Multiple studies have shown that miRNAs like miR-205 promote tumor progression in non-small cell lung cancer (NSCLC) by downregulating SMAD4 to inhibit p21 expression [30], while miR-146a-5p and miR-15a suppress cell cycle progression by targeting Cyclin D1/D2 [31]. The gene discussed is SMAD4; the disease is non-small cell lung carcinoma.