A whole cell vaccine expressing human granulocyte macrophage-colony stimulating factor (GM-CSF) with potential antineoplastic activity. Tumor cells from prostate cancer patients are harvested and then genetically modified to secrete GM-CSF, an immune stimulatory growth factor that plays a key role in stimulating the body's immune responses against tumor cells. Because the vaccine is derived from allogeneic cells, it has demonstrated a favorable side effect profile than other approaches of delivering long-lasting GM-CSF.