Breast Cancer–Microbiome Crosstalk

Breast cancer is one of the most common malignancies among women in Saudi Arabia and worldwide (Laborda-Illanes et al., 2020). Tumor-related deaths continue to be high despite progress in the development of numerous medicines. Chemotherapies and targeted therapies are mainly focused on halting the proliferation of breast cancer cells, while immunotherapies activate immune cells to fight cancer. Beside cancer cells, immune cells, and stromal cells as well as the breast cancer microenvironment comprises numerous types of bacteria, which were reported to play a defensive role in breast carcinogenesis by affecting estrogen levels, promoting antitumor protection, and supporting immune surveillance (Chan et al., 2016). On the other hand, breast cancer cells provide favorable conditions for these microorganisms to develop and survive (Al-Ansari et al., 2021). While many labs, including ours had studied the effect of the microbiomes on breast cancer cells, the interaction of breast cancer cells and the breast bacterial-microbiota has not been elucidated. The aim of this study is to investigate whether bacterial cells from the breast microbiota will be affected by secreted factors from breast cancer cells and whether this could contribute to disease progression. To this end, Cells Free-Serum Media (CF-SFM) as a control or Serum Free-Conditioned Media (SF-CM) will be collected from breast cancer cells (MCF-7) or normal breast epithelial cells (MCF-10A). The CF-SFM or SF-CM will then be mixed at different concentration levels for various time points with different types of bacterial culture, which are known to be part of the breast microbiome (Escherichia coli, Enterococcus faecalis, and Pseudomonas aeruginosa). The bacteria that were treated with different SF-CM and CF-SFM will then be collected and characterized. The outcome of this study will advance our understanding of the potential role of the cancer microbiome cells that are present in the breast tumor microenvironment and could open a novel therapeutic window to target specific metabolites in combinations with other therapies to effectively halt the disease’s advancement.