Insulin-like growth factor binding protein-6 inhibits prostate cancer cell proliferation: implication for anticancer effect of diethylstilbestrol in hormone refractory prostate cancer

The Pros and Cons of Estrogens in Prostate Cancer: An Update with a Focus on Phytoestrogens

The role of estrogens in prostate cancer (PCa) is shrouded in mystery, with its actions going from angelic to devilish. The findings by Huggins and Hodges establishing PCa as a hormone-sensitive cancer have provided the basis for using estrogens in therapy. However, despite the clinical efficacy in suppressing tumor growth and the panoply of experimental evidence describing its anticarcinogenic effects, estrogens were abolished from PCa treatment because of the adverse secondary effects. Notwithstanding, research work over the years has continued investigating the effects of estrogens, reporting their pros and cons in prostate carcinogenesis. In contrast with the beneficial therapeutic effects, many reports have implicated estrogens in the disruption of prostate cell fate and tissue homeostasis. On the other hand, epidemiological data demonstrating the lower incidence of PCa in Eastern countries associated with a higher consumption of phytoestrogens support the beneficial role of estrogens in counteracting cancer development. Many studies have investigated the effects of phytoestrogens and the underlying mechanisms of action, which may contribute to developing safe estrogen-based anti-PCa therapies. This review compiles the existing data on the anti- and protumorigenic actions of estrogens and summarizes the anticancer effects of several phytoestrogens, highlighting their promising features in PCa treatment.

Insulin-like growth factor family and prostate cancer: new insights and emerging opportunities

Prostate cancer is the second most commonly diagnosed cancer in men. The mammalian insulin-like growth factor (IGF) family is made up of three ligands (IGF-I, IGF-II, and insulin), three receptors (IGF-I receptor (IGF-1R), insulin receptor (IR), and IGF-II receptor (IGF-2R)), and six IGF-binding proteins (IGFBPs). IGF-I and IGF-II were identified as potent mitogens and were previously associated with an increased risk of cancer development including prostate cancer. Several reports showed controversy about the expression of the IGF family and their connection to prostate cancer risk due to the high degree of heterogeneity among prostate tumors, sampling bias, and evaluation techniques. Despite that, it is clear that several IGF family members play a role in prostate cancer development, metastasis, and androgen-independent progression. In this review, we aim to expand our understanding of prostate tumorigenesis and regulation through the IGF system. Further understanding of the role of IGF signaling in PCa shows promise and needs to be considered in the context of a comprehensive treatment strategy.

Prognostic Value of IGFBP6 in Breast Cancer: Focus on Glucometabolism

IGFBP6, a member of the IGF binding protein (IGFBP) family, is a specific inhibitor of insulin-like growth factor II (IGF-II) and can inhibit the growth of malignant tumors overexpressing IGF-II. Type 2 diabetes (T2D) is a basic disorder of glucose metabolism that can be regulated by IGF-related pathways. We performed bioinformatics analysis of the TCGA database to explore the possible mechanism of IGFBP6 in breast cancer (BC) metabolism and prognosis and collected clinical samples from BC patients with and without T2D to compare and verify the prognostic effect of IGFBP6. In our study, the levels of IGFBP1-6 were positively correlated with overall survival (OS) in patients with breast cancer. IGFBP6 was upregulated in estrogen receptor (ER)-positive BC, and ER-positive and progesterone receptor (PR) positive patients had a higher expression level of IGFBP6 than ER-negative and PR-negative patients. IGFBP6 could be used as an independent prognostic factor in BC. The expression of IGFBP6 was decreased in BC tissue, and BC tissue from patients with T2D had lower IGFBP6 expression levels than BC tissue from patients without T2D. IGFBP6 is mainly involved in the PI3K-Akt and TGF-β signaling pathways and tumor microenvironment regulation. In terms of metabolism, the expression of IGFBP6 was negatively correlated with that of most glucose metabolism-related genes. IGFBP6 expression was mainly correlated with mutations in TP53, PIK3CA, CDH1, and MAP3K1. In addition, the upregulation of IGFBP6 in BC increased the drug sensitivity to docetaxel, paclitaxel and gemcitabine. Overall, these results indicated that high expression of IGFBP6 is associated with a good prognosis in BC patients, especially in those without T2D. It is not only involved in the maintenance of the tumor microenvironment in BC but also inhibits the energy metabolism of cancer cells through glucose metabolism-related pathways. These findings may provide a new perspective on IGFBP6 as a potential prognostic marker for BC.

