Renalase　was　discovered　as　a　protein　synthesized　by　the　kidney　and　secreted　in　blood　where　it　circulates　at　a　concentration　of　approximately　3-5　g/ml.　Initial　reports　suggested　that　it　functioned　as　an　NAD(P)H　oxidase　and　could　oxidize　catecholamines.　Administration　of　renalase　lowers　blood　pressure　and　heart　rate　and　also　protects　cells　and　organs　against　ischaemic　and　toxic　injury.　Although　renalase＇s　protective　effect　was　initially　ascribed　to　its　oxidase　properties,　a　paradigm　shift　in　our　understanding　of　the　cellular　actions　of　renalase　is　underway.　We　now　understand　that,　independent　of　its　enzymatic　properties,　renalase　functions　as　a　cytokine　that　provides　protection　to　cells,　tissues　and　organs　by　interacting　with　its　receptor　to　activate　protein　kinase　B,　JAK/STAT,　and　the　mitogen-activated　protein　kinase　pathways.　In　addition,　recent　studies　suggest　that　dysregulated　renalase　signalling　may　promote　survival　of　several　tumour　cells　due　to　its　capacity　to　augment　expression　of　growth-related　genes.　In　this　review,　we　focus　on　the　cytoprotective　actions　of　renalase　and　its　capacity　to　sustain　cancer　cell　growth　and　also　the　translational　opportunities　these　findings　represent　for　the　development　of　novel　therapeutic　strategies　for　organ　injury　and　cancer.