Cell adhesion activity of a 30-kDa major secreted protein from human bladder carcinoma cells

Angiogenesis modulated by CD93 and its natural ligands IGFBP7 and MMRN2: a new target to facilitate solid tumor therapy by vasculature normalization

The tumor vasculature was different from the normal vasculature in both function and morphology, which caused hypoxia in the tumor microenvironment (TME). Previous anti-angiogenesis therapy had led to a modest improvement in cancer immunotherapy. However, antiangiogenic therapy only benefitted a few patients and caused many side effects. Therefore, there was still a need to develop a new approach to affect tumor vasculature formation. The CD93 receptor expressed on the surface of vascular endothelial cells (ECs) and its natural ligands, MMRN2 and IGFBP7, were now considered potential targets in the antiangiogenic treatment because recent studies had reported that anti-CD93 could normalize the tumor vasculature without impacting normal blood vessels. Here, we reviewed recent studies on the role of CD93, IGFBP7, and MMRN2 in angiogenesis. We focused on revealing the interaction between IGFBP7-CD93 and MMRN2-CD93 and the signaling cascaded impacted by CD93, IGFBP7, and MMRN2 during the angiogenesis process. We also reviewed retrospective studies on CD93, IGFBP7, and MMRN2 expression and their relationship with clinical factors. In conclusion, CD93 was a promising target for normalizing the tumor vasculature.

Expression characteristics and their functional role of IGFBP gene family in pan-cancer

BACKGROUND

Insulin-like growth factor binding proteins (IGFBPs) are critical regulators of the biological activities of insulin-like growth factors. The IGFBP family plays diverse roles in different types of cancer, which we still lack comprehensive and pleiotropic understandings so far.

METHODS

Multi-source and multi-dimensional data, extracted from The Cancer Genome Atlas (TCGA), Oncomine, Cancer Cell Line Encyclopedia (CCLE), and the Human Protein Atlas (HPA) was used for bioinformatics analysis by R language. Immunohistochemistry and qRT-PCR were performed to validate the results of the database analysis results. Bibliometrics and literature review were used for summarizing the research progress of IGFBPs in the field of tumor.

RESULTS

The members of IGFBP gene family are differentially expressed in various cancer types. IGFBPs expression can affect prognosis of different cancers. The expression of IGFBPs expression is associated with multiple signal transduction pathways. The expression of IGFBPs is significantly correlated with tumor mutational burden, microsatellite instability, tumor stemness and tumor immune microenvironment. The qRT-PCR experiments verified the lower expression of IGFBP2 and IGFBP6 in gastric cancer and the lower expression of IGFBP6 in colorectal cancer. Immunohistochemistry validated a marked downregulation of IGFBP2 protein in gastric cancer tissues. The keywords co-occurrence analysis of IGFBP related publications in cancer showed relative research have been more concentrating on the potential of IGFBPs as tumor diagnostic and prognostic markers and developing cancer therapies.

CONCLUSIONS

These findings provide frontier trend of IGFBPs related research and new clues for identifying novel therapeutic targets for various cancers.

IGFBP7 downregulation or overexpression effect on bovine preadipocyte differentiation

The insulin-like growth factor binding-protein 7 (IGFBP7) has binding affinities to IGFs and is able to either positively or negatively regulate the IGFs signaling pathway. It also plays a crucial role in cell growth, differentiation and development in an IGF-independent manner. Herein, we investigated the specific regulation of the gene encoding for IGFBP7during the differentiation process of the adipocyte cells of the Yan Yellow Cattle by interfering with or by overexpressing the IGFBP7 gene. As a result, we found that the mRNA expression levels of IGFBP7 were significantly increased during the formation of progenitor cells. In addition, the expression levels of the lipoprotein lipase (LPL) and transcription factors (PPARγ, C/EBPα) were also significantly increased. IGFBP7 gene overexpression and RNA interfering promoted and inhibited respectively the lipid accumulation and triglyceride production in mature adipocytes, and the expression of the LPL and transcription factors (PPARγ, C/EBPα). The changes in the protein expression levels of IGFBP7 and adipogenic factors were in accord with the changes observed in the mRNA levels. In conclusion, our results indicate that IGFBP7 plays an important regulatory role in the differentiation of preadipocyte cells.

Material-induced Senescence (MIS): Fluidity Induces Senescent Type Cell Death of Lung Cancer Cells via Insulin-Like Growth Factor Binding Protein 5

Objective: We propose here material-induced senescence (MIS) as a new therapeutic concept that limits cancer progression by stable cell cycle arrest. This study examined for the first time the effect of material fluidity on cellular senescence in lung carcinoma using poly(ε-caprolactone-co-D, L-lactide) (P(CL-co-DLLA)) with tunable elasticity and fluidity. Methods: The fluidity was varied by chemically crosslinking the polymer networks: the crosslinked P(CL-co-DLLA) shows solid-like properties with a stiffness of 260 kPa, while the non-crosslinked polymer exists in a quasi-liquid state with loss and storage moduli of 33 kPa and 11 kPa, respectively. Results: We found that cancer cells growing on the non-crosslinked, fluidic substrate undergo a non-apoptotic form of cell death and the cell cycle was accumulated in a G0/G1 phase. Next, we investigated the expression of biomarkers that are associated with cancer pathways. The cancer cells on the fluidic substrate expressed several biomarkers associated with senescence such as insulin-like growth factor binding protein 5 (IGFBP5). This result indicates that when cancer cells sense fluidity in their surroundings, the cells express IGFBP5, which in turn triggers the expression of tumor suppressor protein 53 and initiates cell cycle arrest at the G1 phase followed by cellular senescence. Furthermore, the cancer cells on the fluidic substrate maintained their epithelial phenotype, suggesting that the cancer cells do not undergo epithelial to mesenchymal transition. Conclusion: By considering these results as the fundamental information for MIS, our system could be applied to induce senescence in treatment-resistant cancers such as metastatic cancer or cancer stem cells.

Alterations in the proliferative/apoptotic equilibrium in semen of adolescents with varicocele

PURPOSE

To verify if the presence of varicocele (grades II and III) with and without seminal alterations, using the 5^th centile cutoff values in table A1.1 of the World Health Organization (WHO, 2010) manual, alters the seminal plasma levels of proteins DNASE1 (deoxyribonuclease-1) and IGFBP7 (Insulin-like growth factor-binding protein 7), which are related to apoptosis regulation and cell proliferation, respectively, demonstrating that these proteins are important for correct spermatogenesis.

METHODS

This cross sectional study was performed at the Sao Paulo Federal University Paulo between May 2014 and April 2016. A total of 61 male adolescents were included in this study, of which 20 controls without varicocele (C), 22 with varicocele and normal semen analysis (VNS) and 19 with varicocele and altered semen analysis (VAS). Seminal plasma from each patient was used for Western blotting analysis of individual protein levels. Values of each protein were normalized to a testicular housekeeping protein (PARK7-protein deglycase DJ-1).

