25P - Immunohistochemical analysis of ROR1 and BMI-1 expression in luminal breast cancer

Background

Despite the fact that adjuvant hormone therapy (HT) increases 10-year recurrence-free survival by 40-50%, progression is observed in a part of patients with luminal cancer on the background of HT. This determines the relevance of searching for new molecular genetic markers to predict outcomes and personalize treatment.

Methods

A sample of 80 patients (62.1±8.1 y.) T1-2N0-1M0 stages of breast cancer. All patients were in menopause and received surgical treatment and adjuvant HT with aromatase inhibitors. The follow-up period was 3 years. The study of ROR1 and BMI-1 protein expression in the tumor was performed on paraffin sections of tumor tissue by immunohistochemistry. Antibodies to ROR1 (poly, 1:100) and BMI-1 (poly, 1:100) were used. In each case the presence and severity of staining and the percentage of stained tumor cells were evaluated.

Results

In 68 cases there were no signs of disease progression, in 12 cases the appearance of distant metastases was registered. Positive expression of BMI-1 was observed in 64% of cases, ROR1 expression was less frequent - 24%. Patients with positive expression of BMI-1 the size of the primary tumor was significantly larger compared to the group of patients whose tumors did not show immune staining to BMI-1 (p<0.05). No such correlation was found with respect to the frequency and level of ROR1 expression (p>0.05). The number of cases with positive expression of ROR1 factor increased with increasing tumor malignancy grade (p<0.05). In addition, it was found that in the group of patients with the presence of metastatic lesions of regional lymph nodes, the expression of both indicators was significantly higher (p<0.05). Distant metastases was associated with high levels of BMI-1 expression in the tumor (p<0,05).

Conclusions

The conducted study showed that the study of the role of regulatory proteins ROR1 and BMI-1 and clearly demonstrates the interrelation of clinicopathological parameters of tumor in luminal breast cancer. Studying the development of distant metastases with BMI-1 expression in the tumor will help to understand the mechanisms of the development of ineffectiveness of aromatase inhibitor therapy occurring in postmenopausal luminal breast cancer patients despite an initially more favorable prognosis.

Editorial acknowledgement

Clinical trial identification

Legal entity responsible for the study

Cancer Research Institute is a subdivision of the Federal State Budgetary Scientific Institution “Tomsk National Research Medical Center of the Russian Academy of Sciences” (Tomsk NRMC).

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.