Cell surface antigens of human bladder cancer defined by mouse monoclonal antibodies

The 2EF Antibody Targets a Unique N-Terminal Epitope of Trop-2 and Enhances the In Vivo Activity of the Cancer-Selective 2G10 Antibody

Trop-2 proteolytic processing in cancer cells exposes epitopes that were specifically targeted by the 2G10 antibody. We sought additional recognition of Trop-2 within difficult-to-reach, densely packed tumor sites. Trop-2 deletion mutants were employed in immunization and screening procedures, and these led to the recognition of a novel epitope in the N-terminal region of Trop-2, by the 2EF antibody. The 2EF mAb was shown to bind Trop-2 at cell-cell junctions in MCF-7 breast cancer cells, and in deeply seated sites in prostate cancer, that were inaccessible to benchmark anti-Trop-2 antibodies. The 2EF antibody was shown to inhibit the growth of HT29 colon tumor cells in vitro, with the highest activity at high cell density. In vivo, 2EF showed anticancer activity against SKOv3 ovarian, Colo205, HT29, HCT116 colon and DU-145 prostate tumors, with the highest impact on densely packed tumor sites, whereby 2EF outcompeted benchmark anti-Trop-2 antibodies. Given the different recognition modes of Trop-2 by 2EF and 2G10, we hypothesized the effective interaction of the two mAb in vivo. The 2EF mAb was indeed demonstrated to enhance the activity of 2G10 against tumor xenotransplants, opening novel avenues for Trop-2-targeted therapy. We humanized 2EF by state-of-the-art CDR grafting/re-modeling, yielding the Hu2EF for therapy of Trop-2-expressing tumors in patients.

Integrin α3β1 Is a Key Regulator of Several Protumorigenic Pathways during Skin Carcinogenesis

Integrin α3β1 plays a crucial role in tumor formation in the two-stage chemical carcinogenesis model (DMBA and TPA treatment). However, the mechanisms whereby the expression of α3β1 influences key oncogenic drivers of this established model are not known yet. Using an in vivo mouse model with epidermal deletion of α3β1 and in vitro Matrigel cultures of transformed keratinocytes, we demonstrate the central role of α3β1 in promoting the activation of several protumorigenic signaling pathways during the initiation of DMBA/TPA‒driven tumorigenesis. In transformed keratinocytes, α3β1-mediated focal adhesion kinase/Src activation leads to in vitro growth of spheroids and to strong Akt and STAT 3 activation when the α3β1-binding partner tetraspanin CD151 is present to stabilize cell‒cell adhesion and promote Smad2 phosphorylation. Remarkably, α3β1 and CD151 can support Akt and STAT 3 activity independently of α3β1 ligation by laminin-332 and as such control the essential survival signals required for suprabasal keratin-10 expression during keratinocyte differentiation. These data demonstrate that α3β1 together with CD151 regulate the signaling pathways that control the survival of differentiating keratinocytes and provide a mechanistic understanding of the essential role of α3β1 in early stages of skin cancer development.

Absence of integrin α3β1 promotes the progression of HER2-driven breast cancer in vivo

BACKGROUND

HER2-driven breast cancer is correlated with poor prognosis, especially during its later stages. Numerous studies have shown the importance of the integrin α3β1 during the initiation and progression of breast cancer; however, its role in this disease is complex and often opposite during different stages and in different types of tumors. In this study, we aim to elucidate the role of integrin α3β1 in a genetically engineered mouse model of HER2-driven mammary tumorigenesis.

METHODS

To investigate the role of α3β1 in HER2-driven tumorigenesis in vivo, we generated a HER2-driven MMTV-cNeu mouse model of mammary tumorigenesis with targeted deletion of Itga3 (Itga3 KO mice). We have further used several established triple-negative and HER2-overexpressing human mammary carcinoma cell lines and generated ITGA3-knockout cells to investigate the role of α3β1 in vitro. Invasion of cells was assessed using Matrigel- and Matrigel/collagen I-coated Transwell assays under static or interstitial fluid flow conditions. The role of α3β1 in initial adhesion to laminin and collagen was assessed using adhesion assays and immunofluorescence.

RESULTS

Tumor onset in mice was independent of the presence of α3β1. In contrast, the depletion of α3β1 reduced the survival of mice and increased tumor growth and vascularization. Furthermore, Itga3 KO mice were significantly more likely to develop lung metastases and had an increased metastatic burden compared to WT mice. In vitro, the deletion of ITGA3 caused a significant increase in the cellular invasion of HER2-overexpressing SKBR3, AU565, and BT474 cells, but not of triple-negative MDA-MB-231. This invasion suppressing function of α3β1 in HER2-driven cells depended on the composition of the extracellular matrix and the interstitial fluid flow.

CONCLUSION

Downregulation of α3β1 in a HER2-driven mouse model and in HER2-overexpressing human mammary carcinoma cells promotes progression and invasiveness of tumors. The invasion-suppressive role of α3β1 was not observed in triple-negative mammary carcinoma cells, illustrating the tumor type-specific and complex function of α3β1 in breast cancer.

Laminin production and basement membrane deposition by mesenchymal stem cells upon adipogenic differentiation

The aim was to study laminin (LM) synthesis, integration, and deposition into the basement membrane (BM) during adipogenesis. Human bone marrow-derived mesenchymal stromal cells (MSCs) were induced along the adipogenic lineage. LM chain mRNA and protein levels were followed using quantitative real-time polymerase chain reaction (qRT-PCR), immunofluorescence (IF) staining, transmission electron microscopy (TEM), and immunoprecipitation. MSCs produced low levels of LM mRNAs but were not surrounded by BM in IF and TEM imaging. LM-α4, LM-β1, and LM-γ1 mRNAs increased during adipogenesis 3.9-, 5.8-, and 2.8-fold by day 28. LM-411 was immunoprecipitated from the ECM of the differentiated cells. Immunostaining suggested deposition of LM-411 and some LM-421. BM build-up was probably organized in part by integrin (Int) α6β1. At day 28, TEM images revealed BM-like structures around fat droplet-containing cells. The first signs of BM formation and Int α6β1 were seen using IF imaging at day 14. Laminin-411 and Int α6β1 were expressed in vivo in mature human subcutaneous fat tissue. Undifferentiated human MSCs did not organize LM subunits into BM, whereas LM-411 and some LM-421 are precipitated in the BM around adipocytes. This is the first demonstration of LM-411 precipitation during hMSC adipogenesis around adipocytes as a structural scaffold and Int-regulated signaling element.

Expression of Trop2 cell surface glycoprotein in normal and tumor tissues: potential implications as a cancer therapeutic target

Trop2 is a cell-surface glycoprotein reported to be overexpressed in various types of adenocarcinomas with minimal expression in normal tissues. Recent findings that Trop2 expression correlates with tumor aggressiveness have increased interest in Trop2 as a potential target for cancer immunotherapy. The goal of this study was to extensively evaluate Trop2 expression at the transcript and protein levels in normal and tumor tissues. It was determined that Trop2 is overexpressed on some carcinomas relative to the corresponding normal tissue. However, in human and mouse, Trop2 is highly expressed at both the transcript and protein levels on several essential normal tissues. The findings suggest that the development of therapeutic agents to target Trop2 may require strategies that target Trop2 on malignant tissues in order to minimize potential toxicities to essential normal tissues that also express high levels of Trop2.

Tumor-associated calcium signal transducer 2 is required for the proper subcellular localization of claudin 1 and 7: implications in the pathogenesis of gelatinous drop-like corneal dystrophy

Gelatinous drop-like dystrophy (GDLD) is a rare autosomal recessive form of corneal dystrophy characterized by subepithelial amyloid depositions on the cornea. Previous clinical and laboratory observations have strongly suggested that epithelial barrier function is significantly decreased in GDLD. Despite the decade-old identification of the tumor-associated calcium signal transducer 2 (TACSTD2) gene as a causative gene for GDLD, the mechanism by which the loss of function of this causative gene leads to the pathological consequence of this disease remains unknown. In this study, we investigated the functional relationship between the TACSTD2 gene and epithelial barrier function. Through the use of immunoprecipitation and a proximity ligation assay, we obtained evidence that the TACSTD2 protein directly binds to claudin 1 and 7 proteins. In addition, the loss of function of the TACSTD2 gene leads to decreased expression and change in the subcellular localization of tight junction-related proteins, including claudin 1, 4, 7, and ZO1 and occludin, both in diseased cornea and cultured corneal epithelial cells. These results indicate that loss of function of the TACSTD2 gene impairs epithelial barrier function through decreased expression and altered subcellular localization of tight junction-related proteins in GDLD corneas.

