Vasohibin‑2 promotes proliferation in human breast cancer cells via upregulation of fibroblast growth factor‑2 and growth/differentiation factor‑15 expression

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.

[Vasohibin-2 promotes proliferation and metastasis of cervical cancer cells by regulating epithelial-mesenchymal transition]

OBJECTIVE

To explore the role of vasohibin-2 (VASH2) in regulation of proliferation and metastasis of cervical cancer cells.

METHODS

We analyzed the differentially expressed genes between cervical cancer cells with flotillin-1 overexpression and knockdown by RNA-seq combined with analysis of public databases. The expression levels of VASH2 were examined in normal cervical epithelial cells (HcerEpic), cervical cancer cell lines (HeLa, C-33A, Ca ski, SiHa and MS751) and fresh cervical cancer tissues with different lymph node metastasis status. We further tested the effects of lentivirus-mediated overexpression and interference of VASH2 on proliferation, migration, invasion and lymphatic vessel formation of the cervical cancer cells and detected the expression levels of key epithelial-mesenchymal transition (EMT) markers and TGF-β mRNA.

RESULTS

RNA-seq and analysis of public databases showed that VASH2 expression was significantly upregulated in cervical cancer cells exogenously overexpressing flotillin-1 (P < 0.05) and downregulated in cells with flotillin-1 knockdown (P < 0.05), and was significantly higher in cervical cancer tissues with lymph node metastasis than in those without lymph node metastasis (P < 0.01). In cervical cancer cell lines Ca Ski, SiHa, and MS751 and cervical cancer tissue specimens with lymph node metastasis, VASH2 expression was also significantly upregulated as compared with HcerEpic cells and cervical cancer tissues without lymph node metastasis (P < 0.05). Exogenous overexpression of VASH2 significantly promoted proliferation, migration, invasion and lymphatic vessel formation of cervical cancer cells, whereas these abilities were significantly inhibited in cells with VASH2 knockdown (P < 0.05). The cervical cancer cells overexpressing VASH2 showed significant down- regulation of e-cadherin and up- regulation of N-cadherin, Vimentin and VEGF-C, while the reverse changes were detected in cells with VASH2 knockdown (P < 0.05). TGF-β mRNA expression was significantly up-regulated in cervical cancer cells overexpressing VASH2 and down-regulated in cells with VASH2 knockdown (P < 0.001).

CONCLUSION

Flotillin-1 may participate in TGF-β signaling pathway-mediated EMT through its down-stream target gene VASH2 to promote the proliferation, migration, invasion and lymphatic vessel formation of cervical cancer cells in vitro.

IGFBP-6: At the Crossroads of Immunity, Tissue Repair and Fibrosis

Insulin-like growth factors binding protein-6 (IGFBP-6) is involved in a relevant number of cellular activities and represents an important factor in the immune response, particularly in human dendritic cells (DCs). Over the past several years, significant insights into the IGF-independent effects of IGFBP-6 were discovered, such as the induction of chemotaxis, capacity to increase oxidative burst and neutrophils degranulation, ability to induce metabolic changes in DCs, and, more recently, the regulation of the Sonic Hedgehog (SHH) signaling pathway during fibrosis. IGFBP-6 has been implicated in different human diseases, and it plays a rather controversial role in the biology of tumors. Notably, well established relationships between immunity, stroma activity, and fibrosis are prognostic and predictive of response to cancer immunotherapy. This review aims at describing the current understanding of mechanisms that link IGFBP-6 and fibrosis development and at highlighting the multiple roles of IGFBP-6 to provide an insight into evolutionarily conserved mechanisms that can be relevant for inflammation, tumor immunity, and immunological diseases.

Comprehensive Analysis of IGFBPs as Biomarkers in Gastric Cancer

OBJECTIVE

Gastric cancer is the fifth most common cancer worldwide and the third leading cause of cancer-related deaths. Insulin-like growth-factor-binding proteins (IGFBPs) were initially identified as passive inhibitors that combined with insulin-like growth factors (IGFs) in serum. However, more recent data have shown that they have different expression patterns and a variety of functions in the development and occurrence of cancers. Thus, their various roles in cancer still need to be elucidated. This study aimed to explore the IGFBPs and their prognostic value as markers in gastric cancer.

METHODS

Oncomine, Gene Expression Profiling Interactive Analysis (GEPIA), Kaplan-Meier Plotter, cBioPortal, GeneMANIA, and TIMER were used to analyze the differential expression, prognostic value, genetic alteration, and association with immune cell infiltration of IGFPBs in gastric cancer.

