Skip to main content
2024 BMES Annual Meeting Main banner
Icon Legend
This session is not in your schedule.
This session is in your schedule. Click again to remove it.

Womens Health

Women's Health - Poster Session D

Poster L18 - Iron Content Influence Growth of Endometrial Cancer Bacterial Biomarker Porphyromonas somerae

Friday, October 25, 2024
3:30 PM - 4:30 PM EST
Location: Exhibit Hall E, F & G

Introduction:  Endometrial cancer (EC), the sixth most common cancer in women, has seen a significant rise partly due to aging populations, obesity, and diabetes. Despite its prevalence, the mechanistic causes for EC remain unclear, and no effective screening method developed. Prior studies have identified the bacterium Porphyromonas somerae in the uterine microbiome of EC patients, suggesting a potential pathogenic role similar to other Porphyromonas species known to be associated with cancers. P. gingivalis, another gram-negative bacteria associated with periodontal disease and oral cancer, is known for its iron-uptake mechanisms involving specific outer membrane receptors, proteases, and lipoproteins– a method that sets it apart from other gram-negative bacteria. P. gingivalis has also been reported to have enhanced virulence levels under conditions of both heme excess and heme depletion. We investigated how changes in iron concentration over different time intervals affect the growth of P. somerae, particularly in relation to the transition from pre- to post-menopause when iron concentration in the uterus changes due to the cessation of cyclic endometrial shedding. Therefore, this study hypothesizes that the growth of P. somerae may be affected with iron concentration in the uterine environment. Specifically, it proposes that P. somerae growth is inhibited by low iron levels, decreasing iron concentrations, or abrupt decreases in iron concentrations. In addition, we aim to compare the effects of sudden versus gradual onset of menopause on iron levels and microbial growth.

Materials and

Methods:  We tested our hypothesis by examining growth changes from three initial starting points of ‘Low’, ‘Middle’, and ‘High’ levels of iron in P. somerae-inoculated chopped meat broth (CMB) vials, created using 1mM iron chelator stock (2, 2"- Bipyridyl dissolved in Ethanol), CMB stock, and 1mM hemin stock (Hemin dissolved in DMSO) utilizing concentrations based on levels of iron that were previously tested on P. gingivalis. Changes in concentrations were made at 6h in all 9 combinations utilizing the hemin, iron chelator, or neutral stock previously used to create initial conditions. Bacteria was grown under anaerobic conditions and optical density levels were measured to track growth, with measurements taken at 0h, 4h, 6h, 8h, 12h, 24h, 48h, and 72h time points.

To better understand if rate of change impacted growth levels of P. somerae, a secondary experiment was conducted using three initial starting magnitudes of ‘Low,’ ‘Middle,’ and ‘High’ levels of iron with P. somerae in CMB vials. Conditions were tested at three rates of shifting from one condition to the next. The iron concentration gradient altered over the course of 6 hours (faster rate, labeled as ‘1’), 12 hours (middle rate, labeled as ‘2’), or 18 hours (slower rate, labeled as ‘3’). Bacteria was grown under anaerobic conditions and optical density measured growth, with measurements taken at 0h, 6h, 8h, 12h, 18h, 24h.

Results, Conclusions, and Discussions: The bacteria reached exponential growth between 12h-24h. Experimental results indicate that P. somerae thrives in stable or increasing ‘Mid-to-High’ iron conditions. Current assumptions state middle levels of iron are prevalent in the uterine microbiome during menstruation but decline post-menopause, potentially impacting bacterial growth and its association with EC. Significant iron conditions were evaluated using paired t-testing of unequal variance (p <.001), revealing the highest significance in ‘Mid-Mid’ and ‘Mid-High’ conditions, the two conditions with the highest levels of bacterial growth. In addition, ‘Low-High’ displayed high significance, but in the opposite direction, displaying extreme low growth. Analysis into these conditions supports our hypothesis that low iron levels and decreasing iron concentrations.
Regarding the iron concentration rate change, the results preliminarily demonstrated P. somerae proliferated more in slower shift rates, indicating that the rate of iron shift has an impact on the bacterial growth. Significant iron conditions were evaluated using paired t-tests of unequal variance (p <.001), revealing the highest significance in conditions ‘High-Low 1’, ‘High-Low 2’, ‘Low-Mid 2’. ‘Low-Mid 2’ demonstrated robust growth while ‘High-Low 1’ and ‘High-Low 2’ were similar in their significantly weaker growth. These results support our hypothesis that P. somerae growth is inhibited by sudden decreases in iron concentrations, demonstrating that overall, P. somerae growth is hindered by rapid changes in iron levels.
Bacterial growth that started in 'Mid' or 'High' iron concentrations was significantly more robust compared to growth in low initial iron concentrations, even after shifting to a lower iron level at t = 6 hours, demonstrating the importance of the initial condition in the growth process of P. somerae. Future research will examine the impact of changes in iron concentration on P. somerae, exploring broader effects beyond growth. Past work on P. gingivalis showed virulence increases with decreased growth and deregulates periodontal tissue inflammatory response. Upcoming phases will thus explore P. somerae's potential pathogenic role in endometrial cancer, including analyzing collected samples for transcriptomic evidence. Additionally, the effects of iron shifts on P. somerae interactions with endometrial cancer cells will be explored to clarify underlying mechanisms.

Acknowledgements (Optional):  The authors would like to thank the MW-A at Mayo Clinic for their mentorship, especially Dr. Marina Walther-Antonio and Janet Yao. We would also like to thank Jasmine Lunia,
Juan Arbelaez, Thomas Pelowitz, and Cara Chang for their continuous support. Funding for this project was provided by the Mayo Clinic & Illinois Alliance.