PGR and breast cancer: However, there is no significant difference in circulating IL-37 mRNA expression among breast cancer patients with metastasis among the ER+/PR+/HER2+, ER+/PR+, and PR+ breast cancer patients (57), suggesting that IL-37 expression may be stage dependent, i.e. is more protective among the breast cancer patients without metastasis, but less effective on the patients with metastasis.