Gliosarcoma Cell Death After Radiosurgery in a Rat Model

Abstract

Therapeutic radiation and subsequent detection of tumor cell death has been performed mainly in vitro systems, making it difficult to accurately characterize the mechanisms of tumor cell death after radiosurgery. To better characterize what occurs to glioma cells after radiation therapy, we developed a rat model using the 9L gliosarcoma cell line implanted reproducibly to the caudate nucleus in rats. After 1 Gy radiation, 9L tumors in vivo induced mainly necrosis (determined by trypan blue exclusion) of 10 - 74 % at 6 - 72 hours post-radiation. This is in contrast to a previous in vitro study which demonstrated that 18 Gy of radiation induces considerably less cell death as determined by trypan blue exclusion (approximately 20 - 25 % at 6 - 72 hours post-radiation). However, significant amounts of apoptosis were detected as early as 6 hours after radiation. Apoptosis determination was by annexin V (marker of early apoptosis) and propidium iodide (marker of membrane stability) staining followed by flow cytometry detection. When caspase 3 and caspase 8 enzymatic activities (mediators of apoptosis) were measured from freshly explanted tumor cells, peak activity was found 6 hours after 1 Gy radiation (p < 0.01). Taken together, these data indicate the presence of apoptosis early after radiation therapy (1 Gy) which progressed to necrosis in a unique in vivo model of gliosarcoma that may prove useful in determining new therapeutic approaches to radiation therapy and tumor cell biology.

Preclinical evaluation of radiosensitizing activity of Pluronic block copolymers

“…While it is unusual for apoptosis to become evident at 5 h, prior observations of apoptosis on the same time scale (~ 4–6 h after irradiation) have been reported in cells in which apoptosis is the primary method of cell death (Meyn 1997). To further evaluate the role of apoptosis in Gli36 cells and xenografts, other methods such as Annexin V staining and Caspase 3 analysis could be beneficial (Psarros et al 2005). …”