TGF-alpha can act as morphogen and/or mitogen in a colon-cancer cell line

Transforming growth factor alpha (TGF-alpha) has multifunctional biological effects on a variety of mesenchymal and epithelial cells. It is a potent mitogen for a number of normal and transformed cell types, regulates extracellular matrix (ECM) production and promotes breast, kidney and lung morphogenesis. To clarify the role of ECM proteins in the morphogenetic and mitogenic effects of TGF-alpha, we have used a human colon carcinoma cell line (SW1222) which expresses EGF receptor. Here we show that TGF-alpha at 1 ng/ml increases the proliferation of SW1222 cells, but only when they are cultured on plastic rather than collagen-coated plates. Higher concentrations of TGF-alpha (10 ng/ml) did not increase cell proliferation but significantly enhanced the crypt-like glandular differentiation when cells were grown in 3-dimensional collagen gel (p = 0.027). These effects were accompanied by increased expression of alpha 2 beta 1 and alpha 3 beta 1 integrin molecules, which are receptors for extracellular matrix proteins, and by a statistically significant increase in binding of SW1222 cells to type-1 collagen. The effects of TGF-alpha both on binding to type-1 collagen and on morphological differentiation in 3-dimensional collagen gel were inhibited by monoclonal antibodies recognizing the alpha 2 beta 1 integrin. These data indicate that the morphogenetic or mitogenic activities of TGF-alpha are critically dependent on cellular interactions with extracellular matrix proteins and are primarily mediated by the alpha 2 beta 1 integrin receptor. Inappropriate expression of this growth factor, seen in tumours whose cell-matrix interactions are greatly impaired, could have deleterious effects on the maintenance of normal tissue architecture and growth control.

Beta 1 and beta 4 integrin expression in methacarn and formalin-fixed material from in situ ductal carcinoma of the breast

The integrins are alpha beta heterodimeric transmembrane proteins mediating cell-substratum as well as cell-cell interactions. Previous distribution studies on integrin expression have been limited by the requirement of cryostat sectioned tissues, and consequent poor resolution. We have examined 40 examples of ductal carcinoma in situ (DCIS) for the expression of both beta 1 and beta 4 integrin chains. These showed strong polarized membrane staining of residual myoepithelial cells (correlating with expression of smooth muscle specific actin) and of the basement membrane region with beta 1 and beta 4 antibodies respectively. In 12 out of 40 cases, the DCIS was negative for the beta 1 chain and a variable pattern of reactivity was seen in the remaining cases. The beta 4 chain was detected focally and weakly in the tumour cells of 7/40 DCIS and strongly in one; all of these cases were also positive for the beta 1 chain. Of the 22 cases where co-existent invasion was present, the infiltrating component showed either a similar degree or a diminution of the extent of immunostaining when compared with the in situ component; only one showed enhanced staining (beta 1 only). This study demonstrates that two of the main beta chains, beta 1 and beta 4, can be effectively demonstrated on methacarn and cold (4 degrees C) formalin-fixed tissues by avidin-biotin indirect immunoperoxidase staining and that the results are similar to those achieved using frozen tissue.

Loss of cell-cell and cell-matrix adhesion molecules in colorectal cancer

Adhesion molecules are thought to play a vital role in the induction and maintenance of tissue differentiation and their loss or down-regulation has been implicated in the neoplastic process. Recent studies have shown that the morphoregulatory activities are a consequence of interactive processes between several cell adhesion molecules rather than the function of a single molecule. Therefore, we have investigated a panel of adhesion molecules including members of the integrin, cadherin and immunoglobin superfamily in colorectal cancer. Twenty-eight consecutive colorectal adenocarcinomas were stained using an avidin-biotin indirect immunoperoxidase technique. Our results showed a consistent loss of the alpha 2 and beta 1 integrin subunits (21/28 = 75% and 22/28 = 78.6% respectively) and a decrease in expression of E-cadherin in 5/5 poorly differentiated adenocarcinomas. Carcinoembryonic antigen expression was preserved but with basolateral accentuation seen in tumours. There was no statistical correlation with Dukes' stage. These results provide further evidence that in colorectal cancer there is a widespread deregulated expression of cell-cell and cell-matrix adhesion molecules. Changes in the expression and function of adhesion molecules which regulate growth and differentiation may play a role in the behaviour of colorectal cancer.

