Immunohistochemical distribution of inter-α-trypsin inhibitor chains in normal and malignant human lung tissue

The inter-alpha E E-trypsin inhibitor (ITI) family is a group of plasma proteins built up from heavy (HC1, HC2, HC3) and tight (bikunin) chains synthesized in the liver. In this study we determined the distribution of ITI constitutive chains in normal and cancerous lung tissues using polyclonal antibodies. In normal lung tissue, HZ, H3, and bikunin chains were found in polymorphonuclear cells, whereas H1 and bikunin proteins were found in mast cells. Bikunin was further observed in bronchoepithetial mucous cells. In lung carcinoma, similar findings were obtained on infiltrating polymorphonuclear and mast cells surrounding the tumor islets. Highly differentiated cancerous cells displayed strong intracytoplasmic staining with H1 and bikunin antiserum in both adenocarcinoma and squamous cell carcinoma. Moreover, weak but frequent HZ expression was observed in adenocarcinoma cells, whereas no H3-related protein could be detected in cancer cells. Local lung ITI expression was confirmed by RT-PCR. Although the respective role of inflammatory and tumor cells in ITI chain synthesis cannot be presently clarified, these results show that heavy chains as well as bikunin are involved in malignant transformation of lung tissue.