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ABSTRACT: The PTEN tumor suppressor gene is frequently inactivated in human prostate cancer. Using Osr1 (odd skipped related 1)-Cre mice, we generated a novel conditional Pten knockout mouse strain, Pten(LoxP):Osr1-Cre. Conditional biallelic and monoallelic Pten knockout mice were viable. Deletion of Pten expression was detected in the prostate of Pten(LoxP/LoxP):Osr1-Cre mice as early as 2 weeks of age. Intriguingly, Pten(LoxP/LoxP):Osr1-Cre mice develop high-grade prostatic intraepithelial neoplasms (PINs) with high penetrance as early as one-month of age, and locally invasive prostatic tumors after 12-months of age. Pten(LoxP/+):Osr1-Cre mice show only mild oncogenic changes after 8-weeks of age. Castration of Pten(LoxP/LoxP):Osr1-Cre mice shows no significant regression of prostate tumors, although a shift of androgen receptor (AR) staining from the nuclei to cytoplasm is observed in Pten null tumor cells of castrated mice. Enhanced Akt activity is observed in Pten null tumor cells of castrated Pten(LoxP/LoxP):Osr1-Cre. This study provides a novel mouse model that can be used to investigate a primary role of Pten in initiating oncogenic transformation in the prostate and to examine other genetic and epigenetic changes that are required for tumor progression in the mouse prostate.
PLoS ONE 01/2013; 8(1):e53476. · 4.09 Impact Factor
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ABSTRACT: Using an Lzts2-knockout (KO) mouse model, we characterize the biological role of Lzts2 in tumorigenesis. Both heterozygous and homozygous deletion of the Lzts2-targeted allele in mice shows an increased incidence in spontaneous tumor development, though Lzts2-homozygous knockout mice show much higher incidences than heterozygous mice. Treatment of Lzts2-deficient mice with a carcinogen, N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN), increases the susceptibility to BBN-induced bladder carcinoma development. Further analyses of mouse embryo fibroblasts (MEFs) isolated from Lzts2 knockout embryos show that loss of Lzts2 enhances cell growth. In addition, a pronounced induction of Wnt3a conditioned medium in cell growth appears in Lzts2 null MEFs, suggesting a regulatory role of Lzts2 in Wnt/β-catenin-mediated cell proliferation. Reduction of LZTS2 protein expression was also observed in human prostate cancer tissue samples. These data provide the first line of evidence demonstrating that deletion of Lzts2 increases the susceptibility of spontaneous and carcinogen-induced tumor development, which may be mediated by dysregulation of Wnt/β-catenin signaling.
Journal of Biological Chemistry 12/2012; · 4.77 Impact Factor
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ABSTRACT: Members of the leucine zipper putative tumor suppressor (LZTS) family play crucial roles in transcription modulation and cell cycle control. We previously demonstrated that LZTS2 functions as a novel β-catenin-interacting protein and represses β-catenin-mediated transcription on T-cell factor/lymphoid enhancing factor. Here, we investigate the biological role of LZTS2 using newly established Lzts2 KO mice. Homozygosity for loss-of-function of the Lzts2-targeted allele resulted in severe kidney and urinary tract developmental defects, including renal/ureteral duplication, hydroureter, and hydronephrosis, which were visible prenatally. Altered ureteric bud outgrowth was identified in Lzts2 null embryos. Further analysis indicated that β-catenin subcellular localization was altered in fibroblasts isolated from Lzts2 null embryos. In addition, Wnt growth factor-induced β-catenin-mediated transcriptional activity was increased in Lzts2 null fibroblasts, suggesting a direct role for Lzts2 in the Wnt signaling pathway. These data demonstrate a critical role of LZTS2 in renal development and implicate LZTS2 as a critical regulator of β-catenin-mediated nephrogenesis.
Journal of Biological Chemistry 09/2011; 286(46):40331-42. · 4.77 Impact Factor
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ABSTRACT: The androgen signaling pathway, mediated through the androgen receptor (AR), is critical in prostate tumorigenesis. However, the precise role of AR in prostate cancer development and progression still remains largely unknown. Specifically, it is unclear whether overexpression of AR is sufficient to induce prostate tumor formation in vivo. Here, we inserted the human AR transgene with a LoxP-stop-loxP (LSL) cassette into the mouse ROSA26 locus, permitting "conditionally" activated AR transgene expression through Cre recombinase-mediated removal of the LSL cassette. By crossing this AR floxed strain with Osr1-Cre (odd skipped related) mice, in which the Osr1 promoter activates at embryonic day 11.5 in urogenital sinus epithelium, we generated a conditional transgenic line, R26hAR(loxP):Osr1-Cre+. Expression of transgenic AR was detected in both prostatic luminal and basal epithelial cells and is resistant to castration. Approximately one-half of the transgenic mice displayed mouse prostatic intraepithelial neoplasia (mPIN) lesions. Intriguingly, four mice (10%) developed prostatic adenocarcinomas, with two demonstrating invasive diseases. Positive immunostaining of transgenic AR protein was observed in the majority of atypical and tumor cells in the mPIN and prostatic adenocarcinomas, providing a link between transgenic AR expression and oncogenic transformation. An increase in Ki67-positive cells appeared in all mPIN and prostatic adenocarcinoma lesions of the mice. Thus, we demonstrated for the first time that conditional activation of transgenic AR expression by Osr1 promoter induces prostate tumor formation in mice. This new AR transgenic mouse line mimics the human disease and can be used for study of prostate tumorigenesis and drug development.
Journal of Biological Chemistry 07/2011; 286(38):33478-88. · 4.77 Impact Factor