RESULTS

Levels of IGFBP7 protein are increased in varicocele. Levels of DNASE1 are progressively decreased in varicocele (lower in varicocele and normal semen analysis, lowest in varicocele and altered semen analysis) when compared to adolescents without varicocele. DNASE1 levels are positively correlated with sperm concentration and morphology (correlation values of 0.400 and 0.404, respectively; p values of 0.001 and 0.001, respectively).

CONCLUSION

In conclusion, in adolescents, seminal plasma levels of IGFBP7, responsible for proliferative activity, are increased in varicocele grades II and III, and DNASE1, responsible for apoptosis regulation, are lower in varicocele, lowest in varicocele and low semen quality. These proteins demonstrate molecular alterations brought upon by varicocele. Moreover, DNASE1 is capable of discriminating a varicocele that causes alterations to semen quality from one that does not. We propose that the initial response of varicocele is to increase proliferative activity which, if followed by regulation of apoptosis, may lead to the ejaculation of a population of sperm that are in accordance with WHO cutoff values but, in the presence of dysregulated apoptosis, leads to lower sperm concentration and morphology.

IGFBP7 promotes hemocyte proliferation in small abalone Haliotis diversicolor, proved by dsRNA and cap mRNA exposure

Insulin-like growth factor binding protein 7 (IGFBP7) binds IGFs with a low affinity, but in contrast, recognizes insulin with a high affinity. Many studies show that IGFBP7 involves several cellular processes of vertebrates and functions as a tumor suppressor gene in different tumors. However, the function of IGFBP7 in invertebrates is unclear. In this research, we studied the function of IGFBP7 in the proliferation of small abalone Haliotis diversicolor hemocytes by exposure to dsRNA or cap mRNA of saIGFBP7. We found that exposure to dsRNA or cap mRNA of saIGFBP7 could significantly affect the mRNA and protein expression of IGFBP7 in cultured small abalone hemocytes (p<0.05). There was a significant increase in hemocyte density and the number of adherent hemocytes after exposure to cap mRNA of saIGFBP7 (p<0.05). Similarly, exposure to dsRNA of saIGFBP7 could significantly decrease the hemocyte density and the number of adherent hemocytes (p<0.05). These findings suggest that IGFBP7 increases hemocyte growth. It is the first time to report the effect of IGFBP7 on the proliferation of marine invertebrate cells.

Angiomodulin, a marker of cancer vasculature, is upregulated by vascular endothelial growth factor and increases vascular permeability as a ligand of integrin αvβ3

Angiomodulin (AGM) is a member of insulin-like growth factor binding protein (IGFBP) superfamily and often called IGFBP-rP1 or IGFBP-7. AGM was originally identified as a tumor-derived cell adhesion factor, which was highly accumulated in blood vessels of human cancer tissues. AGM is also overexpressed in cancer-associated fibroblasts (CAFs) and activates fibroblasts. However, some studies have shown tumor-suppressing activity of AGM. To understand the roles of AGM in cancer progression, we here investigated the expression of AGM in benign and invasive breast cancers and its functions in cancer vasculature. Immunohistochemical analysis showed that AGM was highly expressed in cancer vasculature even in ductal carcinoma in situ (DCIS) as compared to normal vasculature, while its expression in CAFs was more prominent in invasive carcinomas than DCIS. In vitro analyses showed that AGM was strongly induced by vascular endothelial cell growth factor (VEGF) in vascular endothelial cells. Although AGM stimulated neither the growth nor migration of endothelial cells, it supported efficient adhesion of endothelial cells. Integrin αvβ3 was identified as a novel major receptor for AGM in vascular endothelial cells. AGM retracted endothelial cells by inducing actin stress fibers and loosened their VE-cadherin-mediated intercellular junction. Consequently, AGM increased vascular permeability both in vitro and in vivo. Furthermore, AGM and integrin αvβ3 were highly expressed and colocalized in cancer vasculature. These results suggest that AGM cooperates with VEGF to induce the aberrant functions of cancer vasculature as a ligand of integrin αvβ3.

Insulin-like growth factor binding protein 7, a member of insulin-like growth factor signal pathway, involved in immune response of small abalone Haliotis diversicolor

Insulin-like growth factor binding protein 7 (IGFBP7), the only member of the IGFBP superfamily that binds strongly to insulin, may have different functions from other IGFBPs. Unlike other IGFBPs, there is no knowledge available on aquatic invertebrate IGFBP7. In this study, a molluscan IGFBP7 gene, saIGFBP7, was cloned for the first time from the small abalone Haliotis diversicolor. Its full-length cDNA sequence is 1812 bp, with a 720 bp open reading frame encoding a protein of 239 aa. The molecular mass of the deduced protein is approximately 25.37 kDa with an estimated pI of 5.00, and it shares highest 41% identity to IGFBP7 of Amblyomma americanum. Analysis of conserved domains revealed the presence of an IGFBP N-terminal domain (IB), a kazal-type serine proteinase inhibitor domain (KI), and an immunoglobulin-like C2 domain (IgC2) in saIGFBP7. Furthermore, the 12 cysteine residues and the signature amino acid motif 'xCGCCxxC' which are characterized by the amino terminus region of the IGFBP superfamily are all presented in saIGFBP7. Quantitative real-time PCR and western blot were employed to investigate the tissue distribution of saIGFBP7, and its expression under bacterial challenge. The saIGFBP7 mRNA and protein could be detected in all examined tissues, with the highest expression level in hemocytes, higher expression level in gills, and was up-regulated in hemocytes and gills after bacterial injection. In addition, saIGFBP7 mRNA transcripts were observed in a subset of the branchial epithelium and the nucleus of hemocytes using the in situ hybridization method. Interestingly, saIGFBP7 was detected mainly in the goblet-like cell of the branchial epithelium by immunohistochemistry. These results suggested that saIGFBP7 was likely to be involved in a function associated with pathogenic infection and may play an important role in the adult abalone immune system.

