PNNL

Abstract

Single-cell irradiators and new experimental assays are rapidly expanding our ability to quantify the molecular mechanisms responsible for phenomena such as toxicant-induced adaptations in DNA repair and signal-mediated changes to the genome stability of cells not directly damaged by radiation (i.e., bystander cells). To advance our understanding of, and ability to predict and mitigate, the potentially harmful effects of radiological agents, effective strategies must be devised to incorporate information from molecular and cellular studies into mechanism-based, hierarchical models. A key advantage of the hierarchical modeling approach is that information from DNA repair and other in vitro assays can be systematically integrated into higher-level cell transformation and, eventually, carcinogenesis models. This presentation will outline the hierarchical modeling strategy used to integrate information from in vitro studies into the Virtual Cell (VC) radiobiology software (see Endnote). A new multi-path genomic instability model will be introduced and used to link biochemical processing of double strand breaks (DSBs) to neoplastic cell transformation. Bystander and directly damaged cells are treated explicitly in the model using a microdosimetric approach, although many of the details of the bystander response model are of a necessarily preliminary nature. The new model will be tested against several published radiobiological datasets. Results illustrating how hypothesized bystander mechanisms affect the shape of dose-response curves for neoplastic transformation as a function of Linear Energy Transfer (LET) will be presented. EndNote: R.D. Stewart, Virtual Cell (VC) Radiobiology Software. PNNL-13579, July 2001. Available at http://www.pnl.gov/berc/kbem/vc/ The DNA repair model used in the VC computer program is based on the Two-Lesion Kinetic (TLK) model [Radiat. Res. 156(4), 365-378 October 2001].