Use of GM-CSF as an adjuvant with cancer vaccines: beneficial or detrimental?

Granulocyte-macrophage colony-stimulating factor (GM-CSF) has been utilized in the clinical management of multiple disease processes. Most recently, GM-CSF has been incorporated into the treatment of malignancies as a sole therapy, as well as a vaccine adjuvant. While the benefits of GM-CSF in this arena have been promising, recent reports have suggested the potential for GM-CSF to induce immune suppression and, thus, negatively impact outcomes in the management of cancer patients. The purpose of this review is to critically evaluate these reports, while considering the most recent clinical data on immunotherapies. We aim to demonstrate the utility of this adjuvant, elucidate those instances in which GM-CSF may induce immune suppression and identify potential explanations for these recent findings.