Elevated CDD levels promote the metabolism of gemcitabine to its inactive form.360 Moreover, solute carrier (SLC) transport proteins are primarily involved in the uptake of small molecules into cells, and their absence affects the uptake of chemotherapeutic agents into cancer cells, leading to drug resistance.361 The role of hypoxia in relation to CDD and SLC has not been fully established. This evidence concerns the gene CCL21 and cancer.