HER2-low Breast Cancer: Salivary Metabolic Features and Therapeutic Perspectives.

Background: The features of metabolic processes associated with low human epidermal growth factor receptor 2 (HER2) expression (HER2-low) in breast cancer have not been described to date, including characteristic features of immune system reactivity, the presence and content of tumor markers, and the amino acid profile.

Methods: The case-control study involved 660 volunteers with breast cancer. Saliva was used as a biological fluid; at the time of collection, the patients were not receiving any treatment. Concentrations of 7 cytokines, 4 tumor markers, 12 amino acids, and 11 biochemical parameters were determined in the saliva.

Results: It was found that the HER2-low group was characterized by the highest pro-inflammatory activity, but the lowest metabolic activity. Three functional groups of amino acids were identified, which showed reliable differences in the HER2-low subgroup. The cancer antigen 19-9 (CA 19-9) tumor marker in the HER2-low group showed the greatest deviations from normal values compared to patients in the HER2 (-) and HER2 (+) groups.

Conclusions: Thus, patients with HER2-low breast cancer status had their own characteristic features in the course of the disease, immune response and metabolic activity. Understanding the features of metabolic processes in the HER2-low subgroup can help identify new therapeutic targets for this group of patients.