DNA-Containing Exosomes Derived from Cancer Cells Treated with Topotecan Activate a STING-Dependent Pathway and Reinforce Antitumor Immunity

Abstract

Danger-associated molecular patterns derived from damaged or dying cells elicit inflammation and potentiate antitumor immune responses. In this article, we show that treatment of breast cancer cells with the antitumor agent topotecan (TPT), an inhibitor of topoisomerase I, induces danger-associated molecular pattern secretion that triggers dendritic cell (DC) activation and cytokine production. TPT administration inhibits tumor growth in tumor-bearing mice, which is accompanied by infiltration of activated DCs and CD8 T cells. These effects are abrogated in mice lacking STING, an essential molecule in cytosolic DNA-mediated innate immune responses. Furthermore, TPT-treated cancer cells release exosomes that contain DNA that activate DCs via STING signaling. These findings suggest that a STING-dependent pathway drives antitumor immunity by responding to tumor cell-derived DNA.

Novel chemical compound SINCRO with dual function in STING‐type I interferon and tumor cell death pathways

“…We next examined the mechanism(s) for how SINCRO regulates IFN‐β expression. As dead cell‐derived and exosomal nucleic acids have the potential to induce type I IFN, we asked whether SINCRO induced the release of nucleic acids. To test this, we first stimulated B16F1 cells with SINCRO for 6 hours, removed the compound by washing, and then collected the medium from the cells incubated for another 6 hours.…”

Proteomic Analysis of Extracellular Vesicles for Cancer Diagnostics

“…Short fragments of single‐stranded DNA (ssDNA), dsDNA, and RNA, as well as complete mitochondrial genome (mtDNA) have been found within EVs . While the biological function of EV‐ssDNA and EV‐dsDNA remains to be elucidated, recent study demonstrates that antitumor drug topoisomerase I inhibitor topotecan (TPT)‐treated murine breast cancer E0771 cells release EV‐encapsulated DNA to activate stimulator of interferon genes (STING)‐dependent pathway, thereby enhancing antitumor immunity for tumor suppression . Meanwhile, EV‐mtDNA was found to be horizontally transferred to CAFs to increase self‐renewal potential and subsequent restoration of the oxidative phosphorylation (OXPHOS) function of OXPHOS‐deficient breast cancer cells under hormonal therapy, leading to treatment resistance .…”

Danger signals: Chemotherapy enhancers?

“…(b) DNA ‐mediated activation of STING triggers topotecan‐dependent anti‐tumor immunity against murine breast cancer cells (E0771) in vivo: Topotecan‐treated cancer cells release exosomes that contain DNA that activate DC s via cGAS ‐ STING signaling. DC activation leads to Type I IFN and cytokine production crucial for the anticancer reponse . (c) The danger signal cGAMP boosts the anti‐tumor activity of the chemotherapy 5‐Fluorouracil (5‐ FU ): In mice, the combination of 5‐ FU and cGAMP leads to tumor cell death by immunogenic cell death.…”

“…However, DNase treatments fail to abrogate Sting activation upon topotecan treatment suggesting the possibility that DNA derived from topotecan‐treated E0771 cells is tightly associated with protective structures. Further investigation revealed that topotecan‐treated cancer cells release exosomes that contain DNA that activate DCs via STING signaling (Figure b) . To explore how DNA in the exosome is delivered to DCs, GM‐DCs were incubated with CSFE‐labeled exosomes purified from topotecan‐treated E0771 cell supernatant and analyzed their engulfment by FACS analysis.…”

“…As a consequence, dying malignant cells expose calreticulin ( CRT ) on their surface and release others endoplasmic reticulum chaperones such as HSP 70 and HSP 90 . They also release nucleic acids like ATP, DNA, and RNA that in turn initiate a cell‐intrinsic type I IFN response culminating in the production CXCL 10, and release HMGB 1 and annexin A1 ( ANXA 1) . Upon binding to their respective receptors on the surface of myeloid or lymphoid cells, these danger signals favor the uptake of cell corpses and debris by antigen presenting cells, including DC s. This overall leads to the priming of an adaptive anticancer immune response.…”