The role of hypoxia and p53 in the regulation of angiogenesis in bladder cancer

A Novel Assessment Model Based on Molecular Subtypes of Hypoxia-Related LncRNAs for Prognosis of Bladder Cancer

Hypoxia is a common feature in various tumors that regulates aggressiveness. Previous studies have demonstrated that some dysregulated long non-coding RNAs (lncRNAs) are correlated with tumor progression, including bladder cancer (BCa). However, the prognostic effect of hypoxia-related lncRNAs (HRLs) and their clinical relevance, as well as their regulatory effect on the tumor immune microenvironment, are largely unknown in BCa. A co-expression analysis between hypoxia genes and lncRNA expression, which was downloaded from the TCGA database, was performed to identify HRLs. Univariate Cox regression analysis was performed to select the most desirable lncRNAs for molecular subtype, and further LASSO analysis was performed to develop a prognostic model. This molecular subtype based on four HRLs (AC104653, AL136084, AL139393, and LINC00892) showed good performance in the tumor microenvironment and tumor mutation burden. The prognostic risk model suggested better performance in predicting BCa patients' prognosis and obtained a close correlation with clinicopathologic features. Furthermore, four of five first-line clinical chemotherapies showed different sensitivities to this model, and nine immune checkpoints showed different expression in the molecular subtypes or the risk model. In conclusion, this study indicates that this molecular subtype and risk model based on HRLs may be useful in improving the prognostic prediction of BCa patients with different clinical situations and may help to find a useful target for tumor therapy.

A Robust Hypoxia Risk Score Predicts the Clinical Outcomes and Tumor Microenvironment Immune Characters in Bladder Cancer

Background

Bladder cancer (BLCA) is one of the most common urinary malignancies with poor prognosis. There is an unmet need to develop novel robust tools to predict prognosis and treatment efficacy for BLCA.

Methods

The hypoxia-related genes were collected from the Molecular Signatures Database. The TCGA-BLCA cohort was downloaded from the Cancer Genome Atlas and then was randomly divided into training and internal validation sets. Two external validation cohorts were gathered from Gene Expression Omnibus. Also, another independent validation cohort (Xiangya cohort) was collected from our hospital. The Cox regression model with the LASSO algorithm was applied to develop the hypoxia risk score. Then, we correlated the hypoxia risk score with the clinical outcomes, the tumor microenvironment (TME) immune characteristics, and the efficacy prediction for several treatments, which included cancer immunotherapy, chemotherapy, radiotherapy, and targeted therapies.

Results

Hypoxia risk score was an independent prognostic factor. A high-risk score indicated an inflamed TME based on the evidence that hypoxia risk score positively correlated with the activities of several cancer immunity cycles and the infiltration levels of many tumor-infiltrating immune cells, such as CD8 + T cells, Dendritic cells, and NK cells. Consistently, the hypoxia risk score was positively related to the expression of several immune checkpoints, such as PD-L1, PD-1, CTLA-4, and LAG-3, as well as the T cell inflamed score. Furthermore, the hypoxia risk score positively correlated with the enrichment scores of most immunotherapy-positive gene signatures. Therefore, patients with higher risk score may be more sensitive to cancer immunotherapy. Meanwhile, the hypoxia risk score was positively related to the sensitivities of several chemotherapeutic drugs, including Cisplatin, Docetaxel, Paclitaxel, Bleomycin, Camptothecin, and Vinblastine. Similarly, the enrichment scores for radiotherapy-predicted pathways and EGFR ligands were higher in the high-risk score group. Conversely, the enrichment scores of several immunosuppressive oncogenic pathways were significantly higher in the low-risk score group, such as the WNT-β-catenin network, PPARG network, and FGFR3 network.

Conclusions

We developed and validated a new hypoxia risk score, which could predict the clinical outcomes and the TME immune characteristics of BLCA. In general, the hypoxia risk score may aid in the precision medicine for BLCA.

Identification of a Hypoxia-Related Signature for Predicting Prognosis and the Immune Microenvironment in Bladder Cancer

Accumulating evidence indicates that hypoxia is highly associated with bladder cancer genesis, progression, and immune microenvironment. Nevertheless, few studies have identified the role of hypoxia-related genes as a prognostic signature in bladder cancer. This study aimed to establish a hypoxia-related signature with high accuracy for prognosis and immune microenvironment prediction in bladder cancer. We obtained expression profiles and clinical information from Gene Expression Omnibus and The Cancer Genome Atlas. Then the univariate Cox regression, random survival forest algorithm, and multivariate Cox regression analysis were conducted to identify the core genes and four hypoxia-related genes (ANXA2, GALK1, COL5A1, and HS3ST1) were selected to construct the signature. Kaplan-Meier survival analysis demonstrated that patients with a low-risk score had a higher disease-specific survival rate (p < 0.0001). The areas under the curve of the signature were 0.829 at 1 year, 0.869 at 3 years, and 0.848 at 5 years, respectively. Additionally, we found this hypoxia-related signature was highly correlated with tumor immune microenvironment and had the potential to predict the efficacy of immunotherapy. In summary, our study developed a hypoxia-related signature, which had high accuracy for prognosis prediction and the potential to guide the immunotherapy for bladder cancer patients.

