In vitro experiments demonstrate that EGF stimulation of EGFR-positive NSCLC cell lines can result in the upregulation of MMP-9 and, likewise, inhibition of EGFR in vivo reduces tumour cell MMP-9 expression (Perrotte et al, 1999; O'Byrne et al, 2001). This evidence concerns the gene MMP9 and non-small cell lung carcinoma.