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Background. Data on the prognostic role of the PIK3CA mutation in hormone receptor-positive (HR+) HER2-negative (HER2–) breast cancer (BC) are contradictory; nevertheless, there are indications of its negative predictive and prognostic significance. This dictates the need for early genetic testing of BC to predict the clinical course, select a primary therapy option and individualize systemic treatment with disease progression. Investigation of regulation of the tumor cell cycle, as well as the relationship between genetic markers, infiltration of tumor-infiltrating lymphocytes (TILs) and subpopulations of immune cells is strategically important for the search for drug therapy targets.Aim. To search for predictive and prognostic markers of the clinical course of PIK3CA-associated HR+ HER2– BC.Materials and methods. The clinical, morphological and molecular features of the tumor of 101 BC patients with PIK3CA mutations (100 women and 1 man) were analyzed. Early and locally advanced HR+ HER2– BC is present in 81 % of cases, where neoadjuvant chemotherapy (NAPCT) was performed in 28 % of patients. Primary metastatic disease was detected in 17 % of cases. An immunohistochemical evaluation was performed on sections from paraffin blocks using monoclonal antibodies to estrogen receptors, progesterone receptors, HER2, Ki-67, CD8, CD4, CD68, CD163, Bcl-2, p53, cyclin D1. TILs were evaluated when stained with hematoxylin and eosin. TILs were evaluated in the stromal component of the tumor. The correlation of clinical and morphological parameters with the type of mutation and clinical outcomes of treatment of patients with early and locally advanced HR+ HER2– BC was evaluated. The statistical analysis was performed using the IBM SPSS Statistics v. 22 statistical package.Results. In BC with the PIK3CA mutation, a low level of TILs infiltration was detected (1 point), which does not differ depending on the presence of mutations in exon 20 and exon 9 (p >0.05). However, the E545K mutation is characterized by a higher TILs level (2 points) (p = 0.05). CD4+ T-TILs and CD8+ T-TILs levels are statistically significantly higher with mutations in exon 20 compared to exon 9 of the PIK3CA gene (p = 0.017 and 0.013, respectively). At the same time, in comparison with other mutations, tumors with H1047R and E545K mutations (p = 0.05) were characterized by a higher level of CD4 and CD8 expression. Regardless of the mutated exon, a high level of CD68+ tumor-associated macrophages (Me = 80 %), was detected due to the CD163+ fraction of immunosuppressive M2-polarized tumor-associated macrophages (Me = 70 %). A feature of the regulation of the PIK3CA-mutated BC cell cycle is the high level of cyclin D1 expression, the absence of p53 expression and the positive expression of the antiapoptotic marker Bcl-2. The median disease-free survival in early and locally advanced HR+ HER2– BC with the PIK3CA mutation was 36 months (95 % confidence interval (CI) 24.720–47.280). The risk of progression was increased by NAPCT (hazard ratio 3.389; 95 % CI 1.530–7.504; p = 0.003). The risk of progression was reduced by age younger than 49 years (hazard ratio 0.54; 95 % CI 0.30–0.96, p = 0.0359) and the absence of expression of the antiapoptotic marker Bcl-2 (hazard ratio 0.36; 95 % CI 0.14–0.97; p = 0.0425).Conclusion. The data obtained indicate that BC with the PIK3CA mutation is a kind of biological subtype of HR+ HER2– BC, which shows the lack of significant efficacy of NAPCT, probably due to the immunosuppressive microenvironment and low TILs levels. At the same time, the predominant population was M2-polarized tumor-associated macrophages. Moreover, the administration of NAPCT and the positive expression of Bcl-2 reduce disease-free survival, which can be explained by the possible effect of increasing the invasiveness and migration potential of the tumor cell. It is important to continue investigation of identified clinical and morphological prognostic markers when planning and developing new strategies for the treatment of early and metastatic HR+ HER2– BC with the PIK3CA mutation, as well as the use of specific targeted therapy at early metastatic disease.

