Stanniocalcin-2 expression in glioblastoma - A novel prognostic biomarker: An observational study

The objective of this study was to assess the prognostic relevance of Stanniocalcin-2 (STC2) expression, as determined via immunohistochemistry in tumor tissue, in a cohort of 83 patients diagnosed with glioblastoma who underwent maximal safe surgical resection followed by radiotherapy concurrent with adjuvant temozolomide. STC2 expression levels were categorized using a 3-tiered semiquantitative system: negative expression (level 0-), low expression (level 1+), and high expression (levels 2 + and 3+). Patients were categorized into 2 distinct groups according to their STC2 expression levels: negative STC2 (-/+) and positive STC2 (++/+++). The primary outcome measure was the relationship between STC2 expression and progression-free survival (PFS), with overall survival (OS) serving as the secondary endpoint. Kaplan-Meier survival analysis confirmed that patients exhibiting high STC2 expression had significantly shorter OS (8 vs 20 months, P < .001) and PFS (6 vs 18 months, P < .001) than those with low or negative STC2 expression. Multivariate analysis revealed that STC2 expression was an independent prognostic factor for both OS (hazard ratio: 0.4; 95% confidence interval: 0.2-0.8; P < .05) and PFS (hazard ratio: 0.3; 95% confidence interval: 0.2-0.4; P < .05) in patients with glioblastoma. Furthermore, elevated STC2 expression in GBM was correlated with several established aggressive clinicopathological characteristics, including advanced age (≥65 years), low ECOG PS (≥2), and isocitrate dehydrogenase mutation negativity. These findings underscore that heightened STC2 expression within the tumor tissue of GBM patients functions as an adverse prognostic marker, correlating with an elevated risk of progression and reduced OS. Therapeutic interventions targeting the AKT-mTOR, ERK1-2, and mitogen-activated protein kinase pathways as well as immune checkpoint inhibitors and vascular endothelial growth factor blockade, as well as potential forthcoming antibody-drug conjugates targeting the STC2 molecule, have the potential to broaden the scope of combined treatment strategies.

Integrative Analysis Reveals STC2 as a Prognostic Biomarker of Laryngeal Squamous Cell Carcinoma

Stanniocalcin 2 (STC2) is involved in many tumour types, but it remains unclear what its biological function is in laryngeal squamous cell carcinoma (LSCC). Therefore, we investigated STC2's expression, potential function, and prognostic significance of in LSCC. The expression and prognosis of STC2 in LSCC were described using the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) databases. In the TCGA database, the relationship between STC2 and immune infiltration, expression of immune cell chemokine and receptor genes, immune cell molecular marker genes, and epithelial‒mesenchymal transition (EMT) marker genes were analysed. The biological processes involved in STC2 and its expression-related genes were analysed comprehensively using bioinformatics. The single-gene ceRNA network of STC2 was constructed in the TCGA database. Finally, LSCC patients' tumour tissue STC2 expression was verified. STC2 silencing with the RNAi technique was used for the determination of cellular functions in a laryngeal cancer cell line. STC2 expression was higher in most tumours, including LSCC, than in normal tissues and was associated with poor prognosis. The relative proportions of naïve B, plasma, follicular helper T, and macrophage M0 cells in LSCC and normal samples differed significantly. STC2 expression correlated significantly positively with that of TGFB1 (biomarker of Tregs) and significantly negatively with that of D79A and CD19 (biomarkers of B cells). Furthermore, STC2 affected chemokine and receptor gene expression in immune cells. STC2 expression correlated with EMT marker gene expression in LSCC. STC2 was enriched in the PI3K/AKT signalling pathway, extracellular matrix (ECM) organisation, ECM-receptor interaction, and other tumour-related signalling pathways. STC2 was highly expressed in our clinical samples. N-cadherin and vimentin expression were decreased in the TU686 cell line after successful silencing of STC2, indicating that high STC2 expression may prompt LSCC cells to adopt a mesenchymal cell phenotype. STC2 silencing substantially reduced proliferation and migration in the TU686 cell line. STC2 may be a promising predictive biomarker for tumours, providing new approaches for LSCC diagnosis and treatment monitoring.

Identifying a Risk Signature of Methylation-Driven Genes as a Predictor of Survival Outcome for Colon Cancer Patients

Aberrant expression of gene is driven by its promoter methylation and is the key molecular basis of carcinogenic processes. This study aimed at identifying a risk signature of methylation-driven (MD) genes and evaluating its prognostic value for colon cancer (CC) patients. The expression profiles of methylation and mRNA in CC samples were obtained from the TCGA database, and the MethylMix algorithm was used to identify MD genes. The relationships between their expression levels and overall survival (OS) of CC patients were analyzed, and a prognostic signature of MD genes was established. The risk score of gene signature was calculated, and the median was used to divide all patients into high (H) and low (L) risk groups. The prognostic value of gene signature was tested by the TCGA cohort and an independent validation cohort (GSE17538 dataset). In total, 69 MD genes were identified, and 7 were associated with OS of CC patients. Ultimately, 4 (TWIST1, LDOC1, EPHX3, and STC2) were screened out to establish a risk signature. The H-risk patients (>0.923) had a worse OS than L-risk patients (≤0.923) in both the TCGA (5-year cumulative survival: 52.9% vs 72.0%, P=0.005) and GSE17538 cohort (49.4% vs 69.3%, P=0.004). The AUC values of MD genes signature for the prediction of 3- and 5-year OS were 0.648 and 0.643 in the TCGA dataset and 0.634 and 0.624 in the GSE17538 dataset, respectively. The risk signature of four MD genes was identified as an independent predictor of OS for CC patients (HR for TCGA dataset: 2.071, 95% CI=1.196-3.586, P=0.009; HR for GSE17538 dataset: 2.021, 95% CI=1.290-3.166, P=0.002). The risk signature of four MD genes might be a useful prognostic tool and help doctors improve the clinical management of CC patients.

The down-regulation of STC2 mRNA may serve as a biomarker for death from mechanical asphyxia

Death from mechanical asphyxia (DMA) is a common cause of death in forensic pathology. However, due to the lack of biomarkers, the authentication of DMA now relies on a series of non-specific signs, which may cause troubles in the judicial trials, especially when the criminal scene is not fully elucidated. To search for the potential biomarkers for DMA, brain samples of DMA and craniocerebral injury groups were screened by microarray. The obtained mRNAs were validated by animal and human samples. Primary cell culture was conducted to explore the biochemical changes under hypoxia. 415 differentially expressed mRNAs between two groups were discovered. Ten mRNAs were examined in both human and animal samples died of different causes of death. Stanniocalcin-2 (STC2) showed significant down-regulation in DMA samples compared to other groups, regardless of PMI, age, or temperature. Cellular experiments indicated that ROS level peaked after 15-min-hypoxic culture, when the expression level of STC2 was significant down-regulated simultaneously. The ER-stress-related proteins also showed potential connection with STC2. In general, it is indicated that the down-regulation of STC2 may serve as a biomarker for DMA.