RESULTS

Expression levels of IGFBP3, IGFBP4, and IGFBP7 were significantly elevated in gastric cancer tissues, whereas those of IGFBP1 were reduced in normal tissues. IGFBP1/5/7 expression was significantly associated with overall survival whereas IGFBP6/7 expression was significantly correlated with disease-free survival in gastric cancer patients. IGFBP3/5/6/7 were associated with clinical cancer stage. Gene ontology and Kyoto Encyclopedia of Genes and Genome analyses showed that IGFBP3/5/7 were mainly enriched in focal adhesion, extracellular matrix structural constituent, cell-substratist junction, extracellular structure, and matrix organization. Stomach adenocarcinoma (STAD) and gastric cancer had more IGFBP1-7 mutations than other tumor types. Hub gene analysis showed that TP53 and IGF2 expression was significantly elevated in STAD patients; PLG, PAPPA, AFP, and CYR61 were associated with overall survival rate; and IGFALS, PLG, IGF1, AHSG, and FN1 were associated with disease-free survival. Finally, IGFBP3-7 were all associated with cancer-associated fibroblast infiltration in STAD, colon adenocarcinoma, and rectal adenocarcinoma.

CONCLUSION

Our study provides a comprehensive analysis and selection of IGFBPs as prognostic biomarkers in STAD. This was the first bioinformatic analysis study to describe the involvement of IGFBPs, especially IGFBP7, in gastric cancer development through the extracellular matrix.

Post-translational modifications of tubulin: their role in cancers and the regulation of signaling molecules

Microtubules play an important role in regulating several vital cellular activities, including cell division and tissue organization, through their dynamic protofilament network. In addition to forming the cytoskeleton, microtubules regulate the intracellular trafficking of cytoplasmic components and various signaling molecules, depending on the presence of post-transitional modifications (PTMs) and binding proteins. Accumulating evidence indicates the significant role of microtubule PTMs on cancer behavior. The PTMs that frequently occur on microtubules include acetylation, detyrosination, tyrosination, polyglutamylation, and polyglycylation. Alterations in these PTMs cause global effects on intracellular signal transduction, strongly linked to cancer pathogenesis. This review provides an update on the role of microtubule PTMs in cancer aggressiveness, particularly regarding cell death, sensitivity to chemotherapy, cell migration, and invasion. Additionally, it provides a mechanistic explanation of the molecular signaling pathways involved. This information might prove useful for predictive or therapeutic purposes.

Growth differentiation factor-15 and lactoferrin immuno-expression in breast cancer: relationship with body iron-status and survival outcome

We aimed to evaluate the expression of growth differentiation factor-15 (GDF-15) and lactoferrin (Lf) in tumor and their relationship with the body iron-status and overall survival (OS) outcome of patients with breast cancer. A retrospective cohort study of female patients with primary breast cancer was performed. Clinical tumor samples from the Second Affiliated Hospital of Soochow University between December 2008 and June 2014 were collected. The immuno-expression of GDF-15 and Lf was stratified into positive or negative expression. Kaplan-Meier method and Cox proportional hazards regression model were used for data analysis. 74 breast cancer patients with a mean age of 52 years were included into our study. 14 (18.9%) patients were died by the end of August 1, 2019. The serum iron level of patients with GDF-15 (+)/Lf(-) expression was higher than that of patients with other expression patterns (18.2 ± 5.4 vs. 15.5 ± 5.0 μmol/L, P = 0.038), but was not associated with OS. In univariate Cox analyses, GDF-15(+) and GDF-15(+)/Lf(-) were significantly correlated with high mortality risk (HR = 3.75, 95%CI 1.05-13.48, P = 0.025; HR = 5.00, 95%CI 1.56-16.04, P = 0.004, respectively). After adjusted for age, menopause status and primary tumor grade, the association between GDF-15 and OS disappeared. However, the association between GDF-15/Lf and OS still existed in GDF-15(+)/Lf(-) (HR = 4.50, 95%CI 1.31-15.51, P = 0.017). The combined immuno-expression pattern of GDF-15 and Lf was significant associated with high serum iron level. GDF-15/Lf could be a powerful biomarker to predict survival outcome of patients with breast cancer but still needed to be confirmed by future studies.

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.

