OXTR and breast cancer: For instance, OTR is upregulated in the uterine smooth muscle cells during gestation and mammary gland myoepithelial cells during lactation, resulting in higher OT sensitivity [56]; serum deprivation (a similar situation to nutrition deprivation in the solid tumour) of Hs578T breast cancer cells results in loss of OTR expression and OT-induced intracellular calcium accumulation, while serum restoration recovers OTR expression and responsiveness to OT [19].