Cancer stem cells (CSCs), which act as an important bridge between cancer formation and
embryonic development, represent a small population associated with tumor initiation, drug
resistance, metastasis and recurrence. CSCs have the ability to form spheroids in three-
dimensional culture systems. Tumor spheroids derived from CSCs with symmetric and
asymmetric division patterns were found to contain highly heterogeneous cell groups. The
biological behavior patterns which some CSCs display serve as an important bridge …