Although downregulation of CYP2J2 by pSilencer-let-7b did not result in the eradication of tumors, the reverse correlation between the expression level of CYP2J2 and let-7b in human cancer tissue and the effectiveness of inhibiting the tumor-promoting functions of CYP2J2 revealed the potential therapeutic benefit of let-7b in human cancers. The gene discussed is CYP2J2; the disease is neoplasm.