An engineered TNFR1-selective human lymphotoxin-alpha mutant delivered by an oncolytic adenovirus for tumor immunotherapy.

Lymphotoxin α (LTα) is a soluble factor produced by activated lymphocytes which is cytotoxic to tumor cells. Although a promising candidate in cancer therapy, the application of recombinant LTα has been limited by its instability and toxicity by systemic administration. Secreted LTα interacts with several distinct receptors for its biological activities. Here, we report a TNFR1-selective human LTα mutant (LTα Q107E) with potent antitumor activity. Recombinant LTα Q107E with N-terminal 23 and 27 aa deletion (named LTα Q1 and Q2, respectively) showed selectivity to TNFR1 in both binding and NF-κB pathway activation assays. To test the therapeutic potential, we constructed an oncolytic adenovirus (oAd) harboring LTα Q107E Q2 mutant (named oAdQ2) and assessed the antitumor effect in mouse xenograft models. Intratumoral delivery of oAdQ2 inhibited tumor growth. In addition, oAdQ2 treatment enhanced T cell and IFNγ-positive CD8 T lymphocyte infiltration in a human PBMC reconstituted-SCID mouse xenograft model. This study provides evidence that reengineering of bioactive cytokines with tissue or cell specific properties may potentiate their therapeutic potential of cytokines with multiple receptors.