VASH2 Promotes Cell Proliferation and Resistance to Doxorubicin in Non-Small Cell Lung Cancer via AKT Signaling

Vasohibin2 (VASH2), a proangiogenic factor, has been demonstrated to play an oncogenic role in some common human cancers. However, the detailed function of VASH2 in non-small cell lung cancer (NSCLC) has not previously been studied. In this study, we found that VASH2 was significantly upregulated in NSCLC tissues and cell lines, and its increased expression was associated with NSCLC progression and poor prognosis of patients. Knockdown of VASH2 markedly inhibited cell proliferation and P-glycoprotein expression in NSCLC cells. Overexpression of VASH2 enhanced cell proliferation, P-glycoprotein expression, as well as doxorubicin resistance in NSCLC cells. Moreover, the expression levels of VASH2 were significantly increased in newly established doxorubicin-resistant NSCLC cells. Molecular mechanism investigation revealed that inhibition of VASH2 expression in NSCLC cells suppressed the activity of AKT signaling, and overexpression of VASH2 enhanced the activity of AKT signaling. We further showed that downregulation of AKT signaling activity using AKT inhibitor LY294002 markedly inhibited NSCLC cell proliferation and resistance to doxorubicin induced by VASH2. In conclusion, the findings in the present study indicate that VASH2 promotes NSCLC cell proliferation and resistance to doxorubicin via modulation of AKT signaling. Thus, we suggest that VASH2 may become a potential therapeutic target for the treatment of NSCLC.

Gene expression profiling of spontaneously occurring canine mammary tumours: Insight into gene networks and pathways linked to cancer pathogenesis

Spontaneously occurring canine mammary tumours (CMTs) are the most common neoplasms of unspayed female dogs leading to thrice higher mortality rates than human breast cancer. These are also attractive models for human breast cancer studies owing to clinical and molecular similarities. Thus, they are important candidates for biomarker studies and understanding cancer pathobiology. The study was designed to explore underlying molecular networks and pathways in CMTs for deciphering new prognostic factors and therapeutic targets. To gain an insight into various pathways and networks associated with the development and pathogenesis of CMTs, comparative cDNA microarray expression profiling was performed using CMT tissues and healthy mammary gland tissues. Upon analysis, 1700 and 1287 differentially expressed genes (DEGs, P ≤ 0.05) were identified in malignant and benign tissues, respectively. DEGs identified from microarray analysis were further annotated using the Ingenuity Systems Pathway Analysis (IPA) tool for detection of deregulated canonical pathways, upstream regulators, and networks associated with malignant, as well as, benign disease. Top scoring key networks in benign and malignant mammary tumours were having central nodes of VEGF and BUB1B, respectively. Cyclins & cell cycle regulation and TREM1 signalling were amongst the top activated canonical pathways in CMTs. Other cancer related significant pathways like apoptosis signalling, dendritic cell maturation, DNA recombination and repair, Wnt/β-catenin signalling, etc. were also found to be altered. Furthermore, seven proteins (ANXA2, APOCII, CDK6, GATC, GDI2, GNAQ and MYH9) highly up-regulated in malignant tissues were identified by two-dimensional gel electrophoresis (2DE) and MALDI-TOF PMF studies which were in concordance with microarray data. Thus, the study has uncovered ample number of candidate genes associated with CMTs which need to be further validated as therapeutic targets and prognostic markers.

C5a induces A549 cell proliferation of non-small cell lung cancer via GDF15 gene activation mediated by GCN5-dependent KLF5 acetylation

Non-small cell lung cancer (NSCLC) is the most common type of lung cancer, and multiple evidence has confirmed that C5a production is elevated in NSCLC microenvironment. Although NSCLC cell proliferation induced by C5a has been reported, the involved mechanism has not been elucidated. In this study, we examined the proliferation-related genes (i.e., KLF5, GCN5, and GDF15) and C5a receptor (C5aR) expression in tumor tissues as well as C5a concentration in plasma of NSCLC patients, and then determined the roles of KLF5, GCN5, and GDF15 in C5a-triggered NSCLC cell proliferation and the related mechanism both in vitro and in vivo. Our results found that the expression of KLF5, GCN5, GDF15, C5aR, and C5a was significantly upregulated in NSCLC patients. Mechanistic exploration in vitro revealed that C5a could facilitate A549 cell proliferation through increasing KLF5, GCN5, and GDF15 expression. Besides, KLF5 and GCN5 could form a complex, binding to GDF15 promoter in a KLF5-dependent manner and leading to GDF15 gene transcription. More importantly, GCN5-mediated KLF5 acetylation contributing to GDF15 gene transcription and cell proliferation upon C5a stimulation, the region (−103 to +58 nt) of GDF15 promoter which KLF5 could bind to, and two new KLF5 lysine sites (K335 and K391) acetylated by GCN5 were identified for the first time. Furthermore, our experiment in vivo demonstrated that the growth of xenograft tumors in BALB/c nude mice was greatly suppressed by the silence of KLF5, GCN5, or GDF15. Collectively, these findings disclose that C5a-driven KLF5–GCN5–GDF15 axis had a critical role in NSCLC proliferation and might serve as targets for NSCLC therapy.

