Over-expression of insulin-like growth factor binding protein-related protein-1(IGFBP-rP1/mac25) in the M12 prostate cancer cell line alters tumor growth by a delay in G1 and cyclin A associated apoptosis

Vinclozolin-induced mouse penile malformation and "small testis" via miR132, miR195a together with the Hippo signaling pathway

Vinclozolin (VCZ) is a fungicide with antiandrogen activity. Exposure to VCZ in maternal uterus may cause uterine, ovarian and testicular damage, hypospadias and prostate abnormality in the offspring. Hippo pathway, which is highly conservative and may be activated by miR132 and miR195a, can control organ size and tissue regeneration, and participate in injury and deformity. In the present study, VCZ was found to have caused penile malformation in the male offspring and also induced "small testis" when it was administered to the pregnant mice orally at a dose of 400 mg kg^-1 day^-1 on Days 12-18 of gestation. At 1, 3 and 7 weeks of age, VCZ could increase miR132, Mst1, Sav1, phosphorylated Yes-associated protein (pYap) and pLats, and decrease Yap in offspring penises and testes. Besides, it could also raise miR195a both in the testes of 1, 7-week and in the penises of all the three ages. In addition, we found the levels of some cyclin (Ccn) genes elevated in the testes, the expression of the androgen receptor (Ar) gene dereased and Jnks changed in the penises of offspring aged 1, 3 and 7 weeks. The results suggest that that gestational VCZ exposure could not only increase miR132 and miR195a in penises and testes of the offspring, but also activate Hippo pathway and down-regulate Ar. These may directly inhibit cell proliferation, accelerate cell death by up-regulating the expression of some Ccns, and ultimately lead to penile and testicular damage and malformations in the offspring.

Insulin Growth Factor Binding Protein 7 (IGFBP7)-Related Cancer and IGFBP3 and IGFBP7 Crosstalk

The insulin/insulin-like growth factors (IGFs) have crucial tasks in the growth, differentiation, and proliferation of healthy and pernicious cells. They are involved in coordinated complexes, including receptors, ligands, binding proteins, and proteases. However, the systems can become dysregulated in tumorigenesis. Insulin-like growth factor-binding protein 7 (IGFBP7) is a protein belonging to the IGFBP superfamily (also termed GFBP-related proteins). Numerous studies have provided evidence that IGFBP3 and IGFBP7 are involved in a variety of cancers, including hepatocellular carcinoma (HCC), breast cancer, gastroesophageal cancer, colon cancer, prostate cancer, among many others. Still, very few suggest an interaction between these two molecules. In studying several cancer types in our laboratories, we found that both proteins share some crucial signaling pathways. The objective of this review is to present a comprehensive overview of the relationship between IGFBP7 and cancer, as well as highlighting IGFBP3 crosstalk with IGFBP7 reported in recent studies.

IGFBP7 Induces Differentiation and Loss of Survival of Human Acute Myeloid Leukemia Stem Cells without Affecting Normal Hematopoiesis

Leukemic stem cells (LSCs) are thought to be the major cause of the recurrence of acute myeloid leukemia (AML) due to their potential for self-renewal. To identify therapeutic strategies targeting LSCs, while sparing healthy hematopoietic stem cells (HSCs), we performed gene expression profiling of LSCs, HSCs, and leukemic progenitors all residing within the same AML bone marrow and identified insulin-like growth factor-binding protein 7 (IGFBP7) as differentially expressed. Low IGFBP7 is a feature of LSCs and is associated with reduced chemotherapy sensitivity. Enhancing IGFBP7 by overexpression or addition of recombinant human IGFBP7 (rhIGFBP7) resulted in differentiation, inhibition of cell survival, and increased chemotherapy sensitivity of primary AML cells. Adding rhIGFBP7 reduced leukemic stem and/or progenitor survival and reversed a stem-like gene signature, but it had no influence on normal hematopoietic stem cell survival. Our data suggest a potential clinical utility of the addition of rhIGFBP7 to current chemotherapy regimens to decrease AML relapse rates.

Dual inhibition of topoisomerases I and IIα by ruthenium(II) complexes containing asymmetric tridentate ligands

Five novel ruthenium(II) complexes, [Ru(dtzp)(dppt)](2+) (1), [Ru(dtzp)(pti)](2+) (2), [Ru(dtzp)(ptn)](2+) (3), [Ru(dtzp)(pta)](2+) (4) and [Ru(dtzp)(ptp)](2+) (5) (where dtzp = 2,6-di(thiazol-2-yl)pyridine, dppt = 3-(1,10-phenanthroline-2-yl)-5,6-diphenyl-as-triazine), pti = 3-(1,10-phenanthroline-2-yl)-as-triazino-[5,6-f]isatin, ptn = 3-(1,10-phenanthroline-2-yl)-as-triazino[5,6-f]naphthalene, pta = 3-(1,10-phenanthroline-2-yl)-as-triazino[5,6-f]acenaphthylene, and ptp = 3-(1,10-phenanthroline-2-yl)-as-triazino[5,6-f]-phenanthrene), were synthesised and characterised. The structures of complexes 3-5 were determined by X-ray diffraction. The DNA binding behaviours of the complexes were studied by spectroscopic and viscosity measurements. The results suggested that the Ru(II) complexes, except for complex 1, bind to DNA in an intercalative mode. Topoisomerase inhibition and DNA strand passage assay confirmed that Ru(II) complexes 3, 4, and 5 acted as efficient dual inhibitors of topoisomerases I and IIα. In vitro cytotoxicity assays indicated that these complexes exhibited anticancer activity against various cancer cell lines. Ruthenium(ii) complexes were confirmed to preferentially accumulate in the nucleus of cancer cells and induced DNA damage. Flow cytometric analysis and AO/EB staining assays indicated that these complexes induced cell apoptosis. With the loss of the mitochondrial membrane potential, the Ru(ii) complexes induce apoptosis via the mitochondrial pathway.

