Our core observations are that (1) the function of Pgp1 mainly functions to efflux drugs out of MDR tumor cells, (2) NSC23925 was observed to inhibit the efflux of substrates of Pgp1, such as paclitaxel and doxorubicin, (3) NSC23925 at 10 μM for 48 hours does not inhibit the expression level of Pgp1, and (4) NSC23925 stimulates Pgp ATPase activity. The gene discussed is CD44; the disease is neoplasm.