Pro-inflammatory
cytokines regulate the growth, differentiation, and activation of immune cells and can play a role in antitumor responses.
GM-CSF and
IL-2 induce
tumor rejection in animal models when expressed by
tumor cells, and
IL-2 is used for the treatment of
melanoma and
renal cell cancer. However, high doses of
GM-CSF and
IL-2 are associated with severe side effects in
cancer patients. We generated a dual
cytokine fusion
protein for simultaneous targeted delivery of human
GM-CSF and
IL-2 to human
tumors. The fusion
protein is based on a heterodimeric core structure formed by human CH1 and C kappa domains (heterominibody) with C-terminally fused human
cytokines and N-terminally fused human single-chain Ab fragments (scFv) specific for the
tumor-associated
surface antigen epithelial cell adhesion molecule (
Ep-CAM). The dual
cytokine heterominibody (DCH) was well expressed and secreted by CHO cells, preserved the specific proliferative activities of the two
cytokines, and showed
Ep-CAM-specific binding to
tumor cells. DCH induced potent
tumor cell lysis in vitro by two distinct mechanisms. One was activating PBMCs to lyse
tumor cells, which was superior to cytotoxicity induced by equimolar ratios of free recombinant human
IL-2 and
GM-CSF. The other mechanism was redirected lysis, as seen with isolated human T cells, which was solely dependent on the
IL-2 fusion part. The therapeutic principle of dual
cytokine targeting may warrant in vivo testing of murine-specific analogues in appropriate mouse models and further preclinical development of the less immunogenic, human
cytokine- and human
Ep-CAM-specific DCH molecule described here.