Staphylococcus Aureus Membrane Vesicles Kill Tumor Cells Through a Caspase-1-Dependent Pyroptosis Pathway

Abstract

Mengyang Li,1,* Yuting Wang,2,* He Liu,2 Xiaonan Huang,2 Huagang Peng,2 Yi Yang,2 Zhen Hu,2 Jianxiong Dou,2 Chuan Xiao,2 Juan Chen,3 Weilong Shang,2 Xiancai Rao1,2 1Department of Microbiology, School of Medicine, Chongqing University, Chongqing, 400044, People’s Republic of China; 2Department of Microbiology, College of Basic Medical Sciences, Army Medical University, Key Laboratory of Microbial Engineering Under the Educational Committee in Chongqing, Chongqing, 400038, People’s Republic of China; 3Department of Pharmacy, The Second Affiliated Hospital, Army Medical University, Chongqing, 400037, People’s Republic of China*These authors contributed equally to this workCorrespondence: Xiancai Rao; Weilong Shang, Department of Microbiology, College of Basic Medical Sciences, Army Medical University, Key Laboratory of Microbial Engineering under the Educational Committee in Chongqing, Chongqing, 400038, People’s Republic of China, Email [email protected]; [email protected]: Nanosized outer membrane vesicles (OMVs) from Gram-negative bacteria have attracted increasing interest because of their antitumor activity. However, the antitumor effects of MVs isolated from Gram-positive bacteria have rarely been investigated.Methods: MVs of Staphylococcus aureus USA300 were prepared and their antitumor efficacy was evaluated using tumor-bearing mouse models. A gene knock-in assay was performed to generate luciferase Antares2–MVs for bioluminescent detection. Cell counting kit-8 and lactic dehydrogenase release assays were used to detect the toxicity of the MVs against tumor cells in vitro. Active caspase-1 and gasdermin D (GSDMD) levels were determined using Western blot, and the tumor inhibition ability of MVs was determined in B16F10 cells treated with a caspase-1 inhibitor.Results: The vesicular particles of S. aureus USA300 MVs were 55.23 ± 8.17 nm in diameter, and 5 μg of MVs remarkably inhibited the growth of B16F10 melanoma in C57BL/6 mice and CT26 colon adenocarcinoma in BALB/c mice. The bioluminescent signals correlated well with the concentrations of the engineered Antares2–MVs (R2 = 0.999), and the sensitivity for bioluminescence imaging was 4 × 10− 3 μg. Antares2–MVs can directly target tumor tissues in vivo, and 20 μg/mL Antares2–MVs considerably reduced the growth of B16F10 and CT26 tumor cells, but not non-carcinomatous bEnd.3 cells. MV treatment substantially increased the level of active caspase-1, which processes GSDMD to trigger pyroptosis in tumor cells. Blocking caspase-1 activation with VX-765 significantly protected tumor cells from MV killing in vitro and in vivo.Conclusion: S. aureus MVs can kill tumor cells by activating the pyroptosis pathway, and the induction of pyroptosis in tumor cells is a promising strategy for cancer treatment. Keywords: Staphylococcus aureus, membrane vesicles, Antares2, cancer therapy, pyroptosis, caspase-1, GSDMD

Keywords

• staphylococcus aureus
• membrane vesicles
• antares2
• cancer therapy
• pyroptosis
• caspase-1
• gsdmd