Transforming growth factor-beta distribution in basal cell carcinomas: relationship to proliferation index

Transforming growth factor-beta (TGF-beta) distribution in basal cell carcinomas (BCCs) was studied using polyclonal antibodies recognizing intra- (precursor) and extracellular (activated) forms (LC 1-30 and CC 1-30), and compared with an index of cell proliferation (PCNA immunoreactivity). Intracellular TGF-beta is found in suprabasal keratinocytes and the outer root sheath. Extracellular TGF-beta is largely absent from normal skin, but is abundant in the intracellular spaces of hyperplastic epidermis overlying BCCs. Twenty-five of 29 BCCs showed increased extracellular TGF-beta in the desmoplastic stroma, with intercellular staining in nine of these. Intracellular TGF-beta was present in fibroblasts and endothelial cells, although only 17 of 29 BCCs were positive, predominantly in central cells showing apparent maturation. Little correlation was seen between the degree of staining of tumour cells and the distribution of extracellular TGF-beta. PCNA immunoreactivity was greater in BCCs compared with normal epidermis in 24 of 37 cases (P = 0.005), and was concentrated on the periphery of nodular BCCs. Strongest stromal reactivity for TGF-beta and maximal PCNA index also showed a significant correlation (P = 0.023). This study demonstrated abundant TGF-beta in the active stroma around BCCs, which may account for many of the morphological and functional characteristics of this tumour, but which may be a product of stromal rather than tumour cells.

Expression of gelatinase A and TIMP-2 mRNAs in desmoplastic fibroblasts in both mammary carcinomas and basal cell carcinomas of the skin

AIMS

To compare the localisation of mRNAs for the basement membrane degrading enzyme gelatinase A (72 kilodalton type IV collagenase) and its inhibitor TIMP-2 in carcinomas of the breast and basal cell carcinomas of the skin which have little or no ability to metastasize.

METHODS

In situ hybridisation was performed on formalin fixed, paraffin wax embedded blocks using 35S-labelled riboprobes on 16 mammary carcinomas, three fibroadenomas, and a benign phyllodes tumour, and on 15 basal cell carcinomas of the skin (BCC).

RESULTS

Labelling for both mRNAs was detectable in 14 of 16 mammary carcinomas and in 13 of 15 BCC, most often over organising desmoplastic fibroblasts in the stroma around invasive epithelial aggregates. Some sparse labelling was seen over malignant epithelial cells in six of the mammary carcinomas but not in the BCC. Some expression of gelatinase A mRNA was also seen in fibroblasts of breast lobules adjacent to the mammary carcinomas and around engulfed adnexal elements in the BCC, but not in unaffected breast tissues, fibroadenomas, the phyllodes tumour or unaffected skin.

CONCLUSIONS

Maximal expression of gelatinase A and TIMP-2 mRNAs occurs in malignant neoplasms as part of the host response to the presence of established neoplastic cells rather than as an initial response to invasion. The degree to which this is present suggests this may be a highly relevant mechanism modulating tumour differentiation, growth and progression, possibly entailing uptake via specific receptors on the tumour cell surface.

Morphoregulatory activities of E-cadherin and beta-1 integrins in colorectal tumour cells

The cadherin family of adhesion molecules are prime mediators of cell-cell interactions while the integrins predominantly mediate cell-matrix and to a lesser extent cell-cell binding specificity. We have recently shown that a human colon carcinoma cell line (SW1222) organizes into glandular structures, with well defined polarity when cultured in three-dimensional type I collagen gel. The current study indicates that SW1222 cells display high levels of E-cadherin (E-cd, epithelial cadherin) by western blotting and immunohistochemical staining. A monoclonal antibody (HECD-1) specific for human E-cd blocks cell-cell adhesion (100%) and inhibits (up to 75%) the glandular differentiation of SW1222 cells growing in collagen gel. Furthermore the anti-beta 1 integrin monoclonal antibody (mAb13) inhibits the glandular differentiation of SW1222 cells (61%) and their cellular binding to type I collagen (60%). However, no significant inhibition of cell-cell adhesion was demonstrated using mAb13 nor the anti-carcinoembryonic antigen monoclonal antibody (PR3B10). These results are consistent with E-cd being a cell-cell adhesion molecule expressed by SW1222 cells. These data indicate that E-cd and beta 1 integrins mediate cell-cell and cell-collagen interactions required for the induction and maintenance of the glandular differentiation of colorectal tumour cells. Thus the down-regulation or loss of E-cd and beta 1 integrins seen in poorly differentiated colorectal tumours may represent one of the abnormalities underlying their progression towards an undifferentiated phenotype in vivo.

Integrins and their accessory adhesion molecules in mammary carcinomas: loss of polarization in poorly differentiated tumors

