Immunohistochemical subtyping and evaluation of the prognosis of basal-like triple-negative breast cancer based on IDO1 protein expression

Background. Known subtypes of triple-negative breast cancer, despite the common basal-like profile, have certain features that differ in terms of the course and prognosis of the disease. Therefore, the study of molecular markers that make it possible to identify subtypes of basal-like carcinomas and evaluate a probable prognosis based on their expression indicators is relevant today. Aim. Conduct immunohistochemical subtyping of basal-like triple-negative breast cancer based on the assessment of IDO1 protein expression, compare the obtained data with clinical and morphological characteristics, as well as indicators of tumor sensitivity to neoadjuvant therapy. Material and methods. The study was retrospective and included 42 patients diagnosed with triple negative breast cancer (mean age 50.512.7 years), disease stage T14dN03M0. The patients were treated in the Departments of Chemotherapy and General Oncology of the Research Institute of Oncology of the Tomsk National Research Medical Center from 2016 to 2021. A morphological study of tumor tissue samples, breast core biopsies, and surgical material was performed. Immunohistochemical study was carried out on sections of core biopsies. The expression of markers was evaluated, the obtained data were compared with clinical and morphological characteristics, as well as with indicators of tumor sensitivity to neoadjuvant therapy. Statistical analysis was carried out using the Statistica 10.0 program, data comparison was performed using the methods of descriptive statistics and nonparametric method of Pearson's 2 test. Results. The immunoactivated subtype was determined with the status of CK5/6+/IDO1+ carcinomas, such tumors were dominant and accounted for 81.25% (n=26/32). In these cases (CK5/6+/IDO1+), the presence of metastatic lesions in the axillary lymph nodes was statistically significantly less common, and the frequency of complete pathomorphological regression was higher than in carcinomas, the molecular profile of which corresponds to the immunosuppressive subtype (CK5/6+/IDO1). Conclusion. Expression of the IDO1 protein may serve as a molecular and biological marker allowing immunohistochemical identification of subtypes of basal-like triple-negative breast cancer.