For instance, HCAR1 was shown to mediate pro-angiogenic mediator amphiregulin (AREG) production to promote angiogenesis via the phosphatidylinositol 3-kinase (PI3K)/AKT serine/threonine kinase (Akt)-cAMP response element-binding protein (CREB) pathway in breast cancer cells (Figure 4), though the involvement of lactate in this regulation remained unclear in the study [57]. Here, HCAR1 is linked to breast cancer.