Feasibility and limitations of the rat model by C6 gliomas implanted at the subcutaneous region

Although rat models implanted with C6 glioma cells have been widely utilized for the assessment of new therapeutic modalities, a convenient in vivo model is still required. We implanted C6 glioma cells into the brains and the abdominal subcutaneous regions of Wistar rats, and evaluated the volumes of the growing tumors. The cultures of 5 x 10(6) cells had successfully formed tumors at 100% (52/52) of sites in the subcutaneous regions on day 5 after implantation. It was easy to measure the visible tumors with a sliding caliper. The tumor volume at the subcutaneous region reached a maximum volume (950 mm3+/-167 SE) on day 15, after which it diminished. In contrast, tumors implanted in the intracerebral region showed a maximum volume on day 20 after the implantation of 1 x 10(5) cultured cells. Pathological examinations of the subcutaneous and intracranial tumors on day 15 showed similar findings exhibiting high nuclear cell ratio, mitosis and pseudopalisading with small populations of GFAP positive cells. The results suggested that rat C6 glioma models with implantation into the subcutaneous abdomen are available from day 5 to day 15 as a convenient model for the assessment of anti-proliferative drugs. The usefulness and the limitations of the rat C6 glioma model are discussed in this manuscript.