Reactive Oxygen Species in Normal and Tumor Stem Cells

Abstract

Reactive oxygen species (ROS) play an important role in determining the fate of normal stem cells. Low levels of ROS are required for stem cells to maintain quiescence and self-renewal. Increases in ROS production cause stem cell proliferation/differentiation, senescence, and apoptosis in a dose-dependent manner, leading to their exhaustion. Therefore, the production of ROS in stem cells is tightly regulated to ensure that they have the ability to maintain tissue homeostasis and repair damaged tissues for the life span of an organism. In this chapter, we discuss how the production of ROS in normal stem cells is regulated by various intrinsic and extrinsic factors and how the fate of these cells is altered by the dysregulation of ROS production under various pathological conditions. In addition, the implications of the aberrant production of ROS by tumor stem cells for tumor progression and treatment are also discussed.

Microenvironment in Vagina as a Key-Player on Cervical Cancer: Interaction of Polymorphic Genetic Variants and Vaginal Microbiome as Co-Factors

“…This idyllic scenario is considered for normal cells or untransformed cells, which have a wide antioxidant regulatory defence system that serves to prevent the oxidative stress and the development of neoplasms [20]. Nevertheless, the papillomavirus infected cells (in particular by oncogenic types HPV 16, 33, 31) are resistant to this pathway of apoptosis induction.…”

125I Brachytherapy in Locally Advanced Non-Small Cell Lung Cancer after Progression of Concurrent Radiochemotherapy

“…34 Second, persistent low-dose irradiation could affect the different cell cycle stages, so it can continue to kill tumor cells. 35 Third, when killing tumor cells, the rays have lower oxygen 36 Last, it increases the relative biological effect. 37 In the present study, the 125 I particle combined with the preoperative TPS allows the PTV to cover more than 95% of the tumor volume, which will receive 100% of the radiation dose.…”

Tumor Interstitial Fluid Promotes Malignant Phenotypes of Lung Cancer Independently of Angiogenesis

“…The systemic reduction of interstitial fluid prevents the excretion of cytotoxic components by cancer cells and prevents the use of recycled nutrients, which would result in starvation of the cancer cells. Indeed, abundant ROS and catabolic enzymes are present, which on the one hand may cause cell death and degradation and thus produce recycled nutrients; on the other hand, these enzymes may lead to the induction of EMT and an increase in stemness (31)(32)(33). It is not surprising that in this study, TIF impaired the proliferation and migration of fibroblasts in a wound-healing assay, whereas it promoted the stemness of cancer cells.…”