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

The inter-alpha-trypsin inhibitor (ITI) family is a group of plasma proteins built up from heavy (HC1, HC2, HC3) and light (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, H2, H3, and bikunin chains were found in polymorphonuclear cells, whereas H1 and bikunin proteins were found in mast cells. Bikunin was further observed in bronchoepithelial 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 H2 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.(J Histochem Cytochem 47:1625-1632, 1999)

Assembly and secretion of recombinant chains of human inter-alpha-trypsin inhibitor in COS-7 cells.

The inter-alpha-trypsin inhibitor (ITI) family is a group of structurally related plasma serine protease inhibitors. The ITI family members consist of combinations of mature heavy chains named HC1, HC2, HC3 linked to bikunin (a Kunitz-type protease inhibitor) by a covalent interchain protein-glycosaminoglycan-protein cross-link. The biosynthesis of the ITI family members takes place in the liver. In this report we examine the biosynthesis of these proteins using transient transfected COS-7 cells expressing one or more combinations of human ITI chains. The processing and secretion of alpha1-microglobulin and bikunin does not require the ITI heavy chains. A small proportion of the H3 chain seems to be processed into the HC3 form in the absence of the other ITI chains. In contrast, the processing of H2 into HC2 needs the presence of the L chain. The COS-7 cells are able to link the HC2 and HC3 heavy chains with bikunin by means of a chondroitin sulfate bridge, and thus to generate 260-kDa ITI-like proteins as well as pre-alpha-trypsin inhibitor (PalphaI). However, the maturation of the Hl chain into HC1 and the assembly of HC1 inside multichain proteins may take place according to a mechanism which differs from that of the H2 and H3 chains. These results indicate that the assembly of the constituent chains of the ITI-like proteins and PalphaI is not dependent on the liver machinery.

A model of spontaneous lung metastases visualised in fresh host tissue by green fluorescent protein expression.

The authors describe a model of spontaneous lung metastases in nude mice using green fluorescent protein (GFP) expression as a marker. The human lung cell line H460M was transfected with the humanised GFP-S65T cDNA and a stable fluorescent cell line termed H460M(GFP) was obtained. The latter kept in vitro biological features when compared to the parental H460M cell line, which suggests that GFP-expression does not influence H460M(GFP) cell line behaviour. In order to evaluate their metastatic potential and to determine the number of spontaneous metastases, H460M(GFP) cells were subcutaneously inoculated into nude mice. Animals were sacrificed at time intervals and tissues (lung, liver, spleen, node, and kidney) were analysed under fluorescence microscopy. These experiments demonstrated that 2 weeks after subcutaneous inoculation, 75% of animals exhibited fluorescent spontaneous lung micrometastases. From the third week, 100% of animals exhibited an increasing number of metastases (10-16) which were only localised in the lungs. At the end of the study, the number of lung metastases had dramatically increased (42-400 at 7 weeks). Although these metastases were mainly localised in lung, a few mice had an invasion of neighbouring lymph nodes. The H460M(GFP) cell line allowed to follow the seeding and development of spontaneous lung metastases and may be considered a simple and powerful tool to study each step of the metastasis to screen new anticancer drugs.

Human inter-alpha-trypsin inhibitor heavy chain H3 gene. Genomic organization, promoter analysis, and gene linkage.

To understand more about the human inter-alpha-trypsin inhibitor heavy chain H3 (ITIH3) expression and the relationship between this gene and the family of other ITI heavy chain genes, an analysis of the structure of the ITIH3 gene and its promoter region was performed. This gene is a single copy gene, 14 kilobase pair in length and consists of 22 exons. ITIH3 shares highly conserved exon size and intron-exon borders with other ITI heavy chain genes. We determined that the human ITIH1, ITIH3, and ITIH4 genes are closely linked within a 45-kilobase pair. They are arranged in the order of H1-H3-H4, with the ITIH4 gene transcribed in the opposite direction. A model for the evolution of the ITI heavy chain gene family is presented that involves multiple rounds of gene duplication plus inversion events. The minimum promoter region (-135 to +75) is identified in HepG2 cells. The transient transfection study in various cell lines indicates that the activity of the ITIH3 promoter is not liver-specific. DNase I footprinting, mobility shift assays, and cotransfection experiments reveal a functional CCAAT/enhancer-binding protein site (C/EBP, -1344 to -1305) which interacts with C/EBPalpha and C/EBPbeta factors. The latter factors control the transcription of the ITIH3 gene positively.