Tumor suppressor U19/EAF2 regulates thrombospondin-1 expression via p53

Inactivation of U19/EAF2 has been shown previously to lead to tumorigenesis in multiple organs; however, the mechanism of U19/EAF2 tumor suppression remains unclear. In this paper, we report that the expression of an anti-angiogenic protein, thrombospondin-1 (TSP-1) is down-regulated in the prostate and liver of U19/EAF2 knockout mouse. The U19/EAF2 knockout liver displayed increased CD31-positive blood vessels, suggesting that the TSP-1 down-regulation can contribute to increased angiogenesis. TSP-1 is reported to be a p53-target gene and p53 is a known binding partner of ELL, which binds to U19/EAF2. Here, we show that U19/EAF2 can co-localize and co-immunoprecipitate with p53 in transfected cells. In a TSP-1 promoter-driven luciferase reporter assay, p53 transfection suppressed the TSP-1 promoter activity and U19/EAF2 co-transfection blocked the p53 suppression of TSP-1 promoter. However, U19/EAF2 transfection alone had little or no effect on the TSP-1 promoter. The above observations together suggest that U19/EAF2 regulates the expression of TSP-1 via blocking p53 repression of the TSP-1 promoter.

Elongation factor ELL (Eleven-Nineteen Lysine-rich Leukemia) acts as a transcription factor for direct thrombospondin-1 regulation

The eleven-nineteen lysine-rich leukemia (ELL) gene undergoes translocation and fuses in-frame to the multiple lineage leukemia gene in a substantial proportion of patients suffering from acute forms of leukemia. Studies show that ELL indirectly modulates transcription by serving as a regulator for transcriptional elongation as well as for p53, U19/Eaf2, and steroid receptor activities. Our in vitro and in vivo data demonstrate that ELL could also serve as a transcriptional factor to directly induce transcription of the thrombospondin-1 (TSP-1) gene. Experiments using ELL deletion mutants established that full-length ELL is required for the TSP-1 up-regulation and that the transactivation domain likely resides in the carboxyl terminus. Moreover, the DNA binding domain may localize to the first 45 amino acids of ELL. Not surprisingly, multiple lineage leukemia-ELL, which lacks these amino acids, did not induce expression from the TSP-1 promoter. In addition, the ELL core-response element appears to localize in the -1426 to -1418 region of the TSP-1 promoter. Finally, studies using zebrafish confirmed that ELL regulates TSP-1 mRNA expression in vivo, and ELL could inhibit zebrafish vasculogenesis, at least in part, through up-regulating TSP-1. Given the importance of TSP-1 as an anti-angiogenic protein, our findings may have important ramifications for better understanding cancer.

Neoadjuvant treatment of colorectal cancer with bevacizumab: the perioperative angiogenic balance is sensitive to systemic thrombospondin-1 levels

PURPOSE

Colorectal cancer patients receiving neoadjuvant treatment with bevacizumab, a monoclonal antibody neutralizing vascular endothelial growth factor (VEGF), may suffer from wound healing complications after surgery as the antibody persists in patient blood. We characterized the systemic angiogenic balance in the perioperative period to evaluate its effect on physiologic angiogenesis.

EXPERIMENTAL DESIGN

Nineteen patients receiving combination chemotherapy and bevacizumab for six neoadjuvant cycles were compared with 14 patients receiving chemotherapy without bevacizumab. Plasma from perioperative days -1, +1, +7, and +21 was analyzed for VEGF, thrombospondin-1 (TSP-1), and PD-ECGF concentrations. The angiogenic capacity was further tested in an in vitro assay of endothelial cell proliferation and migration.

RESULTS

On day +1, the onset of wound healing was reflected in a change of balance, i.e., an increase of proangiogenic factors VEGF and platelet-derived endothelial cell growth factor compared with low TSP-1 inhibitor levels in both treatment groups. Patients with bevacizumab therapy showed significantly higher blood levels of total VEGF throughout the evaluation period. However, most VEGF molecules were inactive, i.e., complexed with antibody. Nevertheless, the capacity to stimulate endothelial growth was higher for these plasma samples and was reflected in low TSP-1 levels and an altered TSP-1 sensitivity. When purified TSP-1 protein was added, plasma samples of the bevacizumab but not the chemotherapy group showed reduced endothelial growth.

CONCLUSIONS

Feedback mechanisms of bevacizumab therapy are not restricted to VEGF expression but seem to involve additional factors, such as TSP-1, which influences the systemic angiogenic balance and permits endothelial growth.