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.

Direct repression of the oncogene CDK4 by the tumor suppressor miR-486-5p in non-small cell lung cancer

MicroRNAs are a class of non-coding single-stranded RNA, 20-23 nucleotide in length, which can be involved in the regulation of gene expression. Through binding with 3′-untranslated regions (3′-UTR), microRNAs can cause degradation of target mRNAs or inhibition of translation, and thus regulating the expression of genes at the post-transcriptional level. In this study, we found that miR-486-5p was significantly downregulated in non-small cell lung cancer (NSCLC) tissues and cell lines, suggesting that miR-486-5p might function as a tumor suppressor in lung cancer. Additionally, we showed that CDK4, an oncogene that plays an important role in cell cycle G1/S phase progression, was directly targeted by miR-486-5p. Furthermore, our data reveals that knockdown of CDK4 by siRNA can inhibit cell proliferation, promote apoptosis, and impede cell-cycle progression. In epigenetics, the upstream promoter of miR-486-5p was strongly regulated by methylation in NSCLC. Collectively, our results suggest that miR-486-5p could not only inhibit NSCLC by downregulating the expression of CDK4, but also be as a promising and potent therapy in the near future.

The roles of vasohibin and its family members: Beyond angiogenesis modulators

Vasohibin-1 is an intrinsic angiogenesis inhibitor, and is expressed in endothelial cells via induction by pro-angiogenesis factors. It is known to inhibit several processes of angiogenesis, with different mechanisms from extrinsic angiogenesis inhibitors. Vasohibin-2 is mainly expressed by mononuclear cells which have been mobilized from bone marrow. It not only promotes angiogenesis, but also modulates the releases of FGF-2 and VEGF, which are the two major inducers for vasohibin1. Hypoxic environment induces the expression of hypoxia-inducible Factor 1α with a result of VEGF release nearly in all tumor cell lines and tissues. However, it has been observed that hypoxia reduces the inducible effects of VEGF on vasohibin, which indicates that a complicated mechanism exists in the angiogenesis. Vasohibin and its family members play important roles in both the physiological and pathological procedures, in contrary but complementary patterns. Furthermore, human aortic smooth muscle cells and fibroblast have also been detected to express vasohibin on a moderate to weak scale range. Recently, the results of an increasing number of studies in vivo have shown that vasohibin can also be detected in several cancers, and is associated with micro-vessel densities, histology grades, invasions, poor clinical features, metastasis, and dissemination in abdominal cavities, as well as EMT. In more recent reports, it has been confirmed that, along with being angiogenesis regulators, a variety of other roles have been associated with this family. The focus of this study was the upstream regulatory mechanisms of vasohibin expressions, and their role in regard to the downstream target proteins of vasohibin, especially in carcinoma. Vasohibin is considered to be an original angiogenesis inhibitor, and has a much broader significance in pathological processes. It can be taken as an independent prognostic factor, as well as a potential strategy for cancer therapy programs.

Vasohibin 2 as a potential predictor of aggressive behavior of triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a subtype breast cancer with aggressive behavior, advanced disease status and poor prognosis. Because of the lack of targeting agents and limited therapeutic options, treatment of TNBC remains a great clinical challenge. Vasohibin 2 (VASH2) was previously identified as an angiogenic factor, but its role in TNBC tumorigenesis is unknown. Using quantitative PCR and western blot analyses, we found that VASH2 is overexpressed in TNBC cells and tissues. Knockdown of VASH2 via siRNA inhibited the proliferation of the TNBC cell lines by delaying cell cycle progression and increasing apoptosis. Further analyses showed that the VASH2-mediated increase in the transcription of fibroblast growth factor-2, vascular endothelial growth factor and vasohibin 1 may be the mechanism underlying these effects. Taken together, these data indicate that VASH2 is abnormally expressed in TNBC, indicating a novel and important role for VASH2 in TNBC malignant transformation.

