Let-7 expression was repressed in patients with PDAC who were not eligible for surgery: restoring let-7 levels in cancer-derived cell lines strongly inhibits cell proliferation, Kras expression, and mitogen-activated protein kinase activation, but fails to impede tumor growth progression after intratumoral gene transfer or after implantation of Capan-1 cells stably overexpressing let-7 miRNA [168]. Here, KRAS is linked to cancer.