Effect of Invasion of Borrelia burgdorferi in Normal and Neoplastic Mammary Epithelial Cells

Abstract

Borrelia burgdorferi, the causative agent of Lyme Disease, is known to be able to disseminate and colonize various organs and tissues of its hosts, which is very crucial for its pathogenicity and survival. Recent studies have shown the presence of B. burgdorferi DNA in various breast cancer tissues, in some with poor prognosis, which raises the question about whether B. burgdorferi can interact with mammary epithelial cells and could have any effect on their physiology, including tumorigenic processes. As the model in this study, we have used MCF 10A normal and MDA-MB-231 tumorigenic mammary epithelial cells and infected both cell lines with B. burgdorferi. Our immunofluorescence and confocal microscopy results showed that B. burgdorferi is capable of invading normal epithelial and breast carcinoma cell lines within 24 h; however, the infection rate for the breast carcinoma cell lines was significantly higher. While the infection of epithelial cells with B. burgdorferi did not cause any changes in cell proliferation rates, it showed a significant effect on the invasion and migratory capacity of the breast cancer cells, but not on the normal epithelial cells, as determined by Matrigel invasion and wound healing assays. We have also found that the levels of expression of several epithelial–mesenchymal transition (EMT) markers (fibronectin, vimentin, and Twist1/2) changed, with a significant increase in tissue remodeling marker (MMP-9) in MDA-MB-231 cells demonstrated by quantitative Western blot analyses. This observation further confirmed that B. burgdorferi infection can affect the in vitro migratory and invasive properties of MDA-MB-231 tumorigenic mammary epithelial cells. In summary, our results suggest that B. burgdorferi can invade breast cancer tumor cells and it can increase their tumorigenic phenotype, which urges the need for further studies on whether B. burgdorferi could have any role in breast cancer development.

Effect of Borrelia burgdorferi on the Expression of miRNAs in Breast Cancer and Normal Mammary Epithelial Cells

“…Another study identified an upregulated expression of miR-206 in the failing hearts of mice and cardiac fibroblast cells and was found to be associated with reduced TIMP 3 activity [ 42 ]. Previously, our research group detected a significant increase in the expression of MMP9 in B. burgdorferi -infected MDA-MB-231 cells compared to the uninfected control group [ 20 ]. In contrast, the normal mammary epithelial cell line, MCF10A, did not show any change in MMP9 expression after infection with B. burgdorferi [ 20 ].…”

“…In addition, synchronizing cells reduces the variability between cells, creating a more precise way of comparing experimental results and achieving increased reproducibility of experiments [ 27 ]. Following synchronization, a total of one million cells were infected with B. burgdorferi with a multiplicity of infection (MOI) of 60 as previously described [ 20 ].…”

“…Further, it was also observed that by the mechanism of intracellular localization B. burgdorferi could stay hidden from the host’s immune system [ 19 ]. Our research group has recently found evidence that B. burgdorferi can invade the triple-negative MDA-MB-231 breast cancer cells at a significantly higher rate in comparison to normal mammary epithelial cells [ 20 ]. This study also showed that the in vitro invasion and migratory capability of breast cancer cells was significantly increased following B. burgdorferi infection [ 20 ].…”

“…Our research group has recently found evidence that B. burgdorferi can invade the triple-negative MDA-MB-231 breast cancer cells at a significantly higher rate in comparison to normal mammary epithelial cells [ 20 ]. This study also showed that the in vitro invasion and migratory capability of breast cancer cells was significantly increased following B. burgdorferi infection [ 20 ]. Our current research focused on identifying the molecular changes that occur when B. burgdorferi infects breast tissues, and whether these changes could initiate or progress tumor development.…”

Evidence for the presence of Borrelia burgdorferi in invasive breast cancer tissues

“…A recent in vitro study also demonstrated that B. burgdorferi can invade triple-negative breast cancer cells at greater rates than normal mammary epithelial cells and increase cancer cell invasive potential [ 19 ]. Further studies showed a significant change in genome-wide RNA and miRNA expressions upon B. burgdorferi infection in triple-negative breast cancer and normal mammary epithelial cells [ 21 , 22 ].…”