Comprehensive Analysis of Prognostic Value and Immune Infiltration of IGFBP Family Members in Glioblastoma

Glioblastoma (GBM) is the most common primary malignant brain tumor in adults. The insulin-like growth factor-binding protein (IGFBP) family is involved in tumorigenesis and the development of multiple cancers. However, little is known about the prognostic value and regulatory mechanisms of IGFBPs in GBM. Oncomine, Gene Expression Profiling Interactive Analysis, PrognoScan, cBioPortal, LinkedOmics, TIMER, and TISIDB were used to analyze the differential expression, prognostic value, genetic alteration, biological function, and immune cell infiltration of IGFBPs in GBM. We observed that IGFBP1, IGFBP2, IGFBP3, IGFBP4, and IGFBP5 mRNA expression was significantly upregulated in patients with GBM, whereas IGFBP6 was downregulated; this difference in mRNA expression was statistically insignificant. Subsequent investigations showed that IGFBP4 and IGFBP6 mRNA levels were significantly associated with overall survival in patients with GBM. Functional Gene Ontology Annotation and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis revealed that genes coexpressed with IGFBP4 and IGFBP6 were mainly enriched in immune-related pathways. These results were validated using the TIMER and TSMIDB databases. This study demonstrated that the IGFBP family has prognostic value in patients with GBM. IGFBP4 and IGFBP6 are two members of the IGFBP family that had the highest prognostic value; thus, they have the potential to serve as survival predictors and immunotherapeutic targets in GBM.

Decreased expression of IGFBP6 correlates with poor survival in colorectal cancer patients

BACKGROUND

The insulin-like growth factor binding protein 6 (IGFBP6), as a specific inhibitor of IGF-Ⅱ, is a candidate human anti-oncogene in multiple tumors. However, the expression of IGFBP6 in colorectal cancer (CRC) and prognostic significance are unclear.

METHODS

In this study, we examined colorectal cancer tissues and adjacent normal tissues to determine the expression levels of IGFBP6 mRNA and protein by quantitative reverse-transcription polymerase chain reaction and tissue microarray immunohistochemistry analysis respectively. Moreover, we explored the effects of IGFBP6 on cell growth, migration and invasion by Cell Counting Kit-8(CCK8), colony formation and transwell migration assays. We also investigated whether IGFBP6 expression in tumor tissue correlated with various clinical parameters, including overall survival by univariate and multivariate analyses RESULTS: Both IGFBP6 mRNA and protein levels were significantly lower in colorectal cancer tissues than in adjacent normal colon. Downregulating IGFBP6 using RNAi increased CRC cell proliferation, migration and invasion. Low IGFBP6 expression correlated with poor overall survival in both univariate and multivariate analyses.

CONCLUSION

Our data suggest that IGFBP6 may act as a tumor suppressor gene in the development of CRC, and that low IGFBP6 expression could be used as an independent prognostic biomarker in CRC.

Hormonal and Molecular Regulation of Phallus Differentiation in a Marsupial Tammar Wallaby

Congenital anomalies in phalluses caused by endocrine disruptors have gained a great deal of attention due to its annual increasing rate in males. However, the endocrine-driven molecular regulatory mechanism of abnormal phallus development is complex and remains largely unknown. Here, we review the direct effect of androgen and oestrogen on molecular regulation in phalluses using the marsupial tammar wallaby, whose phallus differentiation occurs after birth. We summarize and discuss the molecular mechanisms underlying phallus differentiation mediated by sonic hedgehog (SHH) at day 50 pp and phallus elongation mediated by insulin-like growth factor 1 (IGF1) and insulin-like growth factor binding protein 3 (IGFBP3), as well as multiple phallus-regulating genes expressed after day 50 pp. We also identify hormone-responsive long non-coding RNAs (lncRNAs) that are co-expressed with their neighboring coding genes. We show that the activation of SHH and IGF1, mediated by balanced androgen receptor (AR) and estrogen receptor 1 (ESR1) signalling, initiates a complex regulatory network in males to constrain the timing of phallus differentiation and to activate the downstream genes that maintain urethral closure and phallus elongation at later stages.

Gene set analysis and reduction for a continuous phenotype: Identifying markers of birth weight variation based on embryonic stem cells and immunologic signatures

BACKGROUND

Gene set analysis is a popular approach to examine the association between a predefined gene set and a phenotype. Few methods have been developed for a continuous phenotype. However, often not all the genes within a significant gene set contribute to its significance. There is no gene set reduction method developed for continuous phenotype. We developed a computationally efficient analytical tool, called linear combination test for gene set reduction (LCT-GSR) to identify core subsets of gene sets associated with a continuous phenotype. Identifying the core subset enhances our understanding of the biological mechanism and reduces costs of disease risk assessment, diagnosis and treatment.

RESULTS

We evaluated the performance of our analytical tool by applying it to two real microarray studies. In the first application, we analyzed pathway expression measurements in newborns' blood to discover core genes contributing to the variation in birth weight. On average, we were able to reduce the number of genes in the 33 significant gene sets of embryonic stem cell signatures by 84.3% resulting in 229 unique genes. Using immunologic signatures, on average we reduced the number of genes in the 210 significant gene sets by 89% leading to 1603 unique genes. There were 180 unique core genes overlapping across the two databases. In the second application, we analyzed pathway expression measurements in a cohort of lethal prostate cancer patients from Swedish Watchful Waiting cohort to identify main genes associated with tumor volume. On average, we were able to reduce the number of genes in the 17 gene sets by 90% resulting in 47 unique genes.

