Lingjian Yan,1,2,* Fan Wu,1,2,* Jiuyang Jiao,1,* Abudusaimi Maimaiti,3 Yachong Li,1,2 Libin Shao,1,2 Qixiang Liang,4 Xinxin Xiong,5 Zeman Qin1,2 

1Department of Stomatology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, People’s Republic of China; 2Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Guangdong-Hong Kong Joint Laboratory for RNA Medicine, Medical Research Center, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, People’s Republic of China; 3Department of Stomatology, The First People’s Hospital of Kashi Area, Xinjiang Uygur Autonomous Region, People’s Republic of China; 4Department of Stomatology, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, People’s Republic of China; 5The Second Affiliated Hospital, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, Guangzhou Medical University, Guangzhou, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Xinxin Xiong, Email xiongxinxin900209@163.com Zeman Qin, Email qinzm@mail.sysu.edu.cn

Background: Oral squamous cell carcinoma (OSCC) is a common malignancy among Asian populations, and emerging evidence suggests that oral microbiota dysbiosis may play a role in its pathogenesis. This study investigates the role of the oral microbiome, particularly Stomatobaculum longum (S. longum), in OSCC progression and explores the underlying molecular mechanisms involving bacterial extracellular vesicles (EVs).
Methods: 16S rRNA sequencing was conducted on tumor and adjacent non-tumor tissues from OSCC patients to identify microbial composition. In vitro and in vivo experiments were used to evaluate the effects of S. longum on OSCC proliferation and cell cycle progression. GW4869, an inhibitor of EVs’ release, was applied to validate the EVs-mediated mechanisms. Extracellular vesicles from S. longum (SBL-EVs) were isolated using ultracentrifugation and characterized by transmission electron microscopy (TEM) and nanoparticle tracking analysis (NTA). High-throughput sequencing and functional assays were performed to identify signaling pathways regulated by SBL-EVs.
Results: Tumor tissues exhibited a significant enrichment of S. longum compared to non-tumor tissues. S. longum promoted OSCC proliferation and cell cycle progression both in vitro and in vivo, which was reversed by GW4869 treatment. SBL-EVs were successfully isolated and characterized, and they were found to promote OSCC progression by activating the BRCA1/EXO1/TP53BP1 signaling axis.
Conclusion: This study demonstrates the oncogenic role of S. longum in OSCC, mediated through EVs-dependent regulation of the BRCA1/EXO1/TP53BP1 pathway. Targeting bacterial EVs or their downstream signaling may represent a novel therapeutic strategy for OSCC.

Keywords: oral squamous cell carcinoma, Stomatobaculum longum, bacterial vesicles, BRCA1