The integrins are alpha beta heterodimeric transmembrane proteins mediating cell-substratum as well as cell-cell interactions. To identify the pattern of expression of the beta 1, beta 3, and beta 4 integrins and their accessory adhesion molecules in relation to the malignant phenotype of invasive breast cancer, we performed an immunohistochemical study for the alpha 2 beta 1 (VLA-2), alpha 6 beta 1 (VLA-6), alpha v and alpha v beta 3 (vitronectin receptor), alpha 6 beta 4, carcinoembryonic antigen, and carcinoembryonic antigen-related molecules in a series of 37 invasive breast carcinomas. All integrin chains examined showed similar patterns in nonneoplastic breast tissue, with strong membrane staining of the myoepithelial cells and weak to moderate staining on the basolateral surfaces of the luminal cells. We found that downregulation of the alpha 2 chain of VLA-2 occurs more frequently in poorly differentiated grade III invasive ductal carcinomas (IDCs) (P = .048). Loss of alpha 6 beta 4 seems also to occur more frequently in grade III IDC (seven of 11 cases, 63.6%) than in grade I/II IDC (two of eight cases, 25%), although this did not reach statistical significance. Carcinoembryonic antigen and carcinoembryonic antigen-related antigens, which are known to function as accessory adhesion molecules, were found mainly in the cytoplasm of neoplastic cells and there was reduced membrane polarization in poorly organized tumors. In contrast the alpha v beta 3, vitronectin receptor heterodimer recognized by the 23C6 monoclonal antibody was weak or absent in normal breast epithelium, and was weakly expressed in two of 19 (10%) IDCs and in nine of 18 (50%) invasive lobular carcinomas (P = .008). However, the alpha v chain detected with the antibody 13C2 was weakly to moderately expressed on nonneoplastic epithelium and at a similar intensity in 13 of 19 IDCs and 15 of 17 invasive lobular carcinomas, suggesting that in IDC the alpha v chain may be associated with a different beta chain (possibly beta 1 or beta 5). No correlation between integrin expression and estrogen/progesterone receptor status was found. These data provide further evidence that in invasive breast carcinomas there is a widespread deregulated expression of integrins and their accessory adhesion molecules with loss of polarization. Changes in the expression and function of cell adhesion molecules, which control growth and differentiation, may have clinical relevance in the behavior of breast cancer.

Stromal expression of 72 kda type IV collagenase (MMP-2) and TIMP-2 mRNAs in colorectal neoplasia

We undertook an in situ hybridization study to localize the mRNAs for the 72 kda type IV collagenase (MMP-2) and its specific inhibitor (TIMP-2) in 12 colorectal carcinomas, 3 adenomas, and 4 uninvolved resection margins to see how their distributions correlated with that of the reported distribution of MMP-2 protein. Labeling for MMP-2 and TIMP-2 mRNAs was detectable in 10 of 12 carcinomas and in 2 of 3 adenomas. Unexpectedly, we found much stronger signals for MMP-2 and TIMP-2 mRNAs within the mesenchymal cells in the desmoplastic stroma, of endothelial and/or (myo)fibroblastic nature, rather than in tumor epithelial cells in which localization of MMP-2 was anticipated. Our data indicate that stromal cells may have the ability to synthesize a metalloproteinase that degrades basement membrane, and may together with the neoplastic epithelial cells participate actively in the tissue remodeling and disruption of the basement membrane integrity which is characteristic of invasive tumors.

Lysozyme gene expression in inflammatory bowel disease

Riboprobe in situ hybridization (rISH) demonstrates active lysozyme synthesis in ulcerative colitis and Crohn's disease. Maximal labeling was seen in Paneth cells, macrophages, and granulomas. Diffuse infiltration of the mucosa by lysozyme-rich polymorphs characterizes ulcerative colitis but obscures reactivity in other cell lineages in immunohistochemical studies; lysozyme mRNA is not detected in polymorphs, rISH giving a clearer picture than immunohistochemical studies of the active synthesis of lysozyme within the gut in inflammatory bowel disease. In ulcerative colitis, strong signals localized to Paneth cell metaplasia were found in 11 of 20 cases and to a lesser degree in non-Paneth cell lineages in regenerative mucosa in 13 of 20 cases. In Crohn's disease, abundant labeling was seen in tuberculoid granulomas (5 of 20) and over macrophage aggregates in the lamina propria in another 7, characteristic patterns not encountered in ulcerative colitis. Low levels of lysozyme messenger RNA were found in the ulceration-associated cell lineage ("pseudopyloric metaplasia"). These results support the view that neutrophils are largely responsible for elevated fecal lysozyme levels in ulcerative colitis and macrophages for elevated serum lysozyme levels in Crohn's disease.

Over-expression of p53 nuclear oncoprotein in colorectal adenomas

p53 is a nuclear phosphoprotein which controls normal cell growth. Normal p53 protein is undetectable by standard immunohistochemical staining and the over-expression found in neoplastic cells correlates with the presence of point mutations of evolutionary conserved regions of the p53 gene. We examined the expression of p53 protein in a series of 36 colorectal adenomas (13 tubular, 17 tubulovillous, 6 villous) showing different degrees of dysplasia (11 mild, 19 moderate, 6 severe), 11 moderately differentiated adenocarcinomas (6 Duke's A, 4 Duke's B, 1 Duke's C) and 5 metaplastic polyps using the polyclonal antibody CM1 which recognises p53 protein in conventionally fixed and processed histological material. We found that 15 out of 36 colorectal adenomas showed p53 immunoreactivity, although in 4 positive cases (26%) the staining was very focal (less than 0.1% positive cells). More than 80% of severely dysplastic adenomas showed strong p53 immunoreactivity and this over-expression was correlated with increased cell proliferative rate as detected by the proliferating-cell-nuclear-antigen (PCNA) staining. p53 nuclear staining was also seen in 8 out of 11 (65%) colorectal adenocarcinomas as previously shown. Our data suggest that the p53 gene mutation, with the subsequent over-expression of the protein, occurs in colorectal adenomas and may therefore be a fundamental genetic event underlying the dysplasia and loss of proliferative control that are characteristic of adenomas with malignant potential.

