Human chorionic gonadotropin (hCG) is a glycoprotein produced by placental trophoblasts. Previous studies indicated that hCG could be responsible for the pregnancy-induced protection against breast cancer in women. It is reported that hCG decreases proliferation and invasion of breast cancer MCF-7 cells. Our research also demonstrates that hCG can reduce the proliferation of MCF-7 cells by downregulating the expression of proliferation markers, proliferating cell nuclear antigen (PCNA), and proliferation-related Ki-67 antigen (Ki-67). Interestingly, we find here that hCG elevates the state of cellular differentiation, as characterized by the upregulation of differentiation markers, β-casein, cytokeratin-18 (CK-18), and E-cadherin. Inhibition of hCG secretion or luteinizing hormone/hCG receptors (LH/hCGRs) synthesis can weaken the effect of hCG on the induction of cell differentiation. Furthermore, hCG can suppress the expression of estrogen receptor alpha. hCG activated receptor-mediated cyclic adenosine monophosphate/protein kinase A signaling pathway. These findings indicated that a protective effect of hCG against breast cancer may be associated with its growth inhibitory and differentiation induction function in breast cancer cells.
Alex's Notes: hCG is an essential part of pregnancy that gradually increases upon fertilization until weeks 9-12 where it begins to decline again. It can induce ovulation in women, and can stimulate testosterone production in men. Of course, the FDA banned its use in 2011. This followed the "hCG" diet craze, but I'm getting off topic. It appears that hCG protects against breast cancer, which in retrospect is important for women who are going to give birth to offspring that are ideally breastfed. This raises the question of use in women who already suffer from breast cancer.