The use of PDE5 inhibitors has also achieved some success in the context of combination therapy with chemotherapeutic drugs, such as in association with doxorubicin in in vivo models of brain tumors, where they ameliorated drug delivery through the blood brain barrier by selectively increasing tumor capillary permeability and vesicular transport upon cGMP interaction with calcium-dependent potassium (KCa) channels [85], as well as in in vitro breast tumors. This evidence concerns the gene PDE5A and breast neoplasm.