Insulin-like growth factor system in cancer: novel targeted therapies

Insulin-like growth factors (IGFs) are essential for growth and survival that suppress apoptosis and promote cell cycle progression, angiogenesis, and metastatic activities in various cancers. The IGFs actions are mediated through the IGF-1 receptor that is involved in cell transformation induced by tumour. These effects depend on the bioavailability of IGFs, which is regulated by IGF binding proteins (IGFBPs). We describe here the role of the IGF system in cancer, proposing new strategies targeting this system. We have attempted to expand the general viewpoint on IGF-1R, its inhibitors, potential limitations of IGF-1R, antibodies and tyrosine kinase inhibitors, and IGFBP actions. This review discusses the emerging view that blocking IGF via IGFBP is a better option than blocking IGF receptors. This can lead to the development of novel cancer therapies.

Prostate cancer xenografts engineered from 3D precision-porous poly(2-hydroxyethyl methacrylate) hydrogels as models for tumorigenesis and dormancy escape

Synthetic biomaterial scaffolds show promise for in vitro and in vivo 3D cancer models. Tumors engineered in biomaterial scaffolds have shown evidence of being more physiologically relevant than some traditional preclinical model systems, and synthetic biomaterials provide the added benefit of defined and consistent microenvironmental control. Here, we examine sphere-templated poly(2-hydroxyethyl methacrylate) (pHEMA) scaffolds as the basis for engineering xenografts from multiple human prostate cancer cell lines. pHEMA scaffolds seeded and pre-cultured with tumorigenic M12 cells prior to implantation generated tumors in athymic nude mice, demonstrating the ability of the scaffolds to be used as a synthetic vehicle for xenograft generation. pHEMA scaffolds seeded with LNCaP C4-2 cells, which require Matrigel or stromal cell support for tumor formation, were poorly tumorigenic up to 12 weeks after implantation even when Matrigel was infused into the scaffold, demonstrating a lack of necessary pro-tumorigenic signaling within the scaffolds. Finally, M12mac25 cells, which are ordinarily rendered non-tumorigenic through the expression of the tumor suppressor insulin-like growth factor binding protein 7 (IGFBP7), displayed a tumorigenic response when implanted within porous pHEMA scaffolds. These M12mac25 tumors showed significant macrophage infiltration within the scaffolds driven by the foreign body response to the materials. These findings show the potential for this biomaterials-based model system to be used in the study of prostate cancer tumorigenesis and dormancy escape.

Decreased expression of IGFBP7 was a poor prognosis predictor for gastric cancer patients

Increasing evidence indicated that insulin-like growth factor binding protein 7 (IGFBP7) was regarded as a potential tumor suppressor in various human cancers, but its role in gastric cancer is still largely unknown. In the present study, we performed a retrospective study which includes 247 gastric cancer patients. Among them, the IGFBP7 expression was detected by qRT-PCR in 138 cases of gastric cancer and adjacent non-tumor tissues and was further correlated with the expression of p53, Ki-67, and the clinicopathologic features. The results indicated that both IGFBP7 mRNA and protein in gastric cancer tissues were significantly lower than those in the adjacent non-tumor tissues. Additionally, the expression of IGFBP7 was correlated with the depth of invasion, lymph node metastasis, and TNM stage. Interestingly, the expression of IGFBP7 was negatively associated with Ki-67 (r = -0.227, P < 0.001) but positively associated with p53 (r = 0.140, P = 0.028). Univariate analysis showed that low expression of IGFBP7 was associated with poor prognosis (P < 0.001), and multivariate analysis showed that IGFBP7 (HR = 1.87; 95 % CI 1.65-2.17), distant metastasis (HR = 2.68; 95 % CI 1.58-4.56), and tumor size (HR = 1.45; 95 % CI 0.90-2.32) were independent prognostic factors for gastric cancer patients. These results demonstrated that IGFBP7 was downregulated in gastric cancer, and its low expression was potentially correlated with increased cancer cell proliferation and could be used to predicate poor prognosis in these patients.

Insulin-like growth factor binding protein-related protein 1 and cancer

Insulin-like growth factor binding protein-related protein 1 (IGFBP-rP1) belongs to the IGFBP family whose members have a conserved structural homology. It has a low affinity for IGFs and a high affinity for insulin, suggesting that IGFBP-rP1 may have a biological function distinct from other members of the family. IGFBP-rP1 is ubiquitously expressed in normal human tissues and has diverse biological functions, regulating cell proliferation, apoptosis and senescence; it may also have a key role in vascular biology. Increasing evidence suggests that IGFBP-rP1 acts as a tumor suppressor. It elicits its biological effects by both insulin/IGF-dependent and -independent mechanisms. This paper provides a brief overview of the structure and regulation of IGFBP-rP1 and its various biological functions in cancer, as well as the underlying molecular mechanisms.

IGF-1R inhibition enhances radiosensitivity and delays double-strand break repair by both non-homologous end-joining and homologous recombination

Inhibition of type 1 insulin-like growth factor receptor (IGF-1R) enhances tumor cell sensitivity to ionizing radiation. It is not clear how this effect is mediated, nor whether this approach can be applied effectively in the clinic. We previously showed that IGF-1R depletion delays repair of radiation-induced DNA double-strand breaks (DSBs), unlikely to be explained entirely by reduction in homologous recombination (HR) repair. The current study tested the hypothesis that IGF-1R inhibition induces a repair defect that involves non-homologous end joining (NHEJ). IGF-1R inhibitor AZ12253801 blocked cell survival and radiosensitized IGF-1R-overexpressing murine fibroblasts but not isogenic IGF-1R-null cells, supporting specificity for IGF-1R. IGF-1R inhibition enhanced radiosensitivity in DU145, PC3 and 22Rv1 prostate cancer cells, comparable to effects of Ataxia Telangiectasia Mutated inhibition. AZ12253801-treated DU145 cells showed delayed resolution of γH2AX foci, apparent within 1 h of irradiation and persisting for 24 h. In contrast, IGF-1R inhibition did not influence radiosensitivity or γH2AX focus resolution in LNCaP-LN3 cells, suggesting that radiosensitization tracks with the ability of IGF-1R to influence DSB repair. To differentiate effects on repair from growth and cell-survival responses, we tested AZ12253801 in DU145 cells at sub-SF50 concentrations that had no early (⩽48 h) effects on cell cycle distribution or apoptosis induction. Irradiated cultures contained abnormal mitoses, and after 5 days IGF-1R-inhibited cells showed enhanced radiation-induced polyploidy and nuclear fragmentation, consistent with the consequences of entry into mitosis with incompletely repaired DNA. AZ12253801 radiosensitized DNA-dependent protein kinase (DNA-PK)-proficient but not DNA-PK-deficient glioblastoma cells, and did not radiosensitize DNA-PK-inhibited DU145 cells, suggesting that in the context of DSB repair, IGF-1R functions in the same pathway as DNA-PK. Finally, IGF-1R inhibition attenuated repair by both NHEJ and HR in HEK293 reporter assays. These data indicate that IGF-1R influences DSB repair by both major DSB repair pathways, findings that may inform clinical application of this approach.