Elevated expression of angiomodulin (AGM/IGFBP-rP1) in tumor stroma and its roles in fibroblast activation

Angiomodulin (AGM/IGFBP-rP1), a glycoprotein of about 30 kDa, is overexpressed in tumor vasculature as well as some human cancer cell lines, but it has been suggested to be a tumor suppressor. To elucidate roles of angiomodulin (AGM) in tumor progression, we here examined distribution of AGM in three types of human cancer tissues by immunohistochemistry. The results showed that AGM was overexpressed in the stroma as well as the vasculature surrounding tumor cells in the human cancer tissues. AGM and α-smooth muscle actin (α-SMA) as an activated fibroblast marker were often colocalized in cancer-associated fibroblasts (CAFs). In vitro analysis indicated that transforming growth factor (TGF)-β1 might be an important inducer of AGM in normal human fibroblasts. AGM strongly stimulated the expression of fibronectin and weakly that of α-SMA in normal fibroblasts. AGM significantly stimulated the proliferation and migration of fibroblasts. The AGM-induced expression of fibronectin and α-SMA was blocked by a TGF-β signal inhibitor but neither the stimulation of cell growth nor migration. These results imply that AGM activates normal fibroblasts by TGF-β-dependent and independent mechanisms. These findings also suggest that AGM and TGF-β1 cooperatively or complementarily contribute to the stromal activation and connective tissue formation in human cancer tissues, contributing to tumor progression.

IGFBP7 participates in the reciprocal interaction between acute lymphoblastic leukemia and BM stromal cells and in leukemia resistance to asparaginase

The interaction of acute lymphoblastic leukemia (ALL) blasts with bone marrow (BM) stromal cells (BMSCs) has a positive impact on ALL resistance to chemotherapy. We investigated the modulation of a series of putative asparaginase-resistance/sensitivity genes in B-precursor ALL cells upon coculture with BMSCs. Coculture with stromal cells resulted in increased insulin-like growth factor (IGF)-binding protein 7 (IGFBP7) expression by ALL cells. Assays with IGFBP7 knockdown ALL and stromal cell lines, or with addition of recombinant rIGFBP7 (rIGFBP7) to the culture medium, showed that IGFBP7 acts as a positive regulator of ALL and stromal cells growth, and significantly enhances in-vitro resistance of ALL to asparaginase. In these assays, IGFBP7 function occurred mainly in an insulin- and stromal-dependent manner. ALL cells were found to contribute substantially to extracellular IGFBP7 levels in the conditioned coculture medium. Diagnostic BM plasma from children with ALL had higher levels of IGFBP7 than controls. IGFBP7, in an insulin/IGF-dependent manner, enhanced asparagine synthetase expression and asparagine secretion by BMSCs, thus providing a stromal-dependent mechanism by which IGFBP7 protects ALL cells against asparaginase in this coculture system. Importantly, higher IGFBP7 mRNA levels were associated with lower leukemia-free survival (Cox regression model, P=0.003) in precursor B-cell Ph(-) ALL patients (n=147) treated with a contemporary polychemotherapy protocol.

Insulin-like growth factor binding protein-related protein 1 is expressed in rheumatoid synovium and regulates synovial fibroblast proliferation

Insulin-like growth factor binding protein-related protein 1 (IGFBP-rP1) is a secretory protein that shares a structural similarity with IGFBP. Studies have shown that IGFBP-rP1 synergistically increases fibroblast growth with insulin and stimulates angiogenesis in tumor tissues. In this report, we examined the expression and function of IGFBP-rP1 in rheumatoid arthritis (RA). IGFBP-rP1 expression in synovial tissues was examined by reverse transcription-polymerase chain reaction (RT-PCR), real-time PCR, and immunohistochemical analysis. In vitro, IGFBP-rP1 expression was examined in synovial fibroblasts established from rheumatoid synovium (RASFs) by RT-PCR, Western blot, and immunostaining. The effect of IGFBP-rP1 small interfering RNA (siRNA) on RASF proliferation was assessed by alamarBlue assay. IGFBP-rP1 mRNA was detected by RT-PCR in all synovial tissues from RA and OA patients. In immunohistochemical analysis, IGFBP-rP1 was mainly expressed in synovial cells in the lining layers and endothelial cells in the sublining layers of RA synovium. In vitro, constitutive expression of IGFBP-rP1 in RASFs was detected by RT-PCR, Western blot, and immunostaining. Treatment with IGFBP-rP1 siRNA induced a 26% decrease in RASF growth compared to control siRNA. A similar extent of growth-suppressive effect by IGFBP-rP1 siRNA was also observed when RASF proliferation was induced by TNF-α. Collectively, these data suggest that IGFBP-rP1 may regulate synovial fibroblast proliferation in RA.

Expression of IGFBP7 mRNA in corticotrophs in the anterior pituitary of adrenalectomized rats

The number of corticotrophs increases in the anterior pituitary (AP) gland in adrenalectomized (AdX) rats. In this study, aimed at identifying the growth factor implicated in this proliferation, we analyzed proteins secreted from a cDNA library of the AP of AdX rats, using the signal sequence trap method. A PCR analysis of several cDNAs that coded for insulin-like growth factor binding protein (IGFBP) 5, IGFBP7, and vacuolar H+-ATPase accessory subunit Ac45 revealed an increased and decreased expression level of IGFBP7 mRNA in the AP of AdX rats and AdX rats injected with dexamethasone, respectively. IGFBP7 mRNA was predominately expressed in the corticotrophs of the APs of both sham-operated and AdX rats. The AP of AdX rats contained an increased number of IGFBP7 mRNA-expressing cells and corticotrophs compared with that of sham-operated rats, but the ratio of IGFBP7 mRNA-positive corticotrophs per total number of corticotrophs did not significantly change in either group. Histochemical analysis of labeled proliferating cell nuclear antigen (PCNA) and sex-determining region Y box-2 (SOX2) revealed the presence of several PCNA-positive signals and the absence of SOX2 cells among the corticotrophs, suggesting that IGFBP7 mRNA-expressing corticotrophs are derived from in situ corticotrophs and that they increase in number as corticotrophs increase. The possible roles of IGFBP7 in the corticotrophs are also discussed.

Urine collection and processing for protein biomarker discovery and quantification

BACKGROUND

Urine is a useful source of protein for biomarker discovery and assessment because it is readily available, can be obtained by noninvasive collection methods, and enables monitoring of a wide range of physiologic processes and diseases. Urine aliquots provide enough protein for multiple analyses, combining current protocols with new techniques.

CONCLUSIONS

Standardized collection and processing protocols are now being established and new methods for protein detection and quantification are emerging to complement traditional immunoassays. The current state of urine collection, specimen processing, and storage is reviewed with regard to discovery and quantification of protein biomarkers for cancer.

