RELT is overexpressed in human inflammatory bowel disease and breast cancer.

Abstract

Abstract Receptor Expressed in Lymphoid Tissues (RELT) is a human TNFR member that activates NF-kB and is implicated in several cancers. We therefore sought to characterize the association of RELT with inflammatory bowel disease (IBD) and breast cancer (BC). Additionally, we further characterized the association of RELT with Filamin A (FLNA), an actin-binding protein that can promote tumorigenesis, or counteract tumors, depending on its cellular location. Female CB-17 SCID mice were injected with anti-CD40 monoclonal antibody to induce colitis and euthanized seven days later. Immunohistochemistry (IHC) was utilized to compare RELT expression in the mouse colitis model with uninjected control mice. IHC was utilized to compare the expression of RELT in biopsies of human IBD and non-inflamed tissue, as well as human BC versus non-malignant tissue. Luciferase assays and an X-gal morphology assay were utilized to examine cell death in the BC cell line MDA-MB-231 (231). RELT immunostaining is significantly increased in both mouse colitis and human IBD biopsies in comparison to that of species-matched non-inflamed tissue. An apparent association between colonic histological damage and RELT immunostaining was observed in both mice and human specimens. RELT staining was also increased in human BC biopsies versus patient-matched non-malignant tissue. RELT overexpression induced death in 231 cells, an effect that was not abrogated by a RELT mutation in the binding site for the OXSR1 kinase. However, co-expression of a S2152A mutant of FLNA did abrogate the ability of RELT to induce death in 231 cells. Collectively, these results implicate RELT as being important for human disease and further our understanding of the interaction between RELT and FLNA.