Elevated expressions of MMP7, TROP2, and survivin are associated with survival, disease recurrence, and liver metastasis of colon cancer

PURPOSE

Colorectal cancer is one of the most common cancers worldwide. We tested the hypothesis that differences in the expression of certain molecular markers of colon cancer may account for different clinical outcomes.

METHODS

Tissue microarray technology was used to assay the expression of 17 biological markers [beta-catenin, CD44v7, c-myc, cyclin D1, estrogen receptor beta, mitogen-activated protein kinase/extracellular signal-regulated kinase, maspin, matrix metalloproteinase-7 (MMP7), p53, Pin1, peroxisome proliferators-activated receptor-gamma, survivin, T cell transcription factor 4 (TCF4), transforming growth factor beta receptor II (TGFbetaR II), TGFbeta, TROP2, and Wnt] by immunohistochemistry in 620 colon cancer patients. The Cox proportional hazards regression model was applied to analyze the lifetime data, including time to death, time to recurrence, and time to liver metastasis.

RESULTS

All the markers were present at significantly higher expression levels in tumor specimens than in normal colonic specimens. Kaplan-Meier analysis showed that high expression of TROP2, MMP7, and survivin were related to decreased survival; TCF4 and TROP2 were related to disease recurrence; and CD44v7, cyclin D1, MMP7, p53, survivin, and TCF4 were related to liver metastasis. However, the results of the multivariate analysis only showed that expression of MMP7, survivin, and TROP2 were significant predictors of lower patient survival, while TROP2 and MMP7 were significantly related to disease recurrence and liver metastasis, respectively.

CONCLUSIONS

We conclude that elevated survivin, MMP7, and TROP2 expression levels are related to decreased survival. In addition, elevated MMP7 and TROP2 expression levels are predictors of disease recurrence and liver metastasis, respectively.

Podosome-like structures of non-invasive carcinoma cells are replaced in epithelial-mesenchymal transition by actin comet-embedded invadopodia

Podosomes and invadopodia are actin-based structures at the ventral cell membrane, which have a role in cell adhesion, migration and invasion. Little is known about the differences and dynamics underlying these structures. We studied podosome-like structures of oral squamous carcinoma cells and invadopodia of their invasive variant that has undergone a spontaneous epithelial-mesenchymal transition (EMT). In 3D imaging, podosomes were relatively large structures that enlarged in time, whereas invadopodia of invasive cells remained small, but were more numerous, degraded more extracellular matrix (ECM) and were morphologically strikingly different from podosomes. In live-cell imaging, highly dynamic, invadopodia-embedded actin tails were frequently released and rocketed through the cytoplasm. Resembling invadopodia, we found new club-ended cell extensions in EMT-experienced cells, which contained actin, cortactin, vinculin and MT1-matrix metalloproteinase. These dynamic cell extensions degraded ECM and, in field emission scanning electron microscopy, protruded from the dorsal cell membrane. Plectin, αII-spectrin, talin and focal adhesion kinase immunoreactivities were detected in podosome rings, whereas they were absent from invadopodia. Tensin potentially replaced talin in invadopodia. Integrin α₃β₁ surrounded both podosomes and invadopodia, whereas integrin α_vβ₅ localized only to invadopodia heads. Pacsin 2, in conjunction with filamin A, was detected early in podosomes, whereas pacsin 2 was not found in invadopodia and filamin A showed delayed accumulation. Fluorescence recovery after photobleaching indicated faster reorganization of actin, cortactin and filamin A in podosomes compared to invadopodia. In conclusion, EMT affects the invasion machinery of oral squamous carcinoma cells. Non-invasive squamous carcinoma cells constitutively organize podosomes, whereas invasive cells form invadopodia. The club-ended cell extensions, or externalized invadopodia, are involved in ECM degradation and maintenance of contact to adhesion substrate and surrounding cells during invasion.

Laminin isoforms in human embryonic stem cells: synthesis, receptor usage and growth support

To reveal the functional intrinsic niche of human embryonic stem cells (hESC) we examined the production of basement membrane (BM) proteins and the presence of their receptors in feeder-free cell culture conditions. In addition, we investigated binding of hESCs to purified human BM proteins and identified the receptors mediating these contacts. Also, we tested whether purified human laminin (Lm) isoforms have a role in hESC self-renewal and growth in short-term cultures. The results show that hESCs synthesize Lm alpha(1) and Lm alpha(5) chains together with Lm beta(1) and gamma(1) chains suggesting the production of Lms-111 and -511 into the culture medium and deposits on cells. hESCs contain functionally important integrin (Int) subunits, Int beta(1), alpha(3), alpha(6), alpha(5), beta(5) and alpha(V), as well as the Lm alpha(5) receptor, Lutheran (Lu) glycoprotein and its truncated form, basal cell adhesion molecule (B-CAM). In cell adhesion experiments, Int beta(1) was crucial for adhesion to most of the purified human BM proteins. Lu/B-CAM mediated adhesion to Lm-511 together with Int alpha(3)beta(1), and was essential for the adhesion of hESCs to embryonic feeder cells. Adhesion to Lm-411 was mediated by Int alpha(6)beta(1). Lm-511 supported hESC growth in defined medium equally well as Matrigel. These results provide consequential information of the biological role of BM in hESCs, warranting further investigation of BM biology of human pluripotent stem cells.

High expression of TROP2 correlates with poor prognosis in pancreatic cancer

Pancreatic cancer is one of the most devastating human malignancies. Despite considerable research efforts, it remains resistant to almost all available treatment regimens. The human trophoblast cell-surface antigen, TROP2, was found to be strongly expressed in a variety of human epithelial cancers, correlating with aggressiveness and poor prognosis. TROP2 antigen expression was investigated retrospectively by immunohistochemistry in paraffin-embedded primary tumour tissue samples from a series (n=197) of consecutive patients with pancreatic adenocarcinoma. Survival was calculated using Kaplan–Meier curves. Parameters found to be of prognostic significance in univariate analysis were verified in a multivariate Cox regression model. TROP2 overexpression was observed in 109 (55%) of 197 pancreatic cancer patients and was significantly associated with decreased overall survival (P<0.01). By univariate analysis, TROP2 overexpression was found to correlate with the presence of lymph node metastasis (P=0.04) and tumour grade (P=0.01). Furthermore, in the subgroup of patients treated surgically with curative intent, TROP2 overexpression significantly correlated with poor progression-free survival (P<0.01). Multivariate analyses revealed TROP2 to be an independent prognosticator. These findings suggest for the first time that TROP2 could be a novel prognostic biomarker for pancreatic cancer. Targeting TROP2 might be a useful treatment approach for patients with pancreatic cancer overexpressing this cell-surface marker.

Lutheran blood group antigen as a receptor for alpha5 laminins in gingival epithelia

BACKGROUND

Lutheran blood group glycoprotein (Lu) is a transmembrane receptor of the immunoglobulin superfamily. Lu serves as a receptor for alpha5 laminins (Lm). The Lm alpha5 chain is a constituent of Lms-511 and -521. Lm-511 is found in most human basement membranes (BMs) and also is detected in BM of gingival epithelia. Recent studies indicated that Lu mediates cell adhesion to Lms-511/521 independently or in concert with integrins. This study focused on the expression of Lu in gingival epithelia and on cultured immortalized gingival keratinocytes. The role of Lu and alpha(3) and beta(1) integrin subunits in the adhesion of oral epithelial cells to Lms-511/521 was also studied.

METHODS

Immunofluorescence microscopy was used to study the expression of Lu in gingival tissues and in cultured gingival keratinocytes. Immunoprecipitation of radioactively metabolically labeled cells was used to detect Lu. Cell adhesion to Lm-511/521 preparation and to pure Lm-511 was studied in quantitative cell adhesion experiments. Morphological adhesion assays were carried out for visualization of the morphology and adhesion structure formation of the adhering cells.

RESULTS

Immunofluorescence studies on gingiva showed complete coalignment of Lu on basal epithelial cells with the BM Lm alpha5 chain. A surface-confined, punctate immunoreaction for Lu was detected throughout cell surfaces on cultured gingival cells. Immunoprecipitation showed a broad polypeptide with molecular weight 85,000. In quantitative cell adhesion assays, the adhesion of cells to both Lm alpha5 preparations was diminished with monoclonal antibodies (MAbs) against integrin alpha(3) and even more effectively with MAbs against the beta(1) subunit. When the adhesion sites were blocked with soluble recombinant Lu (sol-Lu), the adhesion of gingival epithelial cells to Lms-511/521 was reduced significantly, and sol-Lu increased the inhibition with integrin alpha(3) antibody. Lm-511 did not induce lamellipodia or focal contacts in cultured gingival keratinocytes.