CONCLUSIONS

We conclude that LCT-GSR is a statistically sound analytical tool that can be used to extract core genes associated with a continuous phenotype. It can be applied to a wide range of studies in which dichotomizing the continuous phenotype is neither easy nor meaningful. Reduction to the most predictive genes is crucial in advancing our understanding of issues such as disease prevention, faster and more efficient diagnosis, intervention strategies and personalized medicine.

Integration of Two In-depth Quantitative Proteomics Approaches Determines the Kallikrein-related Peptidase 7 (KLK7) Degradome in Ovarian Cancer Cell Secretome

Kallikrein-related peptidase 7 (KLK7) is a serine peptidase that is over expressed in ovarian cancer. In vitro functional analyses have suggested KLK7 to play a cancer progressive role, although monitoring of KLK7 expression has suggested a contradictory protective role for KLK7 in ovarian cancer patients. In order to help delineate its mechanism of action and thereby the functional roles, information on its substrate repertoire is crucial. Therefore, in this study a quantitative proteomics approach-PROtein TOpography and Migration Analysis Platform (PROTOMAP)-coupled with SILAC was used for in-depth analysis of putative KLK7 substrates from a representative ovarian cancer cell line, SKOV-3, secreted proteins. The Terminal Amine Isotopic Labeling of Substrates (TAILS) approach was used to determine the exact cleavage sites and to validate qPROTOMAP-identified putative substrates. By employing these two technically divergent approaches, exact cleavage sites on 16 novel putative substrates and two established substrates, matrix metalloprotease (MMP) 2 and insulin growth factor binding protein 3 (IGFBP3), were identified in the SKOV-3 secretome. Eight of these substrates were also identified on TAILS analysis of another ovarian cancer cell (OVMZ-6) secretome, with a further seven OVMZ-6 substrates common to the SKOV-3 qPROTOMAP profile. Identified substrates were significantly associated with the common processes of cell adhesion, extracellular matrix remodeling and cell migration according to the gene ontology (GO) biological process analysis. Biochemical validation supports a role for KLK7 in directly activating pro-MMP10, hydrolysis of IGFBP6 and cleavage of thrombospondin 1 with generation of a potentially bioactive N-terminal fragment. Overall, this study constitutes the most comprehensive analysis of the putative KLK7 degradome in any cancer to date, thereby opening new avenues for KLK7 research.

IGFBP6 controls the expansion of chemoresistant glioblastoma through paracrine IGF2/IGF-1R signaling

BACKGROUND

Glioblastomas (GBMs), the most common and most lethal of the primary brain tumors, are characterized by marked intra-tumor heterogeneity. Several studies have suggested that within these tumors a restricted population of chemoresistant glioma cells is responsible for recurrence. However, the gene expression patterns underlying chemoresistance are largely unknown. Numerous efforts have been made to block IGF-1R signaling pathway in GBM. However, those therapies have been repeatedly unsuccessful. This failure may not only be due to the complexity of IGF receptor signaling, but also due to complex cell-cell interactions in the tumor mass. We hypothesized that differential expression of proteins in the insulin-like growth factor (IGF) system underlie cell-specific differences in the resistance to temozolomide (TMZ) within GBM tumors.

METHODS

Expression of IGF-1R was analyzed in cell lines, patient-derived xenograft cell lines and human biopsies by cell surface proteomics, flow cytometry, immunofluorescence and quantitative real time polymerase chain reaction (qRT-PCR). Using gain-of-function and loss-of-function strategies, we dissected the molecular mechanism responsible for IGF-binding protein 6 (IGFBP6) tumor suppressor functions both in in vitro and in vivo. Site direct mutagenesis was used to study IGFBP6-IGF2 interactions.

RESULTS

We determined that in human glioma tissue, glioma cell lines, and patient-derived xenograft cell lines, treatment with TMZ enhances the expression of IGF1 receptor (IGF-1R) and IGF2 and decreases the expression of IGFBP6, which sequesters IGF2. Using chemoresistant and chemosensitive wild-type and transgenic glioma cells, we further found that a paracrine mechanism driven by IGFBP6 secreted from TMZ-sensitive cells abrogates the proliferation of IGF-1R-expressing TMZ-resistant cells in vitro and in vivo. In mice bearing intracranial human glioma xenografts, overexpression of IGFBP6 in TMZ-resistant cells increased survival. Finally, elevated expression of IGF-1R and IGF2 in gliomas associated with poor patient survival and tumor expression levels of IGFBP6 directly correlated with overall survival time in patients with GBM.

CONCLUSIONS

Our findings support the view that proliferation of chemoresistant tumor cells is controlled within the tumor mass by IGFBP6-producing tumor cells; however, TMZ treatment eliminates this population and enriches the TMZ-resistant cell populationleading to accelerated growth of the entire tumor mass.

