FOLH1 and cancer: Farokhzad et al. (2004) demonstrated that aptamers directed against prostate-specific membrane antigen (PSMA) were internalized. Based on this result, Bagalkot et al. (2007) established a quantum dot–aptamer–doxorubicin conjugate that could be used as a targeted cancer therapy. Chu et al. (2006) used streptavidin to conjugate the biotin-labeled anti-PSMA aptamer to siRNA, and used this system to inhibit the target gene in cultured cells.