title: Radiation-Induced Reprogramming of Pre-Senescent Mammary Epithelial Cells Enriches Putative CD44(+)/CD24(-/low) Stem Cell Phenotype.
abstract: The enrichment of putative CD44(+)/CD24(-/low) breast stem cell populations following exposure to ionizing radiation (IR) has been ascribed to their inherent radioresistance and an elevated frequency of symmetric division during repopulation. However, recent studies demonstrating radiation-induced phenotypic reprogramming (the transition of non-CD44(+)/CD24(-/low) cells into the CD44(+)/CD24(-/low) phenotype) as a potential mechanism of CD44(+)/CD24(-/low) cell enrichment have raised the question of whether a higher survival and increased self-renewal of existing CD44(+)/CD24(-/low) cells or induced reprogramming is an additional mode of enrichment. To investigate this question, we combined a cellular automata model with in vitro experimental data using both MCF-10A non-tumorigenic human mammary epithelial cells and MCF-7 breast cancer cells, with the goal of identifying the mechanistic basis of CD44(+)/CD24(-/low) stem cell enrichment in the context of radiation-induced cellular senescence. Quantitative modeling revealed that incomplete phenotypic reprogramming of pre-senescent non-stem cells (reprogramming whereby the CD44(+)/CD24(-/low) phenotype is conveyed, along with the short-term proliferation capacity of the original cell) could be an additional mode of enriching the CD44(+)/CD24(-/low) subpopulation. Furthermore, stem cell enrichment in MCF-7 cells occurs both at lower doses and earlier time points, and has longer persistence, than that observed in MCF-10A cells, suggesting that phenotypic plasticity appears to be less regulated in breast cancer cells. Taken together, these results suggest that reprogramming of pre-senescent non-stem cells may play a significant role in both cancer and non-tumorigenic mammary epithelial populations following exposure to IR, a finding with important implications for both radiation therapy and radiation carcinogenesis.
authors.affiliation: Inserm UMR 1181, Biostatistics, Biomathematics, Pharmacoepidemiology and Infectious Diseases (B2PHI), Paris, France; Institut Pasteur, UMR 1181, B2PHI, Paris, France; Université de Versailles St Quentin, UMR 1181, B2PHI, Paris, France; Center of Cancer Systems Biology, Tufts University, Boston, MA, USA.
authors.forename: Xuefeng
authors.initials: X
authors.lastname: Gao
authors.affiliation: Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, CO, USA; Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX, USA.
authors.forename: Brock J
authors.initials: BJ
authors.lastname: Sishc
authors.affiliation: Department of Environmental and Radiological Health Sciences, Colorado State University , Fort Collins, CO , USA.
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Nelson
authors.affiliation: Center of Cancer Systems Biology, Tufts University , Boston, MA , USA.
authors.forename: Philip
authors.initials: P
authors.lastname: Hahnfeldt
authors.affiliation: Department of Environmental and Radiological Health Sciences, Colorado State University , Fort Collins, CO , USA.
authors.forename: Susan M
authors.initials: SM
authors.lastname: Bailey
authors.affiliation: Center of Cancer Systems Biology, Tufts University , Boston, MA , USA.
authors.forename: Lynn
authors.initials: L
authors.lastname: Hlatky
keywords: breast cancer cells; cancer stem cells; cellular automata; radiation; reprogramming; senescence