In addition to expressing CD133, the human osteosarcoma cell lines Saos-2, OSA-1, OSA-2, and OSA-3 also express nestin, a marker for neural stem cells and brain CSCs, suggesting that nestin and CD133 might be used as co-markers for identifying osteosarcoma CSCs [46]. This evidence concerns the gene PROM1 and obstructive sleep apnea syndrome.