The Role of Cancer Stem Cells in Disease Progression and Therapy Resistance

A small subpopulation of tumour cells, known as cancer stem cells (CSCs), is the main culprit of tumour growth. They are capable of self-renewal, tumour initiation, expansion, metastasis, therapy resistance and cancer relapse. Factors associated with malignant properties of CSCs include decreased apoptotic insults, enhanced activity of drug efflux pumps and capacity to induce DNA repair, expression of detoxification enzymes and ability to become quiescent, i.e. phenotypic and genotypic plasticity of CSC, etc. These extraordinary capabilities of CSCs contribute to therapeutic resistance and cancer recurrence. Moreover, multiple factors including a complex network of tumour stroma, epidermal microenvironment and different subcompartments within the tumour stimulate CSCs plasticity-mediated tumour progression. These factors along with the metabolic flexibility of CSCs help them to become more aggressive, subsequently leading to tumour progression. Therefore, in this chapter, we describe how CSCs are associated with the initiation and progression of cancer. We also discuss the role of CSCs in therapy resistance with detailed molecular mechanisms, all of which could help us in developing promising strategies to benefit cancer treatment.