ABSTRACT
Cancer develops when the regular cellular growth control is disrupted; cells lose contact inhibition and develop resistance to cell death, leading to uncontrolled cellular proliferation and metastasis. The structure and composition of the tumor are incredibly complex with heterogeneous cell populations, which display a large number of mutations and consequent dysregulated gene expressions. In the mid-1800, Joseph Claude and Robert Remak observed that cancer cells resemble embryonic cells in their phenotype, and this marks the foundation for the emergence of the current notion of Cancer Stem Cell (CSCs). CSC interactions with surrounding cancer cells, extracellular matrix, immune cells, cytokines, hormones, and various growth factors show an impact on their sensitivity to therapy. Hypoxia, or low oxygen condition, is one of the critical factors which contributes to the therapy resistance in CSCs by increasing cell survival and proliferation.
