Characterization and Functional Prediction of Bacteria in Ovarian Tissues
Summary
Immunohistochemistry staining and 16S ribosomal RNA gene (16S rRNA gene) sequencing were performed in order to discover and distinguish bacteria in cancerous and noncancerous ovarian tissues in situ. The compositional and functional differences of the bacteria were predicted by using BugBase and Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt).
Abstract
The theory of a “sterile” female upper reproductive tract has been encountering increasing opposition due to advancements in bacterial detection. However, whether ovaries contain bacteria has not yet been confirmed yet. Herein, an experiment to detect bacteria in ovarian tissues was introduced. We chose ovarian cancer patients in the cancer group and noncancerous patients in the control group. 16S rRNA gene sequencing was used to differentiate bacteria in ovarian tissues from the cancer and control groups. Furthermore, we predicted the functional composition of the identified bacteria by using BugBase and PICRUSt. This method can also be used in other viscera and tissues since many organs have been proven to harbor bacteria in recent years. The presence of bacteria in viscera and tissues may help scientists evaluate cancerous and normal tissues and may be aid in the treatment of cancer.
Introduction
Recently, an increasing number of articles have been published that prove the existence of bacteria in abdominal solid viscera, such as the kidney, spleen, liver, and ovary1,2. Geller et al. found bacteria in pancreatic tumors, and these bacteria were resistant to gemcitabine, a chemotherapeutic drug2. S. Manfredo Vieira et al. concluded that Enterococcus gallinarum was portable to the lymph nodes, liver and spleen, and it could drive autoimmunity3.
Since the cervix plays a role as a defender, bacteria in the upper female reproductive tract, which contains the uterus, fallopian tubes, and ovaries, have been minimally researched. However, some new theories have been established in recent years. Bacteria may have access to the uterine cavity during the menstrual cycle due to changes in mucins4,5. Additionally, Zervomanolakis et al. confirmed that the uterus, together with the fallopian tubes, is a peristaltic pump controlled by the endocrine system of the ovaries, and this arrangement enables bacteria to enter the endometrium, fallopian tubes, and ovaries6.
The upper reproductive tract is no longer a mystery anymore thanks to the development of bacterial detection methods. Verstraelen et al. used a barcoded paired-end sequencing method to discover uterine bacteria by targeting at the V1-2 hypervariable region of the 16S RNA gene7. Fang et al. employed barcoded sequencing in patients with endometrial polyps and revealed the presence of diverse intrauterine bacteria8. Additionally, by using the 16S RNA gene, Miles et al. and Chen et al. found bacteria in the genital system of women who had undergone salpingo-oophorectomy and hysterectomy, respectively5,9.
Bacteria in tumor tissues have gained increasing attention in recent years. Banerjee et al. discovered that the microbiome signature differed between ovarian cancer patients and controls10. Anoxynatronum sibiricum was associated with tumor stage, and Methanosarcina vacuolata might be used to diagnose ovarian cancer11. In addition to ovarian cancer, other cancers, such as stomach, lung, prostate, breast, cervix, and endometrium, have been proven to be associated with bacteria12,13,14,15,16,17,18. Poore et al. proposed a new class of microbial-based oncology diagnostics, foreseeing early-stage cancer screening19. In this protocol, we investigated the differences between cancerous and normal ovarian tissues by comparing the composition and function of bacteria in these two tissues.
Immunohistochemistry staining and 16S rRNA gene sequencing were performed to confirm the presence of bacteria in the ovaries. The differences and predicted functions of the ovarian bacteria in cancerous and noncancerous ovarian tissues were studied. The results showed the existence of bacteria in ovarian tissues. Anoxynatronum sibiricum and Methanosarcina vacuolata were related to the stage and the diagnosis of ovarian cancer, respectively. Forty-six significantly different KEGG pathways that were present in both groups were compared.
Protocol
Representative Results
Discussion
Ovarian cancer has a notable influence on women's fertility25. Most ovarian cancer patients are diagnosed at late stages, and the 5-year survival rate is less than 30%18. Confirmation of bacteria in the abdominal solid viscera, including the liver, pancreas and spleen, has been published. The existence of bacteria in the upper female reproductive tract occurs because the cervix is not enclosed2,3,<sup…
Divulgaciones
The authors have nothing to disclose.
Acknowledgements
This work was supported by the Clinical Research Award of the First Affiliated Hospital of Xi'an Jiaotong University, China (XJTU1AF-2018-017, XJTU1AF-CRF-2019-002), the Major Basic Research Project of Natural Science of Shaanxi Provincial Science and Technology Department (2018JM7073, 2017ZDJC-11), the Key Research and Development Project of Shaanxi Provincial Science and Technology Department (2017ZDXM-SF-068, 2019QYPY-138), the Shaanxi Provincial Collaborative Technology Innovation Project (2017XT-026, 2018XT-002), and the Medical Research Project of Xi'an Social Development Guidance Plan (2017117SF/YX011-3). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
We thank the colleagues in the Department of Gynecology of First Affiliated Hospital of Xi'an Jiaotong University for their contributions to collecting samples.
Materials
| 2200 TapeStation Software | Agilgent United States |
||
| AmpliSeq for Illumina Library Prep, Indexes, and Accessories | Illumina | ||
| Image-pro plus 7 | Media Cybernetics | ||
| Leica ASP 300S | Leica Biosystems Division of Leica Microsystems | ||
| Leica EG 1150 | Leica Biosystems Division of Leica Microsystems | ||
| Leica RM2235 | Leica Biosystems Division of Leica Microsystems | ||
| LPS Core monoclonal antibody, clone WN1 222-5 | Hycult Biotech | ||
| Mag-Bind RxnPure Plus magnetic beads | Omega Biotek | M1386-00 | |
| Mag-Bind Universal Pathogen 96 Kit | Omega Biotek | M4029-01 | |
| MiSeq | Illumina | SY-410-1003 | |
| Silva database | Max Planck Institute for Marine Microbiology and Jacobs University | ||
| the QuantiFluor dsDNA System | Promega | E2670 | |
| Trimmomatic | Björn Usadel | ||
| ZytoChem Plus (HRP) Anti-Rabbit (DAB) Kit | Zytomed Systems | HRP008DAB-RB |
Referencias
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