title: Characterization of the stem cell niche and its importance in radiobiological response.
abstract: Normal tissues are organized hierarchically with a small number of stem cells, able to self-renew and give rise to all the differentiated cells found in the respective specialized tissues. The undifferentiated, multipotent state of normal stem cells is codetermined by the constituents of a specific anatomical space that hosts the normal stem cell population, called the "stem cell niche." Radiation interferes not only with the stem cell population but also with the stem cell niche, thus modulating a complex regulatory network. There is now mounting experimental evidence that many solid cancers share this hierarchical organization with their tissue of origin, with the cancer stem cells also occupying specialized niches. In this review, we highlight some of the best-characterized aspects of normal tissue stem cells, cancer stem cells, and their niches in the bone marrow, gut, and brain, as well as their responses to ionizing radiation.
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine, UCLA, Los Angeles, CA; Jonsson Comprehensive Cancer Center, UCLA, Los Angeles, CA. Electronic address: fpajonk@mednet.ucla.edu.
authors.forename: Frank
authors.initials: F
authors.lastname: Pajonk
authors.forename: Erina
authors.initials: E
authors.lastname: Vlashi
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000528:radiation effects; D002490:Central Nervous System / Q000166:cytology / Q000528:radiation effects; D006801:Humans; D007422:Intestines / Q000166:cytology / Q000528:radiation effects; D009369:Neoplasms / Q000532:radiotherapy*; D011853:Radiobiology; D015398:Signal Transduction; D055153:Stem Cell Niche / Q000502:physiology* / Q000528:radiation effects*; D059016:Tumor Microenvironment