Identification of IGFBP-7 by urinary proteomics as a novel prognostic marker in early acute kidney injury

Early diagnosis of acute kidney injury (AKI) and accurate prognostic stratification is a prerequisite for optimal medical management. To identify novel prognostic markers of AKI, urine was collected on the first day of AKI in critically ill patients. Twelve patients with early recovery and 12 matching patients with late/non-recovery were selected and their proteome analyzed by gel electrophoresis and mass spectrometry. We identified eight prognostic candidates including α-1 microglobulin, α-1 antitrypsin, apolipoprotein D, calreticulin, cathepsin D, CD59, insulin-like growth factor-binding protein 7 (IGFBP-7), and neutrophil gelatinase-associated lipocalin (NGAL). Subsequent quantification by ELISA showed that IGFBP-7 was the most potent predictor of renal recovery. IGFBP-7 and NGAL were then chosen for further analyses in an independent verification group of 28 patients with and 12 control patients without AKI. IGFBP-7 and NGAL discriminated between early and late/non-recovery patients and patients with and without AKI. Significant upregulation of the urinary markers predicted mortality (IGFBP-7: AUC 0.68; NGAL: AUC 0.81), recovery (IGFBP-7: AUC 0.74; NGAL: AUC 0.70), and severity of AKI (IGFBP-7: AUC 0.77; NGAL: AUC 0.69), and were associated with the duration of AKI. IGFBP-7 was a more accurate predictor of renal outcome than NGAL. Thus, IGFBP-7 is a novel prognostic urinary marker that warrants further investigation.

IGFBP7's susceptibility to proteolysis is altered by A-to-I RNA editing of its transcript

The selective deamination of adenosines (A) to inosines (I) in messenger RNAs (mRNAs) can alter the encoded protein's amino acid sequence, with often critical consequences on protein stability, localization, and/or function. Insulin-like growth factor-binding protein 7 (IGFBP7) supports cell-adhesion and stimulates fibroblast proliferation with IGF and insulin. It exists in both proteolytically processed and unprocessed forms with altered cell-extracellular matrix interactions. Here we show that editing of IGFBP7 transcripts impacts the protein's susceptibility to proteolytic cleavage, thus providing a means for a cell to modulate its functionality through A-to-I RNA editing.

Low expression of IGFBP7 is associated with poor outcome of pancreatic ductal adenocarcinoma

BACKGROUND

Insulin-like growth factor binding protein 7(IGFBP7) has been implicated as a potential tumor suppressor in various human cancers, although the role of IGFBP7 in pancreatic ductal adenocarcinoma (PDAC) is still unknown. We investigated the expression pattern and clinical significance of IGFBP7 in human PDAC.

METHODS

IGFBP7 expression was evaluated by immunohistochemistry in 190 patients with PDAC who underwent surgical tumor resection. Expression of IGFBP7 was correlated with that of p53 and Ki-67, clinicopathologic features. We also evaluated overall survival (OS) according to expression of IGFBP7 by Kaplan-Meier and Cox regression analyses.

RESULTS

IGFBP7 expression was significantly downregulated in pancreatic cancer tissues compared with adjacent normal pancreas (P < 0.001) and was inversely associated with Ki-67 expression (r = -0.284, P < 0.001). No significant relationships were found for clinicopathologic features, such as diameter of tumor, node status, grade, and stage. Importantly, low expression of IGFBP7 was associated with poor OS, and this was also significant in multivariate Cox regression analysis (hazard ratio [HR], 1.38; 95 % confidence interval [95 % CI], 1.00-1.91; P = 0.05).

CONCLUSIONS

We demonstrate for the first time that IGFBP7 is downregulated in pancreatic cancer, and low expression of IGFBP7 is correlated with increased proliferation and poor postoperative survival. IGFBP7 may be a tumor suppressor in PDAC.

IGFBP7 reduces breast tumor growth by induction of senescence and apoptosis pathways

Insulin-like growth factor binding protein 7 (IGFBP7) has been shown to be a tumor suppressor in a variety of cancers. We previously have shown that IGFBP7 expression is inversely correlated with disease progression and poor outcome in breast cancer. Overexpression of IGFBP7 in MDA-MB-468, a triple-negative breast cancer (TNBC) cell line, resulted in inhibition of growth and migration. Xenografted tumors bearing ectopic IGFBP7 expression were significantly growth-impaired compared to IGFBP7-negative controls, which suggested that IGFBP7 treatment could inhibit breast cancer cell growth. To confirm this notion, 14 human patient primary breast tumors were analyzed by qRTPCR for IGFBP7 expression. The TNBC tumors expressed the lowest levels of IGFBP7 expression, which also correlated with higher tumorigenicity in mice. Furthermore, when breast cancer cell lines were treated with IGFBP7, only the TNBC cell lines were growth inhibited. Treatment of NOD/SCID mice harboring xenografts of TNBC cells with IGFBP7 systemically every 3-4 days inhibited tumorigenesis, with associated anti-angiogenic effects, together with increased apoptosis. Upon examining the mechanism of IGFBP7-mediated growth inhibition in TNBC cells, we found that cells not only were arrested in G1 phase of the cell cycle but also underwent senescence as a result of treatment with IGFBP7. Interestingly, IGFBP7 treatment was also associated with strong activation of the stress-associated p38 MAPK pathway, together with upregulation of p53 and the cyclin-dependent protein kinase (CDK) inhibitor, p21(cip1). Prolonged treatment of cells with IGFBP7 resulted in increased cell death, marked by an increase in apoptotic cells and associated cleaved PARP. This is the first study showing that exogenous IGFBP7 inhibits TNBC cell growth both in vitro and in vivo. Taken together, these results suggest IGFBP7 treatment might have therapeutic potential for TNBC.