STC2 is a potential biomarker of hepatocellular carcinoma with its expression being upregulated in Nrf1α-deficient cells, but downregulated in Nrf2-deficient cells

Nrf1 (encoded by Nfe2l1) and Nrf2 (encoded by Nfe2l2), as two key members of the CNC-bZIP transcription factor, exhibit significant functional differences in their pathophysiology. Our previous findings demonstrated that loss of Nrf1α (i.e., a full-length isoform of Nrf1) promotes HepG2-derived tumor growth in xenograft mice, but malgrowth of the xenograft tumor is significantly suppressed by knockout of Nrf2. To gain insights into the mechanism underlying such marked distinctions in their pathologic phenotypes, we mined transcriptome data from liver cancer in the TCGA database to establish a prognostic model and calculate predicted risk scores for each cell line. The results revealed that knockout of Nrf1α markedly increased the risk score in HepG2 cells, whereas the risk score was reduced by knockout of Nrf2. Notably, stanniocalcin 2 (STC2), a biomarker associated with liver cancer, that is upexpressed in hepatocellular carcinoma (HCC) tissues with a reduction in the overall survival ratio of those patients. We observed increased expression levels of STC2 in Nrf1α-/- cells but decreased expression in Nrf2-/- cells. These findings suggested that STC2 may play a role in mediating the distinction between Nrf1α-/- and Nrf2-/-. Such potential function of STC2 was further corroborated through a series of experiments combined with transcriptomic sequencing. The results revealed that STC2 functions as a dominant tumor-promoter, because the STC2-leading increases in clonogenicity of hepatoma cells and malgrowth of relevant xenograft tumor were almost completely abolished in STC2-/- cells. Together, these demonstrate that STC2 could be paved as a potential therapeutic target, albeit as a diagnostic marker, for HCC.

Stanniocalcin 2 (STC2): a universal tumour biomarker and a potential therapeutical target

Stanniocalcin 2 (STC2) is a glycoprotein which is expressed in a broad spectrum of tumour cells and tumour tissues derived from human breast, colorectum, stomach, esophagus, prostate, kidney, liver, bone, ovary, lung and so forth. The expression of STC2 is regulated at both transcriptional and post-transcriptional levels; particularly, STC2 is significantly stimulated under various stress conditions like ER stress, hypoxia and nutrient deprivation. Biologically, STC2 facilitates cells dealing with stress conditions and prevents apoptosis. Importantly, STC2 also promotes the development of acquired resistance to chemo- and radio- therapies. In addition, multiple groups have reported that STC2 overexpression promotes cell proliferation, migration and immune response. Therefore, the overexpression of STC2 is positively correlated with tumour growth, invasion, metastasis and patients' prognosis, highlighting its potential as a biomarker and a therapeutic target. This review focuses on discussing the regulation, biological functions and clinical importance of STC2 in human cancers. Future perspectives in this field will also be discussed.

Electrical modulation of transplanted stem cells improves functional recovery in a rodent model of stroke

Stroke is a leading cause of long-term disability worldwide, intensifying the need for effective recovery therapies. Stem cells are a promising stroke therapeutic, but creating ideal conditions for treatment is essential. Here we developed a conductive polymer system for stem cell delivery and electrical modulation in animals. Using this system, electrical modulation of human stem cell transplants improve functional stroke recovery in rodents. Increased endogenous stem cell production corresponds with improved function. Transcriptome analysis identified stanniocalcin 2 (STC2) as one of the genes most significantly upregulated by electrical stimulation. Lentiviral upregulation and downregulation of STC2 in the transplanted stem cells demonstrate that this glycoprotein is an essential mediator in the functional improvements seen with electrical modulation. Moreover, intraventricular administration of recombinant STC2 post-stroke confers functional benefits. In summation, our conductive polymer system enables electrical modulation of stem cells as a potential method to improve recovery and identify important therapeutic targets.

The significance of Stanniocalcin 2 in malignancies and mechanisms

Human stanniocalcin 2 (STC2) is an ortholog of fish stanniocalcins (STCs) and is widely expressed in various organs and tissues. The gene is localized on chromosome 5q33 or 5q35. STC2 has been implicated in glucose homeostasis and phosphorus metabolism. It is also reported to be implicated in various malignancies. STC2 was found to be implicated in breast cancer and gynecologic cancers, suggesting hormone-specific or -dependent activities in these malignancies. Moreover, it was reported to be involved in gastrointestinal tumors, including esophageal, gastric, colorectal, and liver cancers, and respiratory cancers, including laryngeal and lung cancers. It also influenced renal carcinoma and prostate cancer. Notably, as a secreted phosphoprotein, STC2 was detectable in serum and possessed promising predictive value in several malignancies. This review aims to improve the understanding of the role of STC2 in patient diagnosis and prognosis, and tumor development and progression, as well as the mechanisms involved.

Construction of a circRNA-miRNA-mRNA Regulatory Network Reveals Potential Mechanism and Treatment Options for Osteosarcoma

Background

Osteosarcoma is a common malignant primary bone tumor in adolescents and children. Numerous studies have shown that circRNAs were involved in the proliferation and invasion of various tumors. However, the role of circRNAs in osteosarcoma remains unclear. Here, we aimed to explore the regulatory network among circRNA-miRNA-mRNA in osteosarcoma.

Methods

The circRNA (GSE140256), microRNA (GSE28423), and mRNA (GSE99671) expression profiles of osteosarcoma were collected from the Gene Expression Omnibus (GEO) database. Differentially expressed circRNAs, miRNAs and mRNAs were identified. CircRNA-miRNA interactions and miRNA-mRNA interactions were determined by Circular RNA Interactome (CircInteractome) database and microRNA Data Integration Portal (mirDIP) database, respectively. Then, we constructed a regulatory network. Function enrichment analysis of miRNA and mRNA was performed by DIANA-miRPath v3.0 and Metascape database, respectively. mRNAs with significant prognostic value were identified based on expression profiles from The Cancer Genome Atlas (TCGA) database, and we constructed a subnetwork for them. To make the most of the network, we used the CLUE database to predict potential drugs for the treatment of osteosarcoma based on mRNA expression in the network. And we used the STITCH database to analyze and validate the interactions among these drugs and mRNAs, and to further screen for potential drugs.

Results

A total of 9 circRNAs, 19 miRNAs, 67 mRNAs, 54 pairs of circRNA-miRNA interactions and 110 pairs of miRNA-mRNA interactions were identified. A circRNA-miRNA-mRNA network was constructed. Function enrichment analysis indicated that these miRNAs and mRNAs in the network were involved in the process of tumorigenesis and immune response. Among these mRNAs, STC2 and RASGRP2 with significantly prognostic value were identified, and we constructed a subnetwork for them. Based on mRNA expression in the network, three potential drugs, quinacridine, thalidomide and zonisamide, were screened for the treatment of osteosarcoma. Among them, quinacridine and thalidomide have been proved to have anti-tumor effects in previous studies, while zonisamide has not been reported. And a corresponding drug-protein interaction network was constructed.

