THE ROLE OF NESPRIN-4 IN BREAST CANCER INVASION AND METASTASIS

Abstract

Cancer metastasis is responsible for most cancer-related deaths. Migration and invasion, key steps in the metastatic cascade, require nuclear pliability to pass through physical constrictions presented by the extracellular matrix and cell-cell junctions. The nuclear envelope (NE) contains LINC complex proteins, including Nesprin-4, which regulate nuclear integrity, stiffness, and cell movement. We report that Nesprin-4 expression is upregulated in most breast cancer samples but downregulated in triple negative breast cancer (TNBC) samples. Analysis of 62 breast cancer cell lines revealed that less invasive cells show Nesprin-4 expression while TNBC cell lines have reduced or no Nesprin-4 expression. We modulated Nesprin-4 expression levels in three breast cancer cell lines: MCF7, T47D (luminal A and Nesprin-4-positive), and MDA-MB-231 (TNBC and Nesprin-4-negative). Analysis of these cells indicates that Nesprin-4 promotes migration and invasion by driving cell polarization. However, we found that Nesprin-4 impedes intravasation into endothelial microvessels. Thus, Nesprin-4 appears to play a dual role in breast cancer, promoting efficient migration and invasion, but blocking intravasation. Since Nesprin-4 expression varies across the breast cancer subtypes, we aimed to understand the mechanisms regulating its expression. Published data have identified putative sterol regulatory element-binding protein (SREBP) binding sites on the Nesprin-4 promoter, and both SREBP and Nesprin-4 are co-expressed in breast tissues, with upregulation observed in breast cancer. Moreover, correlation analysis demonstrated a strong association between Nesprin-4 and SREBP expression in breast cancer, further suggesting that SREBP plays a regulatory role in Nesprin-4 expression. To validate this hypothesis, we performed a luciferase reporter assay and electrophoretic mobility shift assay (EMSA), both of which confirmed that SREBP regulates Nesprin-4 expression. These findings suggest that SREBP-mediated transcriptional control could be a key mechanism for modulating Nesprin-4 levels in breast cancer cells.

Date of Award	2025
Original language	American English
Awarding Institution	HBKU College of Health & Life Sciences