Plasma and tissue insulin-like growth factor-I receptor (IGF-IR) as a prognostic marker for prostate cancer and anti-IGF-IR agents as novel therapeutic strategy for refractory cases: a review

Cancer database analysis indicates that prostate cancer is one of the most seen cancers in men meanwhile composing the leading cause of morbidity and mortality among developed countries. Current available therapies are surgery, radiotherapy and androgene ablation for prostate carcinoma. The response rate is as high nearly 90% however, most of these recur or become refractory and androgene independent (AI). Therefore recent studies intensified on molecular factors playing role on development of prostate carcinoma and novel treatment strategies targetting these factors and their receptors. Insulin-like growth factor-I (IGF-I) and its primary receptor insulin-like growth factor receptor-I (IGF-IR) are among these factors. Biologic functions and role in malign progression are primarily achieved via IGF-IR which is a type 2 tyrosine kinase receptor. IGF-IR plays an important role in mitogenesis, angiogenesis, transformation, apoptosis and cell motility. It also generates intensive proliferative signals leading to carcinogenesis in prostate tissue. So IGF-IR and its associated signalling system have provoked considerable interest over recent years as a novel therapeutic target in cancer. In this paper it is aimed to sum up the lately published literature searching the relation of IGF-IR and prostate cancer in terms of incidence, pathologic features, and prognosis. This is followed by a discussion of the different possible targets within the IGF-1R system, and drugs developed to interact at each target. A systems-based approach is then used to review the in vitro and in vivo data in the published literature of the following compounds targeting IGF-1R components using specific examples: growth hormone releasing hormone antagonists (e.g. JV-1-38), growth hormone receptor antagonists (e.g. pegvisomant), IGF-1R antibodies (e.g. CP-751,871, AVE1642/EM164, IMC-A12, SCH-717454, BIIB022, AMG 479, MK-0646/h7C10), and IGF-1R tyrosine kinase inhibitors (e.g. BMS-536942, BMS-554417, NVP-AEW541, NVP-ADW742, AG1024, potent quinolinyl-derived imidazo (1,5-a)pyrazine PQIP, picropodophyllin PPP, nordihydroguaiaretic acid Insm-18/NDGA). And the other end point is to yield an overview on the recent progress about usage of this receptor as a novel anticancer agent of targeted therapies in treatment of prostate carcinoma.

Insulin-like growth factor-binding protein-7 functions as a potential tumor suppressor in hepatocellular carcinoma

PURPOSE

Hepatocellular carcinoma (HCC) is a highly virulent malignancy with no effective treatment, thus requiring innovative and effective targeted therapies. The oncogene astrocyte-elevated gene-1 (AEG-1) plays a seminal role in hepatocarcinogenesis and profoundly downregulates insulin-like growth factor-binding protein-7 (IGFBP7). The present study focuses on analyzing potential tumor suppressor functions of IGFBP7 in HCC and the relevance of IGFBP7 downregulation in mediating AEG-1 function.

EXPERIMENTAL DESIGN

IGFBP7 expression was detected by immunohistochemistry in HCC tissue microarray and real-time PCR and ELISA in human HCC cell lines. Dual FISH was done to detect LOH at IGFBP7 locus. Stable IGFBP7-overexpressing clones were established in the background of AEG-1-overexpressing human HCC cells and were analyzed for in vitro proliferation and senescence and in vivo tumorigenesis and angiogenesis.

RESULTS

IGFBP7 expression is significantly downregulated in human HCC samples and cell lines compared with normal liver and hepatocytes, respectively, and inversely correlates with the stages and grades of HCC. Genomic deletion of IGFBP7 was identified in 26% of patients with HCC. Forced overexpression of IGFBP7 in AEG-1-overexpressing HCC cells inhibited in vitro growth and induced senescence, and profoundly suppressed in vivo growth in nude mice that might be an end result of inhibition of angiogenesis by IGFBP7.

CONCLUSION

The present findings provide evidence that IGFBP7 functions as a novel putative tumor suppressor for HCC and establish the corollary that IGFBP7 downregulation can effectively modify AEG-1 function. Accordingly, targeted overexpression of IGFBP7 might be a potential novel therapy for HCC.

Chiral ruthenium(II) anthraquinone complexes as dual inhibitors of topoisomerases I and II

DNA topoisomerases (I and II) have been one of the excellent targets in anticancer drug development. Here two chiral ruthenium(II) anthraquinone complexes, Δ- and Λ-[Ru(bpy)(2)(ipad)](2+), where bpy is 2,2'-bipyridine and ipad is 2-(anthracene-9,10-dione-2-yl)imidazo[4,5-f][1,10]phenanthroline, were synthesized and characterized. As expected, both of the Ru(II) complexes intercalate into DNA base pairs and possess an obviously greater affinity with DNA. Topoisomerase inhibition and DNA strand passage assay confirmed that the two complexes are efficient dual inhibitors of topoisomerases I and II by interference with the DNA religation. In MTT cytotoxicity studies, two Ru(II) complexes exhibited antitumor activity against HeLa, MCF-7, HepG2 and BEL-7402 tumor cell lines. Flow cytometry analysis shows an increase in the percentage of cells with apoptotic morphological features in the sub-G1 phase for Ru(II) complexes. Nuclear chromatin cleavage has also been observed from AO/EB staining assay and alkaline single-cell gel electrophoresis (comet assay). The results demonstrated that Δ- and Λ-[Ru(bpy)(2)(ipad)](2+) act as dual inhibitors of topoisomerases I and II, and cause DNA damage that can lead to cell cycle arrest and/or cell death by apoptosis.

