Abstract LB-076: Spatial regulation of β-actin monomer synthesis controls epithelial-mesenchymal tissue fate specification: consequences for cancer and metastasis progression

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA The purpose of this study is to investigate the extent to which spatially regulating β-actin gene expression controls epithelial-mesenchymal fate specification in healthy and cancer tissue culture models. We utilize mRNA zipcode antisense oligonucleotide masking of the β-actin transcript and translation site imaging to assess the consequences of perturbing the location of monomer synthesis during cancer and healthy epithelial tissue establishment and maintenance. Additionally, we developed a novel method to quantify adherens junction assembly based on fluorescence covariance between E-cadherin and F-actin during Ca2+ switch experiments to assess the consequences of β-actin monomer synthesis mislocalization in epithelial tissue culture model systems. Using these methods we demonstrate that perturbing the location of β-actin monomer synthesis by mRNA zipcode antisense oligonucleotide masking in healthy 2D and 3D epithelial tissue culture models perturbs adherens junction assembly and causes epithelial-mesenchymal transition. Moreover, perturbing E-cadherin expression or function causes β-actin monomer synthesis mislocalization, perturbs adherens junction assembly, and causes epithelial-mesenchymal transition. By contrast, β-actin mRNA zipcode antisense nucleotide masking in 3D colon cancer tissue culture models causes no additional structural defects since adherens junctions are already disorganized. Importantly, western blot analysis of whole tissue lysates from these colon cancer models reveals altered expression of key components of the pathway used to regulate the spatial location of β-actin monomer synthesis such as E-cadherin or Zipcode Binding Protein-1. Together, these data support a model where E-cadherin regulates the location of β-actin monomer synthesis by modulating Zipcode Binding Protein-1/mRNA zipcode interactions to control adherens junction homeostasis and consequently epithelial-mesenchymal cell fate specification. Using β-actin antisense zipcode oligonucleotide masking during Ca2+ switch experiments we demonstrate 3D colon cancer tissue culture models have already lost function of the β-actin spatial translation pathway and therefore are not further perturbed during this assay. Consequently, we hypothesize that spatially regulating β-actin monomer synthesis is a key aspect of controlling epithelial-mesenchymal cell fates specification and loss of this pathway is expected to predispose epithelial tissues to cancer and metastasis progression. This is an attractive hypothesis explaining the molecular and cellular mechanism of how E-cadherin and Zipcode Binding Protein-1 function as potent metastasis inhibitors and highlights the importance of spatially regulating β-actin gene expression as an approach to establish and maintain healthy epithelial tissues. Citation Format: Pavan Vedula, Lissette A. Cruz, Alexis J. Rodriguez. Spatial regulation of β-actin monomer synthesis controls epithelial-mesenchymal tissue fate specification: consequences for cancer and metastasis progression. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-076. doi:10.1158/1538-7445.AM2015-LB-076