Fig. 8.

Pathways involve in the progression of bone invasion by OSCC. a Osteoclasts play the main role to degrade the bone matrix, growth factors such as TGF-β are released from the bone components. b TGF-β may induce EMT of OSCC cells and promote expressions of MMPs, which directly facilitate invasion of cancer cells through stromal tissues or micro-cavities of bone marrow within the bone. c TGF-β may also promote cytokines such as osteoclasts-related factors, which activate more osteoclasts and prolong their survival favouring the invasion of cancer cells