IGFBP7 is a p53-responsive gene specifically silenced in colorectal cancer with CpG island methylator phenotype

A subset of colorectal cancers (CRCs) show simultaneous methylation of multiple genes; these tumors have the CpG island methylator phenotype (CIMP). CRCs with CIMP show a specific pattern of genetic alterations, including a high frequency of BRAF mutations and a low frequency of p53 mutations. We therefore hypothesized that genes inactivated by DNA methylation are involved in the BRAF- and p53-signaling pathways. Among those, we examined the epigenetic inactivation of insulin-like growth factor-binding protein 7 (IGFBP7) expression in CRCs. We found that in CRC cell lines, the silencing of IGFBP7 expression was correlated with high levels of DNA methylation and low levels of histone H3K4 methylation. Luciferase and chromatin immunoprecipitation assays in unmethylated cells revealed that p53 induces expression of IGFBP7 upon binding to a p53 response element within intron 1 of the gene. Treating methylated CRC cell lines with 5-aza-2'-deoxycytidine restored p53-induced IGFBP7 expression. Levels of IGFBP7 methylation were also significantly higher in primary CRC specimens than in normal colonic tissue (P < 0.001). Methylation of IGFBP7 was correlated with BRAF mutations, an absence of p53 mutations and the presence of CIMP. Thus, epigenetic inactivation of IGFBP7 appears to play a key role in tumorigenesis of CRCs with CIMP by enabling escape from p53-induced senescence.

Glioblastoma-secreted factors induce IGFBP7 and angiogenesis by modulating Smad-2-dependent TGF-beta signaling

Insulin-like growth factor-binding protein 7 (IGFBP7) is a selective biomarker of glioblastoma (GBM) vessels, strongly expressed in tumor endothelial cells and vascular basement membrane. IGFBP7 gene regulation and its potential role in tumor angiogenesis remain unclear. Mechanisms of IGFBP7 induction and its angiogenic capacity were examined in human brain endothelial cells (HBECs) exposed to tumor-like conditions. HBEC treated with GBM cell (U87MG)-conditioned media (-CM) exhibited fourfold upregulation of IGFBP7 mRNA and protein compared to control cells. IGFBP7 gene regulation in HBEC was methylation independent. U87MG-CM analysed by enzyme-linked immunosorbent assay contained approximately 5 pM transforming growth factor (TGF)-beta1, a concentration sufficient to stimulate IGFBP7 in HBEC to similar levels as U87MG-CM. Both pan-TGF-beta-neutralizing antibody (1D11) and the TGF-beta1 receptor (activin receptor-like kinase 5, ALK5) antagonist, SB431542, blocked U87MG-CM-induced IGFBP7 expression in HBEC, indicating that TGF-beta1 is an important tumor-secreted effector capable of IGFBP7 induction in endothelial cells. HBEC exposed to either U87MG-CM or IGFBP7 protein exhibited increased capillary-like tube (CLT) formation in Matrigel. Both TGF-beta1- and U87MG-CM-induced Smad-2 phosphorylation and U87MG-CM-induced CLT formation in HBEC were inhibited by the ALK5 antagonist, SB431542. These data suggest that proangiogenic IGFBP7 may be induced in brain endothelial cells by TGF-betas secreted by GBM, most likely through TGF-beta1/ALK5/Smad-2 pathway.

Epigenetic inactivation implies independent functions for insulin-like growth factor binding protein (IGFBP)-related protein 1 and the related IGFBPL1 in inhibiting breast cancer phenotypes

PURPOSE

To analyze epigenetic regulation of two related genes, insulin-like growth factor binding protein-related protein 1 (IGFBP-rP1) and IGFBPL1, and its significance as a determinant of clinical phenotypes in human breast cancer.

EXPERIMENTAL DESIGN

We have investigated the expression and epigenetic regulation of IGFBP-rP1 and IGFBPL1 in human breast cancer cell lines and primary and metastatic carcinomas.

RESULTS

Expression of IGFBP-rP1 and IGFBPL1 is down-regulated in breast cancer cell lines. Aberrant methylation in the CpG islands of each gene correlates well with loss of expression at the mRNA level. Analysis of methylation in DNA isolated from human primary breast tumors showed that methylation in either gene was associated with a worse overall survival (OS; P=0.008) and disease-free survival (DFS) following surgery (P=0.04) and worse DFS following adjuvant chemotherapy (P=0.01). Methylation of IGFBP-rP1 alone was associated with a trend toward decreased OS (P=0.10) and decreased DFS (P=0.25). Methylation in IGFBPL1 was clearly associated with worse OS (P=0.001) and DFS (P<0.0001). Methylation in either IGFBP-rP1 or IGFBPL1 was significantly associated with nodal disease (P<0.001).

CONCLUSIONS

Expression of IGFBP-rP1 and IGFBPL1 is regulated by aberrant hypermethylation in breast cancer, implying that inactivation of these genes is involved in the pathogenesis of this malignancy. Analysis of methylation of these genes may have utility in prediction of clinical phenotypes, such as nodal disease and response to chemotherapy.

Strong suppression of tumor growth by insulin-like growth factor-binding protein-related protein 1/tumor-derived cell adhesion factor/mac25

Insulin-like growth factor binding protein-related protein 1 (IGFBP-rP1) has been shown to induce cellular senescence or apoptosis of breast and prostate cancer cell lines in vitro. To examine whether IGFBP-rP1 acts as a tumor-suppressive protein in vivo, we established two model systems. Expression of IGFBP-rP1 in the human bladder carcinoma cell line EJ-1 was blocked by RNA interference. Human colon cancer cell line DLD-1, which did not express endogenous IGFBP-rP1, was transfected with an IGFBP-rP1 expression vector. When injected intraperitoneally or subcutaneously into nude mice, the IGFBP-rP1-expressing EJ-1 and DLD-1 cell lines grew poorly, whereas the IGFBP-rP1 non-producers grew rapidly and produced large tumors. In monolayer culture the IGFBP-rP1 producers and non-producers grew similarly in each model, whereas in soft agar culture the former produced far less colonies than the latter. The IGFBP-rP1 producers had IGFBP-rP1 bound to the cell surface, and adhered more efficiently to fibronectin and laminin-5 than the respective non-producers. Expression of IGFBP-rP1 did not affect the efficiency of insulin signaling. These results demonstrate that IGFBP-rP1 strongly suppresses tumor growth by an insulin-independent or insulin-like growth factor-independent mechanism. Cell surface IGFBP-rP1 may reduce the anchorage-independent growth ability, leading to the marked loss of tumorigenicity.

Decreased expression of insulin-like growth factor binding protein 7 in human colorectal carcinoma is related to DNA methylation

PURPOSE

Insulin-like growth factor binding protein 7 (IGFBP-7) is considered a tumor suppressor in various cancers, but its role in colorectal cancer (CRC) is still uncertain. The aims of this study were to analyze the IGFBP-7 expression, and explore the mechanism responsible for the inactivation of IGFBP-7 in CRC.

METHODS

mRNA expression was studied by RT-PCR and Northern blot analysis of cultured cells. Methylation status was analyzed by treatment with 5-aza-2'-deoxycytidine followed by sequencing of PCR products of sodium bisulfite-treated genomic DNA. IGFBP-7 protein expression was evaluated by immunohistochemistry (IHC) on tissue microarrays.

