Abstract 3442: Non-canonical Wnt pathway stimulation in response to LiCl is related to suppression of cell proliferation in histologically distinct human tumors
Authors: Braun Donald P. , Rosales Adriana , Ali Irshad 
Published: May 2015

Disturbances in cellular proliferation are a fundamental characteristic of malignancy, and have often been associated with dysregulation of the Wnt/B-catenin canonical pathway (CAN). The activity of the CAN pathway is subject to regulation by the non-canonical pathway (N-CAN) which stimulates cellular differentiation. The N-CAN pathway which has been described as a negative regulator of the CAN pathway has not been well studied in human cancers and its activity as a possible negative regulator of cellular proliferation in different tumor histologies is not known. The purpose of this study was to characterize the activation of the N-CAN pathway in relationship to tumor cell proliferation in histologically diverse human tumors. LiCl, a known activator of the CAN pathway was used to investigate effects on proliferation of different human tumors along with its capacity to regulate expression of various Wnt pathway signaling components. Cancer cells were derived from surgical specimens obtained from patients with colorectal (CRC), pancreatic (PC), renal (RCC), breast (BC), stomach (SC) and lung (LC) cancers. Cultured cells were treated with LiCl (20 mM) for 72h. Cell proliferation was determined using the MTS assay and gene expression determined using commercially available quantitative RT-PCR Wnt pathway gene expression arrays. Significant inhibition (p&lt;0.05) of proliferation by LiCl was exhibited by all cell types except LC cells. Furthermore, suppression of proliferation was inversely correlated with upregulation of N-CAN components in all tumor types with failure to upregulate N-CAN components in LC cells. The transmembrane protein, VANGL2, which forms a receptor complex for the N-CAN pathway was upregulated significantly in 1 of 2 PC specimens and in RCC and SC cells (mean 17 fold vs. media alone). In cells with increased VANGL2 expression, PRICKLE1 (N-CAN component that interacts with VANGL2), and FRZB, an inhibitor of the CAN pathway were increased by 2.8 and 4.9 folds respectively. In these cells, additional N-CAN components such as NKD1, DAAM1, and CAN inhibitor Wif1 were increased in some, but not all histologies. In contrast, there was no effect on VANGL2 expression in CRC, 1 of 2 PC cells, and BC cells whereas upregulation of additional N-CAN genes and CAN inhibitors was observed in all tumors that demonstrated inhibition of proliferation in response to LiCl. In cancers without VANGL2 increase there was an increase in expression of the N-CAN component NKD1 (6.6 folds) and decreased expression of β-catenin (2.4 folds). Other changes in Wnt pathway genes in these cells that were observed in some but not all cell types included increased expression of FRZB and WIF1. This study demonstrates differential effects of N-CAN pathway components on the proliferation of histologically distinct human tumors.

Citation Format: Donald P. Braun, Adriana Rosales, Irshad Ali. Non-canonical Wnt pathway stimulation in response to LiCl is related to suppression of cell proliferation in histologically distinct human tumors. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3442. doi:10.1158/1538-7445.AM2014-3442