Towards endothelial-cell-directed cancer immunotherapy: in vitro expression of human recombinant cytokine genes by human and mouse primary endothelial cells.

Recent studies have demonstrated the feasibility of cytokine gene transfer to enhance the antitumor activities of host immune cells. Endothelial cells forming the vascular supply of tumors may be useful vehicles for the delivery of cytokine molecules in order to effect tumor immunotherapy. In order to determine whether primary endothelial cells can express cytokine transgenes efficiently, we constructed two retroviral vectors containing a cDNA encoding either recombinant human interleukin-1 alpha (rhIL-1 alpha) or recombinant human interleukin-2 (rhIL-2), called LNCIL-1 alpha and LNCIL-2 respectively, and studied the expression of the two cytokines in vitro in non-immortalized endothelial cells. Human umbilical vein endothelial cells (HUVEC) transduced with LNCIL-1 alpha or LNCIL-2 secreted 1.8-33 ng/10(6) cells/24 h and 40-246.7 ng/10(6) cells/24 h of biological active rhIL-1 alpha and rhIL-2 respectively. Mouse microvascular endothelial cells (MMEC) transduced with LNCIL-1 alpha and LNCIL-2 secreted 1.5 ng/10(6) cells/24 h and 5.8-24.7 ng/10(6) of biologically active rhIL-1 alpha and rhIL-2 proteins respectively. Cocultivation of HUVEC/IL-2 and MMEC/IL-2 with normal human bone marrow cells generated potent cytotoxic activity against K562, Daudi and other cell targets in a 51Cr-release assay. While IL-2 transgene-expressing HUVEC and MMEC retained their normal morphology, rhIL-1 alpha transgene expression inhibited the growth and altered the morphology of both HUVEC and MMEC in culture. The cytokine-gene-transduced endothelial cells retained other endothelial cell features, including uptake of acetylated low-density lipoprotein (Ac-LDL) and expression of von Willebrand factor, and were euploid as shown by flow cytometry. These results demonstrate that endothelial cells, by sustaining the production of biologically active rhIL-2 at levels that are sufficient for the activation of potent cytotoxic lymphocyte activity, may be useful agents for cancer gene therapy.