Further analyses using coimmunoprecipitation couple with mass spectrometry, in situ proximity ligation assay, AlphaFold protein structure prediction, [35S]GTPγS binding assay, and NanoBiT technology demonstrated that A2aR formed heteromers with mGluR5 during the early stage of CCH under high glutamate conditions, promoting the polarization of microglia toward a proinflammatory phenotype. This evidence concerns the gene GRM5 and columnar cell hyperplasia of the breast.