Tumor microenvironment remodeling with a telomere-targeting agent and its cooperative antitumor effects with a nanovaccine.

The nucleoside analogue 6-thio-2'-deoxyguanosine (6-thio-dG, also known as THIO) is a telomere-targeting agent with important clinical potency. It can selectively kill telomerase-positive tumor cells. We previously reported that THIO could successfully induce immunogenic cell death (ICD) in multiple mouse tumor cell lines. In this study, we further explored the potential impact of THIO on remodeling the tumor microenvironment, regulating anti-tumor immune responses, and its possible synergistic effects with other therapeutic methods, such as tumor vaccines. Our results showed that THIO could also induce ICD in various human tumor cell lines. The induction of ICD in tumor cells promoted the migration and maturation of antigen-presenting cells. Administration of THIO significantly inhibited the growth of established CT26 and TC-1 tumors in mice. Meanwhile, it enhanced the anti-tumor CTL response and reduced the levels of immunosuppressive myeloid-derived suppressor cells (MDSCs) in both the spleen and tumor tissues. Additionally, THIO had a direct inhibitory effect on the proliferation and differentiation of MDSCs. Moreover, when combined with bacterial biomimetic vesicles or a nanovaccine, such as THIO with BBV or different Q11-tumor antigen peptide nanofibers, it exhibited enhanced anti-tumor effects and immune responses compared to monotherapy in either "immune hot" TC-1 tumors or "immune cold" B16-F10 tumors. In summary, THIO has the ability to remodel the tumor microenvironment, exert a specific killing effect on tumor cells, and effectively cooperate with tumor vaccines. This broadens the anti-tumor mechanisms of THIO and provides a promising strategy for improving anti-tumor immunotherapies.