One breast cancer study found that endogenous lactate receptor G protein-coupled receptor 81 (GPR81) mRNA expression is elevated in clinical estrogen receptor alpha-positive (ERα+) and human epidermal receptor-growth factor 2-positive (Her2+) breast cancer versus triple-negative breast cancer (TNBC) and benign tissue samples [139]. The gene discussed is ESR1; the disease is triple-negative breast carcinoma.