Transverse formamide gradients as a simple and easy way to optimise DNA single-strand conformation polymorphism analysis.

Although widely used, the detection of DNA mutations by the single-strand conformation polymorphism (SSCP) method is often hampered by the need to examine a large set of electrophoretic conditions in order to select the one suited to the DNA sequence under study. We show here that the use of transverse chemical gradient gels allows for a quick and easy optimisation of SSCP analysis, as exemplified on two mutations in exon 2 of the alpha-1-antitrypsin gene.

Inter-alpha-trypsin inhibitor proteoglycan family--a group of proteins binding and stabilizing the extracellular matrix.

Extracellular matrix (ECM) is composed of several macromolecules associated in a complex network. This structure allows cells to adhere, migrate and interact. Hyaluronic acid (HA) is a glycosaminoglycan (GAG) and a major representative of ECM. HA-binding proteins such as CD44, aggrecan, and versican, have been implicated in structuring the ECM by stabilizing large macromolecular aggregates. They also play an important role in tumor metastasis and cell motility. Recently, further HA-binding proteins were identified: the inter-alpha-trypsin inhibitor(ITI)-related proteins. ITI is a glycoprotein composed of three polypeptides: two heavy chains (HC1 and HC2) and one light chain (bikunin). Bikunin confers the protease-inhibitor function. The heavy chains' function was unknown. Recent studies have shown that HC1 and HC2 are linked in vivo and in vitro to hyaluronic acid. This linkage greatly improves extracellular matrix stability. It also demonstrates that ITI-related proteins might be considered as HA-binding proteins (HABP). The ITI related proteins are composed of four polypeptides (HC1, HC2, HC3 and the bikunin) encoded by four genes H1, H2, H3 and L. Unlike the majority of plasma protein a non-disulfide covalent linkage exists between heavy chains and bikunin. This review presents the recent progress concerning the interactions between ITI and ECM showing that ITI-related proteins are HABP members. We will focus on the heavy chain linkage with HA, which represents the demonstration of covalent binding between proteins and HA.

Frequency and prognostic evaluation of 3p21-22 allelic losses in non-small-cell lung cancer.

Previous loss of heterozygosity (LOH) studies of chromosome 3p loci have displayed a 60% deletion frequency in non-small-cell lung cancers (NSCLC), as opposed to small-cell lung cancers, in which the 3p deletion is consistently found. However, the high stromal-cell admixture found in NSCLC and the use of the Southern-blot method lead to under-evaluation of this frequency. In this study, we used a very precise microdissection technique followed by PCR amplification of 6 3p21-22 polymorphic genomic sequences to analyze LOH in 86 NSCLC and in normal adjacent tissue. We found the sensitivity of the microdissection-PCR-based LOH technique higher than the sensitivity of the Southern-blot technique: 87% of the squamous-cell carcinomas and 84% of the large-cell undifferentiated carcinomas showed a clear LOH for a 3p21-22 locus. All doubly informative cases but 4 showed concordant deletion at all 3p21-22 loci. The analysis of 3p microsatellite sequences displayed only 2 cases of genomic instability, one of them also displaying features of tumoral heterogeneity as regards the instability genotype. Four carcinomas in situ adjacent to these NSCLC showed the same allelic profile as the invasive tumors. The only prognostic factors in this study were the disease stage and histology. The 3p21-22 deletion was not related to the stage of the disease and did not appear to be a significant prognostic factor of survival. 3p21 loss appears, so far, to be the most frequent and the earliest genetic alteration described in NSCLC, but does not seem to carry significant prognostic information in invasive tumors.

Involvement of the three inter-alpha-trypsin inhibitor (ITI) heavy chains in each member of the serum ITI family.

Partial cDNAs coding for each of the three human inter-alpha-trypsin inhibitor (ITI) heavy chains were expressed in a bacterial plasmid system and rabbits were immunised with the fusion peptides obtained. Despite the strong sequence homology of these chains, the antisera turned out to be highly specific in the analysis of corresponding mRNA translation products or partially digested serum ITI. Besides classical serum ITI members, their use in Western blotting made it possible to evidence an H3-related ITI form and a low-amount H1-related HC/bikunin component. The relative levels of ITI family members was further studied in baboon and foetal calf sera.

Gene expression and protein distribution of inter-alpha-trypsin inhibitor in three human hepatoma cell lines.