Expression of IGFBP7 in acute leukemia is regulated by DNA methylation

The important role of insulin-like growth factor binding protein 7 (IGFBP7) as a tumor suppressor in solid tumors has been revealed in several studies. Interestingly, in a recent study IGFBP7 was also shown to be aberrantly expressed in acute leukemia. Moreover, in acute T-lymphoblastic leukemia (T-ALL), high IGFBP7 expression predicts primary therapy resistance. In order to elucidate the mechanisms underlying aberrant IGFBP7 expression, we used pyrosequencing technology to investigate the DNA methylation of IGFBP7 in 109 T-ALL patient samples. Aberrant methylation was shown and hypomethylation was associated with an early immunophenotype and co-expression of the stem cell markers CD117 (P < 0.001) and CD34 (P < 0.001). In concordance, gene expression profiles of 86 T-ALL patients revealed upregulation of stem cell markers (CD34 and CD133) as well as genes associated with poor outcome and pathogenesis of leukemia (MN1, BAALC, FLT3) in the high IGFBP7 expression group. In conclusion, aberrant IGFBP7 expression is regulated by DNA methylation in acute leukemia. Hypomethylation of the gene is likely to characterize an immature and a more malignant subtype of the disease.

IGFBP-rP1, a potential molecule associated with colon cancer differentiation

BACKGROUND

In our previous studies, we have demonstrated that insulin-like growth factor binding protein-related protein1 (IGFBP-rP1) played its potential tumor suppressor role in colon cancer cells through apoptosis and senescence induction. In this study, we will further uncover the role of IGFBP-rP1 in colon cancer differentiation and a possible mechanism by revealing responsible genes.

RESULTS

In normal colon epithelium, immunohistochemistry staining detected a gradient IGFBP-rP1 expression along the axis of the crypt. IGFBP-rP1 strongly expressed in the differentiated cells at the surface of the colon epithelium, while weakly expressed at the crypt base. In colon cancer tissues, the expression of IGFBP-rP1 correlated positively with the differentiation status. IGFBP-rP1 strongly expressed in low grade colorectal carcinoma and weakly expressed in high grade colorectal carcinoma. In vitro, transfection of PcDNA3.1(IGFBP-rP1) into RKO, SW620 and CW2 cells induced a more pronounced anterior-posterior polarity morphology, accompanied by upregulation with alkaline phosphatase (AKP) activity. Upregulation of carcino-embryonic antigen (CEA) was also observed in SW620 and CW2 transfectants. The addition of IGFBP-rP1 protein into the medium could mimic most but not all effects of IGFBP-rP1 cDNA transfection. Seventy-eight reproducibly differentially expressed genes were detected in PcDNA3.1(IGFBP-rP1)-RKO transfectants, using Affymetrix 133 plus 2.0 expression chip platform. Directed Acyclic Graph (DAG) of the enriched GO categories demonstrated that differential expression of the enzyme regulator activity genes together with cytoskeleton and actin binding genes were significant. IGFBP-rP1 could upreguate Transgelin (TAGLN), downregulate SRY (sex determining region Y)-box 9(campomelic dysplasia, autosomal sex-reversal) (SOX9), insulin receptor substrate 1(IRS1), cyclin-dependent kinase inhibitor 2B (p15, inhibits CDK4) (CDKN2B), amphiregulin(schwannoma-derived growth factor) (AREG) and immediate early response 5-like(IER5L) in RKO, SW620 and CW2 colon cancer cells, verified by Real time Reverse Transcription Polymerase Chain Reaction (rtRT-PCR). During sodium butyrate-induced Caco2 cell differentiation, IGFBP-rP1 was upregulated and the expression showed significant correlation with the AKP activity. The downregulation of IRS1 and SOX9 were also induced by sodium butyrate.

CONCLUSION

IGFBP-rP1 was a potential key molecule associated with colon cancer differentiation. Downregulation of IRS1 and SOX9 may the possible key downstream genes involved in the process.

Therapy-induced senescence in cancer

Cellular senescence is a response to nonlethal stress that results in persistent cytostasis with a distinct morphological and biochemical phenotype. The senescence phenotype, detected in tumors through the expression of mRNA and protein markers, can be generated in cancer cells lacking functional p53 and retinoblastoma protein. Current research suggests that therapy-induced senescence (TIS) represents a novel functional target that may improve cancer therapy. TIS can be induced in immortal and transformed cancer cells by selected anticancer compounds or radiation, and accumulating data indicate that TIS may produce reduced toxicity-related side effects and increased tumor-specific immune activity. This review examines the current status of TIS-regulated mechanisms, agents, and senescence biomarkers with the goal of encouraging further development of this approach to cancer therapy. Remaining hurdles include the lack of efficient senescence-inducing agents and incomplete biological data on tumor response. The identification of additional compounds and other targeted approaches to senescence induction will further the development of TIS in the clinical treatment of cancer.

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.

Proteomic analysis identifies insulin-like growth factor-binding protein-related protein-1 as a podocyte product

The podocyte secretory proteome may influence the phenotype of adjacent podocytes, endothelial cells, parietal epithelial cells, and tubular epithelial cells but has not been systematically characterized. We have initiated studies to characterize this proteome, with the goal of further understanding the podocyte cell biology. We cultured differentiated conditionally immortalized human podocytes and subjected the proteins in conditioned medium to mass spectrometry. At a false discovery rate of <3%, we identified 111 candidates from conditioned medium, including 44 proteins that have signal peptides or are described as secreted proteins in the UniProt database. As validation, we confirmed that one of these proteins, insulin-like growth factor-binding protein-related protein-1 (IGFBP-rP1), was expressed in mRNA and protein of cultured podocytes. In addition, transforming growth factor-β1 stimulation increased IGFBP-rP1 in conditioned medium. We analyzed IGFBP-rP1 glomerular expression in a mouse model of human immunodeficiency virus-associated nephropathy. IGFBP-rP1 was absent from podocytes of normal mice and was expressed in podocytes and pseudocrescents of transgenic mice, where it was coexpressed with desmin, a podocyte injury marker. We conclude that IGFBP-rP1 may be a product of injured podocytes. Further analysis of the podocyte secretory proteome may identify biomarkers of podocyte injury.

