HE staining showed that more lung cancer cells grew in the lung tissues of lv-KCTD21-AS1-treated groups, and siRNA-KCTD21-AS1 and miR-519d-5p suppressed cancer cell proliferation in the lung tissues compared with the control treatment (Fig. 5c; Supplementary Fig. 9b). The gene discussed is KCTD21; the disease is cancer.