The lncRNA H19 mediates breast cancer cell plasticity during EMT and MET plasticity by differentially sponging miR-200b/c and let-7b

Metastasis is a multistep process by which tumor cells disseminate from their primary site and form secondary tumors at a distant site. The pathophysiological course of metastasis is mediated by the dynamic plasticity of cancer cells, which enables them to shift between epithelial and mesenchymal phenotypes through a transcriptionally regulated program termed epithelial-to-mesenchymal transition (EMT) and its reverse process, mesenchymal-to-epithelial transition (MET). Using a mouse model of spontaneous metastatic breast cancer, we investigated the molecular mediators of metastatic competence within a heterogeneous primary tumor and how these cells then manipulated their epithelial-mesenchymal plasticity during the metastatic process. We isolated cells from the primary mammary tumor, the circulation, and metastatic lesions in the lung in TA2 mice and found that the long noncoding RNA (lncRNA) H19 mediated EMT and MET by differentially acting as a sponge for the microRNAs miR-200b/c and let-7b. We found that this ability enabled H19 to modulate the expression of the microRNA targets Git2 and Cyth3, respectively, which encode regulators of the RAS superfamily member adenosine 5'-diphosphate (ADP) ribosylation factor (ARF), a guanosine triphosphatase (GTPase) that promotes cell migration associated with EMT and disseminating tumor cells. Decreasing the abundance of H19 or manipulating that of members in its axis prevented metastasis from grafts in syngeneic mice. Abundance of H19, GIT2, and CYTH3 in patient samples further suggests that H19 might be exploited as a biomarker for metastatic cells within breast tumors and perhaps as a therapeutic target to prevent metastasis.

Targeting human vasohibin-2 by a neutralizing monoclonal antibody for anti-cancer treatment

There are two members of the vasohibin (VASH) family, VASH1 and VASH2. VASH1 is expressed mainly in endothelial cells to inhibit angiogenesis, whereas VASH2 is expressed mainly in cancer cells to stimulate tumor growth. The aim of the present study was to establish neutralizing monoclonal antibody (mAb) against human VASH2 and apply it as an anti‐cancer treatment. We previously raised mAb against several synthetic peptides of hVASH1, and found that one of them exhibited neutralizing activity against hVASH1. Because of the similarity in the amino acid sequences between VASH1 and VASH2, we hypothesized that they shared the bioactive center. When we mutated four amino acids within the region, the mutant VASH2 lost its pro‐angiogenic activity. Therefore, we raised mAb against a synthetic peptide overlapping the mutated amino acids of hVASH2, and isolated one clone (1760) that almost completely inhibited the stimulatory effect of hVASH2 on the migration of and tube formation by endothelial cells. When we used this clone 1760 antibody for cancer treatment, the peritoneal injection of it inhibited both tumor growth and angiogenesis in a mouse xenograft model of human cancer cells. In terms of anti‐tumor activity, 25 mg/kg of clone 1760 was equivalent to 5 mg/kg of bevacizmab. From these results, we propose the targeting of human VASH2 with neutralizing mAb as a new strategy for cancer treatment.

Vasohibin 2 reduces chemosensitivity to gemcitabine in pancreatic cancer cells via Jun proto-oncogene dependent transactivation of ribonucleotide reductase regulatory subunit M2

Background

Vasohibin 2 (VASH2) has previously been identified as an agiogenenic factor and a cancer related protein. Here we investigated the association of VASH2 expression and chemoresistance in pancreatic cancer.

Methods

Immunohistochemical staining for VASH2 was performed on 102 human pancreatic cancer samples. Pancreatic cancer cell line models exhibiting overexpression or knockdown of VASH2 were generated. Gene expression analyses were carried out to determine genes differentially regulated by VASH2. Putative transcription factors that are downstream mediators of gene expression regulated by VASH2 were queried bioinformatically. Dual-luciferase reporter assays and ChIP assays were performed to confirm transactivation of target genes following VASH2 overexpression or knockdown.

