Olga Kuźmycz ^1,2 Aleksandra Kowalczyk ^2* Aleksandra Bolanowska ³ Anna Drozdzowska ³ Jakub Lach ^2,4 Wiktoria Wierzbińska ² Tomasz Kluz ^3,5 Paweł Stączek ²

• ¹ Faculty of Biology and Environmental Protection, University of Lodz, Lodz, Poland
• ² University of Lodz, Faculty of Biology and Environmental Protection, Institute of Microbiology, Biotechnology and Immunology, Department of Molecular Microbiology, Lodz, Poland
• ³ Department of Gynecology and Obstetrics, Fryderyk Chopin University Hospital No. 1, Rzeszow, Poland
• ⁴ University of Lodz, Faculty of Biology and Environmental Protection, Biobank Lab, Department of Cancer Biology and Epigenetics, Lodz, Poland
• ⁵ Department of Gynecology, Gynecology Oncology and Obstetrics, Institute of Medical Sciences, Medical College of Rzeszow University, Rzeszow, Poland

The advent of sequencing techniques has facilitated the application of microbiome studies in cancer research. It has been observed that microbial pathogens contribute to tumorigenesis in a significant portion of reported cancer cases. Endometrial cancer (EC) is a prevalent malignancy among women, with several known risk factors such as estrogen exposure, age, obesity, and comorbidities. The upper genital tract of healthy women is typically dominated by Lactobacillus species. Dysbiosis in microbial composition has been observed in EC. In the presented study, the endocervical canal microbiomes of women with EC or endometrial myoma (EM) were examined. Microbial communities in endometrial samples significantly differed between the two groups, with EC samples exhibiting higher microbial diversity. Pathogenic taxa such as Streptococcus, Anaerococcus, Prevotella, Gardnerella, Peptoniphilus, and Porphyromonas were enriched in EC samples. Interestingly, the genus Anaerococcus was found to be a differentiating taxon between microbiomes isolated from women with EC and those with benign lesions (EM). While Prevotella and Gardnerella have been previously associated with uterine dysbiosis, our study uniquely highlights Anaerococcus as a potential biomarker and pathogenic cofactor, addressing a novel aspect of EC microbiota research. We hypothesized that the genus Anaerococcus contributes to endometrial cancer progression by inducing ROS production and promoting dysbiosis in the uterine microbiome. This study explores Anaerococcus vaginalis, a previously uninvestigated microorganism in the context of endometrial cancer (EC). We provide preliminary evidence of its ability to induce reactive oxygen species (ROS) and adhere to non-malignant endometrial cells, suggesting its potential as a novel biomarker for EC-related dysbiosis.