HSP60, a protein downregulated by IGFBP7 in colorectal carcinoma

Background

In our previous study, it was well defined that IGFBP7 was an important tumor suppressor gene in colorectal cancer (CRC). We aimed to uncover the downstream molecules responsible for IGFBP7's behaviour in this study.

Methods

Differentially expressed protein profiles between PcDNA3.1(IGFBP7)-transfected RKO cells and the empty vector transfected controls were generated by two-dimensional gel electrophoresis (2-DE) and mass spectrometry (MS) identification. The selected differentially expressed protein induced by IGFBP7 was confirmed by western blot and ELISA. The biological behaviour of the protein was explored by cell growth assay and colony formation assay.

Results

Six unique proteins were found differentially expressed in PcDNA3.1(IGFBP7)-transfected RKO cells, including albumin (ALB), 60 kDa heat shock protein(HSP60), Actin cytoplasmic 1 or 2, pyruvate kinase muscle 2(PKM2), beta subunit of phenylalanyl-tRNA synthetase(FARSB) and hypothetical protein. The downregulation of HSP60 by IGFBP7 was confirmed by western blot and ELISA. Recombinant human HSP60 protein could increase the proliferation rate and the colony formation ability of PcDNA3.1(IGFBP7)-RKO cells.

Conclusion

HSP60 was an important downstream molecule of IGFBP7. The downregulation of HSP60 induced by IGFBP7 may be, at least in part, responsible for IGFBP7's tumor suppressive biological behaviour in CRC.

Knockdown of IGF-binding protein 7 inhibits transformation of the endometrial gland in an in vitro model

Uterine endometrial glands and their secretory products are critical for the implantation and survival of the peri-implantation embryo, and for the establishment of uterine receptivity. We previously reported that insulin-like growth factor binding protein 7 (IGFBP7) is abundantly expressed in uterine glandular epithelial cells during the secretory phase of the menstrual cycle. In the present study, we used a cultured glandular epithelial cell line of human (EM1) to investigate the significance of IGFBP7 in the function of endometrial glands. EM1 cells formed a mesh-like structure on Matrigel, which was accompanied by elevated levels of intracellular cyclic AMP. However, these morphological changes were blocked by treatment with protein kinase A (PKA) inhibitor (H89). IGFBP7 knockdown using specific short interference RNA (siRNA) inhibited the formation of the mesh-like structure on Matrigel. Cyclic AMP analogs, dibutyryl-cAMP, and N(6)-phenyl-cAMP induced the expression of leukemia inhibitory factor (LIF) which is essential for the onset of implantation. Enhanced LIF expression was suppressed by IGFBP7 siRNA treatment. Western blot analysis revealed that IGFBP7 knockdown results in the aberrant, constitutive expression of the MAPK signaling pathway. These results suggest that IGFBP7 regulates morphological changes of glandular cells by interfering with the normal PKA and MAPK signaling pathways that are associated with the transformation and/or differentiation of endometrial glands.

Proteinopathy-induced neuronal senescence: a hypothesis for brain failure in Alzheimer's and other neurodegenerative diseases

Background

Alzheimer's disease (AD) and a host of other neurodegenerative central nervous system (CNS) proteinopathies are characterized by the accumulation of misfolded protein aggregates. Simplistically, these aggregates can be divided into smaller, soluble, oligomeric and larger, less-soluble or insoluble, fibrillar forms. Perhaps the major ongoing debate in the neurodegenerative disease field is whether the smaller oligomeric or larger fibrillar aggregates are the primary neurotoxin. Herein, we propose an integrative hypothesis that provides new insights into how a variety of misfolded protein aggregates can result in neurodegeneration.

Results

We introduce the concept that a wide range of highly stable misfolded protein aggregates in AD and other neurodegenerative proteinopathies are recognized as non-self and chronically activate the innate immune system. This pro-inflammatory state leads to physiological senescence of CNS cells. Once CNS cells undergo physiological senescence, they secrete a variety of pro-inflammatory molecules. Thus, the senescence of cells, which was initially triggered by inflammatory stimuli, becomes a self-reinforcing stimulus for further inflammation and senescence. Ultimately, senescent CNS cells become functionally impaired and eventually die, and this neurodegeneration leads to brain organ failure.

Conclusion

This integrative hypothesis, which we will refer to as the proteinopathy-induced senescent cell hypothesis of AD and other neurodegenerative diseases, links CNS proteinopathies to inflammation, physiological senescence, cellular dysfunction, and ultimately neurodegeneration. Future studies characterizing the senescent phenotype of CNS cells in AD and other neurodegenerative diseases will test the validity of this hypothesis. The implications of CNS senescence as a contributing factor to the neurodegenerative cascade and its implications for therapy are discussed.

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.

The insulin-like growth factor-I receptor as an oncogene

The insulin-like growth factor-I receptor (IGF-IR) mediates the biological actions of both IGF-I and IGF-II. The IGF-IR is expressed in most transformed cells, where it displays potent antiapoptotic, cell-survival, and transforming activities. IGF-IR expression is a fundamental prerequisite for the acquisition of a malignant phenotype, as suggested by the finding that IGF-IR-null cells (derived from IGF-IR knock-out embryos) are unable to undergo transformation when exposed to cellular or viral oncogenes. This review article will focus on the underlying molecular mechanisms that are responsible for the normal, physiological control of IGF-IR gene expression, as well as the cellular pathways that underlie its aberrant expression in cancer. Examples from the clinics will be presented, including a description of how the IGF system is involved in breast, prostate, pediatric, and gynecological cancers. Finally, current attempts to target the IGF-IR as a therapeutic approach will be described.