Conclusion

Overall, we constructed a circRNA-miRNA-mRNA regulatory network to investigate the possible mechanism in osteosarcoma, and predicted that quinacridine, thalidomide and zonisamide could be potential drugs for the treatment of osteosarcoma.

miRNA-mRNA Regulatory Network and Factors Associated with Prediction of Prognosis in Hepatocellular Carcinoma

The aim of this study was to identify novel gene and miRNA biomarkers of risk and prognostic factors for hepatocarcinogenesis using methods in systems biology. Differentially expressed genes (DEGs), microRNAs (miRNAs), and long non-coding RNA (lncRNAs) were compared between hepatocellular carcinoma (HCC) tumour tissue and normal liver tissues in the Cancer Genome Atlas (TCGA) database. Subsequently, the prognosis-associated gene co-expression network, mRNA-miRNA, and mRNA-miRNA-lncRNA regulatory networks were constructed to identify biomarkers of risk for HCC through Cox survival analysis. Seven prognosis-associated gene co-expression modules were obtained by analyzing these DEGs. An expression module including 120 genes significantly correlated with HCC patient survival. Combined with patient survival data, several mRNAs and miRNAs, including CHST4, SLC22A8, STC2, hsa-miR-326, and hsa-miR-21 were identified from the network to predict HCC patient prognosis. Clinical significance was investigated using tissue microarray analysis of samples from 258 patients with HCC. Functional annotation of hsa-miR-326 and hsa-miR-21-5p indicated specific associations with several cancer-related pathways. The present study provides a bioinformatics method for biomarker screening, which led to the identification of an integrated mRNA-miRNA-lncRNA regulatory network and their co-expression in relation to predicting HCC patient survival.

A prognostic long non-coding RNA-associated competing endogenous RNA network in head and neck squamous cell carcinoma

BACKGROUND

This study aimed to develop multi-RNA-based models using a competing endogenous RNA (ceRNA) regulatory network to provide survival risk prediction in head and neck squamous cell carcinoma (HNSCC).

METHODS

All long non-coding RNA (lncRNA), microRNA (miRNA), and mRNA expression data and clinicopathological features related to HNSCC were derived from The Cancer Genome Atlas. Differentially expressed RNAs were calculated using R. Prognostic factors were identified using univariate Cox regression analysis. Functional analysis was performed using GO, KEGG pathways, and PPI network. Based on the results, we derived a risk signature and compared high- and low-risk subgroups using LASSO regression analysis. Survival analysis and the relationship between risk signature and clinicopathological features were performed using log-rank tests and Cox regression analysis. A ceRNA regulatory network was constructed, and prognostic lncRNAs and miRNA expression levels were validated in vitro and in vivo.

RESULTS

A list of 207 lncRNAs, 18 miRNAs and 362 mRNAs related to overall survival was established. Five lncRNAs (HOTTIP, LINC00460, RMST, SFTA1P, and TM4SF19-AS1), one miRNA (hsa-miR-206), and one mRNA (STC2) were used to construct the ceRNA network. Three prognostic models contained 13 lncRNAs, eight miRNAs, and 17 mRNAs, which correlated with the patient status, disease-free survival (DFS), stage, grade, T stage, N stage, TP53 mutation status, angiolymphatic invasion, HPV status, and extracapsular spread. KEGG pathway analysis revealed significant enrichment of "Transcriptional misregulation in cancer" and "Neuroactive ligand-receptor interaction." In addition, HOTTIP, LINC00460, miR-206 and STC2 were validated in GTEx data, GEO microarrays and six HNSCC cell lines.

CONCLUSIONS

Our findings clarify the interaction of ceRNA regulatory networks and crucial clinicopathological features. These results show that prognostic biomarkers can be identified by constructing multi-RNA-based prognostic models, which can be used for survival risk prediction in patients with HNSCC.

Expression of Stanniocalcin 2 in Breast Cancer and Its Clinical Significance

This study aims to explore the expression of stanniocalcin 2 (STC2) gene in breast cancer and its clinical significance. Female patients with breast cancer from Zhongnan Hospital of Wuhan University admitted during March 2014 to October 2014 were enrolled in this study. All the tissues used in this experiment included 50 cases of breast cancer tissues and corresponding 50 cases of paracancer normal breast tissues with complete patients' information. The real-time quantitative polymerase chain reaction (qPCR) was applied to detect the expression of STC2 gene in 50 cases of breast cancer and paracancer normal breast tissues. The results showed that the expression level of STC2 gene in 50 cases of breast cancer tissues was significantly higher than that in paracancer normal breast tissues (P&lt;0.001). The expression of STC2 gene was correlated with lymph node metastasis, distant metastasis, TNM stage and histological grade (P&lt;0.001). The expression level of STC2 gene was significantly higher in breast cancer tissues with higher expression of Ki-67 (P&lt;0.001). The expression level of STC2 gene was significantly higher in estrogen receptor (ER) positive breast cancer tissues than in ER negative ones (P&lt;0.001). However, different groups of age, pathological type, tumor size, PR expression and human epidermal growth factor receptor-2 (HER2) expression did not show significant differences in STC2 expression (P&gt;0.05). In conclusion, the abnormal overexpression of STC2 gene may play a role in the development and progression of breast cancer, and it can be used as an independent metastasis and prognostic factor of breast cancer. In addition, STC2 gene probably promotes the development and metastasis of breast cancer by interacting with estrogen and ER, and it may become a new direction for breast cancer endocrine therapy.

Prognostic value of high stanniocalcin 2 expression in solid cancers: A meta-analysis

BACKGROUND

Several studies have explored the prognostic value of stanniocalcin 2 (STC2) in various cancers, but obtained inconsistent results. Therefore, this meta-analysis was performed to determine the prognostic and clinicopathologic significance of STC2 in various cancers.

METHODS

Eligible studies were identified by searching the online databases PubMed, Embase, Web of Science, and the China National Knowledge Infrastructure up to March 2019. Hazard ratios (HRs) with 95% confidence intervals (CIs) and were calculated to clarify the correlation between STC2 expression and prognosis of different cancers. Odds ratios (ORs) with 95% CI were selected to appraise the correlation between STC2 with clinicopathologic characteristics of patients with cancer.

RESULTS

A total of 16 eligible studies with 4074 patients with cancer were included in our meta-analysis. The results showed that high STC2 expression can predict poor overall survival (OS) for cancer (HR = 1.48, 95% CI: 1.15-1.90, P = .002). Subgroup analysis found that high STC2 expression was associated with worse OS in Asian (HR = 1.85, 95% CI: 1.35-2.55), the reported directly from articles group (HR = 1.39, 95% CI: 1.05-1.84), survival curves group (HR = 1.93, 95% CI: 1.36-2.74), and gastric cancer (HR = 1.43, 95% CI: 1.04-1.95). Furthermore, high STC2 expression was significantly related to advanced T stage (OR = 1.83, 95% CI: 1.17-2.86, P = .008), lymph node metastasis (OR = 2.29, 95% CI: 1.51-3.45, P < .001), lymphatic invasion (OR = 2.15, 95% CI: 1.53-3.02, P < .001), venous invasion (OR = 1.97, 95% CI: 1.30-2.99, P = .001), and more advanced clinical stage (OR = 2.36, 95% CI: 1.74-3.19, P < .001) CONCLUSION:: Elevated expression of STC2 suggested a poor prognosis in patients with cancer and may serve as a new tumor marker to monitor cancer development and progression.