In Vitro Model for Studying of the Role of IGFBP6 Gene in Breast Cancer Metastasizing

IGFBP6 gene plays an important role in the pathogenesis of breast cancer. In this work, we performed knockdown of IGFBP6 gene in MDA-MB-231 cells and obtained a stable cell line. Knockdown of IGFBP6 gene was confirmed by the real-time PCR. The influence of IGFBP6 gene on migration and proliferation of breast cancer cells was studied. Knockdown of IGFBP6 gene reduced migration activity of MDA-MB-231 cells and increased their proliferation rate. This in vitro cell model can be used for the further analysis of the role of IGFBP6 gene in the pathogenesis of breast cancer.

IGFBP6 is a novel nasopharyngeal carcinoma prognostic biomarker

Insulin-like growth factor binding proteins (IGFBPs) play critical roles in carcinogenesis. This study assessed the impact of IGFBP6 on the progression of nasopharyngeal carcinoma (NPC). Using immunohistochemical analysis, we found that IGFBP6 was differentially expressed in primary malignant NPC tissues. Clinical samples were divided into two groups: IGFBP6(+) and IGFBP6(−). Five years of follow-up revealed that overall survival and distant metastasis-free survival rates were significantly higher in the IGFBP6(+) than IGFBP6(−) group. We also used real-time PCR, ELISA and western blot assays to measure IGFBP6 levels in five NPC cell lines (CNE1, CNE2, HONE1, HK1 and SUNE1). All the cell lines expressed IGFBP6, but at different levels, reflecting disease heterogeneity. In addition, exogenous expression of IGFBP6 inhibited CNE2 cell proliferation and invasion in vitro. IGFBP6 knockdown activated the GSK3β/β-catenin/cyclin D1 pathway and enhanced CNE2 tumor cell growth and metastasis in a mouse model. These results suggest that IGFBP6 may be an independent prognostic biomarker for NPC.

Insulin-like growth factor binding protein-6 released from human mesenchymal stem cells confers neuronal protection through IGF-1R-mediated signaling

Human bone marrow-derived mesenchymal stem cells (hMSCs) are a desirable cell source for cell-based therapy to treat nervous system injuries due to their ability to differentiate into specific cell types. In addition to their multi-potency, hMSCs render the tissue microenvironment more favorable for tissue repair by secreting various growth factors. Our previous study demonstrated that hMSCs secrete several growth factors, including several insulin-like growth factor binding proteins (IGFBPs). Among these, IGFBP-6 binds with high affinity and inhibits insulin growth factor-2 (IGF-2) to inhibit the growth of IGF-2-dependent tumors. However, the function of IGFBP-6 in the nervous system remains to be fully elucidated. The present study investigated the protective effects of IGFBP-6 secreted by hMSCs on H₂O₂-injured primary cortical neuron cultures and lysolecithin-injured organotypic spinal cord slice cultures. Treatment of the H₂O₂-injured cortical neurons with conditioned media from hMSCs (hMSC-CM) increased the phosphorylation of Akt, reduced cell death and mitochondrial translocation of Bax, and regulated extracellular levels of IGF-1 and IGF-2. MTT assay, western blot analysis and ELISA were used to detect the cell viability and protein expression levels, respectively. An inhibitory antibody against IGFBP-6 eliminated this hMSC-CM-mediated neuroprotective effect in the injured cortical neuron cultures and spinal cord slice cultures. In addition, treatment with cyclolignan picropodophyllin, an inhibitor of IGF-1 receptor (IGF-1R), significantly inhibited neuronal protection by hMSC-CM. These findings demonstrated that hMSC-CM-mediated neuroprotection was attributed to IGF-1R-mediated signaling, potentiated via the inhibition of IGF-2 by IGFBP-6. The results of the present study provide insight into the mechanism by which hMSC administration may promote recovery from nerve injury.

Computational Cell Cycle Profiling of Cancer Cells for Prioritizing FDA-Approved Drugs with Repurposing Potential

Discovery of first-in-class medicines for treating cancer is limited by concerns with their toxicity and safety profiles, while repurposing known drugs for new anticancer indications has become a viable alternative. Here, we have developed a new approach that utilizes cell cycle arresting patterns as unique molecular signatures for prioritizing FDA-approved drugs with repurposing potential. As proof-of-principle, we conducted large-scale cell cycle profiling of 884 FDA-approved drugs. Using cell cycle indexes that measure changes in cell cycle profile patterns upon chemical perturbation, we identified 36 compounds that inhibited cancer cell viability including 6 compounds that were previously undescribed. Further cell cycle fingerprint analysis and 3D chemical structural similarity clustering identified unexpected FDA-approved drugs that induced DNA damage, including clinically relevant microtubule destabilizers, which was confirmed experimentally via cell-based assays. Our study shows that computational cell cycle profiling can be used as an approach for prioritizing FDA-approved drugs with repurposing potential, which could aid the development of cancer therapeutics.