Senescence-induced alterations of laminin chain expression modulate tumorigenicity of prostate cancer cells

Prostate cancer is an age-associated epithelial cancer, and as such, it contributes significantly to the mortality of the elderly. Senescence is one possible mechanism by which the body defends itself against various epithelial cancers. Senescent cells alter the microenvironment, in part, through changes to the extracellular matrix. Laminins (LMs) are extracellular proteins important to both the structure and function of the microenvironment. Overexpression of the senescence-associated gene mac25 in human prostate cancer cells resulted in increased mRNA levels of the LM alpha4 and beta2 chains compared to empty vector control cells. The purpose of this study was to examine the effects of these senescence-induced LM chains on tumorigenicity of prostate cancer cells. We created stable M12 human prostate cancer lines overexpressing either the LM alpha4 or beta2 chain or both chains. Increased expression of either the LM alpha4 or beta2 chain resulted in increased in vitro migration and in vivo tumorigenicity of those cells, whereas high expression of both chains led to decreased in vitro proliferation and in vivo tumorigenicity compared to M12 control cells. This study demonstrates that senescent prostate epithelial cells can alter the microenvironment and that these changes modulate progression of prostate cancer.

Senescence-messaging secretome: SMS-ing cellular stress

Oncogene-induced cellular senescence constitutes a strong anti-proliferative response, which can be set in motion following either oncogene activation or loss of tumour suppressor signalling. It serves to limit the expansion of early neoplastic cells and as such is a potent cancer-protective response to oncogenic events. Recently emerging evidence points to a crucial role in oncogene-induced cellular senescence for the 'senescence-messaging secretome' or SMS, setting the stage for cross-talk between senescent cells and their environment. How are such signals integrated into a coordinated response and what are the implications of this unexpected finding?

Circulating IGF-binding protein 7 (IGFBP7) levels are elevated in patients with endometriosis or undergoing diabetic hemodialysis

BACKGROUND

Insulin-like growth factor-binding protein-7 (IGFBP7) is a secretory protein with a molecular mass of approximately 30 kDa. It is abundantly expressed in the uterine endometrium during the secretory phase of the menstrual cycle. Decreased IGFBP7 expression has been observed in some cancers and leiomyomata.

METHODS

To determine whether serum IGFBP7 levels reflect changes in uterine IGFBP7 expression in humans during the menstrual cycle, and to examine whether serum IGFBP7 levels are altered in patients with various disorders, we developed a novel, dual-antibody sandwich enzyme-linked immunosorbent assay (ELISA). Firstly, concentrations of IGFBP7 released into the medium were determined in cultured endometrial stromal and glandular cells. Blood samples were collected from women who had normal menstrual cycles and who had been diagnosed with endometriosis. Serum from hemodialysis patients and gastrointestinal cancers was also used to determine the IGFBP7 levels.

RESULTS

Using this new ELISA, we demonstrated that cultured uterine cells secrete IGFBP7 into the medium. Patients with endometriosis and those with type II diabetes mellitus undergoing hemodialysis had significantly higher serum concentrations of IGFBP7 than the relevant control subjects. There were no differences in serum IGFBP7 levels in women at different stages of the menstrual cycle. Furthermore, serum IGFBP7 levels in patients with colorectal, esophageal, or endometrial cancer were not different than normal healthy subjects.

CONCLUSION

Our observations suggest that IGFBP7 is associated with the pathophysiology of endometriosis and diabetes mellitus, and that serum IGFBP7 levels do not reflect enhanced uterine expression of IGFBP7 mRNA during the menstrual cycle.

Screening of human SNP database identifies recoding sites of A-to-I RNA editing

Single nucleotide polymorphisms (SNPs) are DNA sequence variations that can affect the expression or function of genes. As a result, they may lead to phenotypic differences between individuals, such as susceptibility to disease, response to medications, and disease progression. Millions of SNPs have been mapped within the human genome providing a rich resource for genetic variation studies. Adenosine-to-inosine RNA editing also leads to the production of RNA and protein sequence variants, but it acts on the level of primary gene transcripts. Sequence variations due to RNA editing may be misannotated as SNPs when relying solely on expressed sequence data instead of genomic material. In this study, we screened the human SNP database for potential cases of A-to-I RNA editing that cause amino acid changes in the encoded protein. Our search strategy applies five molecular features to score candidate sites. It identifies all previously known cases of editing present in the SNP database and successfully uncovers novel, bona fide targets of adenosine deamination editing. Our approach sets the stage for effective and comprehensive genome-wide screens for A-to-I editing targets.

Effect of Insulin-Like Growth Factor-Binding Protein 7 on Steroidogenesis in Granulosa Cells Derived from Equine Chorionic Gonadotropin-Primed Immature Rat Ovaries

Insulin-like growth factor (IGF)-binding protein (IGFBP) 7 is a secreted protein that regulates cellular proliferation, adhesion, and angiogenesis, and has low affinity for IGF compared with that of IGFBP1-IGFBP6. We sought to determine whether IGFBP7 is present in follicular fluid and to elucidate whether IGFBP7 participates in the steroidogenesis of rat mature follicles. Follicular fluid and granulosa cells (GCs) were collected from immature rats 2 days after their treatment with equine chorionic gonadotropin (eCG). IGFBP7 protein was detected in the follicular fluid and the conditioned medium of cultured ovarian GCs by immunoblot analysis. When subconfluent GCs were cultured and treated with FSH and activin, coincubation with FSH and activin markedly increased GC expression of Cyp19a1 (aromatase) mRNA and 17beta-estradiol (E(2)) secretion. The addition of recombinant murine IGFBP7 to these cultures decreased in the activin-enhanced, FSH-stimulated Cyp19a1 mRNA levels in the cells and suppressed the 17beta-E(2) levels in the culture medium. Treatment of GCs with Igfbp7-specific small interfering RNA (siRNA), which knocked down Igfbp7 expression, increased the FSH-stimulated levels of Cyp19a1 but not Cyp11a1 expression. Basal and FSH-stimulated 17beta-E(2) secretion into the culture medium was also enhanced by Igfbp7 siRNA. These results suggest that IGFBP7 suppresses estrogen production in GCs. These observations support the notion that this protein, which is secreted into the follicular fluid, may serve as an intraovarian factor that negatively regulates GC differentiation.

