The impact of the integrin β6 on integrin αv heterodimers and their functions

Objectives Integrin β6 (ITGβ6) is associated with the pathogenesis of colorectal cancer (CRC) and exerts its functions as an epithelial cell specific heterodimer with the αv-integrin. ITGβ6 is known to play a significant role in epithelial remodeling, tumor invasion, and fibrotic signaling. However, its regulatory impact on other integrin subunits and associated extracellular matrix (ECM) functions has not been fully elucidated in CRC. This study aimed to examine the influence of ITGβ6 on the expression, interaction, and functional behavior of other αv-associated integrin heterodimers and downstream cellular processes in CRC, with the goal of identifying novel integrin-mediated regulatory mechanisms relevant to tumor biology. Design & Methods CRISPR/Cas9-mediated genome editing was employed to generate ITGβ6 knockout (KO) and wild type (WT) HT-29 CRC cells. Western blotting and cell surface staining confirmed successful gene editing. Protein expression analyses of key integrins and ECM components were conducted. Co-immunoprecipitation (co-IP) assays were performed to evaluate integrin- integrin interactions. Functional assays assessed differences in proliferation, cytokine responsiveness (IL-1β, IFN-γ), HGF-induced migration, and apoptosis between KO and WT cells. Observations & Results Loss of ITGβ6 led to a notable downregulation of collagen type XVI alpha 1 chain (COL16A1), indicating that ITGβ6 may contribute to ECM remodeling by regulating collagen expression. Furthermore, expression of ITGβ5, ITGβ1, ITGβ8, and ITGαv was significantly reduced in KO cells, suggesting that ITGβ6 is essential for the stability of a broader integrin network. Co-IP analyses revealed that ITGβ6 deficiency did not affect the binding of ITGαv to ITGβ5 or ITGβ8, whereas its interaction with ITGβ1 was enhanced. Functionally, KO cells showed reduced proliferation, altered cytokine response, significantly impaired HGF-stimulated migration, and a marked increase in apoptosis following Nutlin-3 treatment. Conclusions ITGβ6 regulates not only its canonical heterodimer formation with ITGαv, but also affects the expression of and interaction with other integrins. Moreover, it regulates ECM composition. It exercises anti-apoptotic function and contributes to stimulation of proliferation and migration. These findings support a broader role of ITGβ6 in the regulation of the integrin network functions in CRC cells. ITGβ6 may therefore represent a promising molecular target for CRC therapy, particularly in tumors reliant on integrin-mediated signaling for survival and invasion.