Transgenic expression of Bmi1 is sufficient to induce intermediate and anterior lobe pituitary tumors but does not induce medulloblastoma or glioma.

<p>(A) Kaplan Meier survival curves of mice carrying tumors because of GCre induced transgenic expression of Bmi1 complemented with loss of Rb. These data show that Bmi1 transgenic mice develop pituitary tumors after about one year. Pituitary tumors are also observed in Rb^Lox/Lox and Bmi1^LSL;Rb^Lox/Lox transgenic mice. (B) Histograms showing the relative frequency and penetrance of tumors generated by the individual genotypic groups. All genotypes shown are GCre positive. Total cohort size: GCre;Bmi1^LSL n = 14, GCre;Rb^Lox/Lox n = 20, GCre;Rb^Lox/Lox;Bmi1^LSL n = 12, GCre;p53^Lox/Lox;Rb^Lox/Lox n = 6, GCre;p53^Lox/Lox;Rb^Lox/Lox; Bmi1^LSL n = 4, WT mice did not develop tumors, n = 7. (C) IHC results showing transgenic Bm1 expression in tumors raised on a GCre;Bmi1^LSL background (5/5), no expression in tumors raised on a Gcre;Rb^lox/lox background (0/5) while some of the GCre;Bmi1^LSL; Rb^lox/lox mice were positive (2/5, 40%). These results are summarized in a histogram (D). Bar is 50 µm.</p

IHC analysis of pituitary hormones in Gcre; Bm1^LSL induced tumors.

<p>n.d., not done, n.o., not observed.</p

Reported over expression of Bmi1 in astroglial and neural tumors.

<p>Reported over expression of Bmi1 in astroglial and neural tumors.</p

Mendelian distribution of transgenic allele before and after birth.

<p>Mendelian distribution of transgenic allele before and after birth.</p

Histology of a representative example of a typical pituitary tumor as found in this study.

<p>(A) Average location of pituitary tumors observed in the GCre;Bmi1^LSL mice showing localization to the pituitary gland (n = 6). Localization is based on Allen’s mouse brain database, (B) H&E staining of a coronal section of the brain showing a typical pituitary tumor. Immunohistochemistry shows expression analysis of (C) Chromogranin A, (D) adrenocorticotropic hormone ACTH, (E) Growth Hormone hGH, (F) Prolactin PRL, (G) Thyroid Stimulating Hormone TSH, (H) cytokeratin 8/18 CAM5.2 and (I) CD56/NCAM. Of these markers, ACTH is clearly positive in this tumor. Electron microscopy (EM) shows secretory vesicles (indicated by the arrowheads) in Bmi1 transgenic tumors (J, K) in a similar way as observed in human tumors (M, N). Ki67 is clearly positive in this tumor (L). Immunohistochemistry of human pituitary adenomas show over expression of BMI1, which is visualized by a nuclear signal (O). Bars, 100 µm unless otherwise noted.</p

Bmi1^LSL conditional transgenic mice express Bmi1 after Cre mediated activation.

<p>(A) Strategy for targeting the CAG promotor-LoxP-PGK-Neo-3xtranscriptionstop-LoxP-Bmi1 cDNA-IRES-Hyg/eGFP cassette into the ROSA26 locus. (B) Southern blot showing germ line transmission of two out of 7 mice. (C) Western blot showing Adenoviral-Cre mediated expression of Bmi1 in cultured mammary epithelial cells (MECS) of a Bmi1<b>^LSL</b> transgene mouse compared to a wild type (WT) mouse. Bmi1 is detected in MECS that received 50 or 100 virus particles per cell. MOI, multiplicity of infection. (D) Immunohistochemistry showing nuclear transgenic Bmi1 expression of hepatocytes of adult mice after adenocre (Ad5Cre) mediated activation using intravenous injection of 10⁹ infectious particles. (E) Immunohistochemistry showing Bmi1 expression in the small intestine and liver of Actin-Cre (Acre) or Acre;Bmi1 mice of embryonic day 18.5 mice.</p

Constitutive transgenic expression of Bmi1^LSL is neonatally lethal.

<p>(A) Histogram showing that constitutive expressing Acre;Bmi1<b>^LSL</b> mice have the same growth kinetics as wild type control mice in utero between embryonic day E12.5 and E18.5. (B) Histogram showing that Acre;Bmi1<b>^LSL</b> transgene mice have less nucleated red blood cells in their lungs compared to Acre control mice at embryonic day E18.5. Nucleated red blood cells are visualized using PTAH staining resulting in blue nuclei, as shown in the lower panels. *p = <0.05, NS: not significant.</p