In standard culture conditions, three human hepatoma cell lines, Hep3B, PLC/PRF/5 and HepG2, were characterised by a predominant transcription of only two (H2 and L) among the four genes involved in the synthesis of inter-alpha-trypsin inhibitor (ITI)-related proteins. Pulse-chase experiments followed by immuno-precipitation with specific anti-L and anti-H ITI antisera showed that the proteins synthesised displayed a restricted L and/or H2 antigenic reactivity. Furthermore, while Hep3B and PLC/PRF/5 lines only synthesised ITI precursors (mainly the L-form), HepG2 cells were able to secrete an ITI-like protein. Immunocytochemical analyses substantiated these results with uneven distribution of heavy and light-chain polypeptide reactivity among the cells. The use of hepatoma cell models for the study of protein synthesis and assembly must therefore be considered cautiously.

The human inter-alpha-trypsin inhibitor genes respond differently to interleukin-6 in HepG2 cells.

The effects of interleukin 6 (IL-6), the major inducer of the acute-phase reaction, on the expression of inter-alpha-trypsin inhibitor (ITI) genes were examined using human HepG2 hepatoma cells. The three ITI heavy-chain genes H1, H2 and H3 were transcriptionally regulated by IL-6 in a dose- and time-dependent manner. The treatment of HepG2 cells with IL-6 resulted in an increase of H1 and H3 mRNA levels and a decrease of H2 and L mRNA levels. Actinomycin D blocked the action of IL-6, suggesting that IL-6 regulated the H1, H2, H3 gene expression. Moreover, the kinetics of the ITI mRNA degradation in untreated and IL-6-treated cells confirmed these data. The nuclear run-on assay supports the regulatory effect of IL-6 at the transcription level of the L and H2 genes. Primer extension experiments showed that the effect of IL-6 on L, H2 and H3 mRNA synthesis was not related to the transcription starting point. Although H1, H2, H3 and L gene products are supposedly present in similar amounts in the ITI and pre-alpha-trypsin inhibitor molecules, the present work shows that these genes are regulated in a different manner, at least under the influence of IL-6.

Tandem orientation of the inter-alpha-trypsin inhibitor heavy chain H1 and H3 genes.

The inter-alpha-trypsin inhibitor H1 (ITIH1) and inter-alpha-trypsin inhibitor H3 (ITIH3) genes have both previously been mapped to chromosomes 3 and 14 in the human and mouse, respectively. We now present evidence that these genes are physically linked. By using cDNA probes, a recombinant DNA phage has been isolated from a bacteriophage DNA library, which contains sequences flanking the 5' end of the ITIH3 gene and the 3' end of the ITIH1 gene. Restriction endonuclease mapping, PCR analysis and DNA sequence determination of the recombinant phage and comparison to genomic DNA revealed that the genes are in tandem, 2721 base pairs apart, with the ITIH1 gene to the 5' side of the ITIH3 gene. Their respective transcriptional units are thus on the same strand of DNA and most probably arose in evolution as the consequence of a duplication of a common ancestral gene.

Post-translational processing of the inter-alpha-trypsin inhibitor in the human hepatoma HepG2 cell line.

In human hepatoma HepG2 cells, the serum inter-alpha-trypsin inhibitor (ITI)-like protein is synthesized from two protein precursors, the heavy chain (H) H2 and the light chain (L). Both of them carry sulphate groups involved in the chondroitin sulphate glycosaminoglycan (GAG) linkage, as demonstrated by [35S]sulphate labelling, chondroitinase digestion and inhibition with beta-D-xyloside, an artificial GAG acceptor. While inhibition of N-glycosylation prevented neither the maturation nor the secretion of the ITI-related entities, brefeldin A induced the accumulation of H and L precursors in the cells, therefore blocking subsequent association and maturation of the precursors before their secretion. The enzyme system involved in the ester linkage between H and L chains is localized in the trans-Golgi network since no ITI-like protein could be obtained in the presence of monensin; instead free heavy-chain protein forms and bikunin were secreted in culture supernatants. The ITI-like protein synthesized by HepG2 cells is therefore composed of two heavy chains HC2 linked to two bikunin chains by chondroitin sulphate bridges, although the GAG linkage between HC2 chains is presumably different. Further, a different maturation route leading to restricted heavy-chain forms, Hm and Hd, could be shown.

The polymorphism of the plasma inter-alpha-trypsin inhibitor (ITI) and its relationship to the heavy chain H1 subunit gene (ITIH1) at 3p211-212.