STC2 Is a Potential Prognostic Biomarker for Pancreatic Cancer and Promotes Migration and Invasion by Inducing Epithelial-Mesenchymal Transition

Aberrant expression of stanniocalcin 2 (STC2) is implicated in cancer development. STC2 acts as a tumor promoter to drive some cancers. However, its contribution to the development of pancreatic cancer remains unclear. This study showed that the expression of STC2 was significantly upregulated in pancreatic cancer tissues. Moreover, its expression was positively correlated with tumor size and lymph node metastasis and negatively correlated with 5-year survival rate of pancreatic cancer patients. Additionally, the expression levels of STC2 were a novel biomarker for predicting overall survival rate after surgery. Furthermore, overexpression of STC2 could promote the proliferation, migration, and invasion of pancreatic cancer cell lines, while knocking down of STC2 led to antiproliferation and antimetastasis activities. Further mechanistic investigations revealed that the expression of STC2 could significantly promote the epithelial-mesenchymal transition (EMT) in pancreatic cancer cells. These data indicated that the overexpression of STC2 in pancreatic cancer contributes to the metastasis through the promotion of EMT, suggesting that STC2 is a potential prognostic biomarker and therapeutic target for pancreatic cancer.

Stanniocalcin 2 (STC2) expression promotes post-radiation survival, migration and invasion of nasopharyngeal carcinoma cells

Background: Stanniocalcin 2 (STC2) expression is upregulated under multiple stress conditions including hypoxia, nutrient starvation and radiation. Overexpression of STC2 correlates with tumor progression and poor prognosis.

Purpose: We previously demonstrated that overexpression of STC2 in nasopharyngeal carcinomas (NPC) positively correlates with radiation resistance and tumor metastasis, two major clinical obstacles to the improvement of NPC management. However, it remains elusive whether STC2 expression is a critical contributing factor for post-radiation survival and metastasis of NPC cells.

Materials and methods: Using the radiation resistant CNE2 cell line as a model, we examined the importance of STC2 expression for post-radiation survival, migration and invasion. Here, we report the establishment of STC2 knockout lines (CNE2-STC2-KO) using the CRISPR/Cas9-based genome editing technique.

Results: Compared with the parental line, STC2-KO cells showed similar proliferation and morphology in normal culture conditions, and loss of STC2 did not compromise the cell tumorigenicity in nude mice model. However, STC2-KO lines demonstrated increased sensitivity to X-radiation under either normoxic or hypoxic conditions. Particularly, upon X-radiation, parental CNE2 cells only slightly whereas STC2-KO cells remarkably decreased the migration and invasion ability. Cell cycle analysis revealed that loss of STC2 accumulated cells in G₁ and G₂/M phases but decreased S-population.

Conclusion: These data indicate that the expression of STC2, which can be stimulated by metabolic or therapeutic stresses, is one important factor to promote survival and metastasis of post-radiation NPC cells. Therefore, targeting STC2 or relative downstream pathways may provide novel strategies to overcome radiation resistance and metastasis of NPC.

Differential Effects of Purinergic Signaling in Gastric Cancer-Derived Cells Through P2Y and P2X Receptors

Gastric cancer (GC) is the one of the most prevalent cancers and one of the leading causes of cancer-induced deaths. Previously, we found that the expression of purinergic P2Y₂ receptor (P2Y₂R) is increased in GC samples as compared to adjacent healthy mucosa taken from GC-diagnosed patients. In this work, we studied in detail purinergic signaling in the gastric adenocarcinoma-derived cell lines: AGS, MKN-45, and MKN-74, and compared them to a nontumoral epithelial cell line: GES-1. In GC-derived cells, we detected the expression of several purinergic receptors, and found important differences as compared to GES-1 cells. Functional studies revealed a strong contribution of P2Y₂Rs in intracellular calcium increases, elicited by adenosine-triphosphate (ATP), uridine-triphosphate (UTP), and the P2Y₂R agonist MRS2768. Responses were preserved in the absence of extracellular calcium and inhibited by P2Y₂R antagonists. In GES-1 cells, ATP and UTP induced similar responses and the combination of P2X and P2Y receptor antagonists was able to block them. Proliferation studies showed that ATP regulates AGS and MKN-74 cells in a biphasic manner, increasing cell proliferation at 10–100 μM, but inhibiting at 300 μM ATP. On the other hand, 1–300 μM UTP, a P2Y₂R agonist, increased concentration-dependent cell proliferation. The effects of UTP and ATP were prevented by both wide-range and specific purinergic antagonists. In contrast, in GES-1 cells ATP only decreased cell proliferation in a concentration-dependent manner, and UTP had no effect. Notably, the isolated application of purinergic antagonists was sufficient to change the basal proliferation of AGS cells, indicating that nucleotides released by the cells can act as paracrine/autocrine signals. Finally, in tumor-derived biopsies, we found an increase of P2Y₂R and a decrease in P2X4R expression; however, we found high variability between seven different biopsies and their respective adjacent healthy gastric mucosa. Even so, we found a correlation between the expression levels of P2Y₂R and P2X4R and survival rates of GC patients. Taken together, these results demonstrate the involvement of different purinergic receptors and signaling in GC, and the pattern of expression changes in tumoral cells, and this change likely directs ATP and nucleotide signaling from antiproliferative effects in healthy tissues to proliferative effects in cancer.

Upregulation of STC2 in colorectal cancer and its clinicopathological significance

Background

Stanniocalcin 2 (STC2) is a glycoprotein hormone involved in many biological processes and a secretory protein that regulates malignant tumor progression. The aim of the present study was to further explore the clinicopathological significance and prognostic role of STC2 in colorectal cancer (CRC).

Methods

In this study, STC2 expression was first investigated in Gene Expression Omnibus and The Cancer Genome Atlas, and then validated with the data from our medical center. Univariate and multivariate analyses were performed to assess the association between prognostic factors and survival outcome.

Results

In Gene Expression Omnibus and The Cancer Genome Atlas databases, bioinformatics analysis confirmed that STC2 was significantly increased in CRC compared with that in normal tissues (P<0.01), and CRC patients with high STC2 expression had a shorter overall survival. By analyzing data from our medical center, the results also showed that STC2 expression of CRC tissues was higher than that in normal tissues, whether the transcriptional or protein levels. In the CRC tissues, high STC2 expression was significantly correlated with lymph node metastasis (P=0.047), distant metastasis (P=0.040), and advanced clinical stage (P=0.047). Moreover, Kaplan–Meier analyses indicated that high STC2 expression predicted a worse prognosis, and multivariate Cox regression analysis revealed that STC2 was an independent prognostic factor for overall survival (HR =1.976, 95% CI: 1.092–3.576, P=0.024) in patients with CRC.

Conclusion

Our results suggested that STC2 played an important role in CRC progression and prognosis, and could be a useful biomarker for survival prediction.

