Abstract 3117: Expression of Hedgehog pathway molecules in patient-derived pancreatic adenocarcinoma xenograft models
Authors: Vuaroqueaux Vincent , Küsters Simon , Fiebig Heinz-Herbert , Foucault Frédéric , Beckers Thomas 
Published: June 2012

Introduction. Pancreatic cancer (PC) is a devastating disease characterized by high failure rates of the conventional therapies. Increasing evidence suggest that PC resistance to therapies is due to their intrinsic ability to develop high contents of fibrotic stroma. It was recently shown that Hedgehog (HH) pathway can influence PC sensitivity to gemcitabine by modulating stroma production via paracrine mechanisms in between tumor cells and its stroma environment. Taking advantage that the stroma in engrafted human tumors in nude mice is produced by the host, we investigated the differential expression of HH pathway molecules by human PC cells and associated murine stroma in PC xenograft models. For this purpose we developed a new species-discriminating qRT-PCR methodology and analyzed a comprehensive collection of 27 patient-derived PC xenograft models previously characterized for their chemosensitivity.

Methods. RNA was extracted from snap frozen PC xenograft samples. After reverse transcription, the samples were assessed using human and mouse species-specific qPCR assays for Tata Binding Protein (TBP), Sonic (SHH), Indian (IHH) and Desert (DHH) Hedgehog ligands, the Hedgehog receptor PATCH1 (PTCH1) and the G-coupled downstream receptor Smoothened (SMO), and for the Zn finger transcription factors GLI1, GLI2, GLI3. Data from human and mouse TBP assays were used for normalization and as surrogate markers of content of human tumor cells vs murine stroma cells in the models.

Results. As measured using TBP, the amount of murine stroma in the PC xenograft models is comparable to that in primary PC tumors and could be as high as 50%. The PC xenograft models with the highest amount of stroma were also most resistant to standard therapies. Among the 27 PC xenograft models the expression of the HH molecules was highly variable. However, we consistently evidenced that the human PC cells preferentially express the HH ligands with much lower or neclectable expression of PTCH1, SMO and GLI transcription factors. SHH and at a lower level IHH were found to be predominant compared to DHH. Of note, tumors cells of few selected xenograft models express however a consistent level of HH receptors and GLI transcription factors. On the opposite, the stroma cells were shown to preferentially express the receptors PTCH1 and SMO as well as GLI transcription factors, but not the HH ligands. In nearly all xenograft models, the transcription factor GLI1 and at lower levels GLI2 were more highly expressed than GLI3.

Conclusion. In PC xenograft models, HH ligands are expressed by tumor cells, whereas respective receptors and downstream signaling molecules are predominantly expressed in the murine stroma. This result argues in favor of a predominantly paracrine mechanism of HH in most of the PC xenograft models investigated. The activity of HH pathway inhibitors to modulate the tumor stroma and affect tumor growth will be investigated.

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 3117. doi:10.1158/1538-7445.AM2011-3117