Low expression of beta 1, alpha 2 and alpha 3 subunits of VLA integrins in malignant mammary tumours

The Very Late Antigens (VLAs) are alpha beta heterodimeric transmembrane proteins mediating cell-substratum as well as cell-cell interactions. Changes in their expression and/or function seem to occur in a number of invasive carcinomas and may at least in part explain their abnormal patterns of growth and differentiation. Using monoclonal antibodies to the beta 1 (DH12, A1A-5), alpha 2 (B1.515) and alpha 3 (E1.56) chains, VLA-2 (alpha 2 beta 1) and VLA-3 (alpha 3 beta 1) were studied on cryostat sections of three fibroadenomas and 43 invasive breast carcinomas (29 ductal, 14 lobular) by the avidin-biotin complex immunoperoxidase technique. In non-neoplastic breast tissue and in fibroadenomas VLA-2 and VLA-3 were expressed by myoepithelial cells and on the basolateral surface of the luminal cells. There was weak or absent expression of alpha 2, alpha 3 and the common beta 1 chain in the majority of invasive carcinomas compared to the adjacent normal breast epithelium and preinvasive (in-situ) carcinomas. In addition, the expression of the alpha 2 chain of VLA-2 was reduced significantly (P less than 0.005) in the poorly differentiated ductal breast carcinomas (Grade III) compared to the well (Grade I) and moderately (Grade II) differentiated ductal tumours. These data give further evidence that loss or down-regulation of VLA-2 and VLA-3 occur relatively frequently in invasive cancers, and, at least in the invasive ductal breast carcinomas. Loss of an extracellular matrix receptor controlling growth and differentiation seems to be one of the abnormalities underlying the progression towards an undifferentiated morphology.

Control of differentiation in a rectal adenocarcinoma cell line: the role of diffusable and cell-associated factors

The rectal adenocarcinoma cell line, HRA-19a1.1, was cultured in a three-dimensional type I collagen gel and then xenografted in nu/nu mice to determine whether the in vivo environment could induce further morphological differentiation of the in vitro collagen gel cultures. Three phenotypic changes were observed. Type I collagen induces glandular differentiation in vitro in which well polarized cells are organized around a central lumen, as has been previously reported. Seven days after xenografting this structure in nu/nu mice, the glandular structures appeared to have 'ballooned' forming cyst-like structures lined by a monolayer of flattened cells. There were no stromal cells associated with the graft at this stage, but with time stromal cells invaded the collagen. At points where these cells were closely associated with the HRA-19 cells there was a marked phenotypic change, with the flattened lining cells seen at day 7 becoming columnar. By 21 days the stromal cells had replaced the collagen and the histology of the graft now resembled that of an adenocarcinoma. Placing this cell-collagen culture in a Millipore chamber prior to grafting resulted in cyst-like structures only. Here we provide conclusive evidence that heterologous connective tissue cells can induce differentiation of a rectal adenocarcinoma cell line by a non- or poorly diffusible factor(s). Furthermore, we show that this cell-collagen xenograft method has certain advantages over conventional xenograft methods: notably, a consistent 100 per cent take rate; considerably fewer cells are required to form a tumour; and the time taken to form a tumour is dramatically reduced.

Distribution of beta 1, alpha 1, alpha 2 and alpha 3 integrin chains in basal cell carcinomas

The integrins are alpha beta heterodimeric transmembrane proteins mediating cell-substratum as well as cell-cell interactions. Changes in their expression and/or function seem to occur in a number of malignant epithelial neoplasms and may in part explain their abnormal patterns of growth and differentiation. Using monoclonal antibodies to the beta 1 (DH12), alpha 1 (TS2/7), alpha 2 (B1.515), and alpha 3 (E1.56) integrin chains, the alpha 1 beta 1 (VLA-1), alpha 2 beta 1 (VLA-2), and alpha 3 beta 1 (VLA-3) integrin receptors were studied on cryostat sections of 22 basal cell carcinomas (BCCs) and adjacent normal tissues by a standard peroxidase-antiperoxidase technique. In non-neoplastic skin, VLA-2 and VLA-3 were found in the basal layer, eccrine glands, and cells of the outer root sheath in which VLA-1 was detected. In BCCs, there was a considerably higher expression of VLA-2 and VLA-3 compared with epidermal basal cells but similar to that seen in hair bulb and outer root sheath. In two cases of nodular BCC showing evidence of regression, both VLA-2 and VLA-3 were completely negative, in contrast to non-regressing foci which were strongly positive. The high level of expression of two adhesion molecules (VLA-2 and VLA-3) involved in cell-substratum as well as cell-cell interactions may account for the more indolent pattern of growth characteristic of BCC and perhaps reflect its high degree of differentiation towards the hair follicle.

