Additionally, significant reduced expression of tumor suppressors miR-185, miR-126, miR-218 and miR-494 in ADR-resistant gastric cancer cells could diminish ADR sensitivity by silencing apoptosis repressor with caspase recruitment domain (ARC), enhancer of zeste homolog 2 (EZH2), smoothened (SMO, a transmembrane protein and member of Hedgehog pathway) and phosphodiesterase 4D (PDE4D), respectively [76–79]. The gene discussed is PDE4D; the disease is gastric cancer.