after administration of Ce6, the Ce6 concentrations in plasma, skin, muscle and tumor were estimated by measuring the fluorescence intensity of tissue extractions with a fluorescence photometer based on the standard curve. A three-dimensional optical imaging system (IVIS spectrum) was used further to characterize the distribution of Ce6 in H-22 tumor. The anti-tumor effects were estimated by measuring tumor size after sonodynamic therapy. RESULTS: Similar pharmacokinetic trends of Ce6 in mice were observed either by fluorescence spectrophotometry or by bio-optical imaging. The results also demonstrated that Ce6 has a preferential localization in tumors, but low accumulation and rapid clearance in normal tissues. The results of anti-tumor effects revealed that at an ultrasound intensity of 4 W/cm(2) and a Ce6 dose of ≥10 mg/kg, a significant synergistic effect of ultrasound combined with Ce6 was observed, reducing the tumor volume significantly. CONCLUSION: Chlorin-e6 is a potential sonosensitizer for fluorescence imaging as well as for sonodynamic therapy for cancer. The anti-tumor effect of ultrasound could be enhanced in the presence of Ce6, which might be involved in a sonochemical mechanism.

Can dietary furanocoumarin ingestion enhance the erythemal response during high-dose UVA1 therapy?

As phototoxic skin reactions caused by psoralen are induced by wavelengths within the UVA1 spectrum, we assessed the potential of the small amount of psoralen in a normal diet to provoke phototoxicity in volunteers with skin types I and II. Threshold erythema was unaffected by ingestion of a 200-g portion of parsnip.

Hypericin: a new laser phototargeting agent for human cancer cells.

Laser activation of anthracycline-related drugs combines chemotherapy with photoablation for improved treatment. Hypericin, a structurally related anthraquinone, was tested for laser activation and cytotoxicity in human cancer cells. Viability of P3 squamous cell carcinoma cells incubated with 1 to 20 microgram/mL hypericin was reduced by more than 95% after 1 minute exposure at 4 degrees C to an argon laser (514 nm, 5 W), a KTP-532 laser (532 nm, 5 W), or a 20-A xenon lamp. Viability was reduced over 90% in six human carcinoma, sarcoma, and melanoma cell lines by this combined treatment, but only trace toxicity was seen after separate exposure to hypericin or light alone. These results show that hypericin is a sensitive agent for phototherapy of human cancer cells in vitro and indicate that this drug may be useful for tumor targeting via minimally invasive imaging-guided laser fiber optics.