RESULTS

mRNA expression was lost in six out of eight CRC cell lines as compared to normal colon cells. DNA methylation was found in the region of exon 1 and intron 1 of IGFBP-7. In tumor tissue, 107 out of 279 samples showed a negative expression of IGFBP-7 by IHC, which was significantly associated with poor prognosis. The analysis of 37 paired cancerous and normal mucosa samples confirmed the downregulation in the tumors, but revealed variable basal expression levels of IGFBP-7 in normal mucosal samples.

CONCLUSIONS

DNA methylation is a mechanism responsible for IGFBP-7 gene silencing providing a target for therapeutic intervention of this tumor suppressor gene.

Expression analysis of IGFBP-rP10, IGFBP-like and Mig30 in early Xenopus development

To date, five members of the insulin-like growth factor-binding protein (IGFBP) superfamily have been described in Xenopus laevis. Here, we report the isolation of two new IGFBPs: xIGFBP-rP10, and xIGFBP-like. The proteins share the same domain architecture, and together with Mig30, form a subgroup within the IGFBP superfamily. Temporal expression analysis shows that they are expressed differentially during early development. xIGFBP-rP10 is continuously expressed, whereas Mig30 expression peaks during gastrulation. IGFBP-like is expressed from neurulation onward. The three genes have characteristic spatial expression domains, which overlap in some regions. Both xIGFBP-rP10 and Mig30 are expressed on the dorsal side of the embryo during gastrulation. Later, xIGFBP-rP10 is expressed in the notochord, the floor plate, the somites, and the fin. xIGFBP-like expression is seen primarily in the developing central nervous system and overlaps with Mig30 expression at the end of neurulation in the developing somites and in tail bud stages in the eyes.

Neuroendocrine-like differentiation of non-small cell lung carcinoma cells: regulation by cAMP and the interaction of mac25/IGFBP-rP1 and 25.1

The need to develop more effective therapies for lung cancer has led to investigations in understanding the molecular mechanisms of the differentiation process, in particular neuroendocrine (NE) differentiation. Recent studies have demonstrated that NE differentiation in non-small cell lung carcinoma (NSCLC) is not uncommon. Those NSCLCs with NE differentiation are considered a form of in transition NE carcinoma and show a more aggressive clinical course compared with NSCLC without NE differentiation. 25.1, a novel protein interacting with mac25/insulin-like growth factor-binding protein-related protein 1 (mac25/IGFBP-rP1), induced NE-like differentiation when collectively overexpressed in M12 prostate cancer cells. We have examined mac25/IGFBP-rP1 and 25.1 as potential molecular regulators in vitro of the NE-differentiation process in lung cancer. In a panel of SCLC and NSCLC cell lines, mac25/IGFBP-rP1 and 25.1 were expressed at higher levels in SCLC. An increase and sustained activation of adenosine 3',5'-cyclic monophosphate (cAMP) levels induced NE-like differentiation in NSCLC cell lines, and a concomitant increase in the expression of mac25/IGFBP-rP1 and 25.1 was observed during the cAMP-regulated differentiation of NCI-H157 cells, suggesting the involvement of these proteins. Furthermore, the collective overexpression of mac25/IGFBP-rP1 and 25.1 in NSCLC cells induced NE-like differentiation as early as 6 h postinfection. The present data suggest that mac25/IGFBP-rP1 and 25.1 may play a functional role in the NE differentiation of NSCLC cell lines and may provide a novel therapeutic target for treating lung cancers, in particular NSCLC with NE differentiation.

Identification of membrane-bound serine proteinase matriptase as processing enzyme of insulin-like growth factor binding protein-related protein-1 (IGFBP-rP1/angiomodulin/mac25)

Insulin-like growth factor (IGF) binding protein-related protein-1 (IGFBP-rP1) modulates cellular adhesion and growth in an IGF/insulin-dependent or independent manner. It also shows tumor-suppressive activity in vivo. We recently found that a single-chain IGFB-rP1 is proteolytically cleaved to a two-chain form by a trypsin-like, endogenous serine proteinase, changing its biological activities. In this study, we attempted to identify the IGFBP-rP1-processing enzyme. Of nine human cell lines tested, seven cell lines secreted IGFBP-rP1 at high levels, and two of them, ovarian clear cell adenocarcinoma (OVISE) and gastric carcinoma (MKN-45), highly produced the cleaved IGFBP-rP1. Serine proteinase inhibitors effectively blocked the IGFBP-rP1 cleavage in the OVISE cell culture. The conditioned medium of OVISE cells did not cleave purified IGFBP-rP1, but their membrane fraction had an IGFBP-rP1-cleaving activity. The membrane fraction contained an 80-kDa gelatinolytic enzyme, which was identified as the membrane-type serine proteinase matriptase (MT-SP1) by immunoblotting. When the membrane fraction was separated by SDS/PAGE, the IGFBP-rP1-cleaving activity comigrated with matriptase. A soluble form of matriptase purified in an inhibitor-free form efficiently cleaved IGFBP-rP1 at the same site as that found in a naturally cleaved IGFBP-rP1. Furthermore, small interfering RNAs for matriptase efficiently blocked both the matriptase expression and the cleavage of IGBP-rP1 in OVISE cells. These results demonstrate that IGFBP-rP1 is processed to the two-chain form by matriptase on the cell surface.

Insulin-Like Growth Factor (IGF) family and prostate cancer

There is abundant in vitro, animal and epidemiologic evidence to suggest that the Insulin-Like Growth Factor (IGF) family is a multi-component network of molecules which is involved in the regulation of both physiological and pathological growth processes in prostate. The IGF family plays a key role in cellular metabolism, differentiation, proliferation, transformation and apoptosis, during normal development and malignant growth. This family also seem essential in prostate cancer bone metastases, angiogenesis and androgen-independent progression. Therapeutic alternatives in men with progressive prostate cancer after androgen ablation are very limited. More effective therapies are needed for these patients. Pharmacologic interventions targeting the IGF family are being devised. Such strategies include reduction of IGF-I levels (growth hormone-releasing hormone antagonists, somatostatin analogs), reduction of functional IGF-I receptor levels (antisense oligonucleotides, small interfering RNA), inhibition of IGF-IR and its signalling (monoclonal antibodies, small-molecule tyrosine kinase inhibitors) and Insulin-Like Growth Factor Binding Proteins.