Recent insights into the actions of IGFBP-6

IGFBP-6 is an O-linked glycoprotein that preferentially binds IGF-II over IGF-I. It is a relatively selective inhibitor of IGF-II actions including proliferation, survival and differentiation of a wide range of cells. IGFBP-6 has recently been shown to have a number of IGF-independent actions, including promotion of apoptosis in some cells and inhibition of angiogenesis. IGFBP-6 also induces migration of tumour cells including rhabdomyosarcomas by an IGF-independent mechanism. This chemotactic effect is mediated by MAP kinases. IGFBP-6 binds to prohibitin-2 on the cell surface and the latter is required for IGFBP-6-induced migration by a mechanism that is independent of MAP kinases. IGFBP-6 may enter the nucleus and modulate cell survival and differentiation. IGFBP-6 expression is decreased in a number of cancer cells and it has been postulated to act as a tumour suppressor. IGFBP-6 expression is increased in a smaller number of cancers, which may reflect a compensatory mechanism to control IGF-II actions or IGF-independent actions. The relative balance of IGF-dependent and IGF-independent actions of IGFBP-6 in vivo together with the related question regarding the roles of IGFBP-6 binding to IGF and non-IGF ligands are keys to understanding the physiological role of this protein.

CC chemokine ligand 18 and IGF-binding protein 6 as potential serum biomarkers for prostate cancer

Prostate cancer (PCa) is the second leading cause of cancer-related death in men globally. However, there are few sensitive biomarkers for PCa, especially those which can distinguish PCa and benign prostate hyperplasia (BPH). Antibody microarrays allow for high-throughput and high-sensitivity detection of multiple proteins simultaneously, providing a powerful tool for biomarker screening. Here, we selected 46 patients with PCa and 42 controls with BPH, and compared the serum levels of different cytokines in PCa and BPH patients using antibody microarrays. The results indicated that serum levels of macrophage colony-stimulating factor (M-CSF) and CC chemokine ligand 18 (CCL-18) were remarkably higher in PCa patients than those in BPH patients, while serum levels of insulin-like growth factor-binding protein 6 (IGFBP-6) and Fas receptor (Fas), also called tumor necrosis factor receptor superfamily member 6 (TNFRSF6), were significantly lower. M-CSF and Fas/TNFRSF6 have been reported to be associated with PCa pathogenesis, and thus were used as positive controls in the present study. CCL-18 is a chemokine primarily involved in recruitment of the adaptive immune system, while IGFBP-6 has been reported to inhibit proliferation of PCa cells. Serum levels of these four cytokines could distinguish PCa from BPH with high sensitivity and high specificity. Furthermore, the area under the ROC curve (AUC) was above 0.925 and 0.835 for CCL-18 and IGFBP-6, respectively, implying their high diagnostic value. In conclusion, we have identified CCL-18 and IGFBP-6 as new potential serum biomarkers for PCa.

Diethylstilboestrol for the treatment of prostate cancer: past, present and future

The aim of this review was to discuss the most recent data from current trials of diethylstilboestrol (DES) to identify its present role in advanced prostate cancer treatment as new hormonal therapies emerge. The most relevant clinical studies using DES in castration-refractory prostate cancer (CRPC) were identified from the literature. The safety, efficacy, outcomes and mechanisms of action are summarized. In the age of chemotherapy this review highlights the efficacy of oestrogen therapy in CRPC. The optimal point in the therapeutic pathway at which DES should be prescribed remains to be established.

Kininogen 1 and insulin-like growth factor binding protein 6: candidate serum biomarkers of proliferative vitreoretinopathy

BACKGROUND

The aim was to validate whether kininogen 1 (KNG1) or insulin-like growth factor binding protein 6 (IGFBP-6) are serum biomarkers of proliferative vitreoretinopathy (PVR).

METHODS

Samples from vitreous and corresponding serum samples were collected from patients with PVR. The donor vitreous samples and serum samples from healthy volunteers and volunteers who had undergone vitrectomies for other conditions were used as controls. The samples were subsequently analysed using Western blotting (WB) and enzyme-linked immunosorbent assay.

RESULTS

The Western blotting outcomes indicated both IGFBP-6 and KNG1 could be specifically detected in the vitreous and serum samples of patients with PVR. The concentrations of KNG1 and IGFBP-6 were significantly higher in both vitreous and serum samples from patients with severe PVR than in the samples from patients with moderate PVR. The serum concentrations of KNG1 or IGFBP-6 had decreased by the post-vitrectomy examinations. The receiver operating characteristic (ROC) analyses when the concentrations of IGFBP-6 or KNG1 were greater than 181.4 pg/ml or 441.75 ng/ml, respectively, predicted severe PVR with both a sensitivity and specificity of over 70 per cent. When the concentrations of IGFBP-6 or KNG1 were greater than 98.5 pg/ml or 88.5 ng/ml, respectively, they predicted the PVR prognosis with both a sensitivity and specificity of 80 per cent.

CONCLUSIONS

KNG1 and IGFBP-6 may be candidate serum biomarkers of PVR.

