A CCL2/ROS autoregulation loop is critical for cancer-associated fibroblasts-enhanced tumor growth of oral squamous cell carcinoma

Cancer-associated fibroblasts (CAFs) have been described to play critical roles in initiation, progression and metastasis of various cancers. However, the involvement of CAFs in oral cancer (OC) has not been well addressed. In this study, we demonstrate that CAFs, when cocultured with OC cells (OCCs), produce high levels of chemokine (C-C motif) ligand 2 (CCL2) and, subsequently, enhance endogenous reactive oxygen species production in cells. Oxidative stress stimulates expression of cell cycle progression proteins in OCCs, leading to promotion of OCC proliferation, migration, invasion and, OC tumor growth. On the other hand, oxidative stress triggered the activation of nuclear factor-kappaB (NF-kappa B) and STAT3 in CAFs, resulting in accelerating CCL2 expression. In this way, CAFs-OCCs coculture creates a favorable cytokine-rich microenvironment, beneficial for both CAFs and OCCs. In addition, upregulation of CCL2 expression has been observed in oral squamous cell carcinoma tumors and patient plasma. We also showed that inhibition of CCL2 reduced OC tumor burden in mice. Therefore, our data suggested that CCL2 represents a potential therapeutic target for treatment of OC.