Essential roles of IGFBP-3 and IGFBP-rP1 in breast cancer

Insulin and insulin-like growth factors (IGFs) have critical functions in growth regulatory signalling pathways. They are part of a tightly controlled network of ligands, receptors, binding proteins and their proteases. However, the system becomes uncontrolled in neoplasia. The insulin-like growth factor binding protein 3 (IGFBP-3) and the insulin-like growth factor binding protein-related protein 1 (IGFBP-rP1) have unique properties among the sixteen known members of the IGFBP superfamily. IGFBP-3 has very high affinity for IGFs (k(d) approximately 10(-10) M), it transports >75% of serum IGF-I and -II, whereas it's affinity for insulin is very low. On the other hand, IGFBP-rP1 binds insulin with very high affinity (500-fold higher compared to other IGFBPs), but has low affinity for IGF-I and -II proteins (k(d) = 3 x 10(-8) M). In this review, we have examined the roles of IGFBP-3 and IGFBP-rP1 in breast cancer, and discuss the potential impact of these two proteins in mammary carcinoma risk assessment and the development of treatments for breast cancer.

Proteolytic processing of IGFBP-related protein-1 (TAF/angiomodulin/mac25) modulates its biological activity

Insulin-like growth factor (IGF) binding protein-related protein-1 (IGFBP-rP1) was previously identified as tumor-derived adhesion factor (TAF) secreted from human bladder carcinoma cells. It exhibits growth-stimulatory activity in synergy with insulin or IGFs. In the present study, we found that IGFBP-rP1 was proteolytically cleaved to a two-chain form. The cleavage sequence suggested that a trypsin-like serine proteinase may be responsible for the processing. The cleavage of IGFBP-rP1 led to an almost complete loss of both insulin/IGF-1-binding activity and insulin/IGF-1-dependent growth-stimulatory activity. On the other hand, the cell attachment activity of IGFBP-rP1 was markedly increased by the proteolytic processing. Syndecan-1 was thought to be a cell surface receptor for both intact and cleaved IGFBP-rP1 forms. Although the proteolytic cleavage of IGFBP-rP1 decreased its heparin-binding activity, the cleaved form could bind syndecan-1 efficiently. Thus the proteolytic processing of IGFBP-rP1 seems to modulate its insulin/IGF-dependent and -independent biological functions.

A combined approach for gene discovery identifies insulin-like growth factor-binding protein-related protein 1 as a new gene implicated in human endometrial receptivity

In the past, human endometrial receptivity has been investigated by chasing specific molecules throughout the menstrual cycle. Now the genomic approach allows us to investigate the hierarchical contribution of a high number of genes to a specific function. In this study, we analyzed differentially the gene expression pattern of 375 human cytokines, chemokines, and related factors, plus that of their receptors, in endometrial receptivity. To do this, we used a combined approach of human endometrium and cell lines. We have compared the gene expression pattern in receptive vs. prereceptive human endometria and contrasted the results with gene expression in the highly adhesive cell line (to JAR cells and mouse blastocysts) RL95-2 vs. HEC-1A, a cell line with markedly less adhesiveness. IGF-binding protein-related protein 1 (IGFBP-rP1), also known as IGFBP-7/mac 25, was the second most up-regulated gene in both of the investigated models. These results were corroborated by performing RT-PCR on the same RNA samples and validated by quantitative fluorescent RT-PCR and in situ hybridization in endometrium throughout the menstrual cycle. Interestingly, a 35-fold increase in expression during the receptive phase was compared with the prereceptive phase followed by a sharp increase in the late luteal. Further quantitative fluorescent RT-PCR experiments using the epithelial and stromal endometrial fraction throughout the menstrual cycle confirmed that IGFBP-rP1 expression was localized in the epithelial and stromal compartments and up-regulated mainly in the latter. In situ experiments confirmed the endometrial localization and regulation of IGFBP-rP1 mRNA. At the protein level, IGFBP-rP1 was localized by immunohistochemistry at the apical part of the luminal and glandular epithelium, stromal, and endothelial cells. In conclusion, using a genomic approach with a combined experimental design of receptivity in vivo and in vitro, we have discovered the implication of IGFBP-rP1 in endometrial physiology, which seems related to endometrial receptivity.

Human endometrial receptivity: a genomic approach

The endometrium is a specialized tissue, hormonally-regulated, that is non-adhesive for embryos throughout most of the menstrual cycle in humans and other primates. Thus, endometrial receptivity is a self-limited period in which the endometrial epithelium (EE) acquires a functional and transient ovarian steroid-dependent status. The luminal EE acquires the ability to adhere (receptivity) the developing human blastocyst during this period due mainly to the presence of progesterone after appropriate 17beta-oestradiol priming. This status is a key element for embryonic implantation and appears to be closely associated with morphological and biochemical changes of EE cells. This specific time window is thought to be open after 4-5 days and closes after 9-10 days of progesterone production or administration, creating a physiological window of receptivity limited to days 19-24 of the menstrual cycle in humans. The scientific knowledge of the endometrial receptivity process is fundamental for the understanding of the human reproduction, but, so far, none of the proposed biochemical markers for endometrial receptivity have been proved clinically useful. In this work new strategies are presented based on molecular biology technologies that aim to clarify the fragmented information in this field using differential display, quantitative PCR and cDNA microarray analysis of endometrial epithelial-derived cell lines and endometrial samples to investigate the hierarchy at the mRNA level of molecules implicated in the process of endometrial receptivity.

Expression of angiomodulin (tumor-derived adhesion factor/mac25) in invading tumor cells correlates with poor prognosis in human colorectal cancer

Angiomodulin (tumor-derived adhesion factor/mac25/insulin-like growth factor binding protein-7), a cell-adhesive glycoprotein, is secreted by cancer cells and vascular endothelial cells. It may be involved in angiogenesis and modulation of the vascular functions necessary for tumor development. Although angiomodulin is expressed in colon cancer, there is limited information on it concerning cancer progression. In the present immunohistochemical study, we examined expression of angiomodulin in human colorectal cancer and its relationship with prognosis. A group of 89 surgically resected colorectal cancers was investigated immunohistochemically. In 37 cases (41.6%), angiomodulin was expressed in invading cancer cells. Early recurrence within 12 months after surgery was higher in patients with angiomodulin-expressing cancer than in those without (p < 0.05). The Kaplan-Meier life table revealed that patients with angiomodulin-positive tumor cells had a shorter survival time than those with negative cells (p < 0.01). The prognosis of patients with Dukes' C and angiomodulin-positive cells was apparently worse than that of patients with Dukes' D and angiomodulin-negative cells. Multivariate analysis with logistic regression indicated that only angiomodulin expression in cancer cells, lymph node metastasis and age remained significant prognostic variables for survival (p < 0.05). Angiomodulin showed correlations with poor prognosis, indicating that it may be a useful prognostic marker in patients with colorectal cancer.

