Immunotherapeutic effects of cytokine-induced killer cells combined with CCL21/IL15 armed oncolytic adenovirus in TERT-positive tumor cells

•We constructed a CCL21/IL15 co-expression CRAds (conditionally replicating adenoviruses) based on AdEasy system.•Oncolytic adenoviruses CRAd-CCL21-IL15 could selectively replicate in TERT-positive tumor cells.•Our results showed that the combination of CIK cells and CRAd-CCL21-IL15 could induce higher antitumor activity.•The treatment of established tumors with the combined therapy of CIK cells and CRAd-CCL21-IL15 resulted in tumor regression.

The effective antitumor immune responses are dependent on coordinate interaction of various effector cells. Thus, the combination of adoptive immunotherapy and target gene therapy is capable of efficiently generating a productive antitumor immune response. We investigated whether combination of cytokine-induced killer (CIK) cells adoptive immunotherapy and CCL21/IL15 armed oncolytic adenovirus could induce the enhanced antitumor activity. The CCL21/IL15 co-expression oncolytic adenoviruses were constructed by using the AdEasy system, which uses homologous recombination with shuttle plasmids and full length Ad backbones. This conditionally replicating adenoviruses CRAd-CCL21-IL15 could induce apoptosis in TERTp-positive tumor cells for viral propagation, but do not replicate efficiently in normal cells, because the E1A promoter was replaced by telomerase reverse transcriptase promoter (TERTp). Our results showed that the combination of CIK cells and CRAd-CCL21-IL15 could induce higher antitumor activity than either CIK cells or CRAd-CCL21-IL15 alone. This combined treatment could induce the tumor specific cytotoxicity of CTLs (cytotoxic T lymphocytes) in vitro. Moreover, the treatment of established tumors with the combined therapy of CIK cells and CRAd-CCL21-IL15 resulted in tumor regression. This study suggests that the combined treatment by adoptive immunotherapy and gene therapy is a promising strategy for the therapy of tumor.