Expression of the angiopoietins and their receptor Tie2 in human renal clear cell carcinomas; regulation by the von Hippel-Lindau gene and hypoxia

Sunitinib resistance in renal cell carcinoma: From molecular mechanisms to predictive biomarkers

Currently, renal cell carcinoma (RCC) is the most prevalent type of kidney cancer. Targeted therapy has replaced radiation therapy and chemotherapy as the main treatment option for RCC due to the lack of significant efficacy with these conventional therapeutic regimens. Sunitinib, a drug used to treat gastrointestinal tumors and renal cell carcinoma, inhibits the tyrosine kinase activity of a number of receptor tyrosine kinases, including vascular endothelial growth factor receptor (VEGFR), platelet-derived growth factor receptor (PDGFR), c-Kit, rearranged during transfection (RET) and fms-related receptor tyrosine kinase 3 (Flt3). Although sunitinib has been shown to be efficacious in the treatment of patients with advanced RCC, a significant number of patients have primary resistance to sunitinib or acquired drug resistance within the 6-15 months of therapy. Thus, in order to develop more efficacious and long-lasting treatment strategies for patients with advanced RCC, it will be crucial to ascertain how to overcome sunitinib resistance that is produced by various drug resistance mechanisms. In this review, we discuss: 1) molecular mechanisms of sunitinib resistance; 2) strategies to overcome sunitinib resistance and 3) potential predictive biomarkers of sunitinib resistance.

Limitations to the Therapeutic Potential of Tyrosine Kinase Inhibitors and Alternative Therapies for Kidney Cancer

Background: Renal cell carcinomas (RCCs) are the most common primary renal tumor. RCCs have a high rate of metastasis and have the highest mortality rate of all genitourinary cancers. They are often diagnosed late when metastases have developed, and these metastases are difficult to treat successfully. Since 2006, the standard first-line treatment for patients with metastatic RCC has been multitargeted tyrosine kinase inhibitors (TKIs) that include mammalian target of rapamycin (mTOR) inhibitors. RCCs are highly vascularized tumors, and their angiogenesis is controlled by tyrosine kinases that play a vital role in growth factor signaling to stimulate this process. TKI therapy was introduced for direct targeting of angiogenesis in RCC. TKIs have been moderately successful in the treatment of metastatic RCC and initially increased cancer-specific survival times. However, RCC rapidly becomes resistant to TKIs, and no current drug has produced a cure for advanced RCC. Methods: We provide an overview of RCC, explain some reasons for therapy resistance in RCC, and describe some therapies that may overcome resistance to TKIs. The key pathways that determine therapy resistance are illustrated. Results: Factors involved in the development and progression of RCC include genetic mutations, activation of hypoxia-inducible factor and related proteins, cellular metabolism, the tumor microenvironment, and growth factors and their receptors. Resistance to the therapeutic potential of TKIs can be acquired or intrinsic. Alternative therapies include other small molecule drugs and immunotherapy based on immune checkpoint blockade. Conclusion: The treatment of RCC is undergoing a paradigm shift from sole use of small molecule antiangiogenesis TKIs as first-line therapy to include newly approved agents for second-line and third-line therapy that now involve the mTOR pathway and immune checkpoint blockade drugs for patients with advanced RCC.

Study of Cathepsin B inhibition in VEGFR TKI treated human renal cell carcinoma xenografts

Several therapeutic options are available for metastatic RCC, but responses are almost never complete, and resistance to therapy develops in the vast majority of patients. Consequently, novel treatments are needed to combat resistance to current therapies and to improve patient outcomes. We have applied integrated transcriptome and proteome analyses to identify cathepsin B (CTSB), a cysteine proteinase of the papain family, as one of the most highly upregulated gene products in established human RCC xenograft models of resistance to vascular endothelial growth factor receptor (VEGFR) tyrosine kinase inhibitors (TKI). We used established RCC models to test the significance of CTSB in the progression of renal cancer. Our evaluation of CTSB showed that stable CTSB knockdown suppressed RCC growth in vitro and in vivo. Stable over-overexpression of wild-type CTSB (CTSB^wt/hi), but not of an CTSB active site mutant (CTSB^N298A), rescued cell growth in CTSB knockdown cells and abolished the efficacy of VEGFR TKI treatment. Genome-wide transcriptome profiling of CTSB knockdown cells demonstrated significant effects on multiple metabolic and stem cell-related pathways, with ALDHA1A (ALDH1) as one of the most significantly downregulated genes. Importantly, survival analysis across 16 major TCGA cancers revealed that CTSB overexpression is associated with low rates of three and five year patient survival rates (P = 2.5e-08, HR = 1.4). These data strongly support a contribution of CTSB activity to RCC cell growth and tumorigenicity. They further highlight the promise of CTSB inhibition in development of novel combination therapies designed to improve efficacy of current TKI treatments of metastatic RCC.

Randomized Phase 2 Study of Trebananib (AMG 386) with or without Continued Anti-Vascular Endothelial Growth Factor Therapy in Patients with Renal Cell Carcinoma Who Have Progressed on Bevacizumab, Pazopanib, Sorafenib, or Sunitinib - Results of NCI/CTEP Protocol 9048

Background:

In renal cell carcinoma (RCC), angiopoietin (Ang) 2 is elevated at the time of progression on anti-vascular endothelial growth factor (VEGF) therapy and may contribute to resistance.

Objective:

We tested trebananib, an Ang 1 and 2 neutralizing peptibody in patients with RCC progressing on anti-VEGF treatment.

Methods:

Patients with measurable RCC progressing despite an anti-VEGF agent within 12 weeks, any number of prior treatments, and good PS were randomized to trebananib 15 mg/kg IV weekly without (Arm A) or with (Arm B) continuation of the prior anti-VEGF agent. The primary endpoint for each arm was tumor response (RECIST 1.1). Secondary endpoints included progression free survival and adverse events.

Results:

Of 41 enrolled patients, 35 were eligible and started treatment (17 Arm A, 18 Arm B) with median age 60 (46–76) and 3 prior treatments (1–8). Four died prior to documented progression and 27 progressed as their first event. Both arms were stopped after interim analysis, 2 responses (11%; 95% C.I. 1–35%) were observed in Arm B. Median PFS of 2.7 (95% C.I. 2.3–4.7) months in Arm A and 5.2 (95% C.I. 2.7–10.8) months in Arm B did not support continued study. Common adverse events including fatigue, nausea, and increased creatinine were generally grade 1–2 and numerically higher in Arm B. The most common grade 3 or higher adverse events were hypertension and dyspnea.

Conclusions:

While tolerable, trebananib either without or with continued anti-VEGF therapy did not show promising activity in RCC patients who recently progressed on anti-VEGF therapy alone.

Résistance aux inhibiteurs des tyrosines kinases dans le cancer du rein

FOCUS ON RESISTANCE TO TYROSINE KINASE INHIBITORS IN RENAL CANCER: The last decade has seen significant advances in understanding the biology and genetics of kidney cancer, some of which have radically changed treatment standards, including the emergence of targeted therapies. TKIs have significantly improved outcome in patients with metastatic disease. Nevertheless, a subset of patients (approximately 25 %) does not show any clinical benefit from targeted therapies. In many cases, patients initially respond to therapy but resistance to targeted agents has been shown to develop after a median of 6-12 months of treatment. Two general models of tumor resistance to anti-angiogenic agents targeting the VEGF pathway have been proposed: an adaptive (evasive) resistance, which occurs after a prolonged application of a drug (providing a period of tumor control), or intrinsic one (preexisting) non-responsiveness despite the presence of an active agent, showing no therapeutic benefit. Intrinsic resistance is related to tumor redundancy of pro-angiogenic pathways. Acquired resistance is associated with activation of alternative pathways either by upregulation of the VEGF pathway or by recruitment of alternative angiogenic factors responsible for tumor revascularization. Because different combinations and sequences of TKI are tested in clinical trials and immunotherapy (alone or in combination) radically alters patient management in its metastatic disease, the current effort aims at identifying resistance processes, evaluating their importance and proposing rational therapeutic approaches in order to obtain an additional clinical benefit. Our article summarizes the different mechanisms of resistance described in the literature.