CONCLUSIONS

Lu was in coalignment with Lm alpha5 chain in gingival epithelia. Lu also seemed to have a role in gingival epithelial cell adhesion together with integrin alpha(3)beta(1).

Clinical significance of TROP2 expression in colorectal cancer

PURPOSE AND EXPERIMENTAL DESIGN

To identify cancer-related genes, the expression profiles of colorectal cancer cells and normal epithelial cells were examined and compared using laser microdissection and cDNA microarray analysis. From these combined techniques, several cancer-related genes, including TROP2, were identified. TROP2 is known as a calcium signal transducer and is highly expressed in several types of tumors. However, no studies have investigated the significance of TROP2 expression in colorectal cancer. Thus, the expression status of TROP2 was investigated in 74 colorectal cancer samples by quantitative real-time reverse transcription-PCR and immunohistochemical studies.

RESULTS

Laser microdissection and cDNA microarray analysis showed that there were 84 overexpressed genes in cancer cells. One of the highly overexpressed genes was TROP2. Quantitative real-time reverse transcription-PCR showed that TROP2 expression in cancer samples was significantly higher than in normal samples (P < 0.001). The samples were divided into high (n = 26) and low (n = 48) TROP2 expression groups. The cases with high TROP2 expression showed a higher frequency of liver metastasis (P = 0.005) and more cancer-related death (P = 0.046). Those cases also had an inclination of deeper depth of invasion (P = 0.064) and more lymph node metastasis (P = 0.125). Interestingly, the patients with high TROP2 expression tumors had poorer prognosis (P = 0.0036). Multivariate analysis showed that TROP2 expression status was an independent prognostic factor (relative risk, 2.38; 95% confidence interval, 1.29-4.74; P < 0.01).

CONCLUSION

TROP2 is one of the cancer-related genes that correlates with biological aggressiveness and poor prognosis of colorectal cancer. Thus, TROP2 is a possible candidate gene for diagnosis and molecular target therapy of colorectal cancer.

Establishment of an immortalized cell line from a precancerous lesion of lung adenocarcinoma, and genes highly expressed in the early stages of lung adenocarcinoma development

Atypical adenomatous hyperplasia (AAH) is classified as a precancerous lesion of lung adenocarcinoma. We established an immortalized AAH cell line (PL16T) and a human non-neoplastic bronchial epithelial cell line (PL16B) from the same patient by transfection with the gene for SV40 large T antigen. The expression profile of PL16T was compared with that of PL16B by the suppression subtractive hybridization method. From 704 selectively hybridized clones, we finally selected 25 fragments of mRNA that showed transcription levels more than three times higher in PL16T than in PL16B. Thirteen (52%) and eight (32%) of them encoded tumor-associated calcium signal transducer 2 (TACSTD2) and S100 calcium binding protein A2 (S100A2), respectively. The high transcription of TACSTD2 and S100A2 in PL16T was confirmed by in situ hybridization. In normal lung tissue, both TACSTD2 and S100A2 were expressed at very low levels, but seven and five of 14 AAH were positive for TACSTD2 and S100A2, respectively. The frequency of TACSTD2 positivity was increased in 16 of 22 bronchioloalveolar carcinomas (BAC) and adenocarcinoma with mixed subtype with BAC component (mixed BAC). Positivity for S100A2 occurred in four of 22 BAC and mixed BAC. The abnormal transcription of TACSTD2 and S100A2 are thought to be unique molecular markers of the preinvasive stage of lung adenocarcinoma.

Localization of laminin alpha4-chain in developing and adult human tissues

Recent studies suggest important functions for laminin-8 (Ln-8; alpha4beta1gamma1) in vascular and blood cell biology, but its distribution in human tissues has remained elusive. We have raised a monoclonal antibody (MAb) FC10, and by enzyme-linked immunoassay (EIA) and Western blotting techniques we show that it recognizes the human Ln alpha4-chain. Immunoreactivity for the Ln alpha4-chain was localized in tissues of mesodermal origin, such as basement membranes (BMs) of endothelia, adipocytes, and skeletal, smooth, and cardiac muscle cells. In addition, the Ln alpha4-chain was found in regions of some epithelial BMs, including epidermis, salivary glands, pancreas, esophageal and gastric glands, intestinal crypts, and some renal medullary tubules. Developmental differences in the distribution of Ln alpha4-chain were detected in skeletal muscle, walls of vessels, and intestinal crypts. Ln alpha4- and Ln alpha2-chains co-localized in BMs of fetal skeletal muscle cells and in some epithelial BMs, e.g., in gastric glands and acini of pancreas. Cultured human pulmonary artery endothelial (HPAE) cells produced Ln alpha4-chain as M(r) 180,000 and 200,000 doublet and rapidly deposited it to the growth substratum. In cell-free extracellular matrices of human kidney and lung, Ln alpha4-chain was found as M(r) 180,000 protein.

Function of laminins and laminin-binding integrins in gingival epithelial cell adhesion

BACKGROUND

In human gingiva, epithelial cells attach to their adjacent tissues by means of specialized molecular adhesion complexes and a basement membrane. Little is known about the synthesis of adhesion proteins by gingival keratinocytes; we, therefore, studied how cultured immortalized gingival epithelial cells produce laminins and express laminin-binding integrins. We presumed that different laminins and integrins would be involved in the adhesion of gingival epithelial cells.

METHODS

We cultured gingival keratinocytes and studied their production of laminins and expression of integrins using immunofluorescence microscopy, immunoprecipitation, and immunoblotting methods and by quantitative cell adhesion experiments. We also studied how gingival tissue expresses these adhesion proteins in vivo by using immunofluorescence microscopy.

RESULTS

In immunofluorescence microscopy, the cells were seen to organize chains of laminin-5 (alpha3beta03gamma2) to extracellular patches, whereas the alpha5 chain of laminin-10 (alpha5betalgamma1) could only be seen intracellularly. Of the laminin-binding integrin subunits, integrin a6 subunit was organized to dotted arrays, typical of prehemidesmosomal adhesions, whereas integrin alpha3 subunit was located at cell-cell junctions, in prehemidesmosomal structures, and at some locations also in small focal-contact like patches. Integrin beta1 subunit was found at cell-cell junctions and in focal contacts. Immunoprecipitation experiments showed that the cells synthesize and secrete chains of laminin-5 and laminin-10. In quantitative cell adhesion experiments, the cells adhered efficiently to these laminins by using cooperatively integrin alpha3beta1 and alpha6beta1 integrin complexes. None of the other known laminin-binding integrin subunits appeared to be significantly involved in cell adhesion to these laminin isoforms.

CONCLUSIONS

Our results provide new information on gingival epithelial cell adhesion and extracellular matrix production and may thus aid in the understanding of periodontal physiology.

The BTA stat test is nonspecific for hematuria: an experimental hematuria model

PURPOSE

An experimental hematuria model was designed to determine whether the bladder tumor antigen (BTA) stat test (Bion Diagnostics, Redmond, Washington) is influenced by microscopic or macroscopic hematuria.

MATERIALS AND METHODS

A total of 25 healthy subjects provided urine and blood samples for the study. All subjects had a negative BTA stat test initially. Normal urine was mixed with autologous blood to cause hematuria of 3 degrees of severity. The test was performed in each sample after the creation of hematuria.

RESULTS

BTA stat assay specificity in the presence of microscopic and gross hematuria was 80% and 24%, respectively. Results varied depending on the severity of hematuria, that is 20% for microscopic and 76% for gross hematuria.

CONCLUSIONS

The results of the BTA stat test in the presence of microscopic hematuria must be interpreted in regard to the degree of hematuria. The test is not reliable in urine samples with gross hematuria due to a high false-positive rate.

