Abstract 2628: Non-canonical Wnt signaling in late-stage PDAC
Authors: Stevens Payton D. , Racette Adam , Tiedemann Rochelle L. , Williams Bart O. 
Published: August 2019

Pancreatic cancer has a disproportionate death-to-incidence rate largely resultant from late stage diagnoses, leading to advanced cancers which have metastasized and have increased resistance to common chemotherapeutics. This malignant progression is characterized by the increase of many molecular markers, and developing novel therapeutics targeting these late stage markers is essential for improving patient prognoses. We have identified several proteins within the non-canonical Wnt pathway that are upregulated in advanced pancreatic ductal adenocarcinomas (PDAC), and we are exploring the mechanisms driving upregulation and the resulting alterations to cell signaling. Analysis of microarray data from human derived organoids (from 6 normal pancreas samples and 38 tumor samples) revealed that two receptors in the Wnt pathway, Frizzled 2 (FZD2) and Frizzled 6 (FZD6), have increased expression levels in late-stage PDAC. The temporal increase of these non-canonical, planar cell polarity altering receptors suggests a previously underappreciated role for Wnt signaling in the progression of pancreatic cancer. The increase of these two receptors in tumor tissue was confirmed through analysis of RNA-sequencing of patient samples, including 179 tumor and 171 normal samples. Interestingly, after analyzing patient overall survival and progression free survival we found that, out of the ten members of the Frizzled receptor family, higher levels of FZD2 and FZD6 result in the worst patient prognoses. Additionally, retrospective analysis of gene expression data from Moffitt et al. suggests that FZD2 and FZD6 are higher in the aggressive “basal-like” sub-category of pancreatic cancer. To begin to understand the mechanism for these changes we have used a panel of PDAC cell lines, grown in both traditional and 3-dimensional culture. We have found that decreasing levels of FZD2 and FZD6, through stable sh-RNA knockdown, results in cells which are less motile (observed via Transwell and scratch assays) and are also less capable of anchorage independent growth. Also, cell lines with increased levels of FZD2 result in cells migrating through 3D-matrix as small cell clusters rather than as single cells, which has also been observed in partial-epithelial to mesenchymal transition cell lines. Taken together, non-canonical Wnt signaling in PDAC, mediated by FZD2 and/or FZD6 receptors, results in phenotypic alterations which are consistent with those often observed during cancer progression. These changes may help explain why patients with increased expression of FZD2 and FZD6 have worse prognoses and may also warrant more exploration into specific Frizzled inhibitors.

Citation Format: Payton D. Stevens, Adam Racette, Rochelle L. Tiedemann, Bart O. Williams. Non-canonical Wnt signaling in late-stage PDAC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2628.