Cancer Stem Cells: Role in Tumor Progression and Treatment Resistance

Abstract

Cancer stem cells (CSCs) or cancer initiating cells are a subpopulation of cells that has the driving force of carcinogenesis. They exhibit distinctive self-renewal, proliferation, and differentiation capabilities that are believed to play a critical role in cancer initiation, maintenance, progression, drug resistance, and cancer recurrence or metastasis. Factors such as increased activation of drug-efflux pumps, enhanced capacity of DNA damage repair, dysregulation of growth and developmental signaling pathways, alterations of cellular metabolism, environmental niche, and impaired apoptotic response are attributed to CSCs in their resistance to the adjuvant chemoradiotherapy to cancer. The development of strategies targeting CSCs via drug transporters, specific surface markers, inhibiting signaling pathways or their components, and destroying their tumor microenvironment have multifocal effects that may improve the clinical outcome of patients with cancer.