Tetraspanin CD151 impairs heterodimerization of ErbB2/ErbB3 in breast cancer cells.

CD151/Tspan24 (SFS-1, PETA3) is one of the best characterized members of the tetraspanin family, whose involvement in breast cancer (BCa) progression was demonstrated both in vitro and in vivo. We have recently reported that in ErbB2-overexpressing BCa cells grown in 3D laminin-rich extracellular matrix, CD151 regulated basal phosphorylation and homodimerization of ErbB2 and sensitized the cells to Herceptin (trastuzumab). Following from these data, we have here analyzed an involvement of CD151 in regulation of ErbB2/ErbB3 heterodimerization and its impact on cell response to Herceptin. CD151 was found to: (1) impair ErbB2/ErbB3 heterodimerization, (2) inhibit heregulin-dependent cell growth in 3D and signaling, and (3) counteract the protective effect of heregulin on Herceptin-mediated growth inhibition. Analysis of tissue samples demonstrated for the first time clinical significance of CD151 in patients with ErbB2-overexpressing BCa undergone trastuzumab-based therapy. Consistent with in vitro results, CD151 impact on disease outcome was ErbB3-dependent. In patients with ErbB3-negative tumors, CD151 significantly improved both overall survival (OS) (hazard ratio [HR] = 0.19, P = 0.034) and progression-free survival (PFS) (HR = 0.36, P = 0.043), while in ErbB3-positive cases it had no significant effect on patient survival (OS: HR = 3.33, P = 0.283; PFS: HR = 2.40, P = 0.208). These results support previous findings and show that CD151 acts as an important component of ErbB2 signaling axis in BCa cells, affecting their sensitivity to ErbB2-targeting therapy.