# Salivary Antioxidant and Peroxidase Activity as a Marker of Steroid Hormone Receptor Expression in Breast Cancer

## TL;DR

This study explores how salivary antioxidant and peroxidase activity relates to hormone receptor expression in breast cancer patients.

## Contribution

It is the first to show that salivary TPA and AOA levels increase in breast cancer patients.

## Key findings

- Salivary lipid peroxidation products increased with positive estrogen receptor expression.
- Salivary TPA and AOA levels were higher in breast cancer patients.
- Antioxidant defense effectiveness was linked to hormone receptor status and cancer prognosis.

## Abstract

The growth and development of breast cancer are accompanied by an increase in oxidative stress. A close relationship is known to exist between the biological activity of several antioxidant enzymes and the regulation of estrogen-mediated signaling in breast cancer. The aim of this study was to study the activity of salivary antioxidant enzymes and the level of lipid peroxidation products in breast cancer before and after surgical treatment. The study included 115 patients with breast cancer (58.7 ± 10.9 years) and 60 healthy volunteers (51.8 ± 12.1 years). Saliva samples were obtained again from 53 patients 4 weeks after surgery. The content of lipid peroxidation products, catalase activity, total antioxidant activity (AOA) and total peroxidase activity (TPA) in saliva were analyzed before and after breast cancer surgery. An increase in lipid peroxidation products in saliva was observed with positive estrogen receptor expression. For the first time, it was shown that in patients with breast cancer, the levels of salivary TPA and AOA increased, which is likely due to the important role of the salivary glands in antioxidant protection. It can be speculated that the effectiveness of antioxidant defense was associated with estrogen and progesterone receptor expression and was reduced in prognostically unfavorable breast cancer phenotypes (non-luminal and triple-negative breast cancer).