Results

VASH2 protein expression was higher in human pancreatic cancer than in paired adjacent tissues and elevated VASH2 levels were associated with gemcitabine chemoresistance. In cell line models of pancreatic cancer, VASH2 expression induced gemcitabine chemoresistance in vitro and in vivo. It was discovered that expression of ribonucleotide reductase regulatory subunit M2 (RRM2) is regulated by VASH2; immunohistochemical analysis demonstrated a positive association of VASH2 expression and RRM2 expression in human pancreatic cancer tissues. Bioinformatics analyses revealed that induction of the Jun proto-oncogene (JUN) by VASH2 is responsible for upregulation of RRM2 expression; this JUN-dependent regulation of RRM2 by VASH2 was confirmed by chromatin immunoprecipitation and dual luciferase reporter assays, which demonstrated that JUN directly binds with the RRM2 promoter to activate transcription.

Conclusions

These data suggest that VASH2 reduces the chemosensitivity to gemcitabine in pancreatic cancer cells via JUN-dependent transactivation of RRM2.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-017-0619-6) contains supplementary material, which is available to authorized users.

Domain architecture of vasohibins required for their chaperone-dependent unconventional extracellular release

Vasohibins (VASH1 and VASH2) are recently identified regulators of angiogenesis and cancer cell functions. They are secreted proteins without any classical secretion signal sequences, and are thought to be secreted instead via an unconventional protein secretion (UPS) pathway in a small vasohibin-binding protein (SVBP)-dependent manner. However, the precise mechanism of SVBP-dependent UPS is poorly understood. In this study, we identified a novel UPS regulatory system in which essential domain architecture (VASH-PS) of VASHs, comprising regions VASH1_91-180 and VASH2_80-169 , regulate the cytosolic punctate structure formation in the absence of SVBP. We also demonstrate that SVBP form a complex with VASH1 through the VASH1_274-282 (SIa), VASH1_139-144 (SIb), and VASH1_133-137 (SIc), leading to the dispersion in the cytosol and extracellular release of VASH1. The amino acid sequences of VASH-SIa and VASH-PS, containing SIb and SIc, are highly conserved among VASH family members in vertebrates, suggesting that SVBP-dependent UPS may be common within the VASH family. This novel UPS regulatory system may open up new avenues for understanding fundamental protein secretion in vertebrates.

Vasohibin 2 promotes epithelial-mesenchymal transition in human breast cancer via activation of transforming growth factor β 1 and hypoxia dependent repression of GATA-binding factor 3

Vasohibin 2 (VASH2) is identified as an angiogenic factor, and has been implicated in tumor angiogenesis, proliferation and epithelial-mesenchymal transition (EMT). To investigate the EMT role of VASH2 in breast cancer, we overexpressed or knocked down expression of VASH2 in human breast cancer cell lines. We observed that VASH2 induced EMT in vitro and in vivo. The transforming growth factor β1 (TGFβ1) pathway was activated by VASH2, and expression of a dominant negative TGFβ type II receptor could block VASH2-mediated EMT. In clinical breast cancer tissues VASH2 positively correlated with TGFβ1 expression, but negatively correlated with E-cadherin (a marker of EMT) expression. Under hypoxic conditions in vitro or in vivo, we found that down-regulation of estrogen receptor 1 (ESR1) in VASH2 overexpressing ESR1 positive cells suppressed E-cadherin. Correlation coefficient analysis indicated that VASH2 and ESR1 expression were negatively correlated in clinical human breast cancer tissues. Further study revealed that a transcription factor of ESR1, GATA-binding factor 3 (GATA3), was down-regulated by VASH2 under hypoxia or in vivo. These findings suggest that VASH2 drives breast cancer cells to undergo EMT by activation of the TGFβ1 pathway and hypoxia dependent repression GATA3-ESR1 pathway, leading to cancer metastasis.

Vasohibins: new transglutaminase-like cysteine proteases possessing a non-canonical Cys-His-Ser catalytic triad

Vasohibin-1 and Vasohibin-2 regulate angiogenesis, tumour growth and metastasis. Their molecular functions, however, were previously unknown, in large part owing to their perceived lack of homology to proteins of known structure and function. To identify their functional amino acids and domains, their molecular activity and their evolutionary history, we undertook an in-depth analysis of Vasohibin sequences. We find that Vasohibin proteins are previously undetected members of the transglutaminase-like cysteine protease superfamily, and all possess a non-canonical Cys-His-Ser catalytic triad. We further propose a calcium-dependent activation mechanism for Vasohibin proteins. These findings can now be used to design constructs for protein structure determination and to develop enzyme inhibitors as angiogenic regulators to treat metastasis and tumour growth.

CONTACT

luis.sanchezpulido@dpag.ox.ac.uk

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

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.