MiR-let-7 acts as a tumor suppressor miRNA that downregulates KRAS expression [231].MiR-let-7 mimics injected into the genetically engineered NSCLC mouse model dramatically reduced its tumor area, size, and metastasis compared to the placebo group, suggesting it could be a specific therapeutic tool for lung cancer [232], and is associated with better prognostic value in lung cancer [233]. The gene discussed is KRAS; the disease is neoplasm.