Immunotherapy of tumors with human telomerase reverse transcriptase immortalized human umbilical vein endothelial cells.

Human umbilical endothelial cells (HUVECs) have been proven to be effective in tumor anti-angiogenesis but the mechanism remained to be further demonstrated. The restricted ability of HUVECs to proliferate in vitro also limits their application on a large scale. In the present study, we immortalized HUVECs with hTERT genes by lentiviral infection and explored the antitumor immunity of hTERT-expressing HUVECs (HUVEC-TERTs). Results showed that HUVEC-TERTs maintained high telomere activity and expressed CD31, VEGFR-II and integrin α5. Passage-30 HUVEC-TERTs were able to form vascular tubes in vitro without showing signs of senescence. In vivo HUVEC-TERTs elicited antitumor immunity in mouse LL2 and CT26 models protectively and therapeutically. Both humoral and cellular immunity participated in the tumor anti-angiogenesis as HUVEC-neutralizing sera antibodies and HUVEC-specific CTL were detected. The subsets of activated spleen T lymphocytes included both CD4(+) T cells and CD8(+) T cells. Moreover, MDSCs and Tregs were decreased while T lymphocytes were aggregated in the tumor microenvironment. Collectively, the present study is the first to confirm the antitumor immunity of hTERT-immortalized HUVECs. Both anti-angiogenesis and tumor microenvironmental regulation participated in the antitumor activity. Transducing hTERT genes might be a new strategy to allow HUVECs to be applied on a large scale in cancer immunotherapy.