Finally and to test the possibility that only intracellularly over-expressed IL-24 would render cancer cells more susceptible to apoptosis, we transiently transfected melanoma and Hek cells with either full length IL-24 or IL-20 as well as with a construct that contains full length IL-24 together with a KDEL ER-targeting sequence (KDEL) as several studies have recently postulated that the apoptosis-inducing effects of IL-24 are mainly mediated by triggering ER stress responses [33], [36]. Here, IL20 is linked to cancer.