Bcl2-Expressing Quiescent Type B Neural Stem Cells in the Ventricular–Subventricular Zone Are Resistant to Concurrent Temozolomide/X-Irradiation. (17th October 2019)

• Record Type: Journal Article
• Authors: Cameron, Brent D.; Traver, Geri; Roland, Joseph T.; Brockman, Asa A.; Dean, Daniel; Johnson, Levi; Boyd, Kelli; Ihrie, Rebecca A.; Freeman, Michael L.
• Is Part Of: Stem cells. Volume 37:Number 12(2019)
• Page Start: 1629
• Page End: 1639
• Publication Date: 2019-10-17
• Subjects: Neural stem cells -- Temozolomide -- Ionizing radiation -- Glioblastoma -- Subventricular zone -- Apoptosis; Cloning -- Periodicals; Clone cells -- Periodicals; Stem cells -- Periodicals; Cell Differentiation -- Periodicals; Cell Division -- Periodicals; Clone Cells -- Periodicals; Hematopoietic Stem Cells -- Periodicals; Stem Cells -- Periodicals; 571.84
• DOI: 10.1002/stem.3081
• Languages: English
• ISSNs: 1066-5099

Abstract

Abstract: The ventricular–subventricular zone (V-SVZ) of the mammalian brain is a site of adult neurogenesis. Within the V-SVZ reside type B neural stem cells (NSCs) and type A neuroblasts. The V-SVZ is also a primary site for very aggressive glioblastoma (GBM). Standard-of-care therapy for GBM consists of safe maximum resection, concurrent temozolomide (TMZ), and X-irradiation (XRT), followed by adjuvant TMZ therapy. The question of how this therapy impacts neurogenesis is not well understood and is of fundamental importance as normal tissue tolerance is a limiting factor. Here, we studied the effects of concurrent TMZ/XRT followed by adjuvant TMZ on type B stem cells and type A neuroblasts of the V-SVZ in C57BL/6 mice. We found that chemoradiation induced an apoptotic response in type A neuroblasts, as marked by cleavage of caspase 3, but not in NSCs, and that A cells within the V-SVZ were repopulated given sufficient recovery time. 53BP1 foci formation and resolution was used to assess the repair of DNA double-strand breaks. Remarkably, the repair was the same in type B and type A cells. While Bax expression was the same for type A or B cells, antiapoptotic Bcl2 and Mcl1 expression was significantly greater in NSCs. Thus, the resistance of type B NSCs to TMZ/XRT appears to be due, in part, to high basal expression of antiapoptotic proteins compared with type A cells. This preclinical research, demonstrating that murine NSCs residing in the V-SVZ are tolerant of standard chemoradiation therapy, supports a dose escalation strategy for treatment of GBM. Stem Cells 2019;37:1629–1639 : Abstract : The brain's ventricular–subventricular zone is a site of type B neural stem cell-mediated neurogenesis and unfortunately for very aggressive glioblastoma. Treatment for glioblastoma consists of resection, concurrent temozolomide, and X-irradiation, followed by adjuvant temozolomide. We show that concurrent temozolomide/X-irradiation followed by adjuvant temozolomide induces apoptosis in type A neuroblasts. In contrast, quiescent neural stem cells, which express high levels of Bcl2 and Mcl1, survive and repopulate type A neuroblasts.