VEGF and VEGFR-1 are coexpressed by epithelial and stromal cells of renal cell carcinoma

New theobromine derivatives inhibiting VEGFR-2: design, synthesis, antiproliferative, docking and molecular dynamics simulations

Background: VEGFR-2 is one of the most effective targets in cancer treatment. Aim: The design and semi-synthesis of new theobromine derivatives as potential VEGFR-2 inhibitors. Methods: In vitro and in silico evaluation of the synthesized compounds. Results: Compound 5b demonstrated excellent antiproliferative and VEGFR-2 inhibitory effects with significant apoptotic activity. It modulated the immune response by increasing IL-2 and reducing TNF-α levels. Docking and molecular dynamics simulations revealed the compound's binding affinity with VEGFR-2. Lastly, computational absorption, distribution, metabolism, excretion and toxicity studies indicated the high potential of compound 5b for drug development. Conclusion: Compound 5b could be a promising anticancer agent targeting VEGFR-2.

Role of VEGFs/VEGFR-1 Signaling and its Inhibition in Modulating Tumor Invasion: Experimental Evidence in Different Metastatic Cancer Models

The vascular endothelial growth factor (VEGF) family members, VEGF-A, placenta growth factor (PlGF), and to a lesser extent VEGF-B, play an essential role in tumor-associated angiogenesis, tissue infiltration, and metastasis formation. Although VEGF-A can activate both VEGFR-1 and VEGFR-2 membrane receptors, PlGF and VEGF-B exclusively interact with VEGFR-1. Differently from VEGFR-2, which is involved both in physiological and pathological angiogenesis, in the adult VEGFR-1 is required only for pathological angiogenesis. Besides this role in tumor endothelium, ligand-mediated stimulation of VEGFR-1 expressed in tumor cells may directly induce cell chemotaxis and extracellular matrix invasion. Furthermore, VEGFR-1 activation in myeloid progenitors and tumor-associated macrophages favors cancer immune escape through the release of immunosuppressive cytokines. These properties have prompted a number of preclinical and clinical studies to analyze VEGFR-1 involvement in the metastatic process. The aim of the present review is to highlight the contribution of VEGFs/VEGFR-1 signaling in the progression of different tumor types and to provide an overview of the therapeutic approaches targeting VEGFR-1 currently under investigation.

Association between vascular endothelial growth factor gene polymorphisms and the risk and prognosis of renal cell carcinoma: A systematic review and meta-analysis

The aim of the meta-analysis was to clarify the associations between vascular endothelial growth factor (VEGF) polymorphisms and the risk and prognosis of renal cell carcinoma (RCC). A meta-analysis was performed by searching the databases PubMed, EMBASE and Web of Science for the relevant available studies until August 1st, 2016, and fourteen studies met the inclusion criteria. The pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to evaluate the strength of such associations. Besides, the pooled hazard ratios (HRs) with 95% CIs were used to evaluate the overall survival (OS). Fixed- or random-effects models were conducted according to existence of heterogeneity. Publication bias was evaluated using Begg's funnel plots and Egger's regression test. Overall, this meta-analysis included a total of 8,275 patients, who had been accrued between November 2002 and September 2015. Meta-analysis indicated that -2578C/A, +936C/T and +405G/C polymorphisms in the VEGF gene correlated with elevated RCC risk, especially in Asian populations. Moreover, VEGF -1154G/A and -634C/G polymorphisms were found significantly associated with poor OS of RCC. Therefore, this meta-analysis revealed that VEGF -2578C/A, +936C/T, +405G/C polymorphisms were associated with an elevated susceptibility to RCC, indicating that these three polymorphisms might be risk factors for RCC, especially in Asian populations.

Role of natural and adaptive immunity in renal cell carcinoma response to VEGFR-TKIs and mTOR inhibitor

Angiogenesis and immunosuppression work hand-in-hand in the renal cell carcinoma (RCC) microenvironment. Tumor growth is associated with impaired antitumor immune response in RCC, which involves T cells, natural killer cells, dendritic cells (DCs) and macrophages. Vascular endothelial growth factor receptor (VEGFR), such as sorafenib, sunitinib, pazopanib and axitinib, and mammalian target of rapamycin (mTOR) inhibitors, such as temsirolimus and everolimus, do exert both antiangiogenic and immunomodulatory functions. Indeed, these agents affect neutrophil migration, as well as T lymphocyte-DC cross-talk, DC maturation and immune cell metabolism and reactivity. In this review, we overview the essential role of innate and adaptive immune response in RCC proliferation, invasion and metastasis and the relationship between tumor-associated immune cells and the response to targeted agents approved for the treatment of metastatic RCC.

The clinical significance of lymphangiogenesis in renal cell carcinoma

Background

The formation of lymphatic vessels (lymphangiogenesis) occurs in tumor tissues and is crucial for tumor development and progression in some cancers. Lymphangiogenesis and its clinical effect on renal cell carcinoma have been less thoroughly investigated in comparison with angiogenesis. The aim of this study was to evaluate the role of lymphangiogenesis as a prognostic factor in renal cell carcinoma (RCC).

Material/Methods

The expression of peritumoral/intratumoral lymphatics was studied by immunohistochemical methods in paraffin-embedded nephrectomy specimens from 133 patients with clear cell carcinoma. Patients were divided into 3 groups depending on postoperative follow-up: I) patients without metastases, II) patients with metastases during follow-up, and III) patients with metastases during the operation. Peritumoral lymphatics (PTL) and intratumoral lymphatics (ITL) were immunostained with a D2-40 antibody.

Results

The mean number of PTL present in each group was I=14.1, II=10.6, III=12.1. The mean number of ITL present in each group was I=0.7, II=2.3, III=2.3. The 3 groups showed statistically significant differences only in the case of ITL. A mean count of ITL ≥1 is significantly associated with an increased risk of regional lymph node involvement and distant metastasis. Patients with expression ITL >0.2 and PTL ≤15.2 had a significantly shorter cancer-specific survival.

Conclusions

The number of ITL showed an association with more aggressive cases of RCC and progression of disease. Therefore, the level of expression ITL, together with stage and histological grading, may provide valuable predictive information about the outcome of treatment.

Knockdown of VEGF receptor-1 (VEGFR-1) impairs macrophage infiltration, angiogenesis and growth of clear cell renal cell carcinoma (CRCC)

Angiogenesis is essential for tumor growth and metastasis. VEGF has been shown to be a central player in this process. The biological activity of VEGF is mainly mediated by two tyrosine kinase receptors, VEGFR-1 and VEGFR-2. While increasing evidence suggests that VEGF/VEGFR-1 signaling is crