Thus, this study revealed that cytoplasmic GPER mediated the biosynthesis and secretion of glutamine via the cAMP/PKA/CREB/GLUL pathway in CAFs through both in vivo and in vitro experiments, further delineating that the unique function of microenvironment GPER signalling has a critical impact on TNBC metabolism to stimulate tumour progression. The gene discussed is CREB1; the disease is neoplasm.