PARTICLE-MEDIATED GENE-TRANSFER OF GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR CDNA TO TUMOR-CELLS - IMPLICATIONS FOR A CLINICALLY RELEVANT TUMOR VACCINE

The necessity for prolonged tissue culture manipulations limits the cl inical application of many farms of gene therapy in patients with mali gnancies. We hypothesized that granulocyte-macrophage colony-stimulati ng factor (GM-CSF) cDNA in a plasmid expression vector could be effect ively introduced into resting tumor cells, without the need for tissue culture propagation prior to or following transfection, and that effi cient expression of transgenic GM-CSF by the transfected tumor cells w ould confer an effective immune response against tumors, GM-CSF cDNA i n expression vectors was coated onto gold particles and accelerated wi th a gene gun device into mouse and human tumor cells, Human tumor tis sue transfected within 4 hr of surgery produced significant levels of transgenic human GM-CSF protein in vitro, Human GM-CSF was readily det ectable in serum and at the injection site following subcutaneous impl antation of these transfected tumor cells into nude mice, Transfected and irradiated murine B16 melanoma cells produced greater than or equa l to 100 ng/ml murine GM-CSF/10(6) cells per 24 hr in vitro for at lea st 10 days, The antitumor efficacy of this nonviral approach was teste d using irradiated B16 tumor cells that were transfected with mGM-CSF cDNA and injected into mice as a tumor ''vaccine.'' Subsequent challen ge of these mice with nonirradiated, nontransfected B16 tumor cells sh owed that 58% of the animals were protected from the tumor by the prio r vaccine treatment, In contrast, only 2% of control animals mere prot ected by prior treatment with irradiated B16 cells transfected with th e vector containing the luciferase gene, These results suggest that pa rticle-mediated transfection of fresh tumor explants with cytokine cDN A is an effective and clinically attractive approach for cancer therap y.