Fig. 8.

Possible mechanism underling periodontal inflammation-induced metastasis. Bacterial wall component, LPS, induces caspase 1 activation and proptosis pathway signaling in gingival fibroblasts in instances of PI. The proinflammatory cytokine, IL-1β, as well as CCL2, CCL5, and CXCL5 are produced and initiate M2 macrophage. In the early stages of primary breast tumor progression, where there is no expected metastasis, IL-1β and the produced cytokines recruit M2 macrophages, as well as MDSC to the lymph node and head and neck area. In the later stages when metastasis has established, MDSC are the main cells implicated and have a role in increasing the tumor burden in the lymph node and head and neck area, where the role of IL-1β is dispensable