Abstract 956: Role of E-cadherin in progression of invasive breast lobular carcinoma

Abstract Invasive lobular carcinoma (ILC) is the second most frequently diagnosed histologic subtype of invasive breast cancer following invasive ductal carcinoma (IDC) and accounts for 15% of all cases. The hallmark of ILC is the genetic loss of E-cadherin (CDH1) causing the disruption of adherens junctions and resulting in discohesive, linear growth of ILC cells in tissues. Beyond its effects on this unique histology, there is limited data on the role of E-cadherin loss in ILC metastasis. Therefore, we generated three ILC cell lines (MDA-MB-134, SUM44PE and BCK4) with inducible E-cadherin overexpression. Using immunoblotting and immunofluorescence microscopy we confirmed E-cadherin expression, re-expression of other adherens junction proteins including α and β-catenin, and re-localization of cytoplasmic p120-catenin to the membrane. Successful cell adhesion to E-cadherin coated plates suggested formation of functional junctions. E-cadherin expression had no effect on 2D growth but did diminish cell growth in ultra-low attachment (ULA) conditions consistent with its previously described role in anoikis. We confirmed increased cell death of MM134 with E-cadherin overexpression compared to control cells when grown in ULA. Overexpression of E-cadherin failed to rescue poor migratory and invasive ability of ILC cell lines as measured by transwell assays. However, E-cadherin expression in SUM44PE lead to decreased haptotaxis to collagen I, and altered morphology from loose grape-like structure to tight sphere-like formation when embedded in collagen I.In vivo analyses revealed reduced primary tumor formation in E-cadherin-overexpression SUM44PE cells after mammary fat pad injection. Additional studies aimed at understanding E-cadherin’s effect on in vivo metastasis are ongoing.Collectively, our studies using novel cell line models will lead to an improved understanding of the hallmark loss of E-cadherin and disease mechanisms in ILC, which we hope will ultimately enable the development of more effective therapies and improve the outcome of patients with this understudied histological subtype of breast cancer. Citation Format: Laura Savariau, Nilgun Tasdemir, Ashuvinee Elangovan, Kai Ding, Pooja Sree Tallapaneni, Jagmohan Hooda, Jennifer M. Atkinson, Adrian V. Lee, Steffi Oesterreich. Role of E-cadherin in progression of invasive breast lobular carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 956.