Although GM-CSF has been extensively investigated in clinical trials as a therapeutic transgene for oncolytic viruses or as a recombinant cytokine for cancer immunotherapy, there are increasing number of evidences that demonstrate the potentially pro-tumorigenic role of GM-CSF and inadequate therapeutic benefit of GM-CSF monotherapy in clinical environment (21–24), suggesting that GM-CSF as sole therapeutic gene may exert suboptimal antitumor immune response. Here, CSF2 is linked to cancer.