Abstract 4112: E-cadherin regulates cell adherence and β-catenin/TCF signaling in multiple myeloma.

Multiple myeloma (MM) is a malignancy of terminally differentiated clonal plasma cells displaying significant molecular heterogeneity. Alterations in cadherin function have been implicated in tumorgenesis. We have previously demonstrated that the majority (80%) of MM express N-cadherin that mediates interactions between MM cells and the bone morrow microenvironment. In this study we determine the role of E-cadherin, another member of the classical cadherin family, in adhesion and regulation of the β-catenin pathway in MM. Cell lysates were prepared from 24 MM cell lines and from CD138+ cells selected from the BM of eight patients with MM. Six (25%) cell lines expressed high levels of E-cadherin protein as determined by western blotting. Of the 8 patients, 5 expressed E-cadherin: One patient showed a high band intensity. This patient did not express N-cadherin. Four patients showed band of intermediate (2 patients) of low (two patients) intensities. PC from these patients also expressed N-cadherin, as did the PC from the 3 patients that did not express E-cadherin. To determine whether E-cadherin mediates MM cell adherence, a cell aggregation assay was performed using the GFP-tagged MM cell line Sach1, which highly expresses E-cadherin protein but no N-cadherin. Cultured in normal growth medium, Sach1 cells aggregated to form clusters. Addition of an E-cadherin neutralizing antibody to these cultures significantly attenuated aggregation of Sach1 cells. Using immunohistochemistry, E-cadherin protein was clearly observed between myeloma cells in aggregation clusters. Cluster formation was significantly diminished in calcium-free medium, indicating that that like N-cadherin, E-cadherin mediated adhesion is calcium dependent. Next we determined the role of E-cadherin in regulation of the β-catenin/TCF signaling pathway. Complexes of E-cadherin/β-catenin measured by immunoprecipitation were observed in 6 of the cell lines that expressed E-cadherin. Furthermore, high levels of endogenous TCF activity, as determined by luciferase reporter assay, were observed in the 6 MM cells lines. Moreover, overexpression of E-cadherin by transfecting plasmids containing E-cadherin cDNA into three MM cell lines significantly increased nuclear β-catenin concentrations and significantly augmented TCF activity, compared with cells transfected with empty vectors. Taken together, these data suggest that similar to N-cadherin, E-cadherin plays a pivotal role in regulating homotypic adhesion between myeloma cells. E-cadherin also up-regulates β-catenin/TCF signaling pathways in MM. Studies are currently underway to determine the mechanism by which E-cadherin enhances β-catenin/TCF pathway in myeloma. Citation Format: Ya-Wei Qiang, Bo Hu, Yu Chen, Peter Stewart, John D. Shaughnessy, Bart Barlogie, Joshua Epstein. E-cadherin regulates cell adherence and β-catenin/TCF signaling in multiple myeloma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4112. doi:10.1158/1538-7445.AM2013-4112