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 4

Lack of SPARC is associated with augmented ROS accumulation, DNA damage, lipid peroxidation, and protein oxidation.

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Lack of SPARC is associated with augmented ROS accumulation, DNA damage,...
(A) Representative bladder cryosections from Sparc–/– and Sparc+/+ mice were incubated with 10 μM DHE for 15 minutes at 37°C. Cells staining positively for the oxidized dye were identified by fluorescent microscopy (DHE fluorescence was detected with excitation/emission at 518/605 nm) and quantified by ImageJ analysis software. Original magnification, ×200. Bars represent mean ± SEM (n = 4 animals/cohort, 10 sections each). *P < 0.05 between Sparc–/– and Sparc+/+, Student’s t test; **P < 0.05 between different cohorts, 1-way ANOVA. (B) DNA damage in total DNA extracted from dissected bladders was determined by 8-OHdG EIA per manufacturer’s instructions. (C) Lipid peroxidation was determined in bladder lysates by 8-isoprostane EIA per manufacturer’s instructions. *P < 0.05 between Sparc–/– and Sparc+/+, unpaired 2-tailed Student’s t test; **P < 0.05 between different cohorts, 1-way ANOVA. (D) Western blots of bladder lysates of Sparc–/– and Sparc+/+ (25 μg, n = 5) showing increased levels of protein oxidation markers NNMT and sulfiredoxin. Equal protein loading was confirmed by reprobing blots with tubulin.