Sexually dimorphic RB inactivation underlies mesenchymal glioblastoma prevalence in males
Tao Sun, … , Rajarshi Sengupta, Joshua B. Rubin
Tao Sun, … , Rajarshi Sengupta, Joshua B. Rubin
Published August 1, 2014
Citation Information: J Clin Invest. 2014;124(9):4123-4133. https://doi.org/10.1172/JCI71048.
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Research Article Oncology

Sexually dimorphic RB inactivation underlies mesenchymal glioblastoma prevalence in males

Abstract

The prevalence of brain tumors in males is common but unexplained. While sex differences in disease are typically mediated through acute sex hormone actions, sex-specific differences in brain tumor rates are comparable at all ages, suggesting that factors other than sex hormones underlie this discrepancy. We found that mesenchymal glioblastoma (Mes-GBM) affects more males as the result of cell-intrinsic sexual dimorphism in astrocyte transformation. We used astrocytes from neurofibromin-deficient (Nf1–/–) mice expressing a dominant-negative form of the tumor suppressor p53 (DNp53) and treated them with EGF as a Mes-GBM model. Male Mes-GBM astrocytes exhibited greater growth and colony formation compared with female Mes-GBM astrocytes. Moreover, male Mes-GBM astrocytes underwent greater tumorigenesis in vivo, regardless of recipient mouse sex. Male Mes-GBM astrocytes exhibited greater inactivation of the tumor suppressor RB, higher proliferation rates, and greater induction of a clonogenic, stem-like cell population compared with female Mes-GBM astrocytes. Furthermore, complete inactivation of RB and p53 in Mes-GBM astrocytes resulted in equivalent male and female tumorigenic transformation, indicating that intrinsic differences in RB activation are responsible for the predominance of tumorigenic transformation in male astrocytes. Together, these results indicate that cell-intrinsic sex differences in RB regulation and stem-like cell function may underlie the predominance of GBM in males.

Authors

Tao Sun, Nicole M. Warrington, Jingqin Luo, Michael D. Brooks, Sonika Dahiya, Steven C. Snyder, Rajarshi Sengupta, Joshua B. Rubin

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Figure 1

Preparation of male and female Nf1–/– DNp53 astrocytes.

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Preparation of male and female Nf1–/– DNp53 astrocytes. (A) Sex determin...
(A) Sex determination of isolated mouse astrocytes by PCR for X- and Y-encoded paralogs Jarid1c and Jarid1d. Shown are results with genomic DNA isolated from adult mouse brain and from 3 independent litters of postnatal day 1 pups. (B) Western blot analysis of NF1 expression in male and female Nf1fl/fl, Nf1–/–, and Nf1–/– DNp53 astrocytes. Actin served as loading control. (C) Purity of astrocyte cultures was assessed by immunofluorescence detection of the astrocyte markers aldolase C (red) and GFAP (green) and the absence of neuronal (NF200) and oligodendrocyte (CNPase) marker expression. Nuclei were counterstained blue with DAPI. (D) Direct fluorescence microscopy of FACS-sorted cells indicated 100% EGFP expression in male and female Nf1–/– DNp53 astrocytes. (E) Western blot analysis indicated equal expression of endogenous p53 and the flag-tagged DNp53 construct (FLAG). Actin served as loading control. (F) PCR for p53 transcriptional targets Bai1, p21, and Gadd45a indicates equal loss of expression in Nf1–/– DNp53 astrocytes. ND, not detected; NS, not significant; M, male; F, female. Scale bar: 100 microns.