STC2 promotes head and neck squamous cell carcinoma metastasis through modulating the PI3K/AKT/Snail signaling

The mammalian peptide hormone stanniocalcin 2 (STC2) plays an oncogenic role in many human cancers. However, the exact function of STC2 in human head and neck squamous cell carcinoma (HNSCC) is unclear. We aimed to examine the function and clinical significance of STC2 in HNSCC. Using in vitro and in vivo assays, we show that overexpression of STC2 suppressed cell apoptosis, promoted cell proliferation, migration, invasion, and cell cycle arrest at the G1/S transition. By contrast, silencing of STC2 inhibited these activities. We further show that STC2 upregulated the phosphorylation of AKT and enhanced HNSCC metastasis via Snail-mediated increase of vimentin and decrease of E-cadherin. These responses were blocked by silencing of STC2/Snail expression or inhibition of pAKT activity. Furthermore, clinical data indicate that high STC2 expression was associated with high levels of pAKT and Snail in tumor samples from HNSCC patients with regional lymph node metastasis (P < 0.01). Thus, we conclude that STC2 controls HNSCC metastasis via the PI3K/AKT/Snail signaling axis and that targeted therapy against STC2 may be a novel strategy to effectively treat patients with metastatic HNSCC.

STC2 promotes the epithelial-mesenchymal transition of colorectal cancer cells through AKT-ERK signaling pathways

The STC2 protein involves in carcinogenesis and progression of many cancers. It remains unclear how STC2 regulates the epithelial-mesenchymal transition (EMT) process and colorectal cancer (CRC) development. Here we systematically investigated STC2-activated early occurrence of EMT and CRC cell migration in vitro, clinical associations of STC2 with CRC development and patient survival. The secretion and expression level of STC2 were both greatly increased in EMT cells and CRC cells compared with the normal epithelial NCM460 cells. And the conditioned media from EMT cells stimulated epithelia and colon cancer cells to obtain EMT characteristics. STC2 overexpression promoted CRC cell growth and cell migration in vitro, and STC2 enhanced tumor growth in a mouse CRC-xenograft model. Corresponding to EMT marker expression changes, several critical signaling pathway molecules including pERK, pAKT, PI3K and Ras were remarkably increased either in NCM460 cells transfected with STC2 plasmids or in cells induced with exogenous STC2 protein. However blocking AKT-ERK signaling pathways attenuated STC2-activated EMT process. Furthermore the elevated STC2 expressions were also confirmed in 77 clinical tumor tissues and sera from CRC patients, and the increased STC2 in tumor tissues and sera correlated with tumor pathologic stage and poor survival for CRC patients. In conclusion, STC2 promotes CRC tumorigenesis and EMT progression through activating ERK/MEK and PI3K/AKT signaling pathways. STC2 protein is also a potential tumor biomarker for CRC diagnosis and prognosis.

Evolution and functions of stanniocalcins in cancer

Stanniocalcin (STC), first isolated from the corpuscles of stannius of teleost fishes, was originally known for its regulation on calcium/phosphate transport. Increasing evidence demonstrates that STCs display the important function in some physiological and pathological behaviors such as calcium regulation, oxidative stress, anti-inflammation, angiogenesis, ischemia reperfusion, nerve diseases, etc. Moreover, STCs are implicated in the development and progression of multiple malignancies through promoting cell growth, proliferation, invasion, metastasis, and apoptotic escape. Some studies have shown that NF-κB upregulates STC expression, thereby activating the downstream HIF-1/ERK1/2 signaling pathway, enhancing the transcriptional activity of tumor-related factors (MMP-2/9, cyclinD1, Bcl-2, N-cadherin, etc) and contributing to tumorigenesis. Here, this brief review describes recent progress of STCs in mammalians, focused mainly on their critical functions in cancer.

Identification and Validation of Reference Genes for RT-qPCR Studies of Hypoxia in Squamous Cervical Cancer Patients

Hypoxia is an adverse factor in cervical cancer, and hypoxia-related gene expression could be a powerful biomarker for identifying the aggressive hypoxic tumors. Reverse transcription quantitative PCR (RT-qPCR) is a valuable method for gene expression studies, but suitable reference genes for data normalization that are independent of hypoxia status and clinical parameters of cervical tumors are lacking. In the present work, we aimed to identify reference genes for RT-qPCR studies of hypoxia in squamous cervical cancer. From 422 candidate reference genes selected from the literature, we used Illumina array-based expression profiles to identify 182 genes not affected by hypoxia in cervical cancer, i.e. genes regulated by hypoxia in eight cervical cancer cell lines or correlating with the hypoxia-associated dynamic contrast-enhanced magnetic resonance imaging parameter A_Brix in 42 patients, were excluded. Among the 182 genes, nine candidates (CHCHD1, GNB2L1, IPO8, LASP1, RPL27A, RPS12, SOD1, SRSF9, TMBIM6) that were not associated with tumor volume, stage, lymph node involvement or disease progression in array data of 150 patients, were selected for further testing by RT-qPCR. geNorm and NormFinder analyses of RT-qPCR data of 74 patients identified CHCHD1, SRSF9 and TMBIM6 as the optimal set of reference genes, with stable expression both overall and across patient subgroups with different hypoxia status (A_Brix) and clinical parameters. The suitability of the three reference genes were validated in studies of the hypoxia-induced genes DDIT3, ERO1A, and STC2. After normalization, the RT-qPCR data of these genes showed a significant correlation with Illumina expression (P<0.001, n = 74) and A_Brix (P<0.05, n = 32), and the STC2 data were associated with clinical outcome, in accordance with the Illumina data. Thus, CHCHD1, SRSF9 and TMBIM6 seem to be suitable reference genes for studying hypoxia-related gene expression in squamous cervical cancer samples by RT-qPCR. Moreover, STC2 is a promising prognostic hypoxia biomarker in cervical cancer.

Stanniocalcin 2 induces oxaliplatin resistance in colorectal cancer cells by upregulating P-glycoprotein

Multidrug resistance (MDR) limits the anticancer effects of chemotherapy in patients with metastatic colorectal cancer (CRC). Oxaliplatin is a common component of combinational therapeutic regimens administered to patients with metastatic CRC; however, it is also used as a constituent of adjuvant therapy for patients at a risk of recurrent disease. In the present study, we investigated the role of stanniocalcin 2 (STC2) in chemoresistance. STC2 knockdown sensitized chemoresistant CRC cells to oxaliplatin. Moreover, the expression of exogenous STC2 in chemonaïve CRC cells induced oxaliplatin resistance. We confirmed that STC2 upregulated P-glycoprotein (P-gp) expression in CRC cells. Furthermore, shRNA against phosphoinositide 3-kinase (PI3K) or Akt inhibited the action of STC2 on P-gp upregulation and MDR in CRC. To our knowledge, this is the first report to demonstrate the induction of oxaliplatin resistance in CRC cells in response to STC2 stimulation of P-gp via the PI3K/Akt signaling pathway.

Stanniocalcin 2 promotes cell proliferation and cisplatin resistance in cervical cancer

Cervical cancer is one of the most common carcinomas in the female reproductive system. Treatment of cervical cancer involves surgical removal and chemotherapy. Resistance to platinum-based chemotherapy drugs including cisplatin has increasingly become an important problem in the treatment of cervical cancer patients. We found in this study that stanniocalcin 2 (STC2) expression was upregulated in both cervical cancer tissues and cell lines. The levels of STC2 expression in cervical cancer cell lines were positively correlated with the rate of cell proliferation. Furthermore, in cisplatin resistant cervical cancer cells, the levels of STC2 expression were significantly elevated. Modulation of STC2 expression by siRNA or overexpression in cisplatin resistant cells resulted in altered cell survival, apoptosis, and cisplatin resistance. Finally, we found that there was significant difference in the activity of the MAPK signaling pathway between cisplatin sensitive and resistant cervical cancer cells, and that STC2 could regulate the activity of the MAPK signaling pathway.

