Quercetin acts at a concentration of 5 μM in H1975 and A549 human lung cancer cell lines, which significantly inhibits nickel-mediated invasion of H1975 and A549 lung cancer cells, inhibits inflammatory mediator secretion, inhibits mRNA and protein expression of TLR4 and Myd88, reduces phosphorylation of IKKβ and IκB, reduces expression of NF-κB and matrix metalloproteinase (MMP)-9, and induces inactivation of the TLR4/NF-κB signaling pathway [50]. This evidence concerns the gene MMP9 and lung cancer.