BIRC5 and cancer: In another example of pH‐ and redox‐responsive gene delivery, a polysaccharide‐enveloped liposome nanocarrier has been synthesized for RNAi via survivin gene silencing.[215] Survivin, an inhibitor of cell apoptosis, is strongly expressed in malignant tumors such as breast cancer and increases of risk of cancer cell proliferation and metastasis.