Analysis of integrin expression in U2OS cells cultured on various calcium phosphate ceramic substrates

Earlier we observed that calcium phosphate (Ca-P)-coated implant substrates stimulated the differentiation of osteoblast-like cells compared to uncoated substrates. This suggests that this difference in osteogenic induction is due to the chemical composition of the substratum. We hypothesized that Ca-P coatings modulate integrin expression patterns, because those receptors are the sensors of the cell. Therefore, in the present study we quantitatively analyzed integrin expression of osteosarcoma cells and their proliferation behavior on various well-defined Ca-P substrates. For this study we used the osteosarcoma cell line U2OS. Five groups of substrates were used: thermanox (Th), uncoated titanium (Ti), dense sintered hydroxyapatite (HA), and two Ca-P-coated titanium discs (TiHA-O% and TiHA-5%). At day 5, cell numbers were significantly lower (p < 0.05) for both types of Ca-P-coated titanium substrates compared to the other substrates. There were no significant differences between HA and uncoated titanium. From day 5 to 8, accumulated cell number was ranking highest to lowest HA > Th = Ti > TiHA-0% > TiHA-5%. Integrin expression at day 5 and day 8 of incubation was analyzed by flow cytometry for integrin subunits beta 1, alpha 3, alpha 4, alpha 5, alpha 6, and alpha v. Fluorescence-activated cell sorting (FACS) analysis showed that the cells express high levels of beta 1, low levels of alpha 4, alpha 5, and alpha 6, and moderate levels of alpha 3 and alpha v integrin subunits on the various biomaterial substrates. Minor differences in integrin expression between the various substrates were seen. Therefore, the observed differences in proliferation between the coatings may reside in modulating the functional properties of integrins.

Laminin synthesis and the adhesion characteristics of immortalized human corneal epithelial cells to laminin isoforms

We have studied the synthesis of laminins (Ln) and determined the specific integrins mediating the adhesion of immortalized human corneal epithelial cells to mouse Ln-1, and human Lns-5 and -10. Immunofluorescence microscopy of the cells demonstrated integrin alpha(2), alpha(3), alpha(6), beta(1)and beta(4)subunits, integrins alpha(6)and beta(4)being found in a typical 'leopard-skin' like manner. Immunoprecipitation studies showed that the cells produced alpha 3, beta 3 and gamma 2 chains of Ln-5, but not Lns-1 or -10. In culture Ln-5 was found as small plaques beneath the adhering cells within 1 hr, while in 4 hr widely spread Ln-5 plaques were observed in colocalization with beta(4)integrin subunit. By using a quantitative cell adhesion assay and function-blocking monoclonal antibodies we showed that integrin beta(1)subunit plays a role in mediating corneal epithelial cell adhesion to mouse Ln-1. However, none of the available function-blocking antibodies to integrin alpha-subunits inhibited the adhesion. Integrin alpha(3)beta(1)complex mediated the adhesion of corneal epithelial cells to human Lns-5 and -10. Integrin complex alpha(3)beta(1), as well as laminin alpha(3)chain, was also shown to mediate cell adhesion to newly produced endogenous Ln-5. The present results show that integrin alpha(3)beta(1)complex mediates the adhesion of corneal epithelial cells to Lns-5 and -10, while a yet unknown integrin alpha subunit appears to play a role in the adhesion to Ln-1. The results also show that among corneal basement membrane laminins, Ln-5 is synthetized by epithelial cells while Ln-10 may be a product of keratocytes.

Ras-transfection up-regulated HaCaT cell migration: inhibition by Marimastat

Cell migration is an essential process in physiological and pathological conditions such as wound healing and tumor invasion. This phenomenon involves cell adhesion on the extracellular matrix mediated by integrins, and cell detachment promoted in part by metalloproteinases (MMPs). In the present study, the migration of two HaCaT-ras clones (metastatic or not), was compared with HaCaT cells, and normal human primary cultured keratinocytes. Using colloidal gold migration assay, the migration index on type I and type IV collagen was similar for primary cultured keratinocytes and HaCaT, whereas it was markedly higher for the HaCaT-ras clones. High motility of ras-transfected cells was confirmed from an in vitro wound healing assay. It was not correlated with changes in integrin expression or related to a different adhesion on extracellular matrix. The Marismastat (BB-2516), a MMP inhibitor, inhibited in a dose-dependent effect the migration in both assays, demonstrating the important role of MMPs in the migration process. Under our experimental conditions, MMP-1 activity was not detected in HaCaT and MMP-9 activity was secreted by these cells only after their stimulation by EGF. Here, MMP-2 was the major gelatinolytic activity secreted by all the cells and its secretion was markedly higher for HaCaT-nis clones compared with HaCaT. In addition, Western blotting results confirmed a higher expression of MMP-2 associated with a lower expression of TIMP-2 in HaCaT-ras compared with HaCaT. These results suggest that Ha-ras oncogene could be a stimulating factor of migration and might modified the balance between MMP-2 and TIMP-2 in keratinocyte cell lines.

Basement membrane laminin-5 is deposited in colorectal adenomas and carcinomas and serves as a ligand for alpha3beta1 integrin

Interplay between laminin-5 (Ln-5) and its integrin (Int) receptors alpha2beta1, alpha3beta1 and alpha6beta4 has been implicated in the progression and invasion of carcinomas. In this study we found abundant immunoreactivity for chains of Ln-5 (alpha3-beta3-gamma2) and Ln-10 (alpha5-beta1-gamma1), as well as for type VII collagen, in basement membranes (BM) of colorectal adenomas. In carcinomas of all differentiation grades, Lns were seen in tumor BMs, whereas type VII collagen was almost absent. Ln-5 appeared to accumulate along the invading edges of carcinomas, while Ln-10 was mostly absent. Immunoreactivity for Ln al chain, a component of Lns-1 and -3, was not seen in adenomas or carcinomas. Immunoreactivity for alpha2, alpha6, beta1 and beta4 Ints was found in all tumors and that for alpha3 Int in all adenomas and most of the carcinomas, often in colocalization with Ln-5. Immunoblotting of carcinoma tissues showed that the gamma2 chain of Ln-5 was present as typical Mr 105000 and 155000 isoforms. Immunoprecipitation experiments showed production of Ln-5 by cultured colon carcinoma cells. In quantitative cell adhesion experiments, function-blocking MAbs to alpha3 and beta1 Int subunits, but not those to Int alpha2 or alpha6 subunits, significantly inhibited the adhesion of cells to Ln-5. Our results suggest that BM composition in colorectal adenomas reflects the properties of surface epithelial BM of colorectal mucosa. In invading carcinomas, trimeric Ln-5, produced by carcinoma cells, is a major BM component and the cells use the alpha3beta1 Int complex for adhesion to Ln-5.

Expression of laminins and their integrin receptors in different conditions of synovial membrane and synovial membrane-like interface tissue

OBJECTIVE

To demonstrate the expression of laminins (Lns) and their integrin (Int) receptors in different synovial samples and synovial membrane-like interface tissues from well fixed and aseptically loosened total hip replacement (THR), and the potential role of Ln-Int interaction in the production of collagenases and cytokines.

METHODS

Immunohistochemical staining was done to detect the distribution of EHS Ln, Ln alpha2, alpha3, alpha5, beta1, beta2 chains and Int alpha1, alpha2, alpha3, alpha6, beta1, beta4 subunits in different samples. Double immunofluorescence labelling was used to find colocalisation of Int alpha6 subunit and collagenase-1/collagenase-3/TNFalpha/IL6.

RESULTS

General Ln immunoreactivity was detected in all specimens. Ln alpha5, beta1 and beta2, but not alpha2 and alpha3 chains were seen in the synovial lining and the basement membrane of blood vessels with the intensity/extent of labelling in the following rank order: rheumatoid arthritis (RA) loosened prostheses, osteoarthritis, well fixed prostheses, traumatic knees. Among Int subunits, staining for beta1 was usually the strongest, followed by staining for Int alpha6, alpha1, alpha3, and alpha2 subunits, with the same rank order for overall expression of Lns. Int beta4 subunit was not detectable in most of the specimens. Double labelling focused on Int alpha6 subunit disclosed its frequent colocalisation with collagenases 1 and 3 and with tumour necrosis factor alpha and interleukin 6 in synovial lining.

CONCLUSION

Synovial lining contains Ln-10, Ln-11, and Int alpha6beta1 and alpha1beta1 receptors. In aseptic loosening of THR, interface tissue has a similar Ln subtype and Int receptor composition as RA synovium, which confirms its "lining-like" phenotype. Synovial lining does not contain Ln-5 (alpha3beta3gamma2) or Int alpha6beta4, which are components of epithelial hemidesmosomes. The expression of Lns and their Int receptors is upregulated in inflammation. The close spatial relation between Ln and its Int receptors in synovial lining cells containing proteinases and cytokines suggests a potential role in joint destruction and prosthetic loosening.