STC2 overexpression mediated by HMGA2 is a biomarker for aggressiveness of high-grade serous ovarian cancer

High-grade serous cancer (HGSC) is a lethal form of ovarian cancer due to invasion and early metastasis. Gain of epithelial-mesenchymal transition (EMT) contributes to the aggressiveness of HGSC. High-mobility gene group A2 (HMGA2), an architectural transcription factor, plays a major role in HGSC through the regulation of EMT gene expression. Based on the gene profiling analysis, we found that the potent EMT gene, stanniocalcin 2 (STC2), was highly correlated with HMGA2 expression. In the present study, we demonstrated that STC2 was directly regulated by HMGA2 at the transcriptional level. Overexpressing STC2 in vitro directly enhanced cell migration and invasion. To investigate the correlation of STC2 and HMGA2 expression and the potential biomarker for ovarian cancer, three independent large cohorts of ovarian cancer (cohort 1=278, cohort 2=150 and cohort 3=95 cases) were examined in the present study. The results showed that the expression of HMGA2 and STC2 was positively correlated. Furthermore, STC2 expression was significantly associated with tumor grade and histotype. HGSC had significantly higher levels of STC2 expression and was inversely correlated with patient survival. These findings suggested that STC2 is an important new biomarker that can be used for HGSC.

Clinical significance of stanniocalcin expression in tissue and serum of gastric cancer patients

PURPOSE

Stanniocalcin (STC) has been recognized as a potential biomarker in a variety of cancers. The aim of this study was to examine STC1 and STC2 expression in tumor and serum samples from gastric cancer (GC) patients.

METHODS

A total of 83 GC patients treated with radical resection were enrolled in this study. Immunohistochemistry was used to detect STC protein expression in paired tumor and adjacent normal tissues. Serum STC levels were determined by enzyme-linked immunosorbent assay (ELISA). The receiver operating characteristics (ROC) curve was constructed to describe diagnostic specificity and sensitivity.

RESULTS

Both of STC1 and STC2 protein expression were upregulated in GC tissues compared with that in normal ones. Moreover, the high/moderate of STC1 protein was significantly associated with lymph metastasis, clinical stage and adverse 3-year progression-free survival (PFS). In addition, serum STC1 and STC2 expression in GC patients were much higher than that in patients with benign gastric disease, which decreased at postoperative 7-10 days. The sensitivity of serum STC protein also showed superiority over CEA and CA19-9.

CONCLUSIONS

STC upregulation plays an important role in GC development, and serum STC1 and STC2 might function as promising tumor markers for GC diagnosis and prognosis.

Stanniocalcin-2 (STC2): A potential lung cancer biomarker promotes lung cancer metastasis and progression

The homodimeric glycoprotein, stanniocalcin 2 (STC2) is previously known to be involved in the regulation of calcium and phosphate transport in the kidney and also reported to play multiple roles in several cancers. However, its function and clinical significance in lung cancer have never been reported and still remain uncertain. Here, we investigated the possibility of STC2 as a lung cancer biomarker and identified its potential role in lung cancer cell growth, metastasis and progression. Proteomic analysis of secretome of primary cultured lung cancer cells revealed higher expression of STC2 in cancers compared to that of adjacent normal cells. RT-PCR and Western blot analyses showed higher mRNA and protein expressions of STC2 in lung cancer tissues compared to the adjacent normal tissues. Knockdown of STC2 in H460 lung cancer cells slowed down cell growth progression and colony formation. Further analysis revealed suppression of migration, invasion and delayed G0/G1 cell cycle progression in the STC2 knockdown cells. STC2 knockdown also attenuated the H202-induced oxidative stress on H460 cell viability with a subsequent increase in intracellular ROS levels, which suggest a protective role of STC2 in redox regulatory system of lung cancer. These findings suggest that STC2 can be a potential lung cancer biomarker and plays a positive role in lung cancer metastasis and progression. This article is part of a Special Issue entitled: Medical Proteomics.

Stanniocalcin 2 expression predicts poor prognosis of hepatocellular carcinoma

Previous studies have shown that the expression level of stanniocalcin 2 (STC2) is associated with tumor progression. However, to date, the association between STC2 and clinicopathological factors in hepatocellular carcinoma (HCC) has not been investigated. The clinical significance of STC2 was investigated in 30 fresh HCC samples using western blot analysis and in 240 HCC tissues using immunohistochemical analysis. The level of STC2 in cancerous tissue was higher than in the matched non-cancerous tissues. Using immunohistochemistry, the STC2-positive group exhibited a higher incidence of lymph node metastasis and venous invasion compared with the STC2-negative group. Kaplan-Meier survival analysis revealed that the positive expression of STC2 correlated with poor overall survival (OS) and disease-free survival of HCC patients (P<0.01). STC2 expression was observed to be an independent prognostic factor for OS in HCC patients by multivariate analysis (hazard ratio, 2.39; 95% confidence interval, 1.04–5.89; P=0.013). These data suggest that STC2 expression may be a useful indicator of poor prognosis in HCC patients.

MicroRNA-206 suppresses gastric cancer cell growth and metastasis

Gastric cancer is one of the leading causes of cancer death world-wide and carries a high rate of metastatic risk. In addition to other protein-coding oncogenes and tumor suppressor genes, microRNAs play an important role in gastric cancer tumorigenic progression. Here, we show that miR-206 is expressed at markedly low levels in a cohort of gastric tumors compared to their matching normal tissues, and in a number of gastric cancer cell lines. Down-regulation of miR-206 was particularly significant in tumors with lymphatic metastasis, local invasion, and advanced TNM staging. We find that forced expression of miR-206 suppressed the proliferation, colony-formation, and xenograft tumorigenesis of SCG-7901 cells, a line of gastric cancer cells. Forced expression of miR-206 also suppressed SCG-7901 cell migration and invasion, as well as metastasis in cell culture or tail-vein injected mouse models, respectively. The anti-metastatic effect of miR-206 is likely mediated by targeting metastasis regulatory genes STC2, HDAC4, KLF4, IGF1R, FRS2, SFRP1, BCL2, BDNF, and K-ras, which were drastically down-regulated by stable expression of exogenous miR-206 in SCG-7901 cells. Taken together, our results indicate that miR-206 is a tumor suppressor of gastric cancer acting at steps that regulate metastasis.

Expression of stanniocalcin-1 and stanniocalcin-2 in laryngeal squamous cell carcinoma and correlations with clinical and pathological parameters

Background

Stanniocalcin-1 (STC1) and stanniocalcin-2 (STC2) are secreted glycoprotein hormones involved in various types of human malignancies. The roles of STC1 and STC2 in laryngeal squamous cell carcinoma (LSCC) remain unknown. We investigated correlations between STC1 and STC2 expression and clinicopathological or prognostic factors in LSCC.

