Expression of gamma-aminobutyric acid type A receptor subunit π and minichromosome maintenance-3 in breast cancer patients treated with neoadjuvant chemotherapy: a target molecule or a proliferation marker?

OBJECTIVE: The receptors and cell membrane channels found in breast cancer in high numbers have been promising for drugs in the past and in the future. In addition, analyses of proliferation indices play an essential role in predicting the success of these treatments. METHODS: Gamma-aminobutyric acid type A receptor subunit π and minichromosome maintenance-3 expressions were studied by immunohistochemical staining from tissue samples obtained by trucut biopsy from epidermal growth factor receptor 2-negative breast cancer patients who received neoadjuvant chemotherapy. RESULTS: The study included 101 patients. Almost 96.0% of the breast tumor tissues expressed gamma-aminobutyric acid type A receptor subunit π. The median value for gamma-aminobutyric acid type A receptor subunit π was calculated as 30% (19 patients) and the median for minichromosome maintenance-3 as 80% (13 patients). When neoadjuvant chemotherapy response was evaluated, pathological complete response was achieved in 23.8% of patients (n=24). Pathological complete response was achieved in 16.4% of patients for hormone receptor positivity and in 38.2% of patients for triple-negative breast cancer. When the factors predicting pathological complete response were evaluated with univariate analysis, age (p=0.044), molecular subtype (p=0.017), menopausal status (p=0.032), Ki-67 increase (p<0.001), estrogen receptor decrease (p<0.006), progesterone receptor decrease (p<0.002), and grade (p<0.001) predicted treatment response. There was no relationship between gamma-aminobutyric acid type A receptor subunit π (p=0.945) and minichromosome maintenance-3 (p=0.985) and treatment response. CONCLUSION: Our study found that gamma-aminobutyric acid type A receptor subunit π is highly expressed in breast cancer cells but absent in normal breast tissue, making it a potential therapeutic target. Additionally, we determined that minichromosome maintenance-3 is not a reliable proliferation index or predictor of treatment response.