Anti-angiogenic Targets: Angiopoietin and Angiopoietin Receptors

Tumor blood vessel formation (angiogenesis) is essential for tumor growth and metastasis. Two main endothelial ligand–receptor pathways regulating angiogenesis are vascular endothelial growth factor (VEGF) receptor and angiopoietin-TIE receptor pathways. The angiopoietin-TIE pathway is required for the remodeling and maturation of the blood and lymphatic vessels during embryonic development after VEGF and VEGF-C mediated development of the primary vascular plexus. Angiopoietin-1 (ANGPT1) stabilizes the vasculature after angiogenic processes, via tyrosine kinase with immunoglobulin-like and EGF-like domains 2 (TIE2) activation. In contrast, ANGPT2 is upregulated at sites of vascular remodeling. ANGPT2 is secreted by activated endothelial cells in inflammation, promoting vascular destabilization. ANGPT2 has been found to be expressed in many human cancers. Intriguingly, in preclinical models inhibition of ANGPT2 has provided promising results in preventing tumor angiogenesis, tumor growth, and metastasis, making it an attractive candidate to target in tumors. However, until now the first ANGPT2 targeting therapies have been less effective in clinical trials than in experimental models. Additionally, in preclinical models combined therapy against ANGPT2 and VEGF or immune checkpoint inhibitors has been superior to monotherapies, and these pathways are also targeted in early clinical trials. In order to improve current anti-angiogenic therapies and successfully exploit ANGPT2 as a target for cancer treatment, the biology of the angiopoietin-TIE pathway needs to be profoundly clarified.

Molecular Regulation of Sprouting Angiogenesis

The term angiogenesis arose in the 18th century. Several studies over the next 100 years laid the groundwork for initial studies performed by the Folkman laboratory, which were at first met with some opposition. Once overcome, the angiogenesis field has flourished due to studies on tumor angiogenesis and various developmental models that can be genetically manipulated, including mice and zebrafish. In addition, new discoveries have been aided by the ability to isolate primary endothelial cells, which has allowed dissection of various steps within angiogenesis. This review will summarize the molecular events that control angiogenesis downstream of biochemical factors such as growth factors, cytokines, chemokines, hypoxia-inducible factors (HIFs), and lipids. These and other stimuli have been linked to regulation of junctional molecules and cell surface receptors. In addition, the contribution of cytoskeletal elements and regulatory proteins has revealed an intricate role for mobilization of actin, microtubules, and intermediate filaments in response to cues that activate the endothelium. Activating stimuli also affect various focal adhesion proteins, scaffold proteins, intracellular kinases, and second messengers. Finally, metalloproteinases, which facilitate matrix degradation and the formation of new blood vessels, are discussed, along with our knowledge of crosstalk between the various subclasses of these molecules throughout the text. Compr Physiol 8:153-235, 2018.

Resistance to Targeted Therapies in Renal Cancer: The Importance of Changing the Mechanism of Action

Renal cell carcinoma (RCC) is a complex disease characterized by mutations in several genes. Loss of function of the von Hippel-Lindau (VHL) tumour suppressor gene is a very common finding in RCC and leads to up-regulation of hypoxia-inducible factor (HIF)-responsive genes accountable for angiogenesis and cell growth, such as platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF). Binding of these proteins to their cognate tyrosine kinase receptors on endothelial cells promotes angiogenesis. Promotion of angiogenesis is in part due to the activation of the phosphatidylinositol-3-kinase (PI3K)/AKT/mechanistic target of rapamycin (mTOR) pathway. Inhibition of this pathway decreases protein translation and inhibits both angiogenesis and tumour cell proliferation. Although tyrosine kinase inhibitors (TKIs) stand as the main first-line treatment option for advanced RCC, eventually all patients will become resistant to TKIs. Resistance can be overcome by using second-line treatments with different mechanisms of action, such as inhibitors of mTOR, c-MET, programmed death 1 (PD-1) receptor, or the combination of an mTOR inhibitor (mTORi) with a TKI. In this article, we briefly review current evidence regarding mechanisms of resistance in RCC and treatment strategies to overcome resistance with a special focus on the PI3K/AKT/mTOR pathway.

Expression of angiopoietins in central nervous system hemangioblastomas is associated with cyst formation

PURPOSE

This study aimed to determine the expression of angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2), and endothelial tyrosine kinase receptor (Tie-2) in central nervous system (CNS) hemangioblastomas (HBs) and explore the correlation with peritumoral cyst formation.

METHOD

A total of 22 paraffin-embedded specimens derived from 11 cyst-associated and 11 solid solitary CNS HBs were collected for streptavidin-peroxidase immunohistochemical staining. The expression levels of Ang-1, Ang-2 and Tie-2 in cystic and solid HBs were estimated and compared according to the integrated optical density (IOD) of staining in the sections. To further confirm the differential expression of Ang-1 and Ang-2 between cystic and solid HBs, an additional 9 frozen specimens from 5 cyst-associated and 4 solid solitary HBs were collected for Western blot analysis. Clinical histories and radiological records of the patients were reviewed retrospectively.

RESULTS

Compared to normal cerebellum tissue, Ang-1, Ang-2 and Tie-2 were prominently overexpressed in both the stromal cells and endothelial cells of CNS HBs. The expression of Ang-2 and the ratio of Ang-2/Ang-1 in the cystic group were significantly higher than those in the solid group. The intensity of Ang-2 expression in the cystic group was negatively correlated with age. There was no correlation between the expression level of the proteins and sex, tumor location, tumor volume or cyst volume.

CONCLUSIONS

Ang/Tie signaling is upregulated in HBs and is likely associated with the process of intense vascularization and cyst formation. Higher Ang-2 levels and a higher Ang-2/Ang-1 ratio may contribute to cyst formation by increasing the vascular permeability. The decrease in Ang-2 expression with advanced age in cystic-associated HBs may be associated with the reduced growth rate of peritumoral cysts among elderly patients. Ang-2 shows great potential as an effective therapeutic target of symptomatic CNS HBs associated with cysts.

Novel Angiogenesis Markers as Long-Term Prognostic Factors in Patients With Renal Cell Cancer

OBJECTIVE

To evaluate Ang-2 expression alone and in combination with expression of cell proliferation and cell survival markers (MIB-1 and Bcl-2) and angiogenesis markers (VEGFR3 and CD31), and the associations of these markers with renal cell cancer (RCC) in long-term survival.

PATIENTS AND METHODS

Our study included 224 patients with RCC who were treated before the availability of antiangiogenic agents between 1985 and 1995, at the Pirkanmaa Hospital District in Finland. All tumor samples were reclassified and reevaluated by an experienced uropathologist, and parallel tissue microarrays (TMA) were performed for immunohistochemical analysis. Kaplan-Meier's survival estimation method and Cox proportional hazards models were used for survival analysis.

RESULTS

The percentage of Ang-2 expression in the tumor area varied from 0.07 to 25.65. Ang-2 expression was significantly associated with the tumor grade and stage, as well as the MIB-1, Bcl-2, and VEGFR3 expression (P = .042, P = .019, P = .039, P = .013, and P = .005, respectively). The highest Ang-2 expression predicted better survival, P < .05. High Bcl-2 and low MIB-1 expression combined with Ang-2 expression was associated with better survival. Multivariate analysis showed poorer survival in patients with low Ang-2 or high MIB-1 expressions: HR 1.89, 95% CI 1.16 to 3.08, P = .010 and HR 2.20, 95% CI 1.36 to 3.54, P = .001, respectively.

