Abstract A56: The role of Pentraxin 3 (PTX3) in pancreatic ductal adenocarcinoma
Authors: Watt Jennifer , Siddique Imran , Dowe Thomas , Crnogorac-Jurcevic Tatjana , Bhattacharya Satyajit , Allavena Paola , Kocher Hemant M. 
Published: October 2015

Background: Pancreatic ductal adenocarcinoma (PDAC) is a disease with dismal prognosis and is invariably diagnosed late. Current tests used to diagnose or monitor PDAC are invasive and expensive.

Tumour-supportive desmoplastic stroma, an important modulator of PDAC, is laid down by pancreatic stellate cells (PSC). All-trans Retinoic Acid (ATRA), a pleiotropic agent modulating multiple signalling pathways, renders activated stellate cells quiescent. Pentraxin 3 (PTX3) gene level expression is downregulated upon rendering stellate cells quiescent.

The interaction between PTX3 and TSG-6 has been shown in other disease states to stabilise hyaluranon (HA) present in the extracellular matrix. PDAC extracellular matrix is known to be rich in HA.

Methods: Human serum PTX3 levels were measured by ELISA. Twelve pancreatic cell lines, primary and immortalised pancreatic stellate cell lines were screened for PTX3 and TSG-6 expression at protein and mRNA levels. Distribution of PTX3, TSG-6 and HA in organotypic 3D cultures, transgenic mice and patient samples was determined using immunohistochemistry and immunofluorescence.

Results: PDAC patients have significantly higher serum PTX3 levels (median 15.32 ng/ml, range 5.42-39.87 ng/ml, n= 43 ) compared to patients with other pancreatic diseases (median=7.09 ng/ml, range 4.45-14.01 ng/ml, n=36, 2 way anova P=0.014) and healthy individuals (median 3.72 ng/ml, range 1.97-8.82 ng/ml, n=22, 2 way anova P=0.001)

ROC curve analysis ((AUC=0.946 (95%CI= 0.9-0.99, P&lt;0.0001) demonstrates that serum PTX3 levels greater than 8ng/mL can diagnose pancreatic cancer with a sensitivity of 89.47 (CI =78.48 to 96.04%) and specificity of 72.09 (CI 56.33 to84.67%). This is being validated in an independent cohort.

Western blotting and immunofloursecnce demonstrate PTX3 is present maximally in stellate cells and also in some pancreatic cancer cell lines and is secreted in heavily glycosylated form. Rendering PSC quiescent reduced expression and secretion of PTX3.

In the 3D organotypic culture model secreted PTX3 stains both cancer cells and PSC. However, in ATRA treated organotypics only the PSC are positive.

Immunofluorescent examination reveals HA expression at the cellular membrane of PSC with no expression in cancer cells. In the organotypic model there is strong HA expression in the PSC layer.

Immunohistochemistry staining of human PDAC tissues shows PTX3 to be predominantly expressed in the tumour stroma, a small proportion of patients also express PTX3 in the epithelial component of their tumours.

Conclusions: PTX3 distinguishes pancreatic cancer from other diseases of the pancreas and can be tested using a simple blood test. Activated PSC produce this marker and its expression is down regulated on rendering these cells quiescent. PTX3 could be used as a marker for monitoring stromal response in stroma-targeted therapy. The interaction of PTX3 with HA in PDAC is the subject of ongoing investigation.

Citation Format: Jennifer Watt, Imran Siddique, Thomas Dowe, Tatjana Crnogorac-Jurcevic, Satyajit Bhattacharya, Paola Allavena, Hemant M. Kocher. The role of Pentraxin 3 (PTX3) in pancreatic ductal adenocarcinoma. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Innovations in Research and Treatment; May 18-21, 2014; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2015;75(13 Suppl):Abstract nr A56.