Epithelial to Stromal Re-Distribution of Primary Cilia during Pancreatic Carcinogenesis

Background The Hedgehog (HH) pathway is a mediator in pancreatic ductal adenocarcinoma (PDAC). Surprisingly, previous studies suggested that primary cilia (PC), the essential organelles for HH signal transduction, were lost in PDAC. The aim of this study was to determine the presence of PC in human normal pancreas, chronic pancreatitis, and during carcinogenesis to PDAC with focus on both epithelia and stroma. Methods PC were analyzed in paraffin sections from normal pancreas, chronic pancreatitis, intraductal papillary-mucinous neoplasia, and PDAC, as well as in primary human pancreatic stellate cells (PSC) and pancreatic cancer cell lines by double immunofluorescence staining for acetylated alpha-tubuline and gamma-tubuline. Co-staining for the HH receptors PTCH1, PTCH2 and SMO was also performed. Results PC are gradually lost during pancreatic carcinogenesis in the epithelium: the fraction of cells with PC gradually and significantly decreased from 32% in ducts of normal pancreas, to 21% in ducts of chronic pancreatitis, to 18% in PanIN1a, 6% in PanIN2, 3% in PanIN3 and to 1.2% in invasive PDAC. However, this loss of PC in the neoplastic epithelium is accompanied by a gain of PC in the surrounding stroma. The fraction of stromal cells with PC significantly increased from 13% around normal ducts to about 30% around PanIN and PDAC. HH-receptors were detected in tumor stroma but not in epithelial cells. PC are also present in PSC and pancreatic cancer cell lines. Conclusion PC are not lost during pancreatic carcinogenesis but re-distributed from the epithelium to the stroma. This redistribution may explain the re-direction of HH signaling towards the stroma during pancreatic carcinogenesis

Epithelial to Stromal Re-Distribution of Primary Cilia during Pancreatic Carcinogenesis.

The Hedgehog (HH) pathway is a mediator in pancreatic ductal adenocarcinoma (PDAC). Surprisingly, previous studies suggested that primary cilia (PC), the essential organelles for HH signal transduction, were lost in PDAC. The aim of this study was to determine the presence of PC in human normal pancreas, chronic pancreatitis, and during carcinogenesis to PDAC with focus on both epithelia and stroma.PC were analyzed in paraffin sections from normal pancreas, chronic pancreatitis, intraductal papillary-mucinous neoplasia, and PDAC, as well as in primary human pancreatic stellate cells (PSC) and pancreatic cancer cell lines by double immunofluorescence staining for acetylated α-tubuline and γ-tubuline. Co-staining for the HH receptors PTCH1, PTCH2 and SMO was also performed.PC are gradually lost during pancreatic carcinogenesis in the epithelium: the fraction of cells with PC gradually and significantly decreased from 32% in ducts of normal pancreas, to 21% in ducts of chronic pancreatitis, to 18% in PanIN1a, 6% in PanIN2, 3% in PanIN3 and to 1.2% in invasive PDAC. However, this loss of PC in the neoplastic epithelium is accompanied by a gain of PC in the surrounding stroma. The fraction of stromal cells with PC significantly increased from 13% around normal ducts to about 30% around PanIN and PDAC. HH-receptors were detected in tumor stroma but not in epithelial cells. PC are also present in PSC and pancreatic cancer cell lines.PC are not lost during pancreatic carcinogenesis but re-distributed from the epithelium to the stroma. This redistribution may explain the re-direction of HH signaling towards the stroma during pancreatic carcinogenesis

Primary cilia (PC) in pancreatic intra-epithelial neoplasia (PanIN) and pancreatic cancer cells (PDAC).

<p><b>(A)</b> Comparison between PanIN 1a (*) and PanIN 1B (#), the latter showing papillary epithelium and reduced number of cilia. <b>(B)</b> PanIN 3 lesion. Epithelial cells do not carry cilia while PC are present in stromal cells (*). <b>(C)</b> Loss of epithelial PC in PDAC (indicated by arrows), while in the stromal cells there is a noticeable increase of both the length of PC and the number of PC carrying cells (*). <b>(D)</b> Length of epithelial PC is decreased in PanIN lesions in comparison to normal pancreas (donor). <b>(E)</b> Gradual loss of epithelial PC in PanIN lesions. In PDAC, almost no epithelial PC were detected. <b>(F)</b> In stromal tissue around PanIN lesions and PDAC (G1/G2), an increased length of PC and <b>(G)</b> increased fraction of cilia carrying cells was evident compared to normal pancreas (donor). Kruskal-Wallis test: <i>p</i> < 0.0001, post-hoc Dunns test: ***<i>p</i> < 0.001 vs. donor, **<i>p</i> < 0.01 vs donor, *<i>p</i> < 0.01 vs donor, ###<i>p</i> < 0. 001 vs PanIN 1A, ##<i>p</i> < 0. 01 vs PanIN 1A, +++<i>p</i> < 0. 001 vs PanIN 1B, +<i>p</i> < 0. 05 vs PanIN 1B, acetylated α-tubuline: red, γ-tubuline: green, DAPI: blue. Mean ± SEM.</p

Re-Distribution of primary cilia (PC) from epithelial to stromal cells in pancreatic carcinogenesis.

<p>The fraction of primary cilia (PC) carrying cells decreases in epithelia, while there is a simultaneous increase of ciliated cells in stromal tissue during pancreatic carcinogenesis (from PanIN 1A to pancreatic G1/G2 ductal adenocarcinomas (PDAC). Mean ± SEM.</p