miR-34a inhibited cyclin D1 expression in the non-small-cell lung cancer A549 cell line [73], prostate cancer PC3 cells [74], several oesophageal squamous cell carcinoma cell lines [75], the human breast cancer cell line MCF-7 [76] and the human laryngeal carcinoma cell line HEp-2 [77]. Here, CCND1 is linked to breast cancer.