Here, we showed that the PI3K-Akt/mTOR signaling of peripheral blood G-MDSCs is activated and that G-CSF promotes the acquisition of immunosuppressive functions by G-MDSCs by activating the PI3K-Akt/mTOR pathway, suggesting that inhibition of PI3K-Akt/mTOR can inhibit G-MDSC immunosuppressive function and improve immunosuppressive tumor microenvironment. Here, CSF3 is linked to neoplasm.