The role of the arginine-glycine-aspartic acid-directed cellular binding to type I collagen and rat mesenchymal cells in colorectal tumour differentiation

The relationship between the adhesion of five human colorectal carcinoma cell lines to extracellular matrix (ECM) proteins, namely type I collagen, type IV collagen, fibronectin, laminin and basement membrane extract (Matrigel), and the ability of these cells to express morphological differentiation when grown in a basement membrane extract (Matrigel) or on normal rat mesenchymal cells has been examined. Two cell lines, SW1222 and HRA-19, organised into glandular structures, with well-defined polarity when cultured on both substrata as well as in three-dimensional (3D) collagen gel culture as previously shown. The remaining three cell lines (SW620, SW480 and HT29) grew as loose aggregates or as they would normally grow on tissue culture plastic. Addition to the culture medium of a hexapeptide, containing the cell-matrix recognition sequence arginine-glycine-aspartic acid (RGD), inhibited attachment and glandular formation of SW1222 and HRA-19 when these cells were grown on living mesenchymal cells, but not in Matrigel. The morphological differentiation of HRA-19 cells in 3D-collagen was also inhibited by the same RGD-containing peptide, as previously shown for SW1222 cells. Attachment of the remaining three cell lines was inhibited on mesenchyme but not in Matrigel, further supporting the specificity of the peptide effect on epithelial-mesenchymal binding. In conclusion we have shown that colorectal tumour cells are able to bind ECM proteins and that the cellular binding is an essential step in the induction of the morphological differentiation seen on living mesenchymal cells, in basement membrane extracts and in type I collagen gel.(ABSTRACT TRUNCATED AT 250 WORDS)

Carcinoembryonic antigen functions as an accessory adhesion molecule mediating colon epithelial cell-collagen interactions

We have previously shown that a human colon carcinoma cell line (SW1222) expresses a collagen receptor recognizing the Arg-Gly-Asp tripeptide sequence found in collagen. This receptor mediates the cellular attachment to collagen and, subsequently, the glandular differentiation seen in a three-dimensional collagen gel culture. In a search to identify cell surface molecules mediating the adhesion and differentiation of SW1222 cells, we have screened a panel of monoclonal antibodies recognizing epithelial cell surface determinants for their ability to inhibit the collagen binding of SW1222 cells. We have found that four monoclonal antibodies recognizing the 180-kDa carcinoembryonic antigen (CEA) glycoprotein and other members of the CEA family inhibited (up to 87%) the binding of SW1222 cells to type I collagen matrix. Using a cell attachment assay, we have not detected any direct collagen binding of either purified CEA or another CEA-expressing human colon carcinoma cell line (LS174T). These data suggest that CEA is not a collagen-binding protein itself but is likely to be associated with the functional Arg-Gly-Asp collagen receptor expressed by SW1222 cells. We suggest that CEA may function as an accessory molecule, controlling the functional activity of the SW1222 collagen receptor.

Integrin-receptor-mediated differentiation and growth inhibition are enhanced by transforming growth factor-beta in colorectal tumour cells grown in collagen gel

We have studied the role of cell-matrix interactions and the modulating effect on these of transforming growth factor-beta s (TGF-beta s) in controlling differentiation and proliferation in a series of human colorectal carcinoma cell lines. Two (SW1222 and SW480) out of 7 cell lines specifically bound type-I collagen, via integrin-like (SW1222) and non-integrin-like (SW480) collagen receptors. Binding of these receptors may be responsible for regulating the degree of epithelial differentiation of the cells when grown in a 3-dimensional (3D) collagen gel. We have also shown that TGF-beta s enhance the binding of SW1222 cells to collagen and that this is accompanied by greatly increased crypt-like glandular differentiation and inhibition of cell proliferation. Inhibition of cell proliferation was only seen when cells were grown in 3D collagen gel and were thus expressing a fully differentiated phenotype. The enhanced collagen binding induced by TGF-beta s was partially inhibited by an Arg-Gly-Asp (RGD)-containing peptide which is a cell recognition signal for collagen binding. This suggests that TGF-beta s mediate their effects on differentiation of SW1222 cells specifically by modulating the expression of the integrin-like collagen receptor. The other colorectal carcinoma cell lines which lack this integrin-like receptor either failed to bind collagen or, in the case of SW480 binding, exhibited differentiation and proliferation which were not affected by TGF-beta s. This suggests that cell responsiveness to TGF-beta s may depend, at least in part, upon the cell-matrix interaction.

Genetics and biochemistry of collagen binding-triggered glandular differentiation in a human colon carcinoma cell line

We have examined the interaction between collagen binding and epithelial differentiation by using a human colon carcinoma cell line (SW1222) that can differentiate structurally when grown in a three-dimensional collagen gel to form glandular structures. As much as 66% inhibition of glandular differentiation can be achieved by addition to the culture of a synthetic peptide (2 mg/ml) containing the Arg-Gly-Asp-Thr (RGDT) sequence, which is a cell recognition site found in collagen. Arg-Gly-Asp-Thr also inhibited the cell attachment to collagen-coated plates. A control peptide containing the Arg-Gly-Glu-Thr (RGET) sequence had no effect on cell adhesion or cell differentiation. Chromosome 15 was found in all human-mouse hybrid clones [from a cross between SW1222 and a mouse rectal carcinoma cell line (CMT-93)] that could differentiate in the collagen gel and bind collagen. Both binding to collagen and glandular differentiation of the hybrid cells were also inhibited by Arg-Gly-Asp-Thr as for the parent cell line SW1222. The ability of SW1222 cells to express the differentiated phenotype appears, therefore, to be determined by an Arg-Gly-Asp-directed collagen receptor on the cell surface that is controlled by a gene on chromosome 15.

