Abstract 2449: Pancreatic cancer tumor initiating cells are marked by the presence of a primary cilium

Abstract

Abstract Primary cilia are microtubule rich projections eminating from the apical surface of epithelial cells. Primary cilia are responsible for the transduction of growth factor and morphogenetic signaling pathways, including the hedgehog, wnt and platelet-derived growth factor pathways. Initial observations in the field of pancreatic cancer have suggested the absence of primary cilia in human pancreatic intraepithelial neoplasia (PanIN) and pancreatic ductal adenocarcinoma. While absent in the majority of pancreatic cancer cells, primary cilia have been identified in differentiated acinar cells undergoing an acinar to ductal metaplasia. This metaplasia is well characterized in pancreatic injury and regeneration models and accelerates tumor formation in the presence of acinar specific KrasG12D mutations. Thus, we are addressing the hypothesis that primary cilia, while not expressed in bulk tumor populations, are maintained in pancreatic tumor-initiating cells. To address the hypothesis, we have used confocal microscopy to quantify the percentage of cells within low grade human PanIN lesions that express a primary cilium. Performing confocal microscopy on a human PanIN tissue array (n=23), we have determined that in 15% of PanIN lesions, 13-30% of the cells are expressing a primary cilium, as is evidenced by staining for acetylated alpha tubulin. We have also developed a sorting strategy using an acetylated alpha tubulin antibody to isolate ciliated cells by Fluorescence Activated Cell Sorting (FACS) analysis. Using this protocol, we have discovered that human pancreatic cancer cells bearing a primary cilium are markedly enriched in cells also positive for either CD133 or CD24/CD44, representing putative pancreatic cancer stem cell populations. We have functionally analyzed the tumor-initiating capacity of ciliated vs non-ciliated cells using tumor sphere experiments. In this assay, ciliated cells show a significant increase (100 fold) in tumor sphere-forming capacity, suggesting that the presence of a primary cilium may mark a pancreatic cancer tumor initiating population. These data are informative regarding the earliest initiating events in pancreatic 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 2449. doi:10.1158/1538-7445.AM2011-2449