Use of monoclonal antibodies for the diagnosis and treatment of bladder cancer

Although the management of cancer by exploiting properties distinguishing neoplastic and normal cells has always been an attractive concept, it was the development of hybridoma technology and the resulting tumor-associated monoclonal antibodies (MAbs) that offered new prospects for this strategy. Twenty years later, some of the applications of MAbs in oncology are now part of the everyday diagnosis and treatment, while others are the subject of intensive investigation. We reviewed the current applications of MAbs in the diagnosis and treatment of bladder cancer and attempted to put the issue into perspective, with particular presentation of their therapeutic potential.

Monoclonal antibody ONS-M21 recognizes integrin alpha3 in gliomas and medulloblastomas

The monoclonal antibody ONS-M21 recognizes an antigen found on the surface of glioma and medulloblastoma cells but does not react with the antigens of normal brain tissue. We purified and identified the 140-kDa protein by means of an antibody-binding affinity column. This 140-kDa antigen has sequences homologous to the amino-terminal region and five parts of the internal domain of integrin alpha3. When the integrin alpha3-related sequences was amplified and used to analyse the mRNA of glioma and medulloblastoma surgical specimens, the transcription level of integrin alpha3 mRNA appeared to be quantitatively correlated with the grade of malignancy. These findings suggest that the ONS-M21 antibody, which reacts with integrin alpha3, might be useful in the diagnosis of gliomas and medulloblastomas.

Enhancement of metastatic activity of colon cancer as influenced by expression of cell surface antigens

BACKGROUND

Cell surface antigens are contributory factors toward metastatic activity. There have been no detailed studies on changes in cell surface antigens of colon cancer cell lines. To control life-threatening metastasis, it is necessary to evaluate what types of changes in cell surface antigens exert an influence on metastatic activity.

MATERIALS AND METHODS

In vivo selection was performed using the human colon cancer-derived cell line KM12SM to obtain variants of metastatic activity. A murine spleen injection-liver metastasis procedure reflecting the latter half of the metastatic process was adopted and repeated four times. Flow cytometric analyses were carried out to detect expression of antigens: Lewis a (Lea), Lewis x (Lex), sialyl Lewis a (sLea), sialyl Lewis x (sLex), E-cadherin, CD44v6, integrin alpha2 (CD49b), integrin alpha3 (CD49c), integrin alpha4 (CD49d), integrin alpha5 (CD49e), and integrin beta1 (CD29).

RESULTS

In vivo selection produced variants with higher metastatic activity. In the original line KM12SM, sLea, E-cadherin, CD49b, CD49c, or CD29 were positive in more than 40% of the cells. After selection, the percentage of cells positive for Lea, sLea, and all examined integrins significantly increased. Lex, sLex, and CD44v6 increased slightly, while E-cadherin decreased slightly.

CONCLUSIONS

In vivo selection and flow cytometric analysis revealed that Lea, sLea, CD49b, CD49c, and CD29 appear to be involved in the increase of metastatic activity. The changes of integrin expression in this study suggest that integrins collaborate in the promotion of adhesion to an extracellular matrix.

Comparative analysis of integrins in vitro and in vivo in uveal and cutaneous melanomas

Changes in integrin expression have been shown to be important for the growth and metastatic capacity of melanoma cells. In this study, we have examined the expression of alphav integrins by three uveal and four cutaneous malanoma lines. No lines expressed alphavbeta6 and only TXM13, a cutaneous line, expressed alphavbeta8. All lines expressed alphavbeta5 and alphavbeta3 (four out of four cutaneous, two out of three uveal) or avpl (OM431, an uveal line). Thus, OM431 is the second uveal melanoma we have described that expresses alphavbeta1 and this, we report again, functions as an alternative vitronectin/fibronectin receptor. Subcutaneous growth of cell lines in athymic mice correlated with an alphavbeta3-positive, alphavbeta1 -negative phenotype. Analysis of clinical material from cutaneous melanoma showed that although alphav expression was increased in 88% of metastases, this could not all be explained by up-regulation of alphavbeta3, with only 2 out of eight skin metastases expressing this heterodimer. Using antibody SZ.21, which as we report here works in archival material, only 1 out of 15 uveal metastases expressed detectable beta3. Thus, acquisition of alphavbeta3 expression, which has been implicated in cutaneous melanoma progression, may not be required for development of metastases from uveal melanoma or indeed for skin, as distinct from lymph node, metastases of cutaneous melanoma.

Cloning of the murine TROP2 gene: conservation of a PIP2-binding sequence in the cytoplasmic domain of TROP-2

Trop-2 is a novel calcium signal transducer expressed at high levels by most human carcinomas. To develop an animal model to study the function of this molecule in vivo, we have cloned the murine Trop2 gene. Using human TROP2 primers, we amplified by PCR a segment of murine Trop2. This was used as a probe to clone a full-length gene by hybridization of a genomic library. The cloned murine Trop2 gene is functional, as indicated by sequencing and by expression after transfection. The murine Trop2 is 87.4% similar to its human homologue, with the highest conservation in the extracellular region between residues 86 and 157. Essentially all cysteines are conserved between the human and the murine genes, suggesting conservation of the Trop2 disulfide bridges and of its overall structure. Intriguingly, the cytoplasmic tail of Trop2 shows a highly conserved phosphatidylinositol 4,5-bisphosphate (PIP2)-binding sequence, which overlaps with a protein kinase C phosphorylation site. Thus, we speculate that PIP2 might regulate the phosphorylation state of Trop2 and play a role in its signal transduction. Murine Trop2 mRNA is detected in normal kidney, lung, ovary and testis, similarly to the human gene. Interestingly, the highest levels of expression are found in immortalized keratinocytes. Since Trop2 is undetectable in undifferentiated spindle cell carcinomas, this suggests a preferential expression at early stages of tumor progression.

Detection of altered adhesion molecule expression in experimental tumors by a radiolabeled monoclonal antibody

Adhesion molecules play a major role in the processes of invasion and metastasis of malignant tumors. Their expression within tumors has been reported to be quantitatively and qualitatively altered according to the invasiveness and metastatic potential of the tumor. The present study tested whether the intratumoral expression of integrin alpha 3 can be detected by a radiolabeled monoclonal antibody. The in vitro binding study with four different human cancer cells showed that radioiodinated GA17 antibody recognizing integrin alpha 3 bound specifically to these cells to varying degrees, according to the antigen density on each cell. The biodistribution study with 125I- and 111In-labeled antibodies showed specific localization of radiolabeled GA17 to the xenografts. However, the in vivo tumor localization was not proportional to the antigen density calculated in vitro, and antibody metabolism varied among the tumors, as was also confirmed by in vitro radionuclide retention assay. The intratumoral distribution of radioactivities varied reflecting the antigen expression within the tumor. These results indicate that 1) integrin alpha 3 was expressed in various kinds of tumors and could be localized by the radiolabeled antibody, and 2) the expression of integrin alpha 3 and the metabolism of the radiolabeled antibody after binding to the antigen within the tumor were variable among the tumors, which affected the radionuclide distribution characteristics. The expression of adhesion molecules within these tumors was noninvasively detected by a radiolabeled antibody. It may be possible to use integrin alpha 3, when it is overexpressed, as a target of therapy with antibodies radiolabeled with alpha or beta emitters.

Pancreatic carcinomas deposit laminin-5, preferably adhere to laminin-5, and migrate on the newly deposited basement membrane

We studied the adhesion mechanism of pancreatic carcinoma using in vitro adhesion and migration assays of stable cell lines and tumors grown from these cell lines in nude mice. We also compared the results with the expression profiles of laminins and their receptors in pancreatic carcinomas to evaluate the relevance of these mechanisms in vivo. All of the cell lines preferably adhered to laminin-5, irrespective of their capability to synthesize laminin-5. Cell migration was studied in the presence of hepatocyte growth factor, as it increased the speed of migration manyfold. Herbimycin A treatment and antibodies against the beta 1 and alpha 3 integrin subunits and laminin alpha 3 chain almost entirely blocked cell migration of the BxPC-3 cell line, whereas migration was nearly unaffected by RGD peptide and only moderately inhibited by antibody against the alpha 6 integrin subunit. Indirect immunofluorescence microscopy of wounded BxPC-3 cells suggested a rapid endocytosis of alpha 3 integrin subunit in the cells at the margin of the wound and a rapid, polarized rearrangement of the alpha 6 beta 4 integrin. Especially HGF-treated cultures showed a prominent cytoplasmic reaction for laminin-5 at the margin of the wound. Xenografted cells formed tumors that produced and deposited the same laminin chains as the in vitro cultures. Frozen sections of human pancreatic carcinomas showed reactivity for laminin chains suggestive for expression of laminin-1 and laminin-5. Both xenografted tumors and human pancreatic carcinomas also showed stromal reactivity for laminin-5. Electron microscopy of the human tumors suggested that this was due to an abundant reduplication the basement-membrane-like material around the nests of malignant cells. Our results suggest that pancreatic carcinomas synthesize and deposit laminin-5 in the basement membrane in an abnormal manner. Invading cells adhere to this newly produced basement membrane and migrate on it by using the alpha 3 beta 1 integrin receptor recognizing laminin-5.

