A variety of drug-loaded nanoparticles conjugated with antibodies to these markers (CD44, CD133, and ABCG2) have been developed that improve the drug delivery efficiency to CSCs in colon cancer (Bourseau-Guilmain et al., 2012), breast cancer (Swaminathan et al., 2013), and multiple myeloma (Yang et al., 2014). Here, ABCG2 is linked to breast cancer.