Author: David Alcorta, Lindsay Bolino, Olivia Canter, Seifallah Emam, Joseph Farina, Timothy Haystead, Philip Hughes, Keshav Jha, David Loiselle, Mark Oldham, Victoria J. P. Radosova ðĻâðŽ
Affiliation: Duke University Department of Pharmacology and Cancer Biology, Medical Physics Graduate Program, Duke University, Duke University Department of Medicine, Duke University, Duke University Pharmacology and Cancer Biology, Duke Univerity, Department of Radiation Oncology, Duke University Medical Center ð
Purpose: To simulate how Cherenkov light (CL) produced during radiation therapy can activate targeted photodynamic molecules. To experimentally determine dose and concentration thresholds for biological effects in-vitro.
Methods: HS583, a novel verteporfin-tethered heat shock protein 90 (HSP90) inhibitor, was synthesized in house. Solutions of HS583 in optical cuvettes (1cmx4cm) were exposed to controlled amounts of laser light or external beam radiation (0-8Gy) from a clinical Linac (18MV). Reactive Oxygen Species (ROS) generation was quantified by measuring the oxidation of methionine by ROS and analyzed with HPLC. Cell culture experiments were performed using MDA-MB-231, a triple negative breast cancer, and MCF10A, an immortalized non-transformed breast epithelial line. Cells were cultured and treated with HS583 for 90 minutes before being washed and exposed to various doses of laser light and assayed by WST cell proliferation assay. Experimental results were compared to theoretical Monte Carlo simulations performed using Tool for Particle Simulation software (TOPAS), exploring the relation between CL and ROS generation.
Results: Chemical assays demonstrated that HS583 was capable of converting laser light energy into ROS. Similarly, increasing amounts of ROS were generated with higher doses from external beam suggesting conversion of cherenkov light to ROS by the photodynamic molecule verteporfin. Simulations suggest that with 1 J/cm^2 620 nm laser light incident upon it, a 1 ΞM solution of HS583 absorbs 1.4E12¹0.1E12 eV. WST assays showed increased cytotoxicity in MDA-MB-231 when treated with HS583 with an LD50 of 0.24 uM at 2 J/cm2, 0.35 uM at 1 J/cm2, and 4.45 uM at 0.1 J/cm2.
Conclusion: Verteporfin-based photodynamic molecules can enhance tumor control during radiation therapy by CL activation. Tethering verteporfin to an HSP90 inhibitor enables targeted ROS production only in tumor cells, sparing normal tissue toxicity and further increasing the therapeutic ratio.