Quantitative proteomic determination of diethylstilbestrol action on prostate cancer

Diethylstilbestrol (DES) has a direct cellular mechanism inhibition on prostate cancer. Its action is independent from the oestrogen receptors and is preserved after a first-line hormonal therapy. We aimed to identify proteins involved in the direct cellular inhibition effects of DES on prostate cancer. We used a clonogenic assay to establish the median lethal concentration of DES on 22RV1 cells. 22RV1 cells were exposed to standard and DES-enriched medium. After extraction, protein expression levels were obtained by two-dimensional differential in-gel electrophoresis (2D-DIGE) and isotope labelling tags for relative and absolute quantification (iTRAQ). Proteins of interest were analysed by quantitative RT-PCR and western blotting. The differentially regulated proteins (P<0.01) were interrogated against a global molecular network based on the ingenuity knowledge base. The 2D-DIGE analyses revealed DES-induced expression changes for 14 proteins (>1.3 fold; P<0.05). The iTRAQ analyses allowed the identification of 895 proteins. Among these proteins, 65 had a modified expression due to DES exposure (i.e., 23 overexpressed and 42 underexpressed). Most of these proteins were implicated in apoptosis and redox processes and had a predicted mitochondrial expression. Additionally, ingenuity pathway analysis placed the OAT and HSBP1 genes at the centre of a highly significant network. RT-PCR confirmed the overexpression of OAT (P=0.006) and HSPB1 (P=0.046).

Insulin-like growth factor-binding protein-6 and cancer

The IGF (insulin-like growth factor) system is essential for physiological growth and it is also implicated in a number of diseases including cancer. IGF activity is modulated by a family of high-affinity IGF-binding proteins, and IGFBP-6 is distinctive because of its marked binding preference for IGF-II over IGF-I. A principal role for IGFBP-6 is inhibition of IGF-II actions, but recent studies have indicated that IGFBP-6 also has IGF-independent effects, including inhibition of angiogenesis and promotion of cancer cell migration. The present review briefly summarizes the IGF system in physiology and disease before focusing on recent studies on the regulation and actions of IGFBP-6, and its potential roles in cancer cells. Given the widespread interest in IGF inhibition in cancer therapeutics, increasing our understanding of the mechanisms underlying the actions of the IGF ligands, receptors and binding proteins, including IGFBP-6, will enhance our ability to develop optimal treatments that can be targeted to the most appropriate patients.

Inhibition of XO or NOX attenuates diethylstilbestrol-induced endothelial nitric oxide deficiency without affecting its effects on LNCaP cell invasion and apoptosis

Oestrogen protects cardiovascular health partially via an up-regulation of NO• (NO radical) production. Its synthetic analogue DES (diethylstilbestrol), used as a potent androgen deprivation therapy for patients with prostate cancer, is however associated with high incidence of thromboembolic events. Exposure of BAECs (bovine aortic endothelial cells) to pharmacologically relevant dosage (12.5 μmol/l, 24 h) of DES resulted in a marked reduction in endothelial NO• bioavailability determined by ESR (electron spin resonance), while 17β-oestradiol instead increased NO• production as expected. Intriguingly, endothelial O(2)•- (superoxide anion) production was up-regulated by DES in vitro and in vivo, which was, however, attenuated by the ER (oestrogen receptor) antagonist ICI 182780, the XO (xanthine oxidase) inhibitor oxypurinol or the NOX (NADPH oxidase) inhibitor NSC23766. These agents also restored NO• production. DES alone in a cell-free system did not produce any ESR-sound O(2)•- signal. Of note, eNOS (endothelial NO synthase) mRNA and protein remained unchanged in response to DES. These results suggest that receptor-dependent activation of XO or NOX, and subsequent production of O(2)•-, mediate DES-induced NO• deficiency. This could represent a previously unrecognized mechanism that is responsible for cardiovascular complications of DES administration. Importantly, DES-induced suppression of LNCaP cell invasion and apoptosis were not affected by XO or NOX inhibitor. Therefore combinatorial therapy of DES and XO/NOX inhibitor may prove to be an innovative and useful therapeutic option in eliminating cardiovascular complications of DES, while preserving its anti-cancer effects, benefiting patients with advanced cancer who do not respond well to any other treatments but DES.

Patterns of deregulation of insulin growth factor signalling pathway in paediatric and adult gastrointestinal stromal tumours

BACKGROUND

Data regarding the patterns and the mechanisms of deregulation of the insulin growth factor (IGF) pathway in adult and paediatric gastrointestinal stromal tumours (GISTs) are limited.

METHODS

We investigated the expression profiling of the genes encoding the main components of the IGF signalling pathway in 131 GISTs (106 adults, 21 paediatric and four young adults) and 25 other soft-tissue sarcomas (STS) using an Affymetrix U133A platform. IGF2 was investigated for loss of imprinting (LOI) whereas IGF1R was analysed for copy number aberration and mutation.

