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

Primary proximal tubule injury leads to epithelial cell cycle arrest, fibrosis, vascular rarefaction, and glomerulosclerosis

Tubular injury has a major etiological role in fibrosis. For many years, this relationship has been dominated by the perception that epithelial cells are transformed into myofibroblasts that proliferate and generate fibrotic matrix—the so-called epithelial-to-mesenchymal transition. Here we focus on mechanisms by which injury to the tubule results in fibrosis because of paracrine mechanisms. Specific injury to the proximal tubule results in inflammation, reversible injury, and adaptive repair if the insult is mild, self-limited in time, and occurs in a background of a normal kidney. Repeated injury, in contrast, leads to maladaptive repair with sustained tubule injury, chronic inflammation, proliferation of interstitial myofibroblasts, vascular rarefaction, interstitial fibrosis, and glomerular sclerosis. During the maladaptive repair process after the renal insult, many tubular cells become arrested in the G2/M phase of the cell cycle. This results in activation of the DNA repair response with the resultant synthesis and secretion of pro-fibrotic factors. Pharmacologic interventions that enhance the movement through G2/M or facilitate apoptosis of cells that otherwise would be blocked in G2/M may reduce the development of fibrosis after kidney injury and reduce the progression of chronic kidney disease.

Reconstruction of 3-dimensional histology volume and its application to study mouse mammary glands

Histology volume reconstruction facilitates the study of 3D shape and volume change of an organ at the level of macrostructures made up of cells. It can also be used to investigate and validate novel techniques and algorithms in volumetric medical imaging and therapies. Creating 3D high-resolution atlases of different organs(1,2,3) is another application of histology volume reconstruction. This provides a resource for investigating tissue structures and the spatial relationship between various cellular features. We present an image registration approach for histology volume reconstruction, which uses a set of optical blockface images. The reconstructed histology volume represents a reliable shape of the processed specimen with no propagated post-processing registration error. The Hematoxylin and Eosin (H&E) stained sections of two mouse mammary glands were registered to their corresponding blockface images using boundary points extracted from the edges of the specimen in histology and blockface images. The accuracy of the registration was visually evaluated. The alignment of the macrostructures of the mammary glands was also visually assessed at high resolution. This study delineates the different steps of this image registration pipeline, ranging from excision of the mammary gland through to 3D histology volume reconstruction. While 2D histology images reveal the structural differences between pairs of sections, 3D histology volume provides the ability to visualize the differences in shape and volume of the mammary glands.

IGFBP7 induces apoptosis of acute myeloid leukemia cells and synergizes with chemotherapy in suppression of leukemia cell survival

Despite high remission rates after chemotherapy, only 30-40% of acute myeloid leukemia (AML) patients survive 5 years after diagnosis. This extremely poor prognosis of AML is mainly caused by treatment failure due to chemotherapy resistance. Chemotherapy resistance can be caused by various features including activation of alternative signaling pathways, evasion of cell death or activation of receptor tyrosine kinases such as the insulin growth factor-1 receptor (IGF-1R). Here we have studied the role of the insulin-like growth factor-binding protein-7 (IGFBP7), a tumor suppressor and part of the IGF-1R axis, in AML. We report that IGFBP7 sensitizes AML cells to chemotherapy-induced cell death. Moreover, overexpression of IGFBP7 as well as addition of recombinant human IGFBP7 is able to reduce the survival of AML cells by the induction of a G2 cell cycle arrest and apoptosis. This effect is mainly independent from IGF-1R activation, activated Akt and activated Erk. Importantly, AML patients with high IGFBP7 expression have a better outcome than patients with low IGFBP7 expression, indicating a positive role for IGFBP7 in treatment and outcome of AML. Together, this suggests that the combination of IGFBP7 and chemotherapy might potentially overcome conventional AML drug resistance and thus might improve AML patient survival.

Inhibition of HDAC increases the senescence induced by natural polyphenols in glioma cells

Cellular senescence is an irreversible block of cellular division, and induction of senescence is being considered for treatment of many cancer types, mainly those resistant to classical pro-apoptotic therapies. Resveratrol (Rsv) and quercetin (Quer), two natural polyphenols, are able to induce senescence in different cancer models, including gliomas, the most common and aggressive primary brain tumor. These polyphenols modulate the activity of several proteins involved in cell growth and death in cancer cells, including histone deacetylases (HDAC), but the role of HDAC in senescence induced by Rsv and Quer is unclear. The HDAC inhibitor sodium butyrate (NaB) potentiated the pro-senescent effect of Rsv and Quer in human and rat glioma cell lines but not in normal rat astrocytes. Furthermore, the increment of Quer-induced senescence by NaB was accompanied by an increase of reactive oxygen species levels and an increment of the number of cells with nuclear abnormalities. Altogether, these data support a positive role of HDAC inhibition on the senescence induced by these polyphenols, and therefore co-treatment of HDAC inhibitors and polyphenols emerges as a potential alternative for gliomas.

