Using pairs of Human breast cancer cell lines MDA LCC6 versus its P‐gp‐overexpressed subline MDA LCC6 MDR1, and Human ovarian carcinoma cell lines Hela versus its P‐gp‐overexpressed subline ADR‐Hela for the direct comparison, we demonstrated the restored activity of anticancer drug in the resistant cancer cells using the a self‐decomposable silicon dioxide (methylene blue)‐doxorubicin (SiO2(MB)‐Dox) NP carrier drug system. The gene discussed is PGP; the disease is breast cancer.