We investigated the ITI protein polymorphism in linkage analysis, using DraI and SstI as restriction fragment length polymorphism (RFLP) markers for the ITIH1 gene. Isoelectric focusing (IEF) classification from 76 individual plasma samples and RFLP analysis from the corresponding DNA preparations disclosed linkage disequilibrium between the phenotypic IEF patterns of the two common ITI alleles, ITI*1 and ITI*2, and the diallelic DNA polymorphisms of two ITIH1 RFLPs, represented by DraI 4.0 kb and DraI 2.4 + 1.6 kb, and by SstI 6.7 kb and SstI 6.0 + 0.7 kb, for the ITI 1 and ITI 2 IEF phenotypes, respectively, and by DraI 4.0/2.4 + 1.6 kb and SstI 6.7/6.0 + 0.7 kb for the heterozygous ITI 1-2 IEF phenotype. Linked segregation between either of the RFLPs and the polymorphic ITI plasma protein locus has been established in nine informative family pedigrees. The less frequent allele in Europeans, ITI*3, is not represented by a further allelic restriction fragment in either RFLP. The significant linkage disequilibrium observed in this genetic study indicates that the ITI locus, with the alleles ITI*1 and ITI*2, must be close to, or reside within, the ITIH1 gene. The diallelic ITI protein polymorphism therefore provides an informative phenotypic marker system for chromosome 3p211-212.

Light microscopical detection of inter-alpha-trypsin inhibitor and its different mRNAs in cultured hepatoma Hep G2 cells using immunocytochemical and in situ hybridization techniques.

The Hep G2 hepatoma cell line synthesizes the inter-alpha-trypsin inhibitor (ITI). This protease inhibitor and the other proteins of this family include four polypeptides chains: three heavy chains (HC1, HC2, HC3) and one light chain (bikunin). In the present study, we have demonstrated by immunofluorescence that ITI is detected mainly in perinuclear cytoplasmic zones comparable to those of albumin or alpha-1-antitrypsin. The presence of the mRNAs of the four polypeptide chains in all Hep G2 cells of a non-synchronized culture have been demonstrated by in situ hybridization. An evaluation of the transcription of the four ITI genes through an analysis of markings brings to the fore a clearly much higher rate of mRNAs from the light chain than from the heavy chains. The mRNAs corresponding to the HC2 chains are more heavily represented than are those corresponding to the HC1 and HC3 chains. In Hep G2 cells in culture, a quantification of mRNAs based on the in situ hybridization technique shows that their relative quantities, in decreasing order, are those of L, HC2, HC3 and HC1.

Detection by the polymerase chain reaction of two polymorphisms in exon 14 of the human inter-alpha-trypsin inhibitor heavy chain H1 gene.

Two polymorphisms were detected within exon 14 of the inter-alpha-trypsin inhibitor heavy chain H1 (ITIH1) gene. The polymorphisms are detected by digesting the same 202-bp polymerase reaction product with the PstI and Hph1 restriction endonucleases. These gene polymorphisms lead to the change of two amino acids in the mature protein. The polymorphisms can be used for the analysis of 3p21 deletion in human carcinomas as well as to develop a better understanding of the protein polymorphism already described.

Isolation and characterization of the human inter-alpha-trypsin inhibitor heavy-chain H1 gene.

The human inter-alpha-trypsin inhibitor heavy chain H1 (ITI heavy chain H1) gene was isolated from two overlapping clones. It spans 14 kbp and is composed of 22 exons from 15 bp to 281 bp in size and has consensus splice sites. Intron sizes range from 80 bp to 2000 bp. It codes for the precursor of HC1 that is part of the serum ITI form of 220 kDa. Two major transcriptional initiation sites were identified in the 5'-flanking region, which contained putative promoter elements, but no typical TATA and CAAT boxes. mRNA for the ITI heavy chain H1 was found only in liver. The tissue-specific transcription of the gene might be due to the presence of binding sites for the hepatocyte nuclear factor HNF-5 and to the octameric motifs. A previous overlapping of cDNA clones indicated the absence of 29 bp in one of these clones. The present study shows that the 29 bp is located within the gene at the end of exon 21. A reverse-transcriptase polymerase chain reaction mapping analysis of liver mRNA identified the two types of the mRNA for ITI heavy chain H1. Accordingly, the data demonstrate that there is alternative splicing of at least one exon of the ITI heavy chain H1 gene.

