Abstract
Abstract Signaling through cGMP has previously been found to play a role in tissue homeostasis in the intestinal mucosa but the mechanism is not known. Type 2 cGMP-dependent protein kinase (PKG2) is a major cGMP effector in the intestinal epithelium but its role in tissue homeostasis has not previously been examined. The present studies have tested the importance of PKG2 in the regulation of proliferation and differentiation in the mouse colon and in colon cancer cell lines. RT-PCR analysis confirmed that PKG2 is expressed in normal colon mucosa, and although there was no difference in colon tumors, it was undetectable in established colon cancer cell lines. Ectopic expression of PKG2 in LS174T and HT29 cells decreased colony formation in clonogenic assays. This effect of PKG2 on colon cancer cells was not due reduced cell viability but was associated with an increase in G1 arrested cells and increased expression of the differentiation markers CDX2 and MUC2. Consistent with an anti-proliferative and pro-differentiation role of PKG2 in the colon, we observed increased proliferation and larger crypt size in PKG2-/- mice compared to wild type siblings. In addition, there were significantly less mature goblet cells in PKG2-/- mice relative to controls when measured by histological staining with Alcian blue or by immunostaining with anti-MUC2 antibodies. Recent reports suggest that PKG2 might affect differentiation by regulating the transcriptional repressor Sox9. We found that PKG2 could phosphorylate Sox9 at Ser181 in both colon cancer cell lines and in the mouse colon at a position 2/3rd into the crypt. In the colon cancer cell lines, phosphorylation of Sox9 by PKG2 did not affect expression or nuclear localization, and was not sufficient for the regulation of MUC2 or CDX2 expression. The work presented here demonstrates a novel anti-proliferative and pro-differentiation role for PKG2 in the colon, which has an important function in tissue homeostasis. The ability of PKG2 to reduce growth and increase expression of MUC2 and CDX2 tumor suppressors suggests that PKG2 may have therapeutic significance in colon cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3830. doi:10.1158/1538-7445.AM2011-3830
Published Version
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