RESULTS

IGF2 was the most highly overexpressed gene of the IGF pathway in GIST. IGF2 expression was also significantly higher than in other STS. IGF2 expression was correlated to the age onset and mutational status of GIST. Indeed, IGF2 expression was significantly higher in the 'adult' group than in the 'paediatric' and 'young adult' groups. Among adult GIST, IGF2 expression was higher in tumours lacking Homo sapiens v-kit Hardy-Zuckerman 4 feline sarcoma viral oncogene homolog (KIT) or alpha-type platelet-derived growth factor receptor (PDGFRA) mutations in comparison with mutated cases. A trend for a higher expression of IGF2 in resistant GIST in comparison to responsive GIST was also found. Overexpression of IGF2 was not related to LOI. Conversely, the expression of the IGF1R gene was significantly higher in the paediatric group than in the adult group. No copy number gains or mutations of IGF1R were observed.

CONCLUSION

The IGF pathway is deregulated in GIST with distinct patterns according to age onset and mutational status. The IGF pathway may represent a therapeutic target in patients with primary or secondary resistance to imatinib.

Predicting environmental chemical factors associated with disease-related gene expression data

BACKGROUND

Many common diseases arise from an interaction between environmental and genetic factors. Our knowledge regarding environment and gene interactions is growing, but frameworks to build an association between gene-environment interactions and disease using preexisting, publicly available data has been lacking. Integrating freely-available environment-gene interaction and disease phenotype data would allow hypothesis generation for potential environmental associations to disease.

METHODS

We integrated publicly available disease-specific gene expression microarray data and curated chemical-gene interaction data to systematically predict environmental chemicals associated with disease. We derived chemical-gene signatures for 1,338 chemical/environmental chemicals from the Comparative Toxicogenomics Database (CTD). We associated these chemical-gene signatures with differentially expressed genes from datasets found in the Gene Expression Omnibus (GEO) through an enrichment test.

RESULTS

We were able to verify our analytic method by accurately identifying chemicals applied to samples and cell lines. Furthermore, we were able to predict known and novel environmental associations with prostate, lung, and breast cancers, such as estradiol and bisphenol A.

CONCLUSIONS

We have developed a scalable and statistical method to identify possible environmental associations with disease using publicly available data and have validated some of the associations in the literature.

Lupeol inhibits proliferation of human prostate cancer cells by targeting beta-catenin signaling

Lupeol, a dietary triterpene, was shown to decrease serum prostate-specific antigen levels and inhibit the tumorigenicity of prostate cancer (CaP) cells in vivo. Here, we show that Lupeol inhibits the proliferative potential of CaP cells and delineated its mechanism of action. Employing a focused microarray of human CaP-associated genes, we found that Lupeol significantly modulates the expression level of genes such as ERBB2, tissue inhibitor of metalloproteinases-3, cyclin D1 and matrix metalloproteinase (MMP)-2 that are known to be associated with proliferation and survival. A common feature of these genes is that all of them are known to either regulate or act as downstream target of beta-catenin signaling that is highly aberrant in CaP patients. Lupeol treatment significantly (1) reduced levels of beta-catenin in the cytoplasmic and nuclear fractions, (2) modulated expression levels of glycogen synthase kinase 3 beta (GSK3beta)-axin complex (regulator of beta-catenin stability), (3) decreased the expression level and enzymatic activity of MMP-2 (downstream target of beta-catenin), (4) reduced the transcriptional activation of T Cell Factor (TCF) responsive element (marker for beta-catenin signaling) in pTK-TCF-Luc-transfected cells and (5) decreased the transcriptional activation of MMP-2 gene in pGL2-MMP-2-Luc-transfected cells. Effects of Lupeol treatment on beta-catenin degradation were significantly reduced in CaP cells where axin is knocked down through small interfering RNA transfection and GSK3beta activity is blocked. Collectively, these data suggest the multitarget efficacy of Lupeol on beta-catenin-signaling network thus resulting in the inhibition CaP cell proliferation. We suggest that Lupeol could be developed as an agent for chemoprevention as well as chemotherapy of human CaP.

Diethylstilbestrol glutamate as a potential substrate for ADEPT

The combination of systemic toxicity, water insolubility and a labile chemical structure has limited the clinical use of diethylstilbestrol (DES) 1 for the treatment of prostate cancer. To determine if DES could potentially be a prodrug substrate for the pre-targeting strategy known as antibody directed enzyme prodrug therapy (ADEPT), the DES-glutamate 5 was prepared. The synthesis required the activation of the bis-t-butyl glutamate ester 2 to the isocyanate 3 followed by addition of DES 1. The desired DES-glutamate 5 was water-soluble and upon incubation with carboxypeptidase G2 (CPG2) underwent carbamate cleavage to give DES 1. A control reaction in the absence of CPG2 demonstrated that the enzyme was necessary for rapid glutamate cleavage to give DES 1. HPLC analysis was required to follow the reaction of DES-glutamate 5 with CPG2. These preliminary results suggest that it may be possible to examine an ADEPT strategy for DES provided enzymatic kinetics can be measured.