Neuronal differentiation in SH-SY5Y human neuroblastoma cells induces synthesis and secretion of tenascin and upregulation of alpha(v) integrin receptors

Human SH-SY5Y neuroblastoma cells were induced to neuronal differentiation by using 12-0-tetradecanoylphorbol-13-acetate (TPA) and retinoic acid (RA). Both treatments rapidly induced long neurites and increased the content of neurofilaments as shown by immunocytochemistry and immunoblotting. Immunoprecipitation and immunoblotting of the culture medium with monoclonal antibodies demonstrated a rapid onset of synthesis and secretion of Mr 280,000 tenascin (Tn) polypeptide with TPA and both Mr 280,000 and 190,000 Tn polypeptides with RA and an increased secretion of extradomain A cellular fibronectin (EDA-Fn) upon both treatments. Upon RA treatment both Tn polypeptides were also found in extracellular matrix preparations of the differentiated cells. A diffuse extracellular Tn immunoreactivity and a distinct cytoplasmic reaction were seen in differentiated cells especially after exposure to monensin to inhibit cellular secretion. Instead, immunoprecipitation experiments suggested that laminin was synthesized by the cells but was not upregulated upon differentiation. Experiments with purified Tn, used to coat the culture substratum, demonstrated that the undifferentiated cells were unable to adhere or spread on Tn but rapidly acquired the spreading capacity upon differentiation with the inducing agents. In immunofluorescence and immunoblotting the undifferentiated cells presented only a faint heterogenous reaction for beta1 integrin (Int) subunit, whereas cells exposed to RA presented a strong reaction for the Int alpha1 and beta1 subunits, hence suggestive of Int alpha1beta1, and for Int alpha(v) subunit. Cells exposed to TPA showed an enhanced immunoreaction for Int alpha2 and beta1 subunits, suggestive of Int alpha2beta1, and for Int alpha(v) subunit. Immunoreactivity for Int alpha(v) located to distinct punctate plaques in the differentiated cells after both inducing agents. The results suggest that Tn is produced by cultured neuronally differentiating cells, and it is accompanied by the acquitance of an adhesion receptor for Tn.

A homozygous mutation in the integrin alpha6 gene in junctional epidermolysis bullosa with pyloric atresia

The alpha6 integrin subunit participates in the formation of both alpha6beta1 and alpha6beta4 laminin receptors, which have been reported to play an important role in cell adhesion and migration and in morphogenesis. In squamous epithelia, the alpha6beta4 heterodimer is the crucial component for the assembly and stability of hemidesmosomes. These anchoring structures are ultrastructurally abnormal in patients affected with junctional epidermolysis bullosa with pyloric atresia (PA-JEB), a recessively inherited blistering disease of skin and mucosae characterized by an altered immunoreactivity with antibodies specific to integrin alpha6beta4. In this report, we describe the first mutation in the alpha6 integrin gene in a PA-JEB patient presenting with generalized skin blistering, aplasia cutis, and defective expression of integrin alpha6beta4. The mutation (791delC) is a homozygous deletion of a single base (C) leading to a frameshift and a premature termination codon that results in a complete absence of alpha6 polypeptide. We also describe the DNA-based prenatal exclusion of the disease in this family at risk for recurrence of PA-JEB. Our results demonstrate that, despite the widespread distribution of the alpha6 integrin subunit, lack of expression of the alpha6 integrin chain is compatible with fetal development, and results in a phenotype indistinguishable from that caused by mutations in the beta4 chain, which is expressed in a more limited number of tissues.

Influence of spatial configuration on the expression of carcinoembryonic antigen and mucin antigens in human bladder cancer

CEA and cellular mucin antigens have been recognized as potential targets for specific immunotherapy and are frequently expressed in bladder cancer. We studied the coordinated expression of a bladder cancer-associated CEA glycoform and of the mucins MUC1, MUC2 and MAUB under various growth conditions in the MGH-U3 bladder-cancer cell line. CEA and MUC2 mRNAs and proteins were detected in nude mouse tumors and spheroids but not in monolayer cultures. Expression of MAUB and bladder-cancer CEA also was induced according to spatial configuration of cells. MUC1 was always expressed under various growth conditions, but its glycosylation was modulated: in spheroids and mostly in tumor cells, the SM3 protein epitope was unmasked and sialyl-Tn was induced. The kinetics of modulation of MAUB and bladder-cancer CEA were different. The epitope recognized by the monoclonal antibody (MAb) 19A211 was rapidly induced in the aggregation phase of spheroid formation and rapidly lost upon plating of tumor cells, suggesting a relationship with cell contact. By contrast, MAUB induction in spheroids was delayed to the compaction phase, when cell aggregates become resistant to disruption, and loss of expression upon tumor plating occurred slowly over several culture passages. No induction of these 2 antigens was observed in the presence of differentiation agents, endothelial cell products or interferon-gamma, but it occurred when MGH-U3 cells were cultured at high density on extracellular matrix. Our results suggest that CEA and mucin antigen expression in bladder cancer is modulated by the spatial configuration of cells.

Distinct changes in the laminin composition of basement membranes in human seminiferous tubules during development and degeneration

We studied the distribution of laminin (Ln) chains and their integrin (Int) receptors in normal developing and adult and in atrophied human testes by using immunohistochemistry. Immunostaining for EHS Ln and type IV collagen was used to identify basement membranes (BMs). In the BM of seminiferous epithelium of fetal testis, a panel of monoclonal antibodies showed immunoreactivity for Ln alpha 1-, alpha 2-, beta 1-, beta 2- and gamma 1-chains, suggestive of the presence of Lns 1 to 3. In BM of adult seminiferous epithelium with active spermatogenesis, immunoreactivity for Ln beta 2- and gamma 1-chains was found but not for Ln alpha-chains, suggesting a complex of Ln chains not compatible with any known trimers. Instead, with polyclonal Ln antiserum and monoclonal antibody to type IV collagen, a distinct BM-like reactivity was seen. In atrophied testes, prominent immunoreactivities for Ln chains, compatible with Lns 1 to 3, were seen in the thickened BM of seminiferous tubules, hence suggestive of reappearance of fetal Lns. Among the subunits of Ln-binding Int receptors in fetal seminiferous tubules, a strong immunoreactivity for Int beta 1- and Int alpha 6-subunits was seen throughout the seminiferous epithelium, other Int subunits being found in interstitial cells. In the adult and atrophied testes, immunoreactivities for Int beta 1- and Int alpha 6-subunits were seen to be confined to the basal aspect of the seminiferous epithelium whereas immunoreactivities for Int alpha 1-, alpha 2-, alpha 3- and beta 4-subunits were seen in the myoid cells. The results show that both maturation and degenerative changes of human testes are accompanied by distinct changes in the Ln expression of BM of seminiferous epithelium, which appears to accompany epithelial differentiation of the Sertoli cells. Furthermore, they suggest the presence of a novel Ln trimer in BM of adult human seminiferous tubules.

Integrin alpha chain cytoplasmic tails regulate "antibody-redirected" cell adhesion, independently of ligand binding

Here we describe a novel "antibody-redirected cell adhesion" (ARCA) assay. This assay measures heterotypic cell-cell adhesion, resulting from antibody bridging between Fc gamma receptors type II (CD32) on leukocytes, and clustered integrins on adherent cell monolayers. This ARCA activity, facilitated by integrins alpha3 beta1 or alpha4 beta1, required an intact cytoskeleton, but did not involve typical integrin ligand binding sites or divalent cations. Furthermore, deletion of the alpha4 cytoplasmic tail almost completely abrogated integrin ARCA activity, suggesting an alteration of integrin recruitment into adhesive sites. If two or more tail residues were present after the conserved GFFKR motif, then ARCA activity was largely restored. Although alpha4 tail deletion caused loss of ARCA activity, it had no effect on the binding of VCAM-1 to intact alpha4-transfected K562 cells. In conclusion, the integrin alpha chain tail can positively regulate integrin-dependent cell adhesion by a receptor recruitment/clustering mechanism independent of conventional integrin ligand-binding considerations.

