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. 2013 Aug 29;32(35):4078-85.
doi: 10.1038/onc.2012.421. Epub 2012 Sep 17.

Brain and testicular tumors in mice with progenitor cells lacking BAX and BAK

S G Katz  1 , J K Fisher, M Correll, R T Bronson, K L Ligon, L D Walensky
Affiliations

Brain and testicular tumors in mice with progenitor cells lacking BAX and BAK

S G Katz et al. Oncogene. .

Abstract

The proapoptotic BCL-2 family proteins BAX and BAK serve as essential gatekeepers of the intrinsic apoptotic pathway and, when activated, transform into pore-forming homo-oligomers that permeabilize the mitochondrial outer membrane. Deletion of Bax and Bak causes marked resistance to death stimuli in a variety of cell types. Bax(-/-)Bak(-/-) mice are predominantly non-viable and survivors exhibit multiple developmental abnormalities characterized by cellular excess, including accumulation of neural progenitor cells in the periventricular, hippocampal, cerebellar and olfactory bulb regions of the brain. To explore the long-term pathophysiological consequences of BAX/BAK deficiency in a stem cell niche, we generated Bak(-/-) mice with conditional deletion of Bax in Nestin-positive cells. Aged Nestin(Cre)Bax(fl/fl)Bak(-/-) mice manifest progressive brain enlargement with a profound accumulation of NeuN- and Sox2-positive neural progenitor cells within the subventricular zone (SVZ). One-third of the mice develop frank masses comprised of neural progenitors, and in 20% of these cases, more aggressive, hypercellular tumors emerged. Unexpectedly, 60% of Nestin(Cre)Bax(fl/fl)Bak(-/-) mice harbored high-grade tumors within the testis, a peripheral site of Nestin expression. This in vivo model of severe apoptotic blockade highlights the constitutive role of BAX/BAK in long-term regulation of Nestin-positive progenitor cell pools, with loss of function predisposing to adult-onset tumorigenesis.

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Conflict of interest statement

Conflict of Interest

The authors have no competing financial interests related to the work described in this manuscript.

Figures

Figure 1
Figure 1
Progressive megalencephaly with SVZ hyperplasia and Homer-Wright pseudo-rosetting in NestinCreBaxfl/flBak−/− mice. (A) Adult NestinCreBaxfl/flBak−/− mice manifest the heaviest brains among littermate controls, with an observed gene dosage effect (NestinCreBaxfl/flBak−/− [n=46] vs.: WT [n=5], p=0.002; Bak−/−[n=44], p<0.0001; NestinCreBaxfl/fl [n=8], p=0.037; NestinCreBaxfl/flBak+/− [n=17], p=0.03). Data are mean ± s.d. (B) Representative brains of two age-matched Bak−/− and NestinCreBaxfl/flBak−/− mice. (C) Megalencephaly of NestinCreBaxfl/flBak−/− mice progresses with age (15–20 month old cohort vs. <8 month old cohort, p=0.016). Data are mean ± s.d. (D–F) H&E-stained sagittal brain sections demonstrate progressive expansion of the SVZ progenitor cell population, the size of which correlates with the number of Bax and Bak alleles deleted. (G–I) Immunohistochemical analysis of the NestinCreBaxfl/flBak−/− SVZ region revealed abundant expression of NeuN and Sox2, but little to no staining for Olig2. (J–L) H&E-stained sections demonstrate both giant (J) and small (K) rosettes within the SVZ of NestinCreBaxfl/flBak−/− mice. (L) The presence of rosetting correlates with elevated brain weight (p=0.04). Data are mean ± s.d.
Figure 2
Figure 2
Brain tumors of NestinCreBaxfl/flBak−/− mice. (A and B) The majority of tumors were large, round, and well-circumscribed masses that extended from the SVZ to the sub-hippocampal region. (C) Tumor tissue contained rosetting neurocytes, neoplastic neuropil, and occasional neurons with differentiated features, including increased cytoplasm. (D) Tumor rosettes contain MAP2-positive neuropil. (E-H) Tumor cells are positive for NeuN (E) but negative for Sox2 (F) and Olig2 (G), and exhibit a low Ki-67 proliferation index (H).
Figure 3
Figure 3
A subset of NestinCreBaxfl/flBak−/− brain tumors exhibit high grade features. An exemplary aggressive brain tumor was associated with gross head deformity (A) and pronounced compression with midline shift (B and C). Arrow, central sulcus (D–G) H&E-stained sections revealed malignant-appearing cells streaming from the SVZ, with a fasicular growth pattern, perivascular cuffing, mitotic cells, and satellitosis. (H–K) Tumor cells were NeuN- (H), Sox2- (I), and Olig2-positive (J), and exhibited a high Ki-67 proliferation index (K).
Figure 4
Figure 4
Testicular tumors of NestinCreBaxfl/flBak−/− mice. (A) Testicular enlargement was evident on necropsy of affected NestinCreBaxfl/flBak−/− mice. (B and C) H&E stained sections demonstrated effacement of testicular architecture by a striking inter-tubular neoplasia. (D) In contrast to Bax−/− mice, NestinCreBaxfl/flBak−/− animals displayed normal spermatogenesis. Magnification, 600X (E and F) The intertubular Leydig cells marked positive in NestinCreROSALacZ reporter mice (E), but not in ROSALacZ control animals (F).
Figure 5
Figure 5
Gene expression analysis of NestinCreBaxfl/flBak−/− tumors. (A) Gene expression profiling was performed on wild-type (n=2) and tumor-bearing NestinCreBaxfl/flBak−/− (n=4) testes. The testes tumors of NestinCreBaxfl/flBak−/− mice manifested a germ cell signature rather than a Leydig, interstitial, or seminiferous expression profile, as assessed by Gene Set Enrichment Analysis (GSEA). (B) Fraction of total and significant (FDR q <0.25) stem cell signatures enriched in either the wild-type or tumor-bearing NestinCreBaxfl/flBak−/− testes. (C) GSEA of wild-type vs. tumor-bearing NestinCreBaxfl/flBak−/− testes for the Myc, Core and PrC signatures (26). (D) GSEA of wild-type vs. tumor-bearing NestinCreBaxfl/flBak−/− testes for the gene signatures derived from the NestinCreBaxfl/flBak−/− aggressive brain tumor or NestinCreBaxfl/flBak−/− brains bearing SVZ proliferations.
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References

    1. Youle RJ, Strasser A. The BCL-2 protein family: opposing activities that mediate cell death. Nat Rev Mol Cell Biol. 2008;9(1):47–59. Epub 2007/12/22. - PubMed
    1. Wei MC, Zong WX, Cheng EH, Lindsten T, Panoutsakopoulou V, Ross AJ, et al. Proapoptotic BAX and BAK: a requisite gateway to mitochondrial dysfunction and death. Science. 2001;292(5517):727–730. Epub 2001/04/28. - PMC - PubMed
    1. Tait SW, Green DR. Mitochondria and cell death: outer membrane permeabilization and beyond. Nat Rev Mol Cell Biol. 2010;11(9):621–632. Epub 2010/08/05. - PubMed
    1. Lindsten T, Ross AJ, King A, Zong WX, Rathmell JC, Shiels HA, et al. The combined functions of proapoptotic Bcl-2 family members bak and bax are essential for normal development of multiple tissues. Mol Cell. 2000;6(6):1389–1399. Epub 2001/02/13. - PMC - PubMed
    1. Yip KW, Reed JC. Bcl-2 family proteins and cancer. Oncogene. 2008;27(50):6398–6406. Epub 2008/10/29. - PubMed

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