Gliosarcoma cell line K308 was established from a primary tumor specimen removed from a 51-year-old male Han Chinese patient. Besides the typical characteristics of gliosarcoma cells, K308 cells express abundant glutaminase and can release large amount of glutamate. K308 exhibited cell-density-dependent expression of neuronal precursor markers, particularly nestin. At low density, the majority of K308 cells were nestin negative (approximately 70%) and nestin levels remained homogenous within each single-cell-derived colony when K308 proliferated. After reaching confluence, however, the majority of K308 cells turned nestin positive. These confluent K308 cells were also Sox2 positive and could form tumor spheres even in serum-containing media.