Identification of IGFBP-6 as an effector of the tumor suppressor activity of SEMA3B

SEMA3B, a member of class 3 semaphorins, is a tumor suppressor. Competition with vascular endothelial growth factor (VEGF)165 explains a portion of the activity, whereas the VEGF-independent mechanism was not elucidated. We employed a microarray and screened for the genes whose expression was increased by SEMA3B in NCI-H1299 cells. Insulin-like growth factor-binding protein-6 (IGFBP-6), a tumor suppressor, showed greatest difference in the expression level. Introduction of IGFBP-6 cDNA reduced colony formation both on the dish surface and in soft agar. Insulin-like growth factor II, which antagonizes IGFBP-6, partly abrogated the effect. Inhibition of IGFBP-6 by small interfering RNA diminished the sub-G0/G1 population that was induced by SEMA3B and abrogated the growth suppressive effect of SEMA3B. We concluded that IGFBP-6 is the effector of tumor suppressor activity of SEMA3B in NCI-H1299 cells. It has been reported that beta-catenin suppresses the expression of IGFBP-6. Introduction of beta-catenin into the cells partly abrogated the growth suppressive effect of SEMA3B. Our result indicates that semaphorin signaling and beta-catenin signaling converge on IGFBP-6 and antithetically affect their functions.

Differential effects of diabetes induced by streptozotocin and that develops spontaneously on prostate growth in Bio Breeding (BB) rats

We investigated molecular changes in the response to insulin in prostates of spontaneously developed (Bio Breeding) and streptozotocin (STZ)-induced diabetic rats that received sufficient amounts (euglycemic group), or suboptimal doses (hyperglycemic group) of insulin for 32 weeks, using Affymetrix GeneChip analysis of gene expression. Alterations in gene expression levels identified by microarray analysis, having potential biological relevance to prostate growth, were verified by real-time reverse transcription polymerase chain reaction (RT-PCR). A significant decrease in the weight of ventral prostate was observed in the hyperglycemic STZ-induced but not spontaneously developed diabetic group. Microarray analysis revealed that gene expression profiles were distinctly different in each region of the prostate, and that hyperglycemic diabetes in spontaneously developed and STZ-diabetic rats was associated with differential changes in the prostatic expression levels of 856 genes, of which 35 were related to cell growth, proliferation and death. RT-PCR data verified significant differences in the mRNA expression levels of Igfbp6, Tieg, and Clu between euglycemic and hyperglycemic groups, whereas expression levels of these genes in control and euglycemic diabetic groups were not significantly different. In ventral prostate, the mRNA expression levels of Igfbp6 and Tieg were significantly higher in the hyperglycemic STZ-induced diabetic than in the hyperglycemic spontaneously diabetic BBDP/Wor rats. Our data demonstrate that the diabetes induced by STZ in the BBDR/Wor rats affects prostate growth and the molecular response to insulin differently than that observed in BBDP/Wor rats that develop diabetes spontaneously.

Diethylstilbestrol inhibits phospholipase D activity and degranulation by stimulated human neutrophils

In the present study the effects of diethylstilbestrol on phospholipase D activity and degranulation by human neutrophils were examined. Diethylstilbestrol is a synthetic estrogen and has structural similarity to resveratrol. Resveratrol is a natural polyphenolic antioxidant and has been shown to inhibit the activity of phospholipase D in stimulated neutrophils. Phospholipase D catalyzes the hydrolysis of phosphatidylcholine to yield phosphatidic acid and choline. It also catalyzes the transfer of the phosphatidyl group to ethanol forming phosphatidylethanol at the expense of phosphatidic acid. Phospholipase D activation is associated with degranulation by neutrophils stimulated with chemotactic peptide, formyl-methionyl-leucyl-phenylalanine. The results show that diethylstilbestrol at 100 microM induced a complete inhibition of phosphatidic acid formation in neutrophils, the latter activated by chemotactic peptide. In the presence of ethanol, diethylstilbestrol dose dependently reduced phosphatidylethanol formation induced by chemotactic peptide or by phorbol 12-myristate 13-acetate, indicative of diethylstilbestyrol inhibition of phospholipase D activity. The results also demonstrate that diethylstilbestrol inhibited degranulation by chemotactic peptide-stimulated neutrophils. In comparison to resveratrol, diethylstilbestrol exhibits a stronger inhibition on PA formation, phospholipase D activity and degranulation. These findings suggest that diethylstilbestrol-like resveratrol, may have anti-inflammatory effect in vitro.

Endocrine regulation of prostate cancer growth

Prostate cancer is one of the most frequently diagnosed malignant neoplasms in the Western world. The focus of this article is on regulation of proliferation, apoptosis, angiogenesis and differentiation by steroid and peptide hormones. Steroid hormones, in particular androgens and estrogens, exert their effects through respective receptors. The androgen receptor is functional in all stages of the disease and it can be activated in a ligand-dependent and -independent manner. In prostate cancer, expression of some androgen receptor coactivators increases during tumor progression. Interleukins and transforming growth factor-β are multifunctional regulators of prostate growth and proliferation. Signal transduction cascades of fibroblast growth factors and insulin-like growth factors are responsible for increased survival and angiogenesis in prostate cancer. In clinical specimens obtained from prostate cancer, there is an increased phosphorylation of mitogen-activated protein kinase and Akt kinase, whose action in the regulation of cell survival is redundant.

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.