Cancer immunology. Bench to bedside immunotherapy of cancers. Nima Rezaei (Ed.). Springer-Verlag (2015)
The cancer stem cell (CSC) model states that, similarly to adult regenerating tissues, tumors are organized in a hierarchy of heterogeneous cell populations and are sustained from a subset of tumor cells, which possess the same functional hallmarks of stem cells: unlimited self-renewal, multilineage differentiation potential, and reversible transition to a quiescent state [1, 2]. Recent studies have reported evidences of CSC involvement in numerous solid neoplasms, including prostate , colon [4, 5], head and neck , melanoma , lung , liver , breast , brain , pancreas [12–14], ovary,  and mesenchymal malignancies . The cancer stem cell theory underwent a significant evolution to a more comprehensive model throughout the last 40 years, integrating data from clinical observation and biomolecular approach. Albeit appealing, this concept still lacks a consistent unifying model. The definition and identification of CSCs in most tumor types remain elusive; their role in tumor progression and resistance to conventional antiblastic therapies has not been fully elucidated, and even whether or not they exist in all human tumors is still an open question. In this chapter, we will introduce the state-of-the-art and clinical implications of this area of investigation.