Immunohistochemical Evaluation of Integrin β6 Expression in Triple-Negative Breast Cancer as a Predictive Biomarker for Therapeutic and Diagnostic Radionuclides.

Triple-negative breast cancer (TNBC) is an aggressive breast cancer subtype associated with limited therapeutic options and poor clinical outcomes. The aim of this research is to assess the prevalence, intensity, and distribution of integrin αvβ6 expression in TNBC using immunohistochemistry and to evaluate its potential as a predictive biomarker for αvβ6-targeted radionuclide therapy and other αvβ6-targeted theranostic approaches. Immunohistochemical analysis of integrin αvβ6 was performed on formalin-fixed, paraffin- embedded tumor samples from 48 patients with histologically confirmed TNBC. Staining intensity and the proportion of positive tumor cells were assessed using a semi-quantitative scoring system, and expression patterns were analyzed with regard to cellular localization and intratumoral heterogeneity. Moderate to strong integrin αvβ6 expression was observed in 43.8% of cases, with strong expression (≥50% of tumor cells) present in 25%. Expression was predominantly membranous, with occasional cytoplasmic staining, and demonstrated marked inter- and intratumoral heterogeneity. Integrin αvβ6 is frequently expressed in TNBC and represents a promising biomarker for patient selection in αvβ6-targeted radionuclide imaging and therapy. These findings provide a strong biological rationale for the clinical translation of integrin-targeted radioligands and support the development of personalized radiotheranostic strategies in TNBC.