IL6 and neoplasm: Considering the individual influence of IL-6 and IL-8 on the regulation of MMP expression and the role STAT3 plays in driving metastasis and drug resistance, we speculated that different subgroups of MMPs - such as collagenase, gelatinase, matrilysin, stromelysin, and membrane-type - could be regulated by tumor cell density through the synergistic signaling of IL-6 and IL-8.