The role of let-7 as tumor suppressor was clearly demonstrated in lung cancer, following the observation that downregulation of let-7 in lung tissues led to the constitutive overexpression of Ras and high-mobility group AT-hook 2 (HMGA2), both being oncoproteins that contribute to the pathogenesis of cancer [44,45,46]. Here, HMGA2 is linked to neoplasm.