Human pre-alpha-trypsin inhibitor-precursor heavy chain. cDNA and deduced amino-acid sequence.

Pre-alpha-trypsin inhibitor (P alpha I) is a serine-proteinase inhibitor of M(r) 130,000 found in human serum. This protein belongs to the family of proteins called inter-alpha-trypsin inhibitor (ITI). P alpha I is composed of a heavy chain (HC3) and of a light chain (bikunin), synthesized by two separate mRNA. Bikunin is identical to the ITI light chain, the structure of which has already been established. The HC3 is obtained from a precursor called H3. The bikunin is covalently linked to HC3 by a chondroitin-4-sulfate glycosaminoglycan. We report here the H3 full-length cDNA sequence and the deduced amino-acid sequence of the heavy-chain H3 precursor. The high degree of similarity between the nucleotide and amino-acid sequences of ITI heavy-chain families H1, H2, H3 is examined with respect to their probable structure and assembly with bikunin in the final proteins, P alpha I and ITI.

Human inter-alpha-trypsin inhibitor: full-length cDNA sequence of the heavy chain H1.

Inter-alpha-trypsin inhibitor (ITI), called inter-alpha-inhibitor, is a 220 kDa serine proteinase inhibitor found in human serum. It is composed of at least three distinct polypeptide chains. These chains, named H1, H2 and L, are an independently synthesized and proteolytically processed precursor protein. Only the complete structure of H2 and L has been established so far. We used a PCR-based cloning approach and a cDNA screening library to isolate the full-length cDNA H1. The amino acid sequences of the two heavy chains deduced from the cDNA are highly similar (40% identity). Nevertheless, the structure of the signal peptide and propeptide in the N-terminal region is different in these two chains. A complex posttranslational cleavage at both ends of H1 and H2 may be proposed prior to assembly of the ITI chains.

The genes for the inter-alpha-inhibitor family share a homologous organization in human and mouse.

Inter-alpha-inhibitor (I alpha I) and related molecules in human are comprised of three evolutionarily related, heavy (H) chains and one light (L) chain, also termed bikunin. The latter originates from a precursor molecule that is cleaved to yield the bikunin and another protein designated alpha-1-microglobulin (A1m). The four H and L chains are encoded by four distinct genes designated H1, H2, H3, and L. The L and H2 genes are localized onto human chromosomes (chr) 9 and 10, respectively, whereas the H1 and H3 genes are tandemly arranged on chr 3. Mouse poly(A)+ RNAs or endonuclease-restricted mouse DNA were analyzed by standard and pulsed-field gel electrophoresis (PFGE) techniques in agarose gels and blot-hybridized with human H1, H2, H3 or L cDNA probes. The variable sized transcripts and unique restriction fragment patterns detected with each probe indicate that four genes, including one common L gene for A1m and bikunin also exist in mouse. The co-migration of H1- and H3-hybridizing fragments on PFGE suggests that the mouse H1 and H3 genes are also tandemly arranged. An Msp I restriction fragment length polymorphism (RFLP) in the mouse L gene (proposed symbol, Intin-4) links this gene to other genes already mapped at mouse Chr 4 near the brown (b) locus, a homologous region to the human chr 9q32-34 band where the human I alpha I L gene is located. Therefore, a similar number and arrangement of I alpha I genes is found in mouse and human, including the triplication of an H gene ancestor. These results point to an ancient origin of this complex set of genes.

Structural analysis of the human inter-alpha-trypsin inhibitor light-chain gene.

The human inter-alpha-trypsin inhibitor (ITI) light-chain gene, which codes for the two proteins alpha 1-microglobulin (protein HC) and ITI-derived human inhibitor of 30 kDa (HI-30), was isolated from a human genomic library. This gene, present as a single copy in the human genome, is composed of 10 exons and 9 introns distributed over 20 kbp. A single transcriptional initiation site was identified in the 5'-flanking region which contained promoter elements, but no typical TATA box. However a sequence equivalent to the TATA box is present on both sense and anti-sense strands in the 5'-flanking region of the first exon coding for HI-30. The exon-intron organization suggests that the regions coding for protein HC and other members of the lipocalin superfamily evolved from a common ancestral gene that is probably different from that coding for HI-30. These data suggest that two distinct ancestral genes could have existed and fused during evolution. Several direct and one inverted repeats are also found within this gene, as well as potential glucocorticoid-receptor binding sites.