In a recent research by Zhang M, et al. a programmable drug delivery system which is composed of a chondroitin sulfate hydrogel shell and hydrophobic cores was built for delivering anti-tumor drugs into drug-resistant cancer cells and keeping effective drug concentration to sensitizing cancer cells to anti-cancer drugs by down-regulation of the anti-apoptosis protein Bcl-xl [146]. The gene discussed is BCL2L1; the disease is cancer.