Methods

Pre-surgical peripheral blood samples were collected between 2012 and 2013 from 62 patients with LSCC. Quantitative RT-PCR analysis was performed to examine mRNA levels of STC1 and STC2. Immunohistochemistry was performed to retrospectively analyze 90 paraffin-embedded LSCC tissue samples, which were obtained from patients who received surgery between 2006 and 2009. These patients did not have histories of treatment or malignancies. Univariate analysis of patient survival was performed by the Kaplan–Meier method. Multivariate analyses were performed with the Cox proportional hazards model.

Results

The relative mRNA levels of STC1 and STC2 in peripheral blood were significantly greater in LSCC patients than those of healthy volunteers (both P<0.05). STC2 protein expression in tumor tissues was associated with invasion into the thyroid cartilage, T-Stage, lymphatic metastasis, clinical stage, and pathological differentiation (all P<0.05). In addition, STC2 protein expression was an independent prognostic factor for overall survival in patients with LSCC (P = 0.025). In contrast, STC1 expression only correlated with clinical stage (P = 0.026) and was not an independent or significant prognostic factor.

Conclusions

Circulating STC1 and STC2 mRNA are potentially useful blood markers for LSCC. Our results strongly suggest that the STC2 protein, but not STC1, may be a valuable biomarker for LSCC malignancies and a prognostic marker for poor outcome following surgery. Future studies should examine STC2 as a novel molecular target for the treatment of LSCC.

Survival analyses correlate stanniocalcin 2 overexpression to poor prognosis of nasopharyngeal carcinomas

Background

Stanniocalcin 2 (STC2) is overexpressed in several types of human cancers, and its overexpression positively correlates to tumor progression and poor prognosis. However, the clinical significance of STC2 overexpression in nasopharyngeal carcinomas (NPC) has not been investigated. This study examined STC2 expression in a cohort of 94 NPC samples, and explored its value in clinical diagnosis and prognosis.

Methods

Tumor samples from 94 patients diagnosed in 2008 were studied. All samples were obtained prior to treatment start. All cases were clinically diagnosed and pathologically confirmed to be poorly differentiated or undifferentiated NPC without distant metastasis, and have been treated with radical radiation therapy and followed-up for five years. Survival analyses were performed.

Results

Of the 94 NPC samples, STC2 overexpression (STC2+) was detected in 65 samples (69.1%). Overall survival rate of STC2 (+) patients is significantly lower than that of patients with normal STC2 levels (72.2% vs. 96.4%, respectively, P = 0.049). Moreover, STC2 (+) is also strongly predictive of a low progression-free survival and distant metastasis-free survival (63.0% vs 92.9%. P = 0.007; and 77.0% vs 96.4%. P = 0.028). Of the 54 patients treated with IMRT, residual tumors were found in 54.8% of STC2 positive patients (17/31), but only in 17.4% of STC2 negative ones (4/23), suggesting STC2 overexpression predicts a higher risk of residual tumors after IMRT.

Conclusions

STC2 overexpression correlates to poor prognosis for NPC and may be useful as a novel biomarker to predict NPC responses to radiation. Whether STC2 promotes NPC progression and metastasis remains to be investigated.

Anti-VEGF antibody therapy induces tumor hypoxia and stanniocalcin 2 expression and potentiates growth of human colon cancer xenografts

Tumor angiogenesis plays a critical role in colorectal cancer progression. Recent randomized clinical trials have revealed the additive effect of bevacizumab, a humanized monoclonal antibody against vascular endothelial growth factor (VEGF)-A, to conventional chemotherapy in the improved survival of patients with metastatic colorectal cancer. However, a number of preclinical reports indicate the development of resistance to anti-angiogenic therapy. In this study, we addressed the effects of anti-VEGF antibodies on the growth and malignant behavior of colorectal cancer cells. TK-4, a solid tumor strain derived from a colon cancer patient, was subcutaneously or orthotopically implanted into nude mice. Short-term administration of anti-VEGF antibodies inhibited the growth of cecal tumors at day 14 by suppressing mitosis, but prolonged treatment resulted in the recovery of cellular proliferation and suppression of apoptosis at day 35. Intratumoral hypoxia induced by anti-VEGF antibody treatment resulted in activation of hypoxia inducible factor-1α protein and an increased number of aldehyde dehydrogenase 1-positive tumor cells. In microarray analysis, stanniocalcin 2 (STC2) was the most highly upregulated gene in anti-VEGF antibody-treated tumors. In vitro analyses showed that the growth and migration of SW480 colon cancer cells under hypoxic conditions were significantly inhibited by knockdown of STC2. In vivo serial transplantation of TK-4 revealed that long-term administration of anti-VEGF antibodies increased the tumorigenicity of colon cancers and accelerated tumor growth when transplanted into secondary recipient mice. Our data provide a potential molecular explanation for the limited clinical effectiveness of anti-VEGF antibodies.

Clinical significance of stanniocalcin 2 expression as a predictor of tumor progression in gastric cancer

Stanniocalcin 2 (STC2) is a glycoprotein hormone that plays an important role in calcium and phosphate homeostasis. Furthermore, recent studies have demonstrated that STC2 expression in the primary site is correlated with tumor progression in several types of malignancies. However, few reports have investigated the clinical significance of STC2 expression in the blood of patients with gastric cancer. Therefore, we examined STC2 expression as a molecular blood marker for detection of circulating tumor cells (CTCs) and assessed the relationship between STC2 expression and clinico-pathological features including prognosis in patients with gastric cancer. Quantitative PCR assay was used to assess STC2 mRNA expression in 4 gastric cancer cell lines and in blood specimens from 93 patients with gastric cancer and 22 healthy volunteers. The numbers of STC2 mRNA copies were significantly higher in the gastric cancer cell lines and in blood from patients with gastric cancer than in blood from healthy volunteers (P=0.0002 and P=0.01, respectively). STC2 expression was positive in 43 (46.2%) of the 93 patients with gastric cancer, and its expression was significantly correlated with age, depth of tumor invasion, lymph node metastasis, stage and venous invasion (P=0.023, P=0.045, P=0.035, P=0.007 and P=0.027, respectively). The 5-year survival rate was significantly lower in patients with STC2 expression compared to patients without STC2 expression (P=0.014). Our results indicate that STC2 could be a useful molecular blood marker for predicting tumor progression by monitoring CTCs in patients with gastric cancer.

STC2 is upregulated in hepatocellular carcinoma and promotes cell proliferation and migration in vitro

The human glycoprotein, stanniocalcin 2 (STC2) plays multiple roles in several tumor types, however, its function and clinical significance in hepatocellular carcinoma (HCC) remain unclear. In this study, we detected STC2 expression by quantitative real-time PCR and found STC2 was upregulated in HCC tissues, correlated with tumor size and multiplicity of HCC. Ectopic expression of STC2 markedly promoted HCC cell proliferation and colony formation, while silencing of endogenous STC2 resulted in a reduced cell growth by cell cycle delay in G0/G1 phase. Western blot analysis demonstrated that STC2 could regulate the expression of cyclin D1 and activate extracellular signal-regulated kinase 1/2 (ERK1/2) in a dominant-positive manner. Transwell chamber assay also indicated altered patterns of STC2 expression had an important effect on cell migration. Our findings suggest that STC2 functions as a potential oncoprotein in the development and progression of HCC as well as a promising molecular target for HCC therapy.