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.

The specific methylation characteristics of cancer related genes in Chinese colorectal cancer patients

Aberrant DNA methylation at CpG islands has been implicated as a critical player in colorectal cancer (CRC). However, its biological role and clinical significance in carcinogenesis have not been clearly clarified in Chinese CRC patients. In order to examine the methylation status of cancer-related genes in CRC progression, 184 tumor tissues were collected from Chinese patients diagnosed with CRC during 2008-2011. Promoter methylation was assessed by combined bisulphite-restriction analysis, methylation-specific PCR, and bisulphite sequencing PCR . The relationship between the gene promoter methylation status and clinicopathological factors/CRC mortality was examined by using the chi-square test/Cox-proportional hazards models. Promoter hypermethylation of MLH1, p16, SFRP2, PHD3, KLOTHO, and IGFBP7 was observed in 1.6, 10.9, 97.3, 44.0, 59.8, and 88.6 % of CRC samples, respectively. KLOTHO promoter methylation reduced with age (P = 0.018) whereas p16 promoter methylation increased with age (P = 0.044) and was more frequent among males (P = 0.017). Tumor tissues (73.9 %) had concurrent methylation of two or more genes, with the most frequent combination as KLOTHO and IGFBP7 (53.8 %). Concurrent methylation of KLOTHO and IGFBP7 occurred more frequently among patients less than 70 years old (P = 0.035) and those with poor differentiation (P = 0.024). CRC-specific mortality was not associated with promoter methylation and clinicopathological features except for age (P = 0.038; risk ratio (RR), 1.96; 95 % confidence interval (CI), 1.04-3.70) and TNM stage (P = 0.034; RR, 3.47; 95 % CI, 1.10-10.92). Methylation frequencies of MLH1, p16, PHD3, KLOTHO, and IGFBP7 in CRC tissues were significantly higher than that in the paired normal tissues, while promoter hypermethylation of SFRP2 was widespread in normal tissues. In conclusion, we suggest that methylation of some genes (MLH1, PHD3, KLOTHO, p16, and IGFBP7) is important in CRC progression whereas SFRP2 methylation is unlikely to contribute to CRC development in Chinese patients. Besides, by identifying the characteristics of concordant methylation, we confirm the multifactorial nature of tumor progression.

Insulin-like growth factor binding protein-related protein 1 contributes to hepatic fibrogenesis

OBJECTIVE

The aim of this study was to investigate the role of insulin-like growth factor binding protein-related protein 1 (IGFBP-rP1) in the development of hepatic fibrogenesis in experimental disease models and human liver samples.

METHODS

Cellular distribution patterns of IGFBP-rP1 were assessed by immunohistochemistry in fibrotic and cirrhotic human liver specimens. Gene silencing of IGFBP-rP1 was performed on cultured hepatic stellate cells (HSCs) by small interfering RNA (siRNA), and the silencing effect was determined by quantitative real-time polymerase chain reaction (PCR) and Western blot. We also determined the effects of siRNA-mediated gene silencing of IGFBP-rP1 on the production of extracellular matrix (ECM) components by Western blot. The expression of ECM components and transforming growth factor (TGF)-β1 was studied by immunohistochemistry and Western blot in C57BL/6 wild-type mice treated with recombinant IGFBP-rP1 (rIGFBP-rP1).

RESULTS

Expression of IGFBP-rP1 was significantly elevated in fibrotic and cirrhotic human liver specimens, and this increase was positively correlated with the number of collagen fibers observed. siRNA-mediated gene silencing of IGFBP-rP1 resulted in significantly decreased levels of collagen I and fibronectin in HSCs. Moreover, IGFBP-rP1 overexpression significantly increased the production of collagen, fibronectin and TGF-β1 in rIGFBP-rP1-treated mice.

CONCLUSIONS

IGFBP-rP1 contributes to the development of liver fibrosis and may be a novel molecule involved in the progression of hepatic fibrogenesis.

