QUANTITATIVE H-1 NUCLEAR-MAGNETIC-RESONANCE DIFFUSION SPECTROSCOPY OFBT4C RAT GLIOMA DURING THYMIDINE KINASE-MEDIATED GENE-THERAPY IN-VIVO- IDENTIFICATION OF APOPTOTIC RESPONSE

We have investigated the effects of thymidine kinase-mediated gene the rapy in a malignant rat BT4C glioma by using H-1 nuclear magnetic reso nance spectroscopy irt vivo. Ganciclovir has been successfully used in thymidine kinase gene therapy as treatment for various experimental m alignancies. The cell damaging effect seems to be mediated by apoptosi s, optimally leading to eradication of tumor tissue. In this study, we show that ganciclovir treatment of tumors transfected with the herpes simplex thymidine kinase gene causes profound changes in water, metab olites, and macromolecules observable by diffusion spectroscopy. Durin g treatment, a 50% reduction from 0.14 +/- 0.01 x 10(-9) m(2)/s in the apparent diffusion coefficient of choline-containing compounds can be observed, concomitant with a 219% increase in the apparent diffusion coefficient of the rapidly diffusing water component. These changes ar e associated with an increase in the relative fraction of this water c omponent from 87 to 94%, The apparent diffusion coefficients of the sl owly diffusing water component and macromolecules remain unaltered. Th e results imply a reduction in cell size and number, a significant inc rease in intracellular viscosity, and a possible reduction in the hydr odynamic radii of macromolecular components, which are ascribed as bio physical signatures for apoptotic cell death.