SLC28A1 and cancer: Although our study with pyrrolo-gemcitabine serves merely as proof of concept, it is conceivable that the nucleo-pocket structure can be utilized in the design of nucleoside-derived drugs or prodrugs that can be specifically targeted only to cell types that express hCNT1 since expression levels of hCNT1 are closely related to the responsiveness of many different types of normal or cancer cells to chemotherapy treatment (Lane et al., 2010; Naito et al., 2010; Rabascio et al., 2010; Bhutia et al., 2011; Choi, 2012).