CONCLUSIONS

Very high Ang-2 expression was associated with better survival in patients with RCC. Ang-2 expression correlated with tumor stage and grade, but it was still an independent prognostic factor in a multivariate analysis.

Association of Angiopoietin-2 and Ki-67 Expression with Vascular Density and Sunitinib Response in Metastatic Renal Cell Carcinoma

The Angiopoietin-2 (Ang2, Angpt2) growth factor is a context-dependent antagonist/agonist ligand of the endothelial Tie2 receptor tyrosine kinase and known to promote tumour angiogenesis and metastasis. Angiopoietin antagonists have been tested in clinical cancer trials in combination with VEGF-based anti-angiogenic therapy, including sunitinib, which is widely used as a first-line therapy for metastatic renal cell carcinoma (mRCC). However, little is known about Ang2 protein expression in human tumours and the correlation of tumour Ang2 expression with tumour vascularization, tumour cell proliferation and response to anti-angiogenic therapies. Here, we evaluated, using immunohistochemistry, the expression of Ang2, CD31 and the cell proliferation marker Ki-67 in the primary kidney cancer from 136 mRCC patients, who received first-line sunitinib after nephrectomy. Ang2 protein expression was restrained to RCC tumour vessels, and correlated with tumour vascularization and response to sunitinib. High pre-therapeutic Ang2 expression, and more strongly, combined high expression of both Ang2 and CD31, were associated with a high clinical benefit rate (CBR). Low cancer Ki-67 expression, but not Ang2 or CD31 expression, was associated with favourable progression-free (PFS) and overall survival (OS) as compared to patients with high Ki-67 expression (PFS 6.5 vs. 10.6 months, P = 0.009; OS, 15.7 vs. 28.5 months, P = 0.015). In summary, in this study to investigate endothelial Ang2 in mRCC patients treated with first-line sunitinib, high cancer Ang2 expression was associated with the CBR, but not PFS or OS, whereas low Ki-67 expression was significantly associated with long PFS and OS.

Contemporary Treatment of Metastatic Renal Cell Carcinoma

The introduction of targeted therapy has revolutionized the treatment of patients with metastatic renal cell carcinoma (mRCC). The current standard of care focuses on the inhibition of angiogenesis through the targeting of the vascular endothelial growth factor receptor (VEGFR) and the mammalian target of rapamycin (mTOR). Over the past few years, research exploring novel targeted agents has blossomed, leading to the approval of various targeted therapies. Furthermore, results from the CheckMate025 and the METEOR trials have brought about two additional novel options: the programmed cell death 1 (PD-1) checkpoint inhibitor nivolumab and the MET/VEGFR/AXL inhibitor cabozantinib, respectively. With the variety of therapeutic agents available for treatment of mRCC, research examining appropriate sequencing and combinations of the drugs is ongoing. This review discusses the role of prognostic criteria, such as those from the International Metastatic Renal Cell Carcinoma Database Consortium (IMDC) criteria. It also covers the current standard of treatment for mRCC with targeted therapy in first-, second-, and third-line setting. Additionally, the novel mechanism of action of nivolumab and cabozantinib, therapeutic sequencing and ongoing clinical trials are discussed.

Trebananib (AMG 386) in Combination With Sunitinib in Patients With Metastatic Renal Cell Cancer: An Open-Label, Multicenter, Phase II Study

PURPOSE

Trebananib, an investigational recombinant peptide-Fc fusion protein, neutralizes the receptor-ligand interaction between Tie2 and angiopoietin-1/2. This phase II study was conducted to evaluate trebananib plus sunitinib, a vascular endothelial growth factor receptor inhibitor, in patients with metastatic clear cell renal cell carcinoma.

PATIENTS AND METHODS

Adults with metastatic renal cell carcinoma were enrolled sequentially onto two cohorts that received sunitinib 50 mg once per day for 4 weeks on and 2 weeks off and intravenous trebananib once per week at a dose of 10 mg/kg in cohort A or 15 mg/kg in cohort B. The primary end points were incidences of adverse events (AEs) and dose interruptions of sunitinib during the first 12 weeks of treatment. Secondary end points included objective response rate and progression-free survival.

RESULTS

Eighty-five patients were enrolled: 43 in cohort A, and 42 in cohort B. During the first 12 weeks of treatment, 58% and 57% of patients in cohorts A and B, respectively, had sunitinib dose interruptions (dose decrease, withholding, or withdrawal). The most frequent AEs were diarrhea (cohort A, 74%; cohort B, 67%), mucosal inflammation (cohort A, 49%; cohort B, 60%), and hypertension (cohort A, 52%; cohort B, 45%). AEs of grade 3 or greater occurred in 58% of patients in cohort A and in 69% of patients in cohort B. The objective response rate was 58% and 63% in cohorts A and B, respectively. The median progression-free survival time was 13.9 months (95% CI, 10.4 to 19.2) and 16.3 months (95% CI, 13.1 to 21.4) in cohorts A and B, respectively. The median overall survival time was 36 months (95% CI, 25.2 to not estimable) in cohort A and was not estimable (median follow-up, 25 months) in cohort B.

CONCLUSION

Trebananib plus sunitinib seemed to increase toxicity at the tested doses. Efficacy results suggest a potential benefit for the addition of trebananib to sunitinib.

Prospective evaluation of plasma levels of ANGPT2, TuM2PK, and VEGF in patients with renal cell carcinoma

Background

To assess pathological correlations and temporal trends of Angiopoietin-2 (ANGPT2), vascular endothelial growth factor (VEGF) and M2 Pyruvate kinase (TuM2PK), markers of tumor vascular development and metabolism, in patients with renal cell carcinoma (RCC).

Methods

We prospectively collected plasma samples from 89 patients who underwent surgical/ablative therapy for RCC and 38 patients with benign disease (nephrolithiasis, hematuria without apparent neoplastic origin, or renal cysts). In RCC patients, marker levels were compared between at least 1 preoperative and 1 postoperative time point generally 3 weeks after surgery. Marker temporal trends were assessed using the Wilcoxon sign-rank test. Plasma VEGF, ANGPT2, and TuM2PK levels were determined by ELISA and tested for association with pathological variables.

Results

Median age was comparable between groups. 83/89 (93%) of the cohort underwent surgical extirpation. 82% of the tumors were organ confined (T ≤2, N0). Only ANGPT2 exhibited significantly elevated preoperative levels in patients with RCC compared to benign disease (p = 0.046). Elevated preoperative levels of ANGPT2 and TuM2PK significantly correlated with increased tumor size and advanced grade (p < 0.05). Chromophobe RCC exhibited higher levels of ANGPT2 compared to other histologies (p < 0.05). A decline in marker level after surgery was not observed, likely due to the timing of the analyses.

Conclusion

Our results suggest that ANGPT2 is a marker of RCC. Additionally, ANGPT2 and TuM2PK significantly correlated with several adverse pathological features. Further studies are needed to determine clinical applicability.

Angiopoietins promote ovarian cancer progression by establishing a procancer microenvironment

Despite decades of research, the survival rate of ovarian cancer patients is largely unchanged. Current chemotherapeutic drugs are effective only transiently because patients with advanced disease eventually develop resistance. Thus, there is a pressing need for identifying novel therapeutic targets in ovarian cancer. Mounting evidence suggests that angiopoietins (Angpts) may play an essential role in cancer progression; however, the expression profiles and biological effects of Angpts on ovarian cancer remain largely unknown. Here, we show that, compared with their normal counterparts, expressions of Angpt1, Angpt2, and Angpt4 are increased in ovarian cancer cells and tissues and that human ovarian cancer cells also express the Angpt receptor Tie-2-receptor tyrosine kinase. We show that increased expression of Angpt1, Angpt2, or Angpt4 promotes intraperitoneal growth of ovarian cancers and shortens survival of the experimental mice. We further show, for the first time, that Angpts promote accumulation of cancer-associated fibroblasts and tumor angiogenesis in the ovarian cancer microenvironment, as well as enhance ovarian cancer cell proliferation and invasion in vivo. In addition, we establish a novel function of Angpts in promoting proliferation and invasion and inducing Tie-2 and extracellular signal-regulated kinase 1/2 activation in ovarian cancer-associated fibroblasts. Taken together, these data suggest that the Angpt-Tie-2 functional axis is an important player in ovarian cancer progression and an attractive target for ovarian cancer therapy.

