The introduction of the theory of cancer stem cells (CSCs) has provided a new direction and perspective for our understanding of the nature and origin of tumors. Cancer stem cells are believed to be responsible for the treatment failure, drug tolerance, metastasis, and recurrence of tumors. However, it remains a challenge to identify or isolate tumor stem cells and determine their regulatory mechanisms. Therefore, further understanding of the biological characteristics and functions of CSCs is of great practical significance and value to develop new methods of tumor diagnosis and treatment, and may bring new hope patients with cancer.