Stanniocalcin-1 and -2 promote angiogenic sprouting in HUVECs via VEGF/VEGFR2 and angiopoietin signaling pathways

The members of stanniocalcins (STCs: STC-1 and STC-2) family are known to be involved in tumor progression and metastasis. Although current evidences suggest the involvement of STCs in vascular biology, the functional roles of STCs in angiogenesis have not yet been elucidated. The objective of this study was to decipher the roles of STCs in angiogenesis of human umbilical vascular endothelial cells (HUVECs). We prepared STC1 or STC2 lentiviral particles to transduce the cells to reveal their effects on the processes of cell proliferation, migration and tube formation. The stimulatory effects of STCs on these processes were demonstrated, supporting the notion of STCs in angiogenesis. To dissect the molecular components involved, STC1 or STC2 transduction led to significant increases in the expression levels of cell cycle regulators (i.e. cyclin-D and phospho-retinoblastoma), matrix metalloproteinase (MMP)-2 but a decrease of tissue inhibitors of metalloproteases (TIMP)-1. The expression levels of the cell adhesion/junctional proteins vimentin and VE-cadherin, were significantly induced. Moreover the transduction induced both mRNA and protein levels of eNOS, VEGF and VEGFR2 (KDR mRNA and pKDR), highlighting the stimulatory effects of STCs on VEGF-signaling pathway. Furthermore STC2 transduction but not STC1, activated angiopoietin (Ang)-2 pathway. Taken together, STC1 and STC2 play positive roles in angiogenic sprouting. The action of STC1 was mediated via VEGF/VEGFR2 pathway while STC2 were mediated via VEGF/VEGFR2 and Ang-2 pathways.

Nuclear karyopherin-α2 expression in primary lesions and metastatic lymph nodes was associated with poor prognosis and progression in gastric cancer

Karyopherin-α2 (KPNA2) functions as an adaptor that transports several proteins to the nucleus. We investigated the clinical and functional significance of KPNA2 in gastric cancer (GC). Immunohistochemistry was performed to examine KPNA2 expression in primary GC and metastatic lymph nodes. Next, KPNA2 was suppressed by small interfering RNA (siRNA) to examine KPNA2 function in proliferation and cisplatin-induced apoptosis of GC cell lines. Nuclear expression of KPNA2 in marginal regions of primary GC was stronger than in central regions of GC and normal tissues. The high expression of marginal KPNA2 was significantly associated with β-catenin accumulation in the nucleus and poor prognosis in two independent GC cohorts (discovery cohort, n = 90, P = 0.018; validation cohort, n = 89, P = 0.0125). We detected correlations between nuclear KPNA2 expression in marginal region and progression of macroscopic type (P = 0.036), tumor depth (P = 0.013), lymph node metastasis (P = 0.0064), venous invasion (P = 0.034) and clinical stage (P = 0.0006). Nuclear KPNA2 expression in marginal regions of metastatic lymph nodes was significantly higher than in the central region. It was associated with poor survival of GC patients with lymph node metastasis (n = 96; center, P = 0.4384; marginal, P < 0.0001). KPNA2 suppression enhanced cisplatin-induced apoptosis and reduced proliferation in the KPNA2 siRNA group compared with the control siRNA group. The expression of the DNA repair gene NBS1 (NBN) in the nucleus was suppressed in KPNA2-suppressed cells. KPNA2 might be a useful prognostic marker and an effective therapeutic target for GC.

Stanniocalcin 2, forms a complex with heme oxygenase 1, binds hemin and is a heat shock protein

Stanniocalcin 2 (STC2) is a homolog of stanniocalcin 1, a 56kD glycoprotein hormone that originally was found to confer calcitonin-like activity in fish. Human STC2 is expressed in various tissues such as kidney, spleen, heart, and pancreas. STC2 has been demonstrated to be induced by different kinds of stress and display cytoprotective activity, but the molecular mechanism is poorly understood. Heme oxygenase 1 (HO1) degrades heme to biliverdin, carbon monoxide and free iron, and is a stress-responsive protein. Using yeast two-hybrid screening we identified HO1 as a binding partner of STC2. The interaction was validated by in vivo co-immunoprecipitation and immunofluorescence. The binding site for HO1 was located to amino acids 181-200 of STC2. We also found that STC2 binds hemin via a consensus heme regulatory motif. Moreover, STC2 expression was induced by heat shock in HEK293 cells. Taken together, our findings point to three novel functions of STC2, and suggest that STC2 interacts with HO1 to form a eukaryotic 'stressosome' involved in the degradation of heme.

Evolution and roles of stanniocalcin

In fish, stanniocalcin-1 (STC1) is a key endocrine factor that acts on gill, intestine and kidney to regulate serum calcium and phosphate homeostasis. The recent identification and study of mammalian STCs (STC1 and STC2) revealed that the hormones are made in virtually all tissues and they act primarily as paracrine/autocrine factors to regulate various biological functions. Based on their ubiquitous expression patterns and generally undetectable levels in blood serum, it is unlikely that the mammalian STCs play important roles in serum Ca(2+)/P(i) homeostasis. However current evidences still support the local action of STCs in Ca(2+) and P(i) transport, probably via their action on Ca(2+)-channels and Na(+)/P(i) co-transporter. At present, information about the sequence, expression and distribution of the STC receptor(s) is lacking. However, recent emerging evidence hints the involvement of STC1 and STC2 in the sub-cellular functions of mitochondria and endoplasmic reticulum respectively, particularly responding to oxidative stress and unfolded protein response. With increasing evidence that demonstrates the local actions of STCs, the focus of the research has been moved to cellular inflammation and carcinogenesis. This review integrates the information available on STCs in fish and mammals, focusing mainly on their embryonic origin, tissue distribution, their potential regulatory mechanisms and the modes of action, and their physiological and pathophysiological functions, particularly in cancer biology.

Stanniocalcin-2 promotes epithelial-mesenchymal transition and invasiveness in hypoxic human ovarian cancer cells

The human glycoprotein, stanniocalcin-2 (STC2) is a HIF-1 target gene that is found to be associated with tumor development. The relationship of the prognostic outcome to the level of its expression in cancer tissues is controversial; however experimental evidence suggests that STC2 is a positive regulator of cancer progression. In the present study, we investigated if the expression of STC2 in hypoxic cells is associated with cancer invasion and metastasis. We studied the epithelial-mesenchymal transition (EMT) markers in STC2-silenced and over-expressed SKOV3 cells maintained in hypoxic condition. Western blot and immunocytochemical analysis revealed that the stable expression of exogenous STC2 promoted EMT, as revealed by the increase of N-cadherin/vimentin but a decrease of E-cadherin levels. This observation was further confirmed by colony formation assay where the STC2 stably transfected cells showed high degree of motility with fibroblast morphology under hypoxic condition. In conducting invasion assay in hypoxia, the STC2 stably transfected cells showed high degree of invasiveness. This observation was correlated with the significant increase of MMP2 and MMP9 expression in the STC2 stably transfected cells. In HUVEC/SKOV3 co-culture invasion study, endothelial invasion was found to be enhanced by the seeding of STC2 stably transfected cells in the lower compartment. These observations were possibly mediated by an increase of ROS and activated ERK1/2 levels in the cells. Collectively, the finding provides the first evidence that STC2 is a positive regulator in tumor progression at hypoxia.