Background. Currently, there is growth evidence on prognostic and clinical differences in breast cancer (BC) associated with different types of BRCA1 / 2 mutations. At the same time, a triple negative tumor phenotype is not an absolute pathognomonic sign of BRCA1 / 2-associated cancer, where luminal phenotypes are being detected increasingly. In addition, attention is paid to the significance of estrogen signaling mechanism depending on the surrogate tumor type, including a triple negative phenotype due to alternative mechanisms.Objective: to evaluate significance of BRCA1 / 2-mutations in luminal BC subtypes and multiple tumors.Materials and methods. A prospective study conducted in Clinical Oncology Dispensary No. 1 in Krasnodar included 443 patients with breast cancer who underwent a genetic analysis on BRCA1 / 2 genes status by real-time polymerase chain reaction. In diagnostic cases of luminal phenotype and multiple cancers histological material and blood were sent to the N.N. Petrov Research Institute of Oncology of Ministry of Health of Russia to assess the mutation status of the BRCA1 / 2, ATM, CHEK2, NBS1, PALB2 genes by next-generation sequencing (NGS). Statistical analysis of clinical and morphological parameters correlated with mutational status was performed using the IBM SPSS Statistics v.22 statistical package.Results. An interim analysis of data in April 2022 showed that 71 out of 304 breast cancer patients tested by polymerase chain reaction were found to be carriers of BRCA1 gene mutations. NGS method revealed 20 additional mutations of the BRCA1 / 2 genes: 11 BRCA1 mutations and 9 BRCA2 mutations. PALB2 mutation was also detected in 1 patient, NBS1 mutation – in 3, CHEK2 mutation – in 2, ATM mutation – in 2 patients. Out of 91 BRCA1 / 2-associated breast cancer 21 BRCA1-mutated tumors and 9 tumors with BRCA2-mutation demonstrated luminal phenotypes. The median age of breast cancer disease did not differ in BRCA1- and BRCA2-carriers (42 years versus 40 years, p ˃0.05). BRCA1 mutations are associated with poor differentiation (G3), BRCA2 mutations are associated with G2 (p ˂0.001). The BRCA2 mutation is characterized by a luminal tumor phenotype (p ˂0.001). There was no association of BRCA1 / BRCA2 gene mutations with T and N status (p ˃0.05). Of the 91 cases of BRCA-deficient tumors, 30 (33 %) patients had primary multiple cancer: 27 (90 %) with germinal mutation BRCA1 and 3 (10 %) with germinal mutation BRCA2. Contralateral breast cancer in the presence of germinal mutation BRCA1 was detected in 14 patients. The frequency of primary multiple cancer and contralateral breast cancer detection did not depend on the type of BRCA1 / 2 mutations (p ˃0.05).Conclusion. With the primary multiplicity of the tumor process and the luminal subtype of the tumor, the determination of mutations by polymerase chain reaction in real time is clearly insufficient. It is obvious that the NGS method can identify additional pathogenic mutations that predict the clinical course and indicate the possibility of personalizing therapy and the need to test relatives, including tumors with luminal phenotype and tumors of several localizations.

Background. It is suggested that defects in BRCA1 / 2 genes contribute to a high mutational load and high immunogenicity, which modulates immune microenvironment. At the same time, it was shown that BRCA1 / 2-associated breast cancer tumors do not belong to the category of immunoactive ones. These tumors have low expression of immune response genes and exhibit an immunosuppressive type of microenvironment. This indicates the need of antitumor immune response modulation and maintaining of the optimal balance of tumor CD4/CD8 T-lymphocytes ratio. In addition, there is evidence of the additional evaluation of TP53 mutation in these tumors and disruption of the cell death process, which can also be a factor of resistance to therapy, including PARP inhibitors, and serve as a therapeutic target.Materials and methods. The prospective study included 20 patients with BRCA1-associated breast cancer. BRCA1 / 2 mutations (BRCA1 185delAG, 4153delA, 5382insC, 3819delGTAAA, 3875delGTCT, 300T>G, 2080delA, BRCA2 6174delT) were detected in by real-time polymerase chain reaction. Immunohistochemical study was performed on paraffin embedded tissue blocks by an automated method on a ThermoScentific immunohistotainer using monoclonal antibodies. The expression of markers of tumor-infiltrating CD4+ and CD8+ T-lymphocytes, markers of macrophages (CD68, CD163), apoptosis (Bcl-2, p53), cell adhesion markers (E-cadherin, β-catenin) in breast cancer in carriers of BRCA1 mutations was assessed.Results. High CD4/CD8 ratio, which characterizes immunosuppressive microenvironment, occurred in 75 % of cases. BRCA1 5382insC mutation is associated with high level of CD4+ TILs (p˂0.05), G2 is associated with a low CD4/CD8 ratio (p = 0.039) and a high level of CD163 (p = 0.02, AUC = 0.739); T1 correlates with high levels of CD8+ TILs (p = 0.038) and high levels of CD163 (p = 0.033). High Ki-67 is associated with a lack of Bcl-2 expression (p = 0.04) and a low level of E-cadherin (p = 0.02). Negative expression of Bcl-2 occurred in 75 % of cases. High level of p53 expression has been described as the main type of expression in these tumors, suggesting a combination of TB53 and BRCA1 mutations and a violation of cell death mechanism of in these tumors.Conclusion. Breast cancer tumors of patients with hereditary mutations in BRCA1 gene demonstrate immunosuppressive type of microenvironment and a violation of the cell death mechanism. The main directions of future therapy of these tumors may include tumor immune microenvironment modification and activation of cell death mechanisms.