PGP and cancer: Our results showed that Ad-VT downregulated the expression levels of not only p-pI3k, p-Akt and p-mTOR pathway proteins but also P-gp protein in chemoresistant A549/GEM and A549/Paclitaxel cancer cell lines (Fig. 5c), resulting in decreased PI3K/Akt/mTOR signaling pathway function and reduced chemotherapy resistance of drug-resistant lung cancer cell lines.