Emerging role of insulin-like growth factor-binding protein 7 in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a vicious and highly vascular cancer with a dismal prognosis. It is a life-threatening illness worldwide that ranks fifth in terms of cancer prevalence and third in cancer deaths. Most patients are diagnosed at an advanced stage by which time conventional therapies are no longer effective. Targeted molecular therapies, such as the multikinase inhibitor sorafenib, provide a modest increase in survival for advanced HCC patients and display significant toxicity. Thus, there is an immense need to identify novel regulators of HCC that might be targeted effectively. The insulin-like growth factor (IGF) axis is commonly abnormal in HCC. Upon activation, the IGF axis controls metabolism, tissue homeostasis, and survival. Insulin-like growth factor-binding protein 7 (IGFBP7) is a secreted protein of a family of low-affinity IGF-binding proteins termed “IGFBP-related proteins” that have been identified as a potential tumor suppressor in HCC. IGFBP7 has been implicated in regulating cellular proliferation, senescence, and angiogenesis. In this review, we provide a comprehensive discussion of the role of IGFBP7 in HCC and the potential use of IGFBP7 as a novel biomarker for drug resistance and as an effective therapeutic strategy.

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.

Loss of Igfbp7 causes precocious involution in lactating mouse mammary gland

BACKGROUND

Insulin like growth factors (IGFs) and their binding proteins (IGFBPs) are secreted peptides that play major roles in regulating the normal development and maturation of mammary gland. While Igfbp7 has been shown to decrease breast tumor growth, its role in regulating the normal mammary gland development has not been studied. To this end, we generated Igfbp7-null mice and examined the development and maturation of mammary glands in the virgin, pregnant and lactating animals.

RESULTS

We report here that loss of Igfbp7 significantly retards mammary gland development in the virgin animals. More significantly, the pregnant Igfpb7-null glands contained fewer alveolar structures and that during lactation these glands exhibit the morphological changes that are associated with involution. The transcriptome profile of the Igfbp7-null glands on the lactation day 3 revealed a distinct involution-related gene signature compared to the lactating WT glands. Interestingly, we found that the lactating Igfbp7-null glands exhibit increased expression of Stat3 and enhanced activation of (phosphorylated) Stat3, combined with decreased expression of Stat5 suggesting that the absence of Igfbp7 accelerates the onset of involution. We also found that in absence of Igfpb7, the lactating glands contain increased Igfbp5 protein along with decreased expression of IGF-1 Receptor and Akt activation. Finally, we show that during the normal course of involution, Igfbp7 expression is significantly decreased in the mammary gland.

CONCLUSION

Our data suggest that loss of Igfbp7 induces precocious involution possibly through diminished cell survival signals. Our findings identify Igfbp7 as major regulator of involution in the mammary gland.

High expression of IGFBP7 in fibroblasts induced by colorectal cancer cells is co-regulated by TGF-β and Wnt signaling in a Smad2/3-Dvl2/3-dependent manner

Fibroblasts in the tumor microenvironment are a key determinant in cancer progression and may be a promising target for cancer therapy. Insulin-like growth factor binding protein 7 (IGFBP7) is known as a tumor suppressor in colorectal cancer (CRC). The present study investigated the inductive mechanism of IGFBP7 expression in fibroblasts by supernatant from the CRC cell line, SW620. The results showed that the expression of IGFBP7 was up-regulated in the fibroblasts when treated with SW620 supernatant and exogenous TGF-β1. The IGFBP7 induced by SW620 supernatant or TGF-β1 was partially inhibited by the TGF-β1 specific antibody AF and TGF-β1 receptor antagonist SB431542. The Wnt signaling-targeted genes, c-Myc, CCND1 and the proteins Dvl2/3, were all up-regulated in fibroblasts expressing high levels of IGFBP7, and the up-regulation could be inhibited both by the Wnt signaling antagonist Dickkopf-1 (DKK1) and by the TGF-β1 receptor antagonist SB431542. In conclusion, CRC cells promote the high expression of IGFBP7 in fibroblasts, most likely through the co-regulation of TGF-β and Wnt signaling in a Smad2/3-Dvl2/3 dependent manner. Taken together, these data suggest that the fibroblasts could be a novel therapeutic target in tumor therapy.

