Oligodeoxynucleotides Expressing Polyguanosine Motifs Promote Antitumor Activity through the Upregulation of IL-2

Abstract

The primary goal of cancer immunotherapy is to elicit an immune response capable of eliminating the tumor. One approach toward accomplishing that goal uses general (rather than tumor-specific) immunomodulatory agents to boost the number and activity of pre-existing CTLs. We find that the intratumoral injection of polyguanosine (poly-G) oligonucleotides (ODN) has such an effect, boosting antitumor immunity and promoting tumor regression. The antitumor activity of poly-G ODN was mediated through CD8 T cells in a TLR9-independent manner. Mechanistically, poly-G ODN directly induced the phosphorylation of Lck (an essential element of the T cell–signaling pathway), thereby enhancing the production of IL-2 and CD8 T cell proliferation. These findings establish poly-G ODN as a novel type of cancer immunotherapy.