Methods for quantitating HLA gene product expression in the liver during hepatitis B virus infection

HLA antigens play an important role in the immunological responses to transplanted organs and in tumor surveillance and antiviral immunity. In several liver diseases qualitative and quantitative changes in the HLA gene product expression can be found on hepatocytes, bile duct epithelium and sinusoidal lining cells and these changes may affect the efficacy of the immune system in recognizing an exogenous antigen. In this paper we describe methods for quantitating the changes in HLA antigen expression occurring in the liver during various phases of hepatitis B virus infection and the way in which we have attempted to identify possible mechanisms leading to chronicity.

Expression of major histocompatibility complex class II antigens on bile duct epithelium in patients with hepatic graft-versus-host disease after bone marrow transplantation

We studied the expression of major histocompatibility complex (MHC) class II antigens in liver biopsies taken from ten patients with clinical and biochemical evidence of liver damage after bone marrow transplantation. In all six patients who had histologically confirmed graft-versus-host disease, MHC class II antigens were detected on intrahepatic bile ducts. In four patients with no histological features of graft-versus-host disease, MHC class II antigens were not detected. In controls, a positive reaction for bile duct MHC class II antigens was only detected in the patients with primary biliary cirrhosis. Characterisation of the lymphocytes surrounding the bile ducts showed a prevalence of Leu 3+ cells in graft-versus-host disease and primary biliary cirrhosis. We propose that the aberrant expression of class II antigens on bile duct epithelium cells may play a role in the pathogenesis of graft-versus-host disease. A similar pattern in primary biliary cirrhosis may suggest a common pathogenetic mechanism.

Cytotoxic T-cell responses to the nucleocapsid proteins of HBV in chronic hepatitis. Evidence that antibody modulation may cause protracted infection

The nucleocapsid antigens (HBc and HBe) are present on the membranes of HBV-infected hepatocytes from HBV carriers. In autologous cytotoxicity experiments we demonstrate that cytotoxic T cells sensitised to the nucleocapsid proteins of hepatitis B are present in HBe antigen-positive HBV carriers with chronic hepatitis and can be blocked by monoclonal anti-HBc and anti-HBe. Passive immunisation of chimpanzees with monoclonal anti-HBc and anti-HBe offers no protection against HBV infection but in both cases leads to an unusually prolonged hepatitis probably by modulation of HBc and HBe antigen display on the hepatocytes. High-titre anti-HBc in the circulation of HBe antigen-positive patients probably modulates the former protein making HBe the important target antigen for cytotoxic T cells mediating liver damage in chronic carriers. These data also support the hypothesis that passive transfer of IgG anti-HBc across the placenta may be one major factor promoting development of persistent infection in neonates infected from carrier mothers.

Characterisation of the polymerised and monomeric human serum albumin binding sites on hepatitis B surface antigen

Receptors for polymerised human albumin are present on the pre-S sequence of the envelope protein of HBV and on the hepatocyte membrane and are thought to be involved in uptake of the virus by hepatocytes. Using a solid phase radioimmunoassay we demonstrate binding of HBsAg to polymerised human serum albumin (pHSA) in both HBe antigen-positive and -negative patients, and this binding is linearly related to the HBsAg titre in both groups. There are probably several modes of interaction between HBsAg and pHSA. Here we show that pHSA binds to the 22,000-dalton polypeptide of HBsAg, which does not contain the pre-S sequence. This pHSA-HBsAg interaction is inhibited by physiological concentrations of human serum albumin, suggesting that the albumin known to be present in the envelop of HBsAg plays a role in this binding. The inhibition of pHSA/HBsAg interaction by native albumin suggests that this interaction is probably not an important mechanism of virus uptake during infection of hepatocytes.

A review of the efficacy of adenine arabinoside and lymphoblastoid interferon in the Royal Free Hospital studies of hepatitis B virus carrier treatment: identification of factors influencing response rates