Resistance to sunitinib in renal cell carcinoma: From molecular mechanisms to predictive markers and future perspectives

The introduction of agents that inhibit tumor angiogenesis by targeting vascular endothelial growth factor (VEGF) signaling has made a significant impact on the survival of patients with metastasized renal cell carcinoma (RCC). Sunitinib, a tyrosine kinase inhibitor of the VEGF receptor, has become the mainstay of treatment for these patients. Although treatment with sunitinib substantially improved patient outcome, the initial success is overshadowed by the occurrence of resistance. The mechanisms of resistance are poorly understood. Insight into the molecular mechanisms of resistance will help to better understand the biology of RCC and can ultimately aid the development of more effective therapies for patients with this infaust disease. In this review we comprehensively discuss molecular mechanisms of resistance to sunitinib and the involved biological processes, summarize potential biomarkers that predict response and resistance to treatment with sunitinib, and elaborate on future perspectives in the treatment of metastasized RCC.

Statins, 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, potentiate the anti-angiogenic effects of bevacizumab by suppressing angiopoietin2, BiP, and Hsp90α in human colorectal cancer

Background:

Statins, 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, are commonly prescribed because of their therapeutic and preventive effects on cardiovascular diseases. Even though they have been occasionally reported to have antitumour activity, it is unknown whether statins have anti-angiogenic effect in human colorectal cancer (CRC).

Methods:

A total of 11 human CRC cell lines were used to test the effects of bevacizumab, statins, and bevacizumab plus statins on human umbilical vein endothelial cell (HUVEC) viability and invasion in vitro. To determine the molecular mechanism of statins as anti-angiogenic agents, we performed an angiogenesis antibody array and proteomics analysis and confirmed the results using immunoblot assay, HUVEC invasion rescue assay, and siRNA assay. The antitumoural effects of bevacizumab and statins were evaluated in xenograft models.

Results:

A conventional dose of statins (simvastatin 0.2 μM, lovastatin 0.4 μM, atorvastatin 0.1 μM, and pravastatin 0.4 μM) in combination with bevacizumab directly reduced the cell viability, migration, invasion, and tube formation of HUVECs. The culture media of the CRC cells treated with bevacizumab or statins were also found to inhibit HUVEC invasion by suppressing angiogenic mediators, such as angiopoietin2, binding immunoglobulin protein (BiP), and Hsp90α. The combined treatment with bevacizumab and simvastatin significantly reduced the growth and metastases of xenograft tumours compared with treatment with bevacizumab alone.

Conclusions:

The addition of simvastatin at a dose used in patients with cardiovascular diseases (40–80 mg once daily) may potentiate the anti-angiogenic effects of bevacizumab on CRC by suppressing angiopoietin2, BiP, and Hsp90α in cancer cells. A clinical trial of simvastatin in combination with bevacizumab in patients with CRC is needed.

Angiopoietins and non-vascular endothelial growth factor antiangiogenic targets in advanced renal cell carcinoma

The treatment of metastatic renal cell carcinoma has evolved from an era dominated by immune modulation to an era of antiangiogenesis agents. Blockade of vascular endothelial growth factor-mediated pathways and mammalian target of rapamycin pathways has accounted for most of these gains. Although these agents have offered dramatic improvements in survival for kidney cancer patients, resistance inevitably occurs, and new classes of agents are needed to continue to improve outcomes in this setting. We discuss several alternative pathways of angiogenesis, which are being investigated as targets to overcome treatment resistance, including angiopoietin family proteins, fibroblast growth factor, platelet-derived growth factor, and vascular disrupting agents.

Combination therapy in metastatic renal cell cancer

The standard strategy in metastatic renal cell carcinoma (mRCC) is to use sequential treatment. Different pathways are known to be involved in the pathogenesis of mRCC and in the development of resistance to targeted drugs. Combinations of targeted drugs could theoretically achieve better inhibition of a given pathway, inhibition of different pathways, or inhibition of a pathway involved in the resistance to a given drug. However, there is as yet no clear evidence that combination therapy is of clinical benefit and excess toxicity has been observed. In mRCC the majority of studies have explored combinations of vascular endothelial growth factor (VEGF) inhibitors and mammalian target of rapamycin (mTOR) inhibitors. A new generation of VEGF tyrosine kinase inhibitors (TKIs) seems to be more tolerable, and therefore potentially easier to combine with other agents. Trials with PI3K/akt/mTORC1/2 inhibitor combinations and with other new targeted drugs are also ongoing.

The frequency of tumor-infiltrating Tie-2-expressing monocytes in renal cell carcinoma: its relationship to angiogenesis and progression

OBJECTIVE

To examine the frequency of tumor-infiltrating Tie-2-expressing monocytes (TEMs) in renal cell carcinoma (RCC) and its association with microvessel density (MVD) and other clinical-pathologic features.

MATERIALS AND METHODS

This study enrolled 65 consecutive patients with RCC treated with radical nephrectomy. The frequency of tumor-infiltrating TEMs, which was defined as CD14(+) Tie-2(+) cells, was assessed using flow cytometry. MVD was measured by immunohistochemistry using anti-CD34 antibody. The association between clinicopathologic parameters, MVD, and the frequency of tumor-infiltrating TEMs in RCC was assessed.

RESULTS

High frequency of tumor-infiltrating TEMs was significantly associated with advanced stage (P = .018), positive lymph nodes (P = .013), high grade (P = .019), and metastases (P = .006). Correlation analysis revealed that the frequency of TEMs was positively correlated with MVD.

CONCLUSION

Our findings revealed a significant association between prognostic tumor features, MVD, and the frequency of tumor-infiltrating TEMs in RCC and indicated that TEMs may play an important role in angiogenesis and progression of RCC.

Effect of intracavernous administration of angiopoietin-4 on erectile function in the streptozotocin-induced diabetic mouse

INTRODUCTION

Erectile dysfunction (ED) is a highly prevalent complication of diabetes, and the severity of endothelial dysfunction is one of the most important factors in reduced responsiveness to oral phosphodiesterase type 5 inhibitors.

AIM

To study the effects of human angiopoietin-4 (Ang-4) protein on erectile function in diabetic mice.

METHODS

Diabetes was induced by intraperitoneal injection of streptozotocin into 8-week-old C57BL/6J male mice. At 8 weeks after the induction of diabetes, the animals were divided into four groups: control nondiabetic mice and diabetic mice receiving two successive intracavernous injections of phosphate buffered saline (days -3 and 0), a single intracavernous injection of Ang-4 protein (day 0), or two successive intracavernous injections of Ang-4 protein (days -3 and 0).

MAIN OUTCOME MEASURES

One week after treatment, we measured erectile function by electrical stimulation of the cavernous nerve. The penis was harvested and stained with hydroethidine or antibodies to Ang-4, platelet/endothelial cell adhesion molecule-1, and phosphorylated endothelial nitric oxide synthase (eNOS). We also determined the differential expression of Ang-4 in cavernous tissue in the control and diabetic mice. The effect of Ang-4 protein on the phosphorylation of Tie-2, Akt, and eNOS was determined in human umbilical vein endothelial cells (HUVECs) by Western blot.

