Role of GM-CSF in the management of malignant melanoma Unresectable melanoma carries a poor prognosis with lim- ited options for treatment (Parmiani et al 2007). GM-CSF has been shown to induce cytotoxic T-cells and activated DC at tumor sites and draining lymph nodes (Parmiani et al 2007). The use of GM-CSF in combination with IL-2 or IFN-alpha has yielded promising results, but is associated with signiﬁcant systemic toxicity. Table 2 summarizes activ- ity and toxicities of GM-CSF-containing regimens in the treatment of malignant melanoma. Delivery of therapy into local sites of disease may circumvent systemic toxicity and is the subject of current investigation. GM-CSF and cancer vaccine development Addressing questions pertaining to the choice of vector, the speciﬁcity of the antigen, and the choice of co-stimulatory molecules is crucial to the optimal development of cancer vaccines. Tumor-associated antigens from tumor cells (both autologous and allogeneic), proteins, peptides, and nucleic acid have been used as immunogens. Genetically modiﬁed allogeneic tumor cells as well as recombinant viruses or bacterial genes have been utilized as vectors. Pre-existing immunity to the vector itself has limited the use of vaccines based on viral vectors (Rosenberg et al 1998). Vaccination in the absence of the co-stimulatory signals necessary to break tolerance can lead to anergy. Therefore, some vectors have been designed to express not only tumor-associated antigens, but also, co-stimulatory molecules and cytokines. Dranoff et al (1993) introduced GM-CSF as an important adjuvant in cancer vaccine trials, based on his observations that irradiated tumor cells expressing murine GM-CSF could stimulate potent, long-lasting, and tumor-speciﬁc immunity. In order to circumvent systemic toxicity and to increase immune responses, injection into the local tumor environ- ment has been proposed. Hersch and colleagues used intra- tumor injection of HLA-B7/beta2-microglobulin genes as plasmid DNA in lipid into patients with malignant melanoma. In a phase I trial setting, they reported a 36% response at the locally injected tumor and a 19% systemic anti-tumor response (Hersh and Stopeck 1997).Vaccine trials utilizing GM-CSF or engineering tumor cells to secrete GM-CSF showed encouraging results in the treatment of solid tumors including: malignant melanoma, breast carcinoma, pancreatic cancer, renal cell carcinoma, non-small cell carcinoma of the lung and prostate cancer (Schmidt et al 1997; Simons et al 1997; Biologics:Targets & Therapy 2008:2(1) Clinical uses of GM-CSF Hung et al 1998; Soiffer et al 1998; Disis et al 1999; Gaudernack and Gjertsen 1999; Leong et al 1999). Cassaday and colleagues performed a phase I study of immunization using particle-mediated epidermal delivery (PMED) of genes for gp100 and GM-CSF into uninvolved skin of melanoma patients. Two groups of 6 patients each were treated; group 1 received PMED with cDNA for gp100, and group 2 received PMED with cDNA for GM-CSF followed by PMED for gp100 at the same site. Biopsies were obtained and evaluated to assess transgene expression, gold-bead penetration, and dendritic cell inﬁltration. Exploratory studies included ﬂow cytometric analyses of peripheral blood lymphocytes and evaluation of delayed-type hypersensitivity to gp100 peptide in HLA-A2 + patients. Local toxicity in both groups was mild and resolved within 2 weeks. No vaccine-related systemic toxicity was reported, including no induction of pathologic auto-antibodies. GM-CSF transgene expression in vaccinated skin sites was detected. GM-CSF and gp100 PMED yielded a greater inﬁltration of DC into vaccine sites than did gp100 PMED alone. Immunologic monitoring suggested modest activation of an anti-melanoma response (Cassaday et al 2007). This study demonstrated tolerability and induction of anti-melanoma immune responses with a local approach. Additional investigation utilizing this technique is warranted. Bendandi and colleagues tested the hypothesis that immune therapy is more effective in the setting of minimal residual disease (MRD). They documented clearance of the t(14,18) translocation by PCR from the peripheral circulation in 8 of 11 patients with lymphoma and MRD, after administration of a GM-CSF containing vaccine (Bendandi et al 1999). Currently our center participates in a multi-institutional trial of vaccine therapy for AML after remission induction. GM- CSF may enhance antigen presentation by recruiting DC to the (vaccine) site where antigen is taken up, processed, and presented to T-cells in draining lymph nodes, generating systemic tumor-speciﬁc responses (Borrello and Pardoll 2002). Cell-mediated vaccines: role of dendritic cells DC are ideal candidates for use in vaccination, owing to their role in antigen presentation. DC can be isolated from the peripheral circulation by FACS sorting or magnetic bead isolation, or can be generated in large quantities ex-vivo from peripheral blood progenitors in media supplemented with cytokines, including GM-CSF (Berthier et al 2000). These DC may then be matured with cytokine culture prior to loading with antigen. They have yielded promising 21