Frequent expression loss of Inter-alpha-trypsin inhibitor heavy chain (ITIH) genes in multiple human solid tumors: A systematic expression analysis

Abstract

Background: The inter-alpha-trypsin inhibitors (ITI) are a family of plasma protease inhibitors, assembled from a light chain – bikunin, encoded byAMBP– and five homologous heavy chains (encoded byITIH1,ITIH2,ITIH3,ITIH4, andITIH5), contributing to extracellular matrix stability by covalent linkage to hyaluronan. So far, ITIH molecules have been shown to play a particularly important role in inflammation and carcinogenesis.Methods: We systematically investigated differential gene expression of theITIHgene family, as well asAMBPand the interacting partnerTNFAIP6in 13 different human tumor entities (of breast, endometrium, ovary, cervix, stomach, small intestine, colon, rectum, lung, thyroid, prostate, kidney, and pancreas) using cDNA dot blot analysis (Cancer Profiling Array, CPA), semiquantitative RT-PCR and immunohistochemistry.Results: We found thatITIHgenes are clearly downregulated in multiple human solid tumors, including breast, colon and lung cancer. Thus,ITIHgenes may represent a family of putative tumor suppressor genes that should be analyzed in greater detail in the future. For an initial detailed analysis we choseITIH2expression in human breast cancer. Loss ofITIH2expression in 70% of cases (n = 50, CPA) could be confirmed by real-time PCR in an additional set of breast cancers (n = 36). Next we studied ITIH2 expression on the protein level by analyzing a comprehensive tissue micro array including 185 invasive breast cancer specimens. We found a strong correlation (p < 0.001) between ITIH2 expression and estrogen receptor (ER) expression indicating that ER may be involved in the regulation of this ECM molecule.Conclusion: Altogether, this is the first systematic analysis on the differential expression ofITIHgenes in human cancer, showing frequent downregulation that may be associated with initiation and/or progression of these malignancies.