Table 2.

The ability of microbial species to modulate anti-tumor responses and bone homeostasis.

Microorganism	Cancer targeted	Impact on ICI therapy/anti-tumor response		Additional role in bone health/homeostasisa	References
		Immunotherapy given	MOA of ICI promotion/anti-tumor activity
Bifidobacteria	Breast	Anti-PD-1 therapy	Increased NK cell tumor infiltration, decreased production of pro-tumor macrophages	Suppresses differentiation and functional activity of RANKL-induced osteoclaststs	(Di Modica et al., 2021; Kim et al., 2021; Sapra et al., 2022)
Lactobacillus	Breast	anti-PD-1/PD-L1	Indole acetic acid production and CD8+ T cell activation via AhR signaling	Improve osteogenesis and inhibit osteoclastogenesis	(Peng et al., 2020; Sapra et al., 2021)
Prevotella	Prostate	–	Decrease levels of androgens and delayed onset of cancer	Inhibits osteoclastic bone resorption and slows down bone loss in PMO	(Chen et al., 2023; Fujita et al., 2023; Lee et al., 2014; Pernigoni et al., 2021; Ponzetti and Rucci, 2019)
Akkermansia	Lung cancer	–	Enhanced CD8+ cytotoxicity, granzyme and IFN production, supressed PDL-1 expression	Increase in osteoblast population and improves bone quality	(Keshavarz Azizi Raftar et al., 2021; Xu et al., 2024)

PD-1: Programmed Cell Death Protein 1, PD-L1: Programmed Cell Death Ligand 1, DC: Dendritic cell, AhR: Aryl hydrocarbon receptor, IL: Interleukin, pTregs: Peripherally derived Tregs, IFN: Interferon, MDSCs: Myeloid-derived suppressor cells, RANK-L: Receptor activator for nuclear factor kappa-B ligand, PMO: Post-menopausal osteoporosis.

^aThis column is unrelated from the cancer-studies mentioned in rest of the columns of the table but instead it includes independent studies demonstrating the contributory role of corresponding bacterial species in maintaining bone homeostasis. Thereby suggesting the prospect of using these bacterial species for managing the metastasis of the primary malignancies like breast and prostate to the bone.