The VHL tumor suppressor protein regulates tumorigenicity of U87-derived glioma stem-like cells by inhibiting the JAK/STAT signaling pathway

Abstract

The signal transducer and activator of transcription 3 (STAT3) factor plays an important role in the tumorigenicity of cancer stem cells. The purpose of this study was to investigate the inhibitory mechanism of this pathway acting through the tumor suppressor von Hippel-Lindau (VHL) protein in glioma cancer stem cells. We isolated floating neurosphere-forming CD133+ cells as glioma stem-like cells (GSLCs) by the MACS method. Furthermore, we examined these cells for their growth rate, ability to form colonies and neurospheres in soft agar, capacity for implantation into SCID mice and expression of CD133, STAT3, JAK2, Elongin A, PTEN and VHL. Furthermore, we transferred the VHL gene, an inhibitor of STAT3, into GSLCs using an adenovirus vector and compared these transfectants with control vector-transfected GSLCs. GSLCs proved to be implantable and formed a tumor in the subcutaneous tissue of SCID mice, the histology of which was similar to that of human glioblastomas. In addition, GSLCs exhibited a high capacity for soft agar colony and neurosphere formation, nearly all of which were CD133 positive. The majority of GSLCs were immunopositive for STAT3, JAK2 and Elongin A, but immunonegative for PTEN and VHL. When the VHL gene was transferred to GSLCs and these cells were transplanted into SCID mice, they did not result in tumor formation. Their capacity for soft agar colony and neurosphere formation was significantly inhibited, although their proliferation was only moderately inhibited. Regarding the expression of various factors, that of CD133 was decreased in the VHL transfectants and those of STAT3, JAK2 and Elongin A were eliminated. However, the expression of PTEN and of VHL was upregulated. These findings suggest that VHL regulated the tumorigenicity and self-renewal ability of glioma cancer stem cells by inhibiting the JAK/STAT signaling pathway.

MicroRNA-566 activates EGFR signaling and its inhibition sensitizes glioblastoma cells to nimotuzumab

“…We then further confirmed the target of miR-566. VHL was shown to be involved in the tumorigenesis of glioma [9,21], and we found that the 3’ UTR of VHL contained 2 potential complimentary binding sites for miR-566. To validate this, we performed luciferase reporter assays using 3’ UTR sequence fragments of the VHL transcript containing the two predicted binding sites for miR-566 (Figure 3A).…”

The role of glioma stem cells in chemotherapy resistance and glioblastoma multiforme recurrence

“…Studies now support retroversion of differentiated cells to a more stem-like or progenitor state, a change recently suggested to occur spontaneously in some cases, or to be induced or potentiated by TMZ therapy and possibly other cellular stressors including hypoxia and radiation [19]. HIF2α, loss of PTEN, and loss of von Hippel-Lindau have all been proposed as inciting events in GSC conversion [76,77]. Change to a stem-like phenotype from non-GSCs has been confirmed by assessing neurosphere and xenograft tumor formation, as well as cellular activity of classical GSC genes ( OCT4, NANOG, c-MYC , etc.)…”

“…Change to a stem-like phenotype from non-GSCs has been confirmed by assessing neurosphere and xenograft tumor formation, as well as cellular activity of classical GSC genes ( OCT4, NANOG, c-MYC , etc.) [19,76,77]. Plasticity magnifies the ineffectiveness of current therapy, which not only spares GSCs but also replenishes those best suited to withstand subsequent therapy.…”

Isolation of Multipotent Nestin-Expressing Stem Cells Derived from the Epidermis of Elderly Humans and TAT-VHL Peptide-Mediated Neuronal Differentiation of These Cells

“…Murine multipotent nestin-expressing stem cells, derived from either the hair follicle bulge area or dermal papilla possess sphere-forming capacity [8]. Our isolated multipotent nestin-positive cells also showed sphere-forming ability, which reflects self-renewing capacity [28], and was also found in the case of skin-derived neural crest stem cells [29] or skin-derived precursors [7]. Our isolated stem cells included the cells obtained from seven patients over 70 years of age (the oldest patient, 86 years old), and so our results indicate that skin-derived nestin-expressing follicle stem cells could be isolated even from patients over 70 years of age.…”