RESULTS

The cavernous expression of Ang-4 was downregulated in diabetic mice; Ang-4 was mainly expressed in endothelial cells. Local delivery of Ang-4 protein significantly increased cavernous endothelial content, induced eNOS phosphorylation, and decreased the generation of superoxide anion and apoptosis in diabetic mice. Ang-4 protein strongly increased the phosphorylation of Tie-2, Akt, and eNOS in HUVECs. Repeated intracavernous injections of Ang-4 induced significant restoration of erectile function in diabetic mice (87% of control values), whereas a single intracavernous injection of Ang-4 protein elicited modest improvement.

CONCLUSIONS

Cavernous endothelial regeneration by use of Ang-4 protein may have potential for the treatment of vascular disease-induced ED, such as diabetic ED.

How far is the horizon? From current targets to future drugs in advanced renal cancer

PURPOSE

The proliferative control of renal cell cancer (RCC) via vascular endothelial growth factor and mammalian target of rapamycin inhibition by targeted agents has substantially improved survival rates for RCC patients with metastatic (m) disease. However, the management of mRCC remains challenging because some patients are primarily refractory to the approved targeted agents and most therapies eventually fail because of the development of an intractable drug resistance. Tumor progression is closely related to a persistent or restored proliferation via direct and indirect oncogenic signals. Although the elucidation of cancer cell proliferation in the "-omics era" has revealed an enormous number of new potential targets, a comprehensive overview of the different pathways that might serve as new drug targets has become increasingly complex.

METHODS/RESULTS

This review highlights the well-trodden pathways in mRCC that are inhibited by targeting agents and describes innovative modes of action within these pathways that are currently not targeted but are under exploration in clinical studies. Additionally, this paper highlights as future drug targets the components of tumor metabolism that supply the tumor cells with nutrition.

CONCLUSIONS

These fundamental insights into RCC proliferation as a key driver of progression are urgently needed to overcome the currently improved but still limited targeted drug success.

Serum angiopoietin-2 level as a predictor of tumor invasiveness in patients with hepatocellular carcinoma

BACKGROUND

Because hepatocellular carcinoma (HCC) has important angiogenic activity, the expression of angiopoietin-2 (Ang-2) may have a pathogenic role. The information about the influence of serum Ang-2 (sAng-2) in patients with HCC is scarce.

AIMS

The aim was to assess the association between sAng-2 levels and characteristics of tumor and liver disease in patients with HCC.

METHODS

sAng-2 concentrations in peripheral (sAng-2-P) and hepatic (sAng-2-H) veins were analyzed by ELISA in 33 patients with chronic liver disease who underwent a splanchnic hemodynamic study. Thirty-two patients received treatment for HCC.

RESULTS

The median age was 61 years and 79% were male. Hepatitis C infection (70%) was the main etiology. Most patients were Child-Pugh grade A (72.7%). sAng-2-P and sAng-2-H were well correlated (r = 0.95; p < 0.0001). A significant association was found between sAng-2-H and lobar tumor extension, vascular thrombosis, BCLC staging, infiltrating pattern, abnormal alpha-fetoprotein level, fulfillment of the Milan criteria, and performance of nonsystemic treatment. sAng-2-H also showed a significant correlation with the MELD score (r = 0.49; p = 0.007), albumin (r = -0.63; p < 0.001), and HVPG (r = 0.44; p = 0.02). Eleven patients received treatment with radiofrequency ablation and eight with transarterial chemoembolization. HCC treatment did not influence the sAng-2 concentration while the necrosis response to treatment was not influenced by previous sAng-2 levels.

CONCLUSIONS

Ang-2 seems to play an important role in the angiogenic processes of HCC and its serum levels are associated with tumor characteristics and invasive behavior. Our results suggest that Ang-2 is not related with treatment response and its level is not modified by treatment.

Targeting PI3K and mTORC2 in metastatic renal cell carcinoma: new strategies for overcoming resistance to VEGFR and mTORC1 inhibitors

With the advent of molecularly targeted agents, treatment of metastatic renal cell carcinoma (mRCC) has improved significantly. Agents targeting the vascular endothelial growth factor receptor (VEGFR) and the mammalian target of rapamycin complex 1 (mTORC1) are more effective and less toxic than previous standards of care involving cytotoxic and cytokine therapies. Unfortunately, many patients relapse following treatment with VEGFR and mTORC1 inhibitors as a result of acquired resistance mechanisms, which are thought to lead to the reestablishment of tumor vasculature. Specifically, the loss of negative feedback loops caused by inhibition of mTORC1 leads to upregulation of downstream effectors of the phosphoinositide 3-kinase (PI3K)/AKT/mTOR pathway and subsequent activation of hypoxia-inducible factor, an activator of angiogenesis. De novo resistance involving activated PI3K signaling has also been observed. These observations have led to the development of novel agents targeting PI3K, mTORC1/2 and PI3K/mTORC1/2, which have demonstrated antitumor activity in preclinical models of RCC. Several agents--BKM120, BEZ235 and GDC-0980--are being investigated in clinical trials in patients with metastatic/advanced RCC, and similar agents are being tested in patients with solid tumors. The future success of mRCC treatment will likely involve a combination of agents targeting the multiple pathways involved in angiogenesis, including VEGFR, PI3K and mTORC1/2.

Angiopoietin-2 functions as a Tie2 agonist in tumor models, where it limits the effects of VEGF inhibition

The angiopoietins Ang1 (ANGPT1) and Ang2 (ANGPT2) are secreted factors that bind to the endothelial cell-specific receptor tyrosine kinase Tie2 (TEK) and regulate angiogenesis. Ang1 activates Tie2 to promote blood vessel maturation and stabilization. In contrast, Ang2, which is highly expressed by tumor endothelial cells, is thought to inhibit Tie2 activity and destabilize blood vessels, thereby facilitating VEGF-dependent vessel growth. Here, we show that the inhibition of tumor xenograft growth caused by an Ang2-specific antibody (REGN910) is reversed by systemic administration of the Tie2 agonist Ang1. These results indicate that Ang2 blockade inhibits tumor growth by decreasing Tie2 activity, showing that Ang2 is a Tie2 activator. REGN910 treatment of tumors resulted in increased expression of genes that are repressed by Tie2 activation, providing further evidence that REGN910 inhibits Tie2 signaling. Combination treatment with REGN910 plus the VEGF blocker aflibercept reduced tumor vascularity and tumor perfusion more dramatically than either single agent, resulting in more extensive tumor cell death and more potent inhibition of tumor growth. Challenging the prevailing model of Ang2 as a destabilizing factor, our findings indicate that Ang2 plays a protective role in tumor endothelial cells by activating Tie2, thereby limiting the antivascular effects of VEGF inhibition. Thus, blockade of Ang2 might enhance the clinical benefits currently provided by anti-VEGF agents. .

AMG 386 in combination with sorafenib in patients with metastatic clear cell carcinoma of the kidney: a randomized, double-blind, placebo-controlled, phase 2 study

BACKGROUND

This study evaluated the tolerability and antitumor activity of AMG 386, a peptibody (a peptide Fc fusion) that neutralizes the interaction of angiopoietin-1 and angiopoietin-2 with Tie2 (tyrosine kinase with immunoglobulin-like and EGF-like domains 2), plus sorafenib in patients with clear cell metastatic renal cell carcinoma (mRCC) in a randomized controlled study.

METHODS

Previously untreated patients with mRCC were randomized 1:1:1 to receive sorafenib 400 mg orally twice daily plus intravenous AMG 386 at 10 mg/kg (arm A) or 3 mg/kg (arm B) or placebo (arm C) once weekly (qw). Patients in arm C could receive open-label AMG 386 at 10 mg/kg qw plus sorafenib following disease progression. The primary endpoint was progression-free survival (PFS).

