KRAS and neoplasm: Our study reveals that let-7b repletion selectively downregulates mutant KRAS expression and potentiates the anticancer activity of paclitaxel and gemcitabine in KRAS mutant tumor cells, which is accompanied by attenuated cell proliferation, enhanced apoptosis and the reversal of the epithelial-mesenchymal transition (EMT) phenotype in tumor cells.