We have reviewed the results of treating over 100 HBV carriers with adenine arabinoside, adenine arabinoside monophosphate and lymphoblastoid interferon. In the homosexual group of carriers, adenine arabinoside and its monophosphate have no value. However in this group, lymphoblastoid interferon will produce a response in over 50% of cases. This lack of effectiveness of adenine arabinoside monophosphate in this group may stem from its immunosuppressant properties. In heterosexual carriers both adenine arabinoside monophosphate and lymphoblastoid interferons are effective in approximately 50% to 60% of cases. However, the response rate is different in the various racial groups. Northern European and Mediterranean people appear to respond whereas those from the Far East do not. This may reflect the fact that there are at least two mechanisms by which the chronic carrier state may arise. In 5% to 10% of adults, a relative deficiency of alpha interferon production exists, and this defect is found in the majority of HBV carriers in Western Europe. In these, interferon acts as a replacement therapy and excellent results may be obtained if the patient is treated early in the course of the disease. It would appear that as the duration of the infection increases, the virus may integrate into interferon-reactive consensus sites and prevent the cell from responding to interferon. In patients infected at birth, transplacental anti-HBc appears to modulate the immune response and, along with immaturity of the immune system at this age, results in failure to lyse infected cells. These patients do not benefit from interferon treatment: some form of immune manipulation is required.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship of HLA protein display to activation of 2-5A synthetase in HBe antigen or anti-HBe positive chronic HBV infection

In this study we have examined the density of HLA class I protein display on the hepatocytes of patients with HBe antigen (HBeAg) or anti-HBe (HBeAb) positive chronic hepatitis B virus (HBV) infection and related this to the level of interferon activation of these cells determined by measuring hepatic oligo 2-5A synthetase activity. In HBeAg positive patients the density of HLA class I (HLA-I) protein was not significantly increased above that found in uninfected liver, but levels of 2-5A synthetase were twice normal. In anti-HBe positive patients, HLA-I density was markedly increased in the presence of normal 2-5A synthetase activity. These data are consistent with type I (alpha or beta) interferon activation of the hepatocytes in HBeAg positive patients and type II (gamma) interferon activity in anti-HBe positive subjects.

Virus-neutralizing antibodies to hepatitis B virus: the nature of an immunogenic epitope on the S gene peptide

Using a murine monoclonal antibody (RF-HBs-1) which has been shown to be capable of neutralizing both ad and ay subtypes of hepatitis B virus (HBV), we have devised a competitive inhibition assay to measure the presence of virus-neutralizing antibodies in the sera of patients who have recovered from acute type B hepatitis. The majority of patients have this antibody in their serum. We also show that this antibody inhibits the binding of polymerized human serum albumin (pHSA) to the pHSA receptor site of the HBV particle, which has been proposed as an important site for the entry of HBV into liver cells. We have demonstrated that the epitope recognized by this antibody is dependent on the linkage of 24,000 and 28,000 mol. wt. polypeptides via a disulphide bond. This conformational determinant in the coat of the virus which is part of or near to the pHSA binding site is important in evoking a virus-neutralizing response.

T lymphocyte subsets implicated in cytotoxicity in autologous hepatocytes in chronic active hepatitis patients with active viral replication

We investigated inhibitory effect of various monoclonal antibodies on T-cell-mediated cytotoxicity against autologous hepatocytes in 24 patients with hepatitis B surface antigen/hepatitis B e antigen (HBsAg/HBeAg)-positive chronic active hepatitis. A significant reduction of cytotoxicity index occurred after preincubation of T lymphocytes with anti-Leu 7 (killer-natural killer cells), D1/12 (Ia-positive cells), 5/9 (restricted helper/inducer cells), and MLR4 ("activated" and radiosensitive helper cells) monoclonal antibodies (MAb). Anti-Leu 2a (cytotoxic/suppressor cells) and anti-Leu 3a (helper/inducer cells) MAb did not affect cytotoxic activity. This finding supports the hypothesis that the T cytotoxic reaction in this in vitro system is probably due to two mechanisms: first, spontaneous cell membrane cytotoxicity sustained by anti-Leu-7-positive lymphocytes; and second, specific cytotoxicity mediated by activated Ia-positive cells. We also found that the presence of helper/inducer cells (5/9 positive) appears to be a prerequisite for the cytotoxic reaction.

HLA class I antigens on the hepatocyte membrane during recovery from acute hepatitis B virus infection and during interferon therapy in chronic hepatitis B virus infection

In a chimpanzee model of acute type B hepatitis, at the time of onset of hepatitis B virus replication and before the development of immunity to hepatitis B virus, interferon is present in the plasma. This is followed by an increase in the display of HLA class I, but not class II proteins, on the hepatocyte membrane. In chronic hepatitis B virus infection, there is a low density of HLA class I protein display on the infected hepatocyte. Administration of alpha-interferon enhances HLA display and in many cases is followed by a transaminase elevation, seroconversion of HBe antigen to antibody and disappearance of hepatitis B virus DNA from serum, changes implying clearance of infected hepatocytes. Successful response to interferon therapy may be predicted by a rapidly rising serum beta 2-microglobulin, a component of the HLA class I molecule, during the first 2 weeks of therapy, before the rise in transaminases.