A new and reliable culture system for superficial low-grade urothelial carcinoma of the bladder

Several bladder cancer culture systems have been developed in recent years. However, reports about successful primary cultures of superficial urothelial carcinomas (UC) are sparse. Based on the specific growth requirements of UC described previously, we developed a new and reliable culture system for superficial low-grade UC. Between November 2002 and April 2006, 64 primary cultures of bladder cancer specimens were performed. After incubating the specimens overnight in 0.1% ethylenediaminetetraacetic acid solution, tumour cells could easily be separated from the submucosal tissue. Subsequently, cells were seeded in a low-calcium culture medium supplemented with 1% serum, growth factors, non-essential amino acids and glycine. The malignant origin of the cultured cells was demonstrated by spectral karyotyping. Overall culture success rate leading to a homogenous tumour cell population without fibroblast contamination was 63%. Culture success could be remarkably enhanced by the addition of glycine to the culture medium. Interestingly, 86.4% of pTa tumours were cultured successfully compared to only 50% of the pT1 and 38% of advanced stage tumours, respectively. G1 and G2 tumours grew significantly better than G3 tumours (86, 73 and 41%, respectively). Up to three passages of low-grade UC primary cultures were possible. We describe a new and reliable culture system, which is highly successful for primary culture and passage of low-grade UC of the bladder. Therefore, this culture system can widely be used for functional experiments on early stage bladder cancer.

Thrombospondin-1 expression in urothelial carcinoma: prognostic significance and association with p53 alterations, tumour angiogenesis and extracellular matrix components

Background

Thrombospondin-1 (TSP-1) is an extracellular matrix component glycoprotein, which is known to be a potent inhibitor of angiogenesis and may be important in cancer invasiveness. We examined the TSP-1 expression in correlation with conventional clinicopathological parameters to clarify its prognostic significance in bladder cancer. In addition, the possible correlation of TSP-1 expression with microvessel count, VEGF expression, p53 expression as well as with the expression of the extracellular matrix components was studied to explore its implication in vascularization and tumour stroma remodeling.

Methods

The immunohistochemical expression of TSP-1 in tumour cells and in the tumour stroma was studied in 148 formalin-fixed paraffin-embedded urothelial cell carcinoma tissue samples.

Results

TSP-1 was detected in perivascular tissue, at the epithelial-stromal junction, in the stroma and in tumour cells in the majority of the cases. In tumour cells, low TSP-1 expression was observed in 43% of the cases, moderate and high in 7%, while 50% showed absence of TSP expression. A higher TSP-1 immunoreactivity in well and moderately differentiated tumours compared to poorly differentiated was noted. PT₁ tumours showed decreased TSP-1 expression in comparison to pTa and pT_2–4 tumours. Increased tumour cell TSP-1 expression was related to increased microvessel density. In the tumour stroma, 37% of the cases showed small amount of TSP-1 expression, 7.5% moderate and high, while 55% of the cases showed absence of TSP-1 stromal immunoreactivity. Stromal TSP-1 expression was inversely correlated with tumour stage and tumour size. This expression was also positively correlated with microvessel density, VEGF expression and extracellular matrix components tenascin and fibronectin. Using univariate and multivariate analysis we didn't find any significant correlation of TSP-1 expression in superficial tumours in both tumour cells and tumour stroma in terns of the risk of recurrence and disease progression

Conclusion

Our data suggest that both tumour and stromal TSP-1 expression may play a role in tumour aggressiveness and angiogenesis. In addition, the correlation of stromal TSP-1 expression with extracellular matrix components fibronectin and tenascin indicate its possible implication in tumour stroma remodeling.

Peroxisome Proliferator-Activated Receptor γ Ligands Improve the Antitumor Efficacy of Thrombospondin Peptide ABT510

An expanding capillary network is critical for several pathologic conditions. In cancer, the decrease of antiangiogenic thrombospondin-1 (TSP1) often enables an angiogenic switch, which can be reversed with exogenous TSP1 or its peptide derivative ABT510. TSP1 acts by inducing endothelial cell apoptosis via signaling cascade initiated at CD36, a TSP1 antiangiogenic receptor. Here, we show that the ligands of nuclear receptor peroxisome proliferator-activated receptor γ (PPARγ), 15-deoxy-Δ12,14-prostaglandin J2, troglitazone, and rosiglitazone increased PPARγ and CD36 expression in endothelial cells and improved the efficacy of TSP1 and ABT510 in a CD36-dependent manner. The ABT510 and PPARγ ligands cooperatively blocked angiogenic endothelial functions in vitro and neovascularization in vivo. In tumor xenografts, 15-deoxy-Δ12,14-prostaglandin J2 and troglitazone synergistically improved antiangiogenic and antitumor effects of ABT510. Our data provide one mechanism for the in vivo angioinhibitory effect of PPARγ ligands and show fine-tuning of the antiangiogenic efficacy via targeted up-regulation of the endothelial receptor.

Angiogenesis in bladder cancer--prognostic marker and target for future therapy

Angiogenesis is the process by which tumours induce a blood supply, crucial for growth and metastasis. Evidence for its role in bladder carcinogenesis, its usefulness as a marker of patient prognosis, and potential anti-angiogenic therapies for future development are discussed in this chapter.