CCL2 and head and neck squamous cell carcinoma: Higher doses of MCP-1 might induce activation earlier, resulting in a decline in the phosphorylation of pro-survival factors at the observed time point; however, it seems likely that the high dose of MCP-1 indeed caused negative effects in HNSCC cells, as 100 ng/mL of MCP-1 was also less effective in supporting cell growth under serum starvation condition (Fig. 3A).