Alpha-1 antitrypsin (A1AT) is known as a serum trypsin inhibitor and is a protease inhibitor belonging to the serpin superfamily. Alpha-1 antitrypsin is a single-chain glycoprotein consisting of 394 amino acids in the mature form and exhibits a number of glycoforms.

A1AT is a major inhibitor of human serine proteases in serum, is produced mainly by the liver, but also by extrahepatic cells, including neutrophils and certain cancer cells. AAT is an acute-phase protein and its concentration rises up to 3–4-fold above normal during acute inflammation. Several types of cancer, including non-small cell lung adenocarcinoma, have been associated with increased serum levels of AAT [1][2][3].

Moreover, not only the native, the inhibitory form of AAT but also conformationally modified, non-inhibitory forms are suggested to play a role in modulating tumor growth and invasiveness. For example, Kataoka and co-workers have shown that the C-terminal fragment of AAT can enhance the growth and invasiveness of human pancreas adenocarcinoma cells, in vivo [5].