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.

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.

Imbalance in liver homeostasis leading to hyperplasia by overexpressing either one of the Bcl-2-related genes, zfBLP1 and zfMcl-1a

Apoptosis is an essential part of normal embryonic development in vertebrates, and it is involved in sculpturing organs and controlling cell populations. In previous studies, we identified two novel proteins, zfBLP1 and zfMcl-1a, which are similar to those of the Bcl-2 family as a group of evolutionarily conserved proteins that regulate cellular anti-apoptosis. To evaluate the effect of dysregulated hepatocyte apoptosis during zebrafish hepatogenesis, we demonstrate the transgenic overexpression of either zfBLP1 or zfMcl-1a in zebrafish larval liver. Results showed that 18%-43% of larvae overexpressed zfBLP1 and that 16%-37% of larvae overexpressed zfMc1-1a in the liver leading to liver hyperplasia in 5-day postfertilization (dpf) zebrafish larvae. Histologically, zebrafish larvae exhibiting liver hyperplasia displayed a normal type of hepatocyte and the same cell numbers in their two liver buds compared with only one liver bud of wild-type larvae. Of interest, the expression of cyclin genes (A2, B, D1, and E), hepatocyte nuclear factor genes (HNF-1alpha, beta, -3beta, and 4alpha), and oncogenic markers (P53, c-myc, beta-catenin, N-ras, and gankyrin) were up-regulated, while the expression of C/EBP-alpha was down-regulated in a zfMcl-1a-mediated anti-apoptotic process of the liver. Increased cell death and proliferation was found in both hepatic cells of zebrafish larvae overexpressing either zfBLP1 or zfMcl-1a. However, those zebrafish larvae with liver hyperplasia only lived approximately 10 days. (This finding may have been due to liver abnormalities that led to failure of liver function.) In conclusion, transgenic overexpression of zfBLP1 or zfMcl-1a in zebrafish larvae interrupts regulation of the homeostatic balance between cell proliferation and programmed cell death during hepatogenesis and leads to liver hyperplasia.

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.

hCG-dependent regulation of angiogenic factors in human granulosa lutein cells

As prerequisite for development and maintenance of many diseases angiogenesis is of particular interest in medicine. Pathologic angiogenesis takes place in chronic arthritis, collagen diseases, arteriosclerosis, retinopathy associated with diabetes, and particularly in cancers. However, angiogenesis as a physiological process regularly occurs in the ovary. After ovulation the corpus luteum is formed by rapid vascularization of initially avascular granulosa lutein cell tissue. This process is regulated by gonadotropic hormones. In order to gain further insights in the regulatory mechanisms of angiogenesis in the ovary, we investigated these mechanisms in cell culture of human granulosa lutein cells. In particular, we determined the expression and production of several angiogenic factors including tissue inhibitor of matrix metalloproteinases-1 (TIMP-1), Leptin, connective tissue growth factor (CTGF), meningioma-associated complimentary DNA (Mac25), basic fibroblast growth factor (bFGF), and Midkine. In addition, we showed that human chorionic gonadotropin (hCG) has distinct effects on their expression and production. hCG enhances the expression and production of TIMP-1, whereas it downregulates the expression of CTGF and Mac25. Furthermore it decreases the expression of Leptin. Our results provide evidence that hCG determines growth and development of the corpus luteum by mediating angiogenic pathways in human granulosa lutein cells. Hence we describe a further approach to understand the regulation of angiogenesis in the ovary.

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.

Identification of a novel insulin-like growth factor binding protein gene homologue with tumor suppressor like properties

Here we report the identification of a new insulin-like growth factor binding protein homologue, provisionally designated insulin-like growth factor binding related protein-4 (IGFBP-rP4). IGFBP-rP4 was found to be most closely related to IGFBP-7 with 52% amino acid homology and 43% amino acid identity, and shares a similar domain structure. Semi-quantitative RT-PCR expression analysis demonstrated a pattern of downregulation of this gene in multiple tumor samples including lung and colon cancer, compared to matched adjacent normal tissue. Western blotting revealed a protein of approximately 38kDa expressed in both the cell pellet and secreted into the supernatant of transiently transfected Cos-7 cells. Cos-7 supernatants containing IGFBP-RP4 protein were observed to suppress the growth of HeLa cells in culture compared to vector controls. IGFBP-RP4 directly transiently transfected into HeLa cells also further confirmed the growth suppressive properties of this protein. Together these data suggest that IGFBP-RP4 may be a novel putative tumor suppressor protein.

Suppression of growth and tumorigenicity in the prostate tumor cell line M12 by overexpression of the transcription factor SOX9

Overexpression of mac25 in the prostate cancer cell line M12 effects a dramatic reversal of the transformed phenotype. cDNA array analysis of RNA from cells overproducing the mac25 protein (M12/mac25) indicated upregulation of the sex determining transcription factor SOX9. In this study, we have confirmed increased expression of SOX9 in M12/mac25 cells and have further investigated the physiological effects of increased SOX9 production. Greatly increased levels of SOX9 RNA and mature protein were demonstrated in cells transfected with a SOX9 cDNA (M12/SOX9), and gel mobility shift assays confirmed binding of nuclear protein from these cells to an oligonucleotide containing the SOX9 consensus binding sequence. M12/SOX9 cells assumed the spindle-shaped morphology characteristic of M12/mac25 cells, suggesting that SOX9 mediates some effects of mac25. Elevated expression of SOX9 resulted in a decreased rate of cellular proliferation, cell cycle arrest in G0/G1, and increased sensitivity to apoptosis. Tumor development in athymic nude mice was inhibited by 80%. Finally, prostate-specific antigen and the androgen receptor, two genes whose expression is characteristic of differentiated cells, were both upregulated in M12/SOX9 cells. These data indicate that SOX9 contributes to growth regulation by mac25 via inhibition of cell growth and promotion of differentiation.