Loss of SPARC in bladder cancer enhances carcinogenesis and progression
Neveen Said, … , Rolf A. Brekken, Dan Theodorescu
Neveen Said, … , Rolf A. Brekken, Dan Theodorescu
Published January 16, 2013
Citation Information: J Clin Invest. 2013;123(2):751-766. https://doi.org/10.1172/JCI64782.
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Research Article Oncology

Loss of SPARC in bladder cancer enhances carcinogenesis and progression

Abstract

Secreted protein acidic and rich in cysteine (SPARC) has been implicated in multiple aspects of human cancer. However, its role in bladder carcinogenesis and metastasis are unclear,with some studies suggesting it may be a promoter and others arguing the opposite. Using a chemical carcinogenesis model in Sparc-deficient mice and their wild-type littermates, we found that loss of SPARC accelerated the development of urothelial preneoplasia (atypia and dysplasia), neoplasia, and metastasis and was associated with decreased survival. SPARC reduced carcinogen-induced inflammation and accumulation of reactive oxygen species as well as urothelial cell proliferation. Loss of SPARC was associated with an inflammatory phenotype of tumor-associated macrophages and fibroblasts, with concomitant increased activation of urothelial and stromal NF-κB and AP1 in vivo and in vitro. Syngeneic spontaneous and experimental metastasis models revealed that tumor- and stroma-derived SPARC reduced tumor growth and metastasis through inhibition of cancer-associated inflammation and lung colonization. In human bladder tumor tissues, the frequency and intensity of SPARC expression were inversely correlated with disease-specific survival. These results indicate that SPARC is produced by benign and malignant compartments of bladder carcinomas where it functions to suppress bladder carcinogenesis, progression, and metastasis.

Authors

Neveen Said, Henry F. Frierson, Marta Sanchez-Carbayo, Rolf A. Brekken, Dan Theodorescu

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Figure 5

Loss of SPARC enhances BBN-induced cell-cycle dysregulation in urothelium and in murine urothelial cells in vitro.

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Loss of SPARC enhances BBN-induced cell-cycle dysregulation in urotheliu...
(A) Photomicrographs of Ki67 immunostaining in dissected bladder tissues from the indicated cohorts. Original magnification, ×200. Bars represent mean ± SEM of Ki67-positive nuclei counted in 6 random HPF/slide (n = 5 animals of each genotype/group).*P < 0.05 comparing Sparc–/– and Sparc+/+, 2-tailed Student’s t test. **P < 0.05, 1-way ANOVA. (B) Western blot analysis of 25 μg protein of dissected Sparc+/+ and Sparc–/– urothelium from bladders with the indicated pathology for cell-cycle proteins and their inhibitors. Protein loading was verified by probing the membranes with tubulin. Quantification can be found in Supplemental Figure 1. (C) In vitro proliferation of NU (left) and UC (right) Sparc–/– and Sparc+/+ urothelial cells was determined by CyQuant assay. Cells were allowed to attach in 96 wells for 6 hours in CGM, then were switched to medium with 2% FBS (basal) in the presence and absence of 0–20 μg/ml SPARC or 1 mM NAC for 48 hours. (D) Generation of H2O2 was determined by measuring the fluorescent intensity of DCF of Sparc–/– and Sparc+/+ murine urothelial cells (NU, left; UC, right) under indicated experimental conditions (excitation/emission 488/520 nm). Bars represent mean ± SEM of 2 independent experiments performed in quadruplicate. *P < 0.05 comparing Sparc–/– and Sparc+/+, unpaired 2-tailed Student’s t test; **P < 0.05 comparing the doses of exogenous SPARC, 1-way ANOVA; #P < 0.05 comparing treatment with NAC to control/carrier conditions.