ADCY4 inhibits cAMP-induced growth of breast cancer by inactivating FAK/AKT and ERK signaling but is frequently silenced by DNA methylation.

Local increases in cyclic adenosine monophosphate (cAMP) caused by specific adenylyl cyclases (ACs) can selectively modulate related proteins. AC-selective drugs have an advantage in side effect control, and the specific AC may finally be considered as a therapeutic target. We show that adenylyl cyclase 4 (ADCY4), which is silenced by DNA methylation and is critical for breast cancer (BC) patient survival, plays essential roles in anti-tumor effects in BC cells. DNA methyltransferase inhibitor and histone deacetylase inhibitor can restore ADCY4 mRNA expression in ADCY4-silenced BC cells. ADCY4 directly affects BC cell proliferation, apoptosis, invasion, and metastasis. Mechanistically, ADCY4 converts ATP to cAMP and activates cAMP/PKA signaling, leading to a decrease in the phosphorylation level of downstream FAK/AKT and ERK signaling and creating a suppression environment for cell survival. Ectopic ADCY4 inhibits BC growth, which is blocked by cAMP inhibition, activating AKT and ERK. The present study provides evidence that human BC relies upon this epigenetic silenced ADCY4-associated ATP-cAMP loop for phosphorylation and activation of FAK/AKT and ERK signaling. Also, ADCY4 increases BC cell chemosensitivity to paclitaxel. The observations demonstrates that ADCY4 is a significant tumor suppressor and that loss of ADCY4 functions by DNA methylation hampers cAMP signaling and triggers FAK/AKT and ERK signaling during breast tumorigenesis.