Insulin-like growth factor binding proteins 4 and 7 released by senescent cells promote premature senescence in mesenchymal stem cells

Cellular senescence is the permanent arrest of cell cycle, physiologically related to aging and aging-associated diseases. Senescence is also recognized as a mechanism for limiting the regenerative potential of stem cells and to protect cells from cancer development. The senescence program is realized through autocrine/paracrine pathways based on the activation of a peculiar senescence-associated secretory phenotype (SASP). We show here that conditioned media (CM) of senescent mesenchymal stem cells (MSCs) contain a set of secreted factors that are able to induce a full senescence response in young cells. To delineate a hallmark of stem cells SASP, we have characterized the factors secreted by senescent MSC identifying insulin-like growth factor binding proteins 4 and 7 (IGFBP4 and IGFBP7) as key components needed for triggering senescence in young MSC. The pro-senescent effects of IGFBP4 and IGFBP7 are reversed by single or simultaneous immunodepletion of either proteins from senescent-CM. The blocking of IGFBP4/7 also reduces apoptosis and promotes cell growth, suggesting that they may have a pleiotropic effect on MSC biology. Furthermore, the simultaneous addition of rIGFBP4/7 increased senescence and induced apoptosis in young MSC. Collectively, these results suggest the occurrence of novel-secreted factors regulating MSC cellular senescence of potential importance for regenerative medicine and cancer therapy.

Loss of IGFBP7 expression and persistent AKT activation contribute to SMARCB1/Snf5-mediated tumorigenesis

SMARCB1 (Snf5/Ini1/Baf47) is a potent tumor suppressor, the loss of which serves as the diagnostic feature in malignant rhabdoid tumors (MRT) and atypical teratoid/rhabdoid tumors (AT/RT), two highly aggressive forms of pediatric neoplasms. SMARCB1 is a core subunit of Swi/Snf chromatin remodeling complexes, and loss of SMARCB1 or other subunits of these complexes has been observed in a variety of tumor types. Here, we restore Smarcb1 expression in cells derived from Smarcb1-deficient tumors, which developed in Smarcb1 heterozygous p53(-/-) mice. We find that while re-introduction of Smarcb1 does not induce growth arrest, it restores sensitivity to programmed cell death and completely abolishes the ability of the tumor cells to grow as xenografts. We describe persistent activation of AKT signaling in Smarcb1-deficient cells, which stems from PI3K (phosphatidylinositol 3'-kinase)-mediated signaling and which contributes to the survival and proliferation of the tumor cells. We further demonstrate that inhibition of AKT is effective in preventing proliferation of Smarcb1-deficient cells in vitro and inhibits the development of xenografted tumors in vivo. Profiling Smarcb1-dependent gene expression, we find genes that require Smarcb1 and Swi/Snf for their expression to be enriched for extracellular matrix and cell adhesion functions. We find that Smarcb1 is required for transcriptional activation of Igfbp7, a member of the insulin-like growth factor-binding proteins family and a tumor suppressor in itself, and show that re-introduction of Igfbp7 alone can hinder tumor development. Our results define a novel mechanism for Smarcb1-mediated tumorigenesis and highlight potential therapeutic targets.

RETRACTED: Insulin-like growth factor-binding protein-7 (IGFBP7): a promising gene therapeutic for hepatocellular carcinoma (HCC)

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the editor-in-chief. Similarities were found between images within this article. Image analysis performed by the editorial office confirmed findings of image duplication in Figures 1B, 4, and 8A. This reuse (and in part misrepresentation) of data without appropriate attribution represents a severe abuse of the scientific publishing system. No authors responded when contacted about the retraction.

IGFBP7 binds to the IGF-1 receptor and blocks its activation by insulin-like growth factors

Insulin-like growth factor-binding protein 7 (IGFBP7) is a secreted factor that suppresses growth, and the abundance of IGFBP7 inversely correlates with tumor progression. Here, we showed that pretreatment of normal and breast cancer cells with IGFBP7 interfered with the activation and internalization of insulin-like growth factor 1 receptor (IGF1R) in response to insulin-like growth factors 1 and 2 (IGF-1/2), resulting in the accumulation of inactive IGF1R on the cell surface and blockade of downstream phosphatidylinositol 3-kinase (PI3K)-AKT signaling. Binding of IGFBP7 and IGF-1 to IGF1R was mutually exclusive, and the N-terminal 97 amino acids of IGFBP7 were important for binding to the extracellular portion of IGF1R and for preventing its activation. Prolonged exposure to IGFBP7 resulted in activation of the translational repressor 4E-binding protein 1 (4E-BP1) and enhanced sensitivity to apoptosis in IGF1R-positive cells. These results support a model whereby IGFBP7 binds to unoccupied IGF1R and suppresses downstream signaling, thereby inhibiting protein synthesis, cell growth, and survival.

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.