RESULTS

A total of 152 patients were randomized. Median PFS was 9.0, 8.5, and 9.0 months in arms A, B, and C, respectively (hazard ratio for arms A and B vs arm C, 0.88; 95% confidence interval [CI], 0.60-1.30; P = .523). The objective response rate (95% CI) for arms A, B, and C, respectively, was 38% (25%-53%), 37% (24%-52%), and 25% (14%-40%). Among 30 patients in arm C who had disease progression and subsequently received open-label AMG 386 at 10 mg/kg qw, the objective response rate was 3% (95% CI, 0%-17%). Frequently occurring adverse events (AEs) included diarrhea (arms A/B/C, 70%/67%/56%), palmar-plantar erythrodysesthesia syndrome (52%/47%/54%), alopecia (50%/45%/50%), and hypertension (42%/49%/46%). Fifteen patients had grade 4 AEs (arms A/B/C, n = 3/7/5); 4 had fatal AEs (n = 2/1/1), with 1 (abdominal pain, arm B) considered possibly related to AMG 386.

CONCLUSIONS

In patients with mRCC, AMG 386 plus sorafenib was tolerable but did not significantly improve PFS compared with placebo plus sorafenib.

Molecular profiling of pancreatic neuroendocrine tumors in sporadic and Von Hippel-Lindau patients

PURPOSE

Von Hippel-Lindau (VHL) disease is an inherited syndrome caused by germline mutations in the VHL tumor suppressor gene, predisposing to a variety of neoplasms including pancreatic neuroendocrine tumors (PanNET). In VHL disease, PanNET probably progress according to a specific pathway of carcinogenesis. Our aim was to characterize by molecular quantitative analysis a panel of molecules implicated in the VHL pathway and in tumor progression in the PanNET of patients with VHL.

EXPERIMENTAL DESIGN

The expression of 52 genes was studied by quantitative reverse transcriptase PCR in 18 patients with VHL operated on for PanNET and compared with 16 non-VHL PanNET. The VHL and non-VHL tumors were matched according to their size and cell proliferation. For some genes, we looked for differences in the protein expression in VHL PanNET (n = 31), microadenomas (n = 22), and non-VHL PanNET (n = 16), included in tissue microarray blocks.

RESULTS

Nineteen (36%) genes were significantly upregulated and three (6%) downregulated in VHL PanNET. The upregulated genes were related to (i) hypoxia-inducible factor (HIF) molecules (CA9, HIF2A, and GLUT1), (ii) angiogenesis (CDH5, VEGFR1, EDNRA, ANGPT2, CD34, VEGFR2, VEGFA, and ANGPT1), (iii) the processes of epithelial-mesenchymal transition (VIM) and/or metastasis (LAMA4 and CXCR4), (iv) growth factors and receptors (PDGFB, IRS1, and ERBB1), or (v) cell cycle (CCND1 and CDKN2A). The downregulated genes were related to (i) EMT (OCLN) and (ii) signaling pathways (RPS6KB1 and GADD45B).

CONCLUSION

This study shows that the progression of PanNET in patients with VHL tumors follows a specific pathway and supports that targeting molecules specifically involved may be of therapeutic importance.

Novel therapies for metastatic renal cell carcinoma: efforts to expand beyond the VEGF/mTOR signaling paradigm

With six agents approved for metastatic renal cell carcinoma (mRCC) within the past 5 years, there has undoubtedly been progress in treating this disease. However, the goal of cure remains elusive, and the agents nearest approval (i.e., axitinib and tivozanib) abide by the same paradigm as existing drugs (i.e., inhibition of VEGF or mTOR signaling). The current review will focus on investigational agents that diverge from this paradigm. Specifically, novel immunotherapeutic strategies will be discussed, including vaccine therapy, cytotoxic T-lymphocyte antigen 4 (CTLA4) blockade, and programmed death-1 (PD-1) inhibition, as well as novel approaches to angiogenesis inhibition, such as abrogation of Ang/Tie-2 signaling. Pharmacologic strategies to block other potentially relevant signaling pathways, such as fibroblast growth factor receptor or MET inhibition, are also in various stages of development. Although VEGF and mTOR inhibition have dramatically improved outcomes for patients with mRCCs, a surge above the current plateau with these agents will likely require exploring new avenues.

Sunitinib-induced changes in circulating endothelial cell-related proteins in patients with metastatic renal cell cancer

Vascular endothelial growth factor receptor (VEGFR) tyrosine kinase inhibitors are effective agents in the treatment of metastatic renal cell cancer (mRCC). We here investigated whether inhibition of VEGFR signalin by sunitinib causes changes in plasma proteins associated with tumor endothelium. Forty-three patients with mRCC received sunitinib 50 mg/day in a 4-weeks on 2-weeks off schedule. Sequential plasma samples were obtained before treatment (C1D1), on C1D14, on C1D28, and on C2D1 before start of cycle 2. Plasma levels were assessed for VEGF, soluble vascular cell adhesion molecule-1 (sVCAM-1), soluble intercellular cell adhesion molecule-1 (sICAM-1), von Willebrand factor (vWF), circulating angiopoietin-2 (Ang-2) and soluble Tie-2 (sTie-2). Total tumor burden was calculated at baseline and at first evaluation. Progression-free survival (PFS) and overall survival (OS) were determined. Tumor burden was positively associated with baseline circulating Ang-2 [Spearman's rho (ρ) = 0.378, p = 0.028] and vWF (ρ = 0.417, p = 0.008). During sunitinib treatment, circulating Ang-2 and sTie-2 significantly decreased (p < 0.001 for both), plasma levels of sVCAM-1 and VEGF significantly increased (p = 0.022 and p < 0.001), whereas those of sICAM-1 and vWF remained stable. These protein changes had recovered on C2D1. The reduction in circulating Ang-2 levels on C1D28 was positively correlated with the percentage decrease in tumor burden (ρ = 0.605; p = 0.002). Baseline protein levels and subsequent changes were not associated with PFS or OS. In conclusion, sunitinib-induced changes in Ang-2, sTie-2, sVCAM-1 and VEGF are related to the administration schedule, while reduction in Ang-2 is also associated with decrease in tumor burden.

New insights into the biology of renal cell carcinoma

Ninety percent or more of kidney cancers are believed to be of epithelial cell origin, and are referred to as renal cell carcinoma (RCC), which are further subdivided based on histology into clear-cell RCC (75%), papillary RCC (15%), chromophobe tumor (5%), and oncocytoma (5%). Some genes confer an increased risk of these various histologic RCC subtypes. In practice, there is some overlap among the histologic subtypes, and there are some shared molecular features among these tumor types. This review focuses primarily on the most common form of RCC, clear-cell renal carcinoma, noting some recent advances in the other histologic subtypes.

A Comprehensive Study of Progressive Cytogenetic Alterations in Clear Cell Renal Cell Carcinoma and a New Model for ccRCC Tumorigenesis and Progression

We present a comprehensive study of cytogenetic alterations that occur during the progression of clear cell renal cell carcinoma (ccRCC). We used high-density high-throughput Affymetrix 100 K SNP arrays to obtain the whole genome SNP copy number information from 71 pretreatment tissue samples with RCC tumors; of those, 42 samples were of human ccRCC subtype. We analyzed patterns of cytogenetic loss and gain from different RCC subtypes and in particular, different stages and grades of ccRCC tumors, using a novel algorithm that we have designed. Based on patterns of cytogenetic alterations in chromosomal regions with frequent losses and gains, we inferred the involvement of candidate genes from these regions in ccRCC tumorigenesis and development. We then proposed a new model of ccRCC tumorigenesis and progression. Our study serves as a comprehensive overview of cytogenetic alterations in a collection of 572 ccRCC tumors from diversified studies and should facilitate the search for specific genes associated with the disease.