Homology between HBV-DNA and a sequence regulating the interferon-induced antiviral system: possible mechanism of persistent infection

Treatment of hepatitis B virus (HBV)-infected hepatocytes with lymphoblastoid alpha-interferon (IFN) leads to an increased expression of the core antigen (HBcAg) and reduced expression of surface antigen (HBsAg). We have identified the presence of a nucleotide sequence at the start of the HBc gene in the hepatitis B virus genome similar to a consensus sequence known to occur upstream from genes induced by IFN in mammalian cells. It is possible that interferon influences the expression of the viral genes because of the presence of this homologous sequence. This sequence in the viral genome may determine the site of integration of the virus and could influence the ability of the cell containing the integrated viral sequence to respond to interferon. This "neutralisation" of the interferon system by viral integration might not only facilitate persistent infection but might also adversely affect response to alpha-interferon therapy.

Hepatitis A virus replication in tamarins and host immune response in relation to pathogenesis of liver cell damage

Hepatitis A virus (HAV) shedding in the faeces, appearance of HAV-Ag (antigen) in the liver, and development of humoral immunity to HAV have been studied in experimentally infected tamarins. The appearance of liver damage measured by transaminase elevation and histology, in relation to the above variables, suggests that the virus is not cytopathic and the immune system contributes to the production of liver cell damage. Preliminary data suggest that HAV replication may occur in the mucosa of the small intestine and in the liver.

Identification of factors influencing response rate to antiviral therapy of chronic hepatitis B virus infection. A review of the efficacy of adenine arabinoside and lymphoblastoid interferon in the Royal Free Hospital studies

We have reviewed the results of treating over 100 HBV carriers with adenine arabinoside, adenine arabinoside monophosphate and lymphoblastoid interferon. In the homosexual group of carriers, adenine arabinoside and its monophosphate have no value. However, in this group, lymphoblastoid interferon will produce a response in over 50% of cases. The lack of effectiveness of adenine arabinoside monophosphate in this group may stem from its immunosuppressant properties. In heterosexual carriers both adenine arabinoside monophosphate and lymphoblastoid interferon are effective in approximately 50-60% of cases. However, the response rate is different in the various racial groups. Northern European and Mediterranean people appear to respond whereas those from the Far East do not. This may reflect the fact that there are at least 2 mechanisms by which the chronic carrier state may arise. In 5-10% of adults, a relative deficiency of alpha-interferon production exists and this defect is found in the majority of HBV carriers in Western Europe. In these, interferon acts as a replacement therapy and excellent results may be obtained if the patient is treated early in the course of the disease. It would appear that as the duration of the infection increases, the virus may integrate into interferon-reactive consensus sites and prevent the cell from responding to interferon. In patients infected at birth, transplacental anti-HBc appears to modulate the immune response and along with immaturity of the immune system at this age, results in failure to lyse infected cells. These patients do not benefit from interferon treatment: some form of immune manipulation is required.(ABSTRACT TRUNCATED AT 250 WORDS)

Human lymphoblastoid interferon. In vitro and in vivo studies in hepatocellular carcinoma

We have examined the growth inhibitory effects of human lymphoblastoid interferon (IFN) on the human hepatocellular carcinoma (HCC) cell line PLC/PRF/5. In vitro, PLC/PRF/5 cells were sensitive to the antiproliferative effects of IFN, growth inhibition being noted at concentrations as low as 1.25 i.u. ml-1. Athymic mice with xenografted tumours derived from the PLC/PRF/5 cell line were treated daily with IFN or a saline control. An IFN dose of 2 X 10(5) i.u./day was found capable of significantly slowing tumour growth rate and prolonging mouse survival. Further studies to examine the mechanisms involved in growth inhibition in vivo demonstrated that IFN was capable of inducing the activity of the enzyme 2,5-oligoadenylic acid (2,5 A) synthetase, a potent inhibitor of protein synthesis, in tumour xenografts but not in mouse tissue, and that IFN significantly enhanced the membrane display of HLA class I glycoproteins on tumour cells, though histology did not reveal any increase in tumour infiltration by host lymphocytes. We conclude that IFN exerts potent growth inhibitory effects on the HCC cell line PLC/PRF/5 both in vitro and in vivo and its mode of action in this animal model system appears to be predominantly mediated by a direct antiproliferative effect on tumour cells.

Viruses and immune reactions in the liver

The immunopathology of hepatitis B and delta virus infections of the liver are reviewed. It is clear there are several antigen/antibody systems of importance in acute and chronic HBV infection. Antibodies to HBs, HB core/HBe and antibodies to Dane specific determinants are involved in virus neutralisation. Elimination of virus infected hepatocytes is dependent on recognition of viral determinants in association with HLA proteins on the infected hepatocytes by cytotoxic T cells. The HLA protein display is modulated by exposure to interferon and may regulate the cytotoxic T cell and NK lytic processes. During chronic HBV infection there is evidence of failure of interferon activation of the infected liver cells so that viral protein synthesis is not decreased and there is no enhancement of HLA protein display. These complex interactions between the virus and the immune system determine the heterogeneity of the clinical syndromes seen in patients infected with this agent. The delta virus replicates only in patients with co-existent HBV infection. The agent is cytopathic and therefore always produces liver disease. When there is delta virus superinfection in a carrier of chronic HBV, there is an acceleration of the rate of progression of the liver disease. The presence of delta infection results in IgM and IgG anti-delta responses.