Moreover, exenatide downregulated signal transducer and activator of transcription 3 (STAT3), which suppressed multiple STAT3-targeted genes including MYC and CCND1. Activation of cAMP and PKA by exenatide was confirmed in an in vitro study using hepatoma, colon cancer, and breast cancer cells [43,44]. Here, CCND1 is linked to breast cancer.