Update on novel agents in renal cell carcinoma

Renal cell carcinoma (RCC) is a disease with a variable natural history, sometimes presenting with a very indolent course and other times with an aggressive clinical course and unusual sites of metastasis. Surgical resection for stage I-III tumors represents the standard of care and is the only curative option available to patients. However, 40-50% of patients develop metastatic disease. Prior to the advent of targeted therapy, cytokine therapy was the only treatment for RCC. The administration of high-dose, bolus IL-2 has historically produced consistent, durable responses in a small percentage of patients with advanced RCC. The use of IFN-alpha is currently limited to combination therapies. Multiple new agents targeting the VEGF pathway have been tested and approved, including sunitinib, sorafenib and bevacizumab, with others waiting in the wings. In the majority of cases these drugs induce disease stabilization with eventual disease progression. Hence additional new pathways are being targeted and studied. Mechanisms of drug resistance, novel combinations, sequences and schedules are the focus of current clinical investigations. This review provides an updated list of the novel targeted agents in advanced clinical development for metastatic RCC.

Angiopoietin-2 promotes disease progression of neuroendocrine tumors

PURPOSE

Inhibition of angiogenesis represents a promising therapeutic strategy in neuroendocrine tumors. Angiopoietin-2 (Ang-2), a ligand of the endothelial tyrosine kinase Tie-2, is emerging as a key regulator of vascular remodeling during tumor angiogenesis. We therefore addressed the expression and biological significance of Ang-2 in human neuroendocrine tumors.

EXPERIMENTAL DESIGN

Surgical specimens and serum from neuroendocrine tumor patients were used to determine Ang-2 expression by in situ hybridization or ELISA (circulating Ang-2). Ang-2 biological effects were evaluated following stable transfection into BON human pancreatic neuroendocrine tumor cells. BON clones were grown as orthotopic xenografts in nude mice to determine tumor growth and abdominal metastatic spread. Further analyses included microvessel density, lymphatic vessel density, and nodal invasion.

RESULTS

Specimens from pancreatic neuroendocrine tumors and nontransformed pancreatic tissue revealed uniform expression of Ang-2 mRNA in endothelial cells. In contrast, epithelial expression of Ang-2 mRNA occurred exclusively in neuroendocrine tumors. Overexpression of Ang-2 in BON orthotopic xenografts did not affect primary tumor growth, although successful Ang-2 induction was confirmed from elevated serum levels. However, increased microvessel density and enhanced lymphatic metastasis were evident in Ang-2-expressing tumors, indicating a functional role of Ang-2 in experimental neuroendocrine tumors. Consistent with this notion, circulating Ang-2 was significantly elevated in neuroendocrine tumor patients compared with healthy controls. Circulating Ang-2 furthermore correlated with metastatic versus localized disease. The highest Ang-2 concentrations occurred in patients with liver metastasis, and concentrations >or=75th percentile predicted shorter survival (P = 0.0003).

CONCLUSION

Induction of Ang-2 in neuroendocrine tumors represents a clinically relevant pathomechanism of disease progression and constitutes an adverse prognostic marker.

Novel antiangiogenic agents in the treatment of refractory renal cell carcinoma

The approvals of sunitinib, sorafenib, and temsirolimus have dramatically altered the management of renal cell carcinoma. The combination of bevacizumab and interferon-alpha was recently approved in Europe and could receive regulatory approval in the United States. A recent randomized trial reported improved outcomes with everolimus following first-line tyrosine kinase inhibitors (TKIs). Despite enhanced outcomes with these agents, they are not curative, and more effective therapy is essential. Other novel antiangiogenic agents are being evaluated, including TKIs, monoclonal antibodies, and agents against other novel targets. Additionally, novel combinations of antiangiogenic agents are emerging. The rapid expansion in the therapeutic armamentarium holds the promise of further enhancing outcomes.

Novel therapeutics for metastatic renal cell carcinoma

The treatment of metastatic renal cell carcinoma (RCC) has changed dramatically during the past few years. Sunitinib malate, sorafenib tosylate, bevacizumab with interferon alpha, temsirolimus, and everolimus have improved clinical outcomes in randomized phase 3 trials by inhibiting the vascular endothelial growth factor and related pathways. Combinations and sequences of these agents are being evaluated. Other novel agents are in clinical development, some of which target novel pathways not yet exploited as therapy for RCC. Recently reported and ongoing clinical trials will help further define the role of these agents as therapy for metastatic RCC.

A comparison of plasma versus histologic indices of angiogenic markers in breast cancer

BACKGROUND

Over-expression of angiogenic growth factors and their receptors, and high levels of these molecules in the blood, are a common feature of cancer although the relationships between cell expression and plasma levels are unknown. We hypothesized a significant correlation between the expression and cellular distribution of vascular endothelial growth factor (VEGF), its receptor Flt-1, and the angiopoietin receptor Tie-2 with levels of these molecules in the plasma.

METHODS

The tissue expression of VEGF, Flt-1, and Tie-2 were investigated by immunohistochemistry, and plasma levels assessed by enzyme-linked immunosorbent assay in 36 patients with breast cancer and 15 with benign breast disease.

RESULTS

Despite expected significant differences in plasma levels of the molecules (P<0.03 to <0.001), no significant differences were found in Tie-2, VEGF, and Flt-1 tissue expression between breast cancer and benign disease controls. No significant correlations were observed between plasma levels of their tissue expression.

CONCLUSIONS

Tissue expression of Tie-2, VEGF, and Flt-1 may not be an overly sensitive tool for assessing abnormalities of coagulation, platelet activation, and angiogenesis in human cancer. Plasma markers may not be representative of tumor activity, and may not come wholly from tumor cells. Instead these markers may be indicative of endothelial dysfunction in cancer patients.

Balance between angiopoietin-1 and angiopoietin-2 is in favor of angiopoietin-2 in atherosclerotic plaques with high microvessel density

INTRODUCTION

Atherosclerotic plaque microvessels are associated with plaque hemorrhage and rupture. The mechanisms underlying plaque angiogenesis are largely unknown. Angiopoietin (Ang)-1 and -2 are ligands of the endothelial receptor Tie-2. Ang-1 induces formation of stable vessels, whereas Ang-2 destabilizes the interaction between endothelial cells and their support cells. We studied the expression patterns of Ang-1 and -2 in relation to plaque microvessels.

METHODS AND RESULTS

Carotid endarterectomy specimens were studied (n = 100). Microvessel density (MVD) was correlated with the presence of macrophages and with a (fibro)atheromatous plaque phenotype. A negative correlation was observed between Ang-1 expression and MVD. A positive correlation was observed between the ratio of Ang-2/Ang-1 and MVD. Ang-2 expression was correlated with matrix metalloproteinase-2 (MMP-2) activity. Immunohistochemical staining of Ang-1 was observed in smooth muscle cells, whereas Ang-2 was detected in endothelial cells, smooth muscle cells and macrophages.

CONCLUSIONS

In plaques with high MVD, the local balance between Ang-1 and Ang-2 is in favor of Ang-2. Plaque Ang-2 levels are associated with MMP-2 activity. Ang-2-induced MMP-2 activity might play a role in the development of (unstable) plaque microvessels.

Review: implications of in vitro research on the effect of radiotherapy and chemotherapy under hypoxic conditions

As it is now well established that human solid tumors frequently contain a substantial fraction of cells that are hypoxic, more and more in vitro research is focusing on the impact of hypoxia on the outcome of radiotherapy and chemotherapy. Indeed, the efficacy of irradiation and many cytotoxic drugs relies on an adequate oxygen supply. Consequently, hypoxic regions in solid tumors often contain viable cells that are intrinsically more resistant to treatment with radiotherapy or chemotherapy. Moreover, efforts have been made to exploit hypoxia as a potential difference between malignant and normal tissues.Nowadays, a body of evidence indicates that oxygen deficiency clearly influences some major intracellular pathways such as those involved in cell proliferation, cell cycle progression, apoptosis, cell adhesion, and others. Obviously, when investigating the effects of radiotherapy or chemotherapy or both combined under hypoxic conditions, it is essential to consider the influences of hypoxia itself on the cell. In this review, we first focus on the effects of hypoxia per se on some critical biological pathways. Next, we sketch an overview of preclinical and clinical research on radiotherapy, chemotherapy, and chemoradiation under hypoxic conditions.

