PGP and cancer: It finally led to effective MDR reversing function by synergistic cell cycle arrest and an apoptosis‐inducing effect.138 Besides, through surface modification, MSNs demonstrate the ability to effectively load nucleic acids and specifically deliver them to tumors.139 So far, MSNs have been investigated to carry several kinds of MDR‐related gene targeting siRNAs together with anticancer agents to restore MDR of cancer cells, such as MSNs‐based nanosystems loading with P‐gp targeting siRNA and Dox to overcome MDR MCF‐7/MDR cancer cells.