G protein-coupled oestrogen receptor 1 (GPER), also called
G protein-coupled receptor 30 (GPR30), is attracting considerable attention for its potential role in
breast cancer development and progression. Activation by oestrogen (17β-
oestradiol; E2) initiates short term, non-genomic, signalling events both in vitro and in vivo. Published literature on the prognostic value of GPER
protein expression in
breast cancer indicates that further assessment is warranted. We show, using immunohistochemistry on a large cohort of primary invasive
breast cancer patients (n=1245), that low
protein expression of GPER is not only significantly associated with clinicopathological and molecular features of aggressive behaviour but also significantly associated with adverse survival of
breast cancer patients. Furthermore, assessment of GPER
mRNA levels in the METABRIC cohort (n=1980) demonstrates that low GPER
mRNA expression is significantly associated with adverse survival of
breast cancer patients. Using artificial neural networks, genes associated with GPER
mRNA expression were identified; these included notch-4 and
jagged-1. These results support the prognostic value for determination of GPER expression in
breast cancer.