The angiogenic factor thymidine phosphorylase up-regulates the cell adhesion molecule P-selectin in human vascular endothelial cells and is associated with P-selectin expression in breast cancers

Thymidine phosphorylase (TP) is an angiogenic enzyme, catalysing the reversible phosphorylation of thymidine to thymine and 2-deoxyribose. TP is up-regulated in neoplasia, being associated with advanced tumour stage, microvessel density and prognosis in several tumour types. Although TP is a non-mitogenic migratory factor for endothelium, the mechanism by which TP mediates these effects is still unclear. We compared the gene expression profile of endothelial cells grown in vitro in the presence or absence of TP by cDNA microarray analysis. To determine the time-course of TP angiogenic induction, endothelial cells were stimulated with TP (10 ng/ml) for 5 and 18 h. Gene expression levels of Tie2, angiopoietin (Ang)1 and Ang2, measured by RNase protection assay (RPA), showed maximal alteration at 18 h. cDNA from human umbilical vein endothelial cells (HUVEC) grown for 18 h in the presence or absence of TP (10 ng/ml) was hybridized to a human cDNA cytokine array representing 375 angiogenic genes. Significantly altered expression occurred in 89 human angiogenic genes (72 genes were up-regulated and 17 down-regulated). Changes in five genes relevant to vascular remodelling biology (Tie2, nNos, P-selectin, ephrin-B1 and TP) were validated in triplicate experiments by real-time RT-PCR. But only P-selectin gene expression remained significant. Correlation between P-selectin and TP was assessed by immunohistochemistry on 161 human breast cancers, using human tissue microarray. Tumour cell TP correlated with tumour cell P-selectin but not with endothelial cell P-selectin. These data show that TP stimulates changes in mRNA expression maximally after 18 h culture in vitro. It confirms a role for TP in vascular remodelling involving several classes of genes, including the cell adhesion molecule, P-selectin. Although confirmation of the role of TP-mediated cell adhesion molecule (CAM) induction is required; however, this pathway may provide an attractive therapeutic target, since it is likely to affect several important tumour processes, including angiogenesis and metastasis.

Evaluation of peri-operative peripheral and renal venous levels of pro- and anti-angiogenic factors and their relevance in patients with renal cell carcinoma

OBJECTIVE

To evaluate peri-operative peripheral and renal venous plasma levels of vascular endothelial growth factor (VEGF), platelet-derived growth factor type BB (PDGF-BB), transforming growth factor (TGF)-beta1, endostatin, and thrombospondin-1 (TSP-1) in relation to pathological variables and prognosis, as pro- and anti-angiogenic factors are important for tumour growth and treatment of patients with renal cell carcinoma (RCC).

PATIENTS AND METHODS

The study included 74 consecutive patients with sporadic RCC who had tumour nephrectomy. Peripheral venous blood was drawn 1 day before, immediately and 1, 3 and 5 days after surgery. Renal venous blood was collected in a subgroup of 33 patients during surgery. The variables were analysed using quantitative enzyme-linked immunoassay kits, and associated with pathological variables and disease-specific survival.

RESULTS

Soon after surgery, peripheral venous VEGF, PDGF-BB and TGF-beta1 levels were decreased, whereas endostatin levels were significantly increased. Renal venous VEGF, PDGF-BB and TGF-beta1 levels were higher than in the general venous blood pool. Renal venous VEGF levels were correlated with tumour diameter and associated with grade and vascular invasion. After a mean follow-up of 30 months, higher peripheral preoperative, early peripheral postoperative and renal venous VEGF levels were associated with a poorer prognosis. However, in a multivariate analysis only Tumour-Node-Metastasis stage and Eastern Cooperative Oncology Group performance status were independent prognosticators of disease-specific survival.

CONCLUSIONS

Circulating pro- and anti-angiogenic factors change early after nephrectomy. VEGF, PDGF-BB and TGF-beta1 are higher in the renal vein than in the general venous blood pool. Higher renal venous and peripheral levels of VEGF might be associated with a poorer prognosis.

Angiopoietins lack of prognostic significance in ductal mammary carcinoma

Angiopoietins (Ang) have been shown to regulate the process of vasculature and angiogenesis in tumour. Different angiopoietins have different roles during the angiogenic process. The current study sought to examine the levels of the expression of Ang-1, Ang-2, Ang-3 and their receptor Tie-2 in mammary ductal carcinoma and to assess their relevance to prognosis. Fresh frozen ductal carcinoma tissues (n = 90) and adjacent non-cancerous breast tissues (n = 32) were used. The expression of Ang-1, Ang-2 and Ang-3 transcripts in cancer and normal breast tissues were examined quantitatively using quantitative RT-PCR. The protein expression of Ang-1, Ang-2 and Tie-2 was assessed by immunohistochemistry on frozen sectioned tissues.

Ang-1, Ang-2 and Ang-3 were detected in mammary tissues. Ang-1 was seen in both normal epithelial cells, breast cancer cells as well as in endothelial cells. Ang-2 was seen at a higher level than Ang-1 and it is expressed in epithelial, endothelial as well as stromal cells to certain degree. Ang-1 and Ang-2 transcripts were detected almost equally in cancer and normal breast tissue, and Ang-3 was high in cancer tissue compared to normal breast but not significant (155 ± 123 & 24.1 ± 22.6, P > 0.05). No significant differences were seen between patients with different predicted prognosis (using the Nottingham Prognostic Index as a guide) (Ang-1 p = 0.34, Ang-2 p = 0.26 and Ang-3 p = 0.32, respectively). No significant correlation was seen between Ang-1, Ang-2 and Ang-3 with tumour grade. When the levels of the transcripts were compared against clinical outcome (disease free, developed recurrence and patients who died of breast cancer), levels of Ang-3 transcript was found to be high in breast cancer patient who had bone metastasis 33.8 ± 28.3, although the difference was not significant (p = 0.08). No significant difference was seen with levels of Ang-1 and Ang-2 transcripts and clinical outcomes. Furthermore, no significant trend was observed between Tie-2 receptor and clinical/pathological parameters in the cohort.

These data suggest that angiopoietins (Ang-1, Ang-2 and Ang-3) are expressed in mammary tissues, both in normal and tumour. These molecules have limited value in predicting the prognosis and clinical outcome in patients with mammary ductal carcinoma.

Angiopoietins in malignancy

BACKGROUND

Tumour growth is dependant upon the development of an adequate blood supply. This, in turn, is thought to depend upon a switch by the tumour, from a dormant to angiogenic state. Recent data suggest that this switch may occur when the balance of pro- and anti-angiogenic agents alters to promote angiogenesis. Angiopoietins may be involved in this balance.

METHODS

An electronic literature search was performed with respect to angiopoietins from 1996 to the present. Published data from in-vitro and in-vivo studies were critically analysed. A specific focus was made of studies relating to tumour growth and vasculature.

RESULTS

Since angiopoietin-1 was first described in 1996, three more angiopoietins have been described. All family members bind to the Tie-2 receptor. There is now a considerable accumulation of data that suggests they play a pivotal role in the development and stabilisation of tumour vasculature. angiopoietin-2 appears to be pro-angiogenic whilst angiopoietin-1 appears to be a stabilising factor.

CONCLUSIONS

Recent trials of anti-angiogenic agents show promise in the treatment of solid human cancers. The angiopoietins are a new family of proteins that appear to be influential in the development of the tumour vasculature. Manipulation of the angiopoietin balance may provide a potential therapeutic target in human cancer.