MMP9 and non-small cell lung carcinoma: Nicotine and cigarette smoke extract (CSE) are involved in inducing Epithelial-to-Mesenchymal Transition (EMT) through epigenetic change and histone deacetylase (HDAC)-mediated downregulation of epithelial (E)-cadherin and increasing expression of the mesenchymal markers metalloproteinase 9 (MMP9), vimentin, fibronectin and neural (N)-cadherin in NSCLC cell line A549, leading to lose adhesions/junctions and polarity in epithelial cells [8,9,10].