The let-7 family acts as tumor suppressor miRNAs in MM, with a low level of let-7 inducing cell proliferation and growth by depressing oncogenes such as CCND1, MYC, and RAS. miR-18a is a component of the miR-17-92 cluster in chromosomal region 13q31.3 and was reported to be associated with HIF-1 regulation and tumor metastasis. The gene discussed is CCND1; the disease is neoplasm.