Characterization of insulin-like growth factor-binding protein-related proteins (IGFBP-rPs) 1, 2, and 3 in human prostate epithelial cells: potential roles for IGFBP-rP1 and 2 in senescence of the prostatic epithelium

Insulin-like growth factor (IGF)-binding protein (IGFBP)-related proteins (IGFBP-rPs) are newly described cysteine-rich proteins that share significant aminoterminal structural similarity with the conventional IGFBPs and are involved in a diversity of biological functions, including growth regulation. IGFBP-rP1 (MAC25/Angiomodulin/prostacyclin-stimulating factor) is a potential tumor-suppressor gene that is differentially expressed in meningiomas, mammary and prostatic cancers, compared with their malignant counterparts. We have previously shown that IGFBP-rP1 is preferentially produced by primary cultures of human prostate epithelial cells (HPECs) and by poorly tumorigenic P69SV40T cells, compared with the cancerous prostatic LNCaP, DU145, PC-3, and M12 cells. We now show that IGFBP-rP1 increases during senescence of HPEC. IGFBP-rP2 (also known as connective tissue growth factor), a downstream effector of transforming growth factor (TGF)-beta and modulator of growth for both fibroblasts and endothelial cells, was detected in most of the normal and malignant prostatic epithelial cells tested, with a marked up-regulation of IGFBP-rP2 during senescence of HPEC. Moreover, IGFBP-rP2 noticeably increased in response to TGF-beta1 and all-trans retinoic acid (atRA) in HPEC and PC-3 cells, and it decreased in response to IGF-I in HPEC. IGFBP-rP3 [nephroblastoma overexpressed (NOV)], the protein product of the NOV protooncogene, was not detected in HPEC but was expressed in the tumorigenic DU145 and PC-3 cells. It was also synthesized by the SV40-T antigen-transformed P69 and malignant M12 cells, where it was down-regulated by atRA. These observations suggest biological roles of IGFBP-rPs in the human prostate. IGFBP-rP1 and IGFBP-rP2 are likely to negatively regulate growth, because they seem to increase during senescence of the prostate epithelium and in response to growth inhibitors (TGF-beta1 and atRA). Although the data collected on IGFBP-rP3 in prostate are modest, its role as a growth stimulator and/or protooncogene is supported by its preferential expression in cancerous cells and its down-regulation by atRA.

Structural requirements of heparan sulfate for the binding to the tumor-derived adhesion factor/angiomodulin that induces cord-like structures to ECV-304 human carcinoma cells

Tumor-derived adhesion factor/angiomodulin (AGM) is accumulated in tumor blood vessels and on the endothelial cell surface (Akaogi, K., Okabe, Y., Sato, J., Nagashima, Y., Yasumitsu, H., Sugahara, K., and Miyazaki, K. (1996) Proc. Natl. Acad. Sci. U. S. A. 93, 8384-8389). In cell culture, it promotes cell adhesion and morphological changes to form cord-like structures of the human bladder carcinoma cell line ECV-304. The cord formation is prevented by heparin, which inhibits the binding of AGM to ECV-304 cells. This observation suggests that AGM interacts with cell surface heparan sulfate (HS) proteoglycans. In this study, HS glycosaminoglycans and core proteins of integral transmembrane proteoglycans, syndecan-1 and -4, were identified by immunocytochemistry on ECV-304 cells, and the structural requirements for the interaction of HS with AGM were characterized. Inhibition experiments with sulfated polysaccharides and chemically modified heparin derivatives indicated that sulfate groups were essential for both AGM-HS binding and cord-like structure formation and that the rank order of the different sulfate groups in terms of their contribution was N-sulfate > 6-O-sulfate > 2-O-sulfate. The minimum size of heparin, a chemical analog of HS, required for the binding to AGM was a dodecasaccharide as determined by competition experiments using size-defined heparin oligosaccharides. Thus, a specific sulfation pattern in the HS of cell surface syndecans of ECV-304 cells is required for AGM binding and the morphological changes.

The insulin-like growth factor-binding protein (IGFBP) superfamily

Over the last decade, the concept of an IGFBP family has been well accepted, based on structural similarities and on functional abilities to bind IGFs with high affinities. The existence of other potential IGFBPs was left open. The discovery of proteins with N-terminal domains bearing striking structural similarities to the N terminus of the IGFBPs, and with reduced, but demonstrable, affinity for IGFs, raised the question of whether these proteins were "new" IGFBPs (22, 23, 217). The N-terminal domain had been uniquely associated with the IGFBPs and has long been considered to be critical for IGF binding. No other function has been confirmed for this domain to date. Thus, the presence of this important IGFBP domain in the N terminus of other proteins must be considered significant. Although these other proteins appear capable of binding IGF, their relatively low affinity and the fact that their major biological actions are likely to not directly involve the IGF peptides suggest that they probably should not be classified within the IGFBP family as provisionally proposed (22, 23). The conservation of this single domain, so critical to high-affinity binding of IGF by the six IGFBPs, in all of the IGFBP-rPs, as well, speaks to its biological importance. Historically, and perhaps, functionally, this has led to the designation of an "IGFBP superfamily". The classification and nomenclature for the IGFBP superfamily, are, of course, arbitrary; what is ultimately relevant is the underlying biology, much of which still remains to be deciphered. The nomenclature for the IGFBP related proteins was derived from a consensus of researchers working in the IGFBP field (52). Obviously, a more general consensus on nomenclature, involving all groups working on each IGFBP-rP, has yet to be reached. Further understanding of the biological functions of each protein should help resolve the nomenclature dilemma. For the present, redesignating these proteins IGFBP-rPs simplifies the multiple names already associated with each IGFBP related protein, and reinforces the concept of a relationship with the IGFBPs. Beyond the N-terminal domain, there is a lack of structural similarity between the IGFBP-rPs and IGFBPs. The C-terminal domains do share similarities to other internal domains found in numerous other proteins. For example, the similarity of the IGFBP C terminus to the thyroglobulin type-I domain shows that the IGFBPs are also structurally related to numerous other proteins carrying the same domain (87). Interestingly, the functions of the different C-terminal domains in members of the IGFBP superfamily include interactions with the cell surface or ECM, suggesting that, even if they share little sequence similarities, the C-terminal domains may be functionally related. The evolutionary conservation of the N-terminal domain and functional studies support the notion that IGFBPs and IGFBP-rPs together form an IGFBP superfamily. A superfamily delineates between closely related (classified as a family) and distantly related proteins. The IGFBP superfamily is therefore composed of distantly related families. The modular nature of the constituents of the IGFBP superfamily, particularly their preservation of an highly conserved N-terminal domain, seems best explained by the process of exon shuffling of an ancestral gene encoding this domain. Over the course of evolution, some members evolved into high-affinity IGF binders and others into low-affinity IGF binders, thereby conferring on the IGFBP superfamily the ability to influence cell growth by both IGF-dependent and IGF-independent means (Fig. 10). A final word, from Stephen Jay Gould (218): "But classifications are not passive ordering devices in a world objectively divided into obvious categories. Taxonomies are human decisions imposed upon nature--theories about the causes of nature's order. The chronicle of historical changes in classification provides our finest insight into conceptual revolutions