Toxicity of ribosome-inactivating proteins-containing immunotoxins to a human bladder carcinoma cell line

Immunotoxins were prepared by linking the type 1 ribosome-inactivating proteins (RIP) momordin I, pokeweed antiviral protein from seeds (PAP-S) and saporin-S6 to the 48-127 monoclonal antibody (MAb) recognising a glycoprotein (gp54) expressed on all human bladder tumours tested and on human bladder carcinoma cell lines, in particular on the T24 cell line. T24 cells required a 2 hr contact with immunotoxins to ensure binding and endocytosis. A time course of exposure, followed by further incubation without the immunotoxins, showed that maximum inhibition of protein synthesis by T24 cells was reached after 2 hr of contact followed by 3 days without the immunotoxins. Under optimal conditions, 48-127/RIP immunotoxins at nanomolar concentrations inhibited by 50% protein synthesis of target T24 cells. No toxicity was observed if (i) target cells were treated with non-conjugated RIP, (ii) target cells were treated with momordin I- or PAP-S-containing immunotoxins made with an irrelevant antibody and (iii) a non-target cell line was treated with the same 2 RIP conjugated to 48-127 antibody. The in vitro selective toxicity of these immunotoxins encourages further studies in view of a possible use in clinical trials for the local therapy of human bladder carcinomas.

Establishment and characterization of human gastric carcinoma lines with high metastatic potential in the liver: changes in integrin expression associated with the ability to metastasize in the liver of nude mice

There is a need to establish animal models which are suitable for investigation of human gastric cancer metastasis to the liver. To this end, a human gastric carcinoma line, AZ521 was injected into the spleens of nude mice. Cells from the few liver metastatic foci of injected AZ521 were expanded "in vitro" and subsequently injected into the spleens of nude mice. By repeating these procedures three times, we were able to obtain a cell line, designated as AZ-H3c, with high metastatic potential in nude mice. Liver metastasis developed in 15 of 21 (71%) animals injected with AZ-H3c, but only in 14% of those injected with parental AZ521. Further, AZ-H3c caused faster tumor development than did AZ521. However, the primary AZ-H3c tumors and liver metastatic AZ-H3c tumors showed essentially the same histological appearance. We also analyzed the cell surface expression of adhesion molecules. The data showed that the expression of VLA-1, VLA-2, VLA-3, VLA-4, VLA-5 was enhanced in AZ-H3c. In contrast, the expression of VLA-6, (alpha(v)beta3), E-cadherin, ICAM-1 and LFA-1 was reduced in this high-metastatic line. These results suggest that (beta1) integrins play an important role in the liver metastasis of human gastric carcinoma cells. Our high-metastatic line should be useful for studies aimed at the prevention of liver metastasis.

Expression of integrin alpha 3 in gastric and colorectal cancers: its relation to wall contraction and mode of invasion

We macroscopically classified 25 gastric and 23 colorectal advanced cancers into "contracted" and "uncontracted" types, and found immunohistochemically that integrin subunit alpha 3 was more frequently expressed in the extracellular matrix (ECM) in the former than in the latter (75%:9/12 vs. 38%: 5/13 in gastric and 86%:6/7 vs. 25%:4/16 in colorectal cancers, respectively). Integrin subunit alpha 3 was also expressed more frequently in cancers producing transforming growth factor-beta (TGF-beta), which is related to ECM deposition, integrin expression and cell mobility, than in those which did not produce TGF-beta (67%:10/15 vs. 40%:4/10 in gastric and 57%:4/7 vs. 38%:6/16 in colorectal cancers, respectively). In addition, integrin subunit alpha 3 was not expressed in 2 benign gastric ulcers combined with gastric cancer elsewhere in the stomach. On the other hand, a retrospective analysis of 107 cases of rectal cancer which recurred after a curative operation revealed that local recurrence was more frequent in "contracted" than "uncontracted" types (44%:11/25 vs. 26%:21/82). These results may suggest that the abundant interstitial fibrosis which leads to remarkable gastric or colorectal wall contraction is a result of the interaction between cancer cells and ECM, along with the expression of integrin and/or the production of TGF-beta. This fibrosis may also be closely related to the mode of gastric and colorectal cancer invasion.

Differential expression of laminin chains and their integrin receptors in human gastric mucosa

The proliferating cells of the gastric mucosa are found among the pit and mucous neck cells. These cells migrate upward to renew the surface epithelium and downward to restitute the glandular cells. As the epithelial basement membranes (BMs) function as substrate for cell adhesion and migration as well as signals for their differentiation, we studied, by indirect immunofluorescence microscopy, the distribution of different laminin chains and their integrin receptors in adult human stomach. The immunoreactivity for laminin alpha 2 chain localized to the BMs of glands and the lower parts of the gastric pits whereas the laminin alpha 3 chain (laminin-5/kalinin) immunoreactivity was strictly confined to BMs underneath the surface epithelium and the upper parts of the pits. Proliferating mucosal epithelial cells, identified by Ki-67 antibodies, were confined to the areas containing both alpha 2 and alpha 3 laminin chains. The alpha 1, beta 1, and gamma 1 laminin chains were found in all BMs of the mucosa whereas the beta 2 chain was prominent in mucosal blood vessels and also detectable in some glands. Among the laminin integrin receptors, the alpha 3 and beta 4 subunits were seen to be expressed in cells along the BMs with the alpha 3 laminin chain. The alpha 6 integrin, on the other hand, was seen in all gastric epithelia. The present results demonstrate that in the adult human stomach laminin alpha 2 and alpha 3 chains show zonal distribution in BM underlying gastric mucosal epithelium whereas other laminin chains show a more general distribution.

Cloning of the gene encoding Trop-2, a cell-surface glycoprotein expressed by human carcinomas

We have cloned by expression the cDNA encoding Trop-2, a cell-surface glycoprotein expressed by most human carcinomas. Formal proof of the identity of the clone is the hybridization to DNA and RNA from genomic TROP2 transfectants. TROP2 is a single-copy gene in human cells, hybridizes to a single 1.8-kb mRNA from expressing sources and encodes a 35,709 Da type-1 transmembrane protein with a single transmembrane domain. TROP2 is essentially identical to GA733-1. Thus, we have proven that GA733-1, for which a protein product had not been identified, is a functional gene. TROP2 is also homologous to TROP1/KSA/GA733-2, confirming the serological similarities between the 2 molecules. The homology between the Trop-1 and Trop-2 peptides is clustered in 2 extracytoplasmic domains and in the transmembrane/cytoplasmic region. Twelve cysteines and a potential cytoplasmic tyrosine phosphorylation site are also conserved. Trop-1 and Trop-2 are homologous to serum IGF-II-binding proteins and appear as signal transducers. Thus, they likely represent novel cell-surface receptors and may play a role in regulating the growth of carcinoma cells. On the other hand, we have found no evidence for a role of Trop-2 and Trop-1 as homophilic adhesion molecules.

The human hair follicle: glycoprotein-related antigenic profile of distinct keratinocyte populations in vivo and their alterations in vitro

The cell surface expression of three glycoprotein antigens, as defined by the monoclonal antibodies BT 15, T 43, and MH 99, was investigated in follicular keratinocyte populations in vivo. In addition, the regulation of glycoprotein synthesis was studied in follicular and interfollicular keratinocytes cultured in vitro. The BT 15 antigen was strongly expressed in the inner root sheath and the area above Auber's line of the hair bulb, whereas the T43 antigen was mainly seen in the outer root sheath. Selectively high expression of the MH 99 antigen was found only in outgrowing germ buds of early anagen follicles. Radioimmunoprecipitation revealed strong signals with BT 15 in freshly prepared follicular keratinocytes, two to three times stronger than those in interfollicular keratinocytes, but the signals clearly decreased by 80% under continuing culture conditions. The T 43 antigen was found by FACS analysis and radioimmunoprecipitation in initially low amounts in both populations, but the signals increased dramatically (up to 50 times) in long-term cultures and in subcultures. The MH 99 antigen was also initially present only in low amounts, in interfollicular rather than in follicular keratinocytes, but its expression increased up to 15-fold with continuing culture and any differences between the two populations disappeared. Our investigation revealed that at least three populations of hair follicle keratinocytes are characterized by different surface glycoprotein antigens, clearly related to their state of differentiation and proliferation.(ABSTRACT TRUNCATED AT 250 WORDS)

Host immune response in renal cell cancer: interleukin-4 (IL-4) and IL-10 mRNA are frequently detected in freshly collected tumor-infiltrating lymphocytes

Human renal cell cancer (RCC) is clearly responsive to immunotherapy. Clinical responses may be mediated by "non-specific" (e.g. natural killer, NK, cells) or "specific" MHC-class-I-restricted tumor-specific CD8+ T lymphocytes. Typically RCC progresses, however, despite significant infiltration of various lymphoid cells. We examined freshly isolated RCC tumor-infiltrating lymphocytes (TIL) derived from seven RCC patients for cytokine expression by the polymerase chain reaction (PCR). Established RCC tumor cell lines derived from these RCC patients were negative for interleukin-2 (IL-2), IL-4, IL-10, and interferon gamma and found to be positive for tumor necrosis factor alpha (TNF alpha), IL-6, IL-1 beta, granulocyte/macrophage-colony-stimulating factor (GM-CSF), and transforming growth factor beta 1 (TGF beta 1) message as detected by PCR. An identical pattern of cytokine mRNA expression was identified in other long-term RCC lines and in normal human kidney cells upon culture, but not in two Wilms tumor cell lines tested. Short-term-, and long-term-established RCC lines, but not Wilms tumor lines, secreted substantial levels of GM-CSF, TNF alpha, IL-1 beta, and IL-6 as detected by enzyme-linked immunosorbent assay. Both RCC lines and Wilms tumor lines secreted TGF beta 1. In comparison, normal kidney cells secreted IL-6 and GM-CSF, but not IL-1 beta, or TFG beta 1 under identical in vitro cell culture conditions. We applied PCR-based methods to characterize the cytokine mRNA expression pattern in immune cells infiltrating into renal cell cancer without the need for expansion of such effector cells in vitro. Examining freshly collected RCC TIL by PCR from patients with primary cell cell cancer, we could demonstrate that such cells, but not lympho-mononuclear cells harvested from normal human kidney tissue, typically exhibit IL-4 and IL-10 mRNA expression.

Specific association of CD63 with the VLA-3 and VLA-6 integrins

We screened monoclonal antibodies to cell-surface proteins and selected an antibody, called 6H1, that recognizes a putative integrin-associated protein. The 6H1 monoclonal antibody (mAb) indirectly coprecipitated alpha 3 beta 1 and/or alpha 6 beta 1, but not alpha 2 beta 1, or alpha 5 beta 1 from Brij 96 detergent lysates of multiple cell lines. Large scale purification using the 6H1 mAb yielded a single protein of 45-60 kDa with an amino-terminal sequence that exactly matched CD63. Confirming that the 6H1 mAb recognized the CD63 protein, 6H1 and a known anti-CD63 mAb yielded identical coprecipitation results and identical colocalization into lysosomal granules containing cathepsin D. Furthermore, we used an established anti-CD63 mAb to detect this protein in an alpha 3 beta 1 immunoprecipitate, and also we observed VLA-3 and CD63 colocalization in cellular "footprints." Notably, the cytoplasmic domain of alpha 3 was neither required nor sufficient for CD63 association, suggesting that it occurred elsewhere within the alpha 3 beta 1 complex. Knowledge of these specific CD63-alpha 3 beta 1 and CD63-alpha 6 beta 1 biochemical associations should lead to critical insights into the specialized functions of alpha 3 beta 1, alpha 6 beta 1, and CD63.

alpha 3A beta 1 integrin localizes to focal contacts in response to diverse extracellular matrix proteins

In vitro binding assays and inhibition of cell adhesion with monoclonal antibodies have implicated the integrin alpha 3 beta 1 as a receptor for a variety of extracellular ligands. However, reports of alpha 3 beta 1-ligand interactions are inconsistent, and transfection studies have suggested that alpha 3 beta 1 is not sufficient for cell attachment to ligands other than kalinin/laminin 5. We used immunofluorescence to study subcellular localization of the alpha 3A cytoplasmic domain variant in different cultured cell types. Using standard fixation and permeabilization methods, antibodies specific for alpha 3A stained most cell types in a diffuse pattern, consistent with previous reports. Surprisingly, however, chemical cross-linking of integrins to the extracellular matrix and extraction of the cytoskeleton prior to immunofluorescence revealed alpha 3A in focal contacts of most cells tested, suggesting that the cytoplasmic domain was concealed in intact focal contacts by cytoskeletal or other cytoplasmic proteins. The alpha 3A subunit localized to focal contacts in several cell types cultured on fibronectin, kalinin/laminin 5, EHS-laminin/laminin 1, type IV collagen, or vitronectin. In contrast, alpha 5 and alpha V integrins were detected in focal contacts only in cells grown on their known ligands (fibronectin, and fibronectin or vitronectin, respectively). Therefore, our results show that alpha 3A beta 1 responds to a broad spectrum of extracellular ligands. Time course comparisons of the recruitment of alpha subunits from different fibronectin receptors suggested that localization of alpha 3A beta 1 to fibronectin-induced focal contacts was independent of the recruitment of alpha 5 and alpha 4 integrins. However, other studies have shown that alpha 3A beta 1 does not mediate initial cell adhesion to many of the ligands that induced its focal contact localization, including fibronectin. Therefore, we suggest that alpha 3A beta 1 may be a secondary receptor with post-cell-adhesion functions for a broad spectrum of extracellular matrices.

A novel role for alpha 3 beta 1 integrins in extracellular matrix assembly

To study the biological role of alpha 3 beta 1 integrins in cell adhesion, migration, and in the deposition of extracellular matrix, we stably expressed the human alpha 3 integrin subunit in the alpha 4, alpha 5 integrin deficient CHO cell line B2. The expression of alpha 3 beta 1 integrins enhanced cell adhesion on entactin (also known as nidogen), but not on fibronectin. Using recombinant GST-fusion proteins that span the entire length of the entactin molecule, we located cell adhesive activity to the G2 domain of entactin. These results suggest that the alpha 3 beta 1 integrin functions as an adhesion receptor interacting with the G2 domain of entactin. On the other hand, the expression of alpha 3 beta 1 integrins did not confer the ability to migrate on entactin. Strikingly, the expression of alpha 3 beta 1 dramatically increased the deposition of entactin and fibronectin into the pericellular matrix. This was accompanied by increased binding activity of the 29 kDa amino-terminal domain of fibronectin. Thus, similar to alpha 5 beta 1 integrins, alpha 3 beta 1 integrins can play an important role in modulating the assembly of pericellular matrices. However, unlike fibronectin deposition supported by alpha 5 beta 1, alpha 3 beta 1 supported fibronectin deposition into pericellular matrix was not inhibited by antibodies binding to the RGD containing cell adhesion domain of fibronectin, demonstrating that the two processes are mechanistically distinct. The role of alpha 3 beta 1 in pericellular matrix assembly potentially implicates this receptor in the assembly and/or recognition of entactin-containing pericellular matrices, an observation consistent with its apparent role in the renal glomerulus of the mammalian kidney.

Integrins in human anterior chamber angle

BACKGROUND

Integrins, which are composed of an alpha and beta subunit, are capable of binding to a number of extracellular matrix proteins and, hence, affect cell adhesion and proliferation.

METHODS

The distribution of the integrin beta (beta 1, beta 3-beta 5) and alpha (alpha 1-6 and alpha v) subunits in human anterior chamber angle was studied in eyes from subjects aged 9 months to 81 years using the indirect immunofluorescence technique.

RESULTS

Immunoreaction for the beta 1 subunit was found throughout the trabecular meshwork (TM), in the cribriform layer, and in the endothelial lining of Schlemm's canal (SC). Labelling for the alpha 3 subunit was found in the TM and the cribriform layer only. In infant eyes the alpha 5 subunit was present in all three areas with the highest concentration in the cribriform layer, whereas no reaction was observed in adult eyes. The alpha 6 subunit was localized to the endothelium of SC only. Immunoreaction for the alpha v subunit was present in the TM and the cribriform layer of infants and young adults.

CONCLUSION

The present results suggest the presence of several integrin heterodimers, acting as potential receptors for laminin, collagen, fibronectin, and vitronectin, in the anterior chamber angle.