Novel aspects of the insulin-like growth factor binding proteins

The insulin-like growth factors (IGFs), IGF binding proteins (IGFBPs), and IGFBP proteases regulate somatic growth and cellular proliferation both in vivo and in vitro. IGFs are potent mitogens whose actions are determined by the availability of free IGFs to interact with IGF receptors. IGFBPs comprise a family of six proteins that bind IGFs with high affinity and specificity and thereby regulate IGF-dependent actions. IGFBPs have also recently emerged as IGF-independent regulators of cell growth. Several IGFBP association proteins have been discovered recently which can affect IGFBP action. Cleavage of IGFBPs by specific proteases modulates levels of free IGFs and IGFBPs and thereby their actions. IGFBP-related proteins (IGFBP-rPs) are an emerging group of proteins which bind IGFs with low affinity and also play important roles in cell growth and differentiation. The IGFBPs appear to have emerging roles in the mechanisms underlying human cancer. The GH-IGF-IGFBP axis is complex and powerful. Future research on its physiology promises exciting insights into cell biology as well as advancements in the treatment of a wide range of disease states including cancer, diabetes, vascular disease, asthma, and growth disorders.

Insulin-like growth factor binding proteins: new proteins, new functions

The insulin-like growth factors (IGFs), IGF binding proteins (IGFBPs), and IGFBP proteases regulate somatic growth and cellular proliferation both in vivo and in vitro. IGFs are potent mitogens whose actions are determined by the availability of free IGFs to interact with IGF receptors. IGFBPs comprise a family of six proteins that bind IGFs with high affinity and specificity and thereby regulate IGF-dependent actions. IGFBPs have recently emerged as IGF-independent regulators of cell growth. Cleavage of IGFBPs by specific proteases modulate levels of free IGFs and IGFBPs and thereby their actions. IGFBP-related proteins (IGFBP-rPs) bind IGFs with low affinity and also play important roles in cell growth and differentiation. The GH-IGF-IGFBP axis is complex and powerful. Future research on its physiology promises exciting insights into cell biology as well as therapies for diseases such as cancer and diabetes mellitus.

Insulin-like growth factor binding proteins: a proposed superfamily

The conventional concept is that the insulin-like growth factor binding proteins (IGFBPs) are cysteine-rich proteins, with conserved N- and C-domains, that are capable of binding insulin-like growth factors (IGFs) with high affinity. This dogma was recently challenged by the discovery of a group of cysteine-rich proteins that share important structural similarities with the IGFBPs, but have demonstrably lower affinity for IGFs. It is therefore proposed that these IGFBP-related proteins (IGFBP-rPs) and the IGFBPs constitute an IGFBP superfamily. We speculate that the IGFBP superfamily is derived from an ancestral gene/protein that was critically involved in the regulation of cell growth and was capable of binding IGF peptides. Over the course of evolution, some members (IGFBPs) evolved into high-affinity IGF binders and others (IGFBP-rPs) into low-affinity IGF binders, thereby conferring on the IGFBP superfamily the ability to influence cell growth by both IGF-dependent and IGF-independent means.

Ex vivo expansion of human pancreatic endocrine cells

Cell transplantation as a therapy for type 1 diabetes is facilitated by ex vivo cell expansion of pancreatic beta-cells without loss of differentiative characteristics. The aim of this study was to determine the optimal conditions for in vitro growth of functional human pancreatic endocrine tissue. We examined the mitogenicity of matrixes from a variety of cell lines; proliferation was greater in cells growing on matrixes from bladder carcinoma cell lines, especially in monolayers grown on matrix from the human cell line HTB-9. After 14-day culture, there was a more than 100-fold proliferative increase, which was augmented to a more than 200-fold when hepatocyte growth factor/scatter factor was added; however, hepatocyte growth factor/scatter factor induced a rapid decrease in insulin content. Without the growth factor, fetal cell monolayers expanded 4-fold with no insulin loss; however, after 12-fold expansion, the insulin levels decreased to 40% of those in unexpanded cells. Adult islet cells expanded 3-fold without insulin loss. After 5-fold expansion, insulin levels decreased by 25% compared to those in free floating islets while retaining a normal response to secretagogues. Together, these results indicate that HTB-9 matrix provides the best stimulatory effect on replication of human endocrine cells, with little loss of in vitro function.

Autocrine growth induced by transferrin-like substance in bladder carcinoma cells

Ample evidence confirms that certain cancer cells have the capacity to produce multiple peptides as growth factors and that expression of their receptor may act in tumour cell paracrine and/or autocrine loop mechanisms, either by extracellular release of the growth factor or by the tumour itself. To study the possibility of an autocrine growth mechanism in bladder carcinoma, we investigated the ability of various bladder carcinoma cell lines to proliferate in serum-free medium. A rat bladder carcinoma cell line, BC47, demonstrated exponential and density-dependent growth in serum-free medium. Furthermore, conditioned medium from BC47 cells induced growth-stimulating activity for BC47 cells themselves. Purification and further characterization of this activity was performed by chromatographic methods, SDS-PAGE and N-terminal amino acid analysis. Finally, we have identified that a transferrin-like 70-kDa protein is found to be the main growth-promoting factor in this conditioned medium. In addition, specific antibodies against transferrin and the transferrin-receptor inhibit the in vitro growth of this cell line. Our data suggest that this transferrin-like factor possibly acts as an autocrine growth factor for cancer cells.

Specific accumulation of tumor-derived adhesion factor in tumor blood vessels and in capillary tube-like structures of cultured vascular endothelial cells

Tumor-derived adhesion factor (TAF) was previously identified as a cell adhesion molecule secreted by human bladder carcinoma cell line EJ-1. To elucidate the physiological function of TAF, we examined its distribution in human normal and tumor tissues. Immunochemical staining with an anti-TAF monoclonal antibody showed that TAF was specifically accumulated in small blood vessels and capillaries within and adjacent to tumor nests, but not in those in normal tissues. Tumor blood vessel-specific staining of TAF was observed in various human cancers, such as esophagus, brain, lung, and stomach cancers. Double immunofluorescent staining showed apparent colocalization of TAF and type IV collagen in the vascular basement membrane. In vitro experiments demonstrated that TAF preferentially bound to type IV collagen among various extracellular matrix components tested. In cell culture experiments, TAF promoted adhesion of human umbilical vein endothelial cells to type IV collagen substrate and induced their morphological change. Furthermore, when the endothelial cells were induced to form capillary tube-like structures by type I collagen, TAF and type IV collagen were exclusively detected on the tubular structures. The capillary tube formation in vitro was prevented by heparin, which inhibited the binding of TAF to the endothelial cells. These results strongly suggest that TAF contributes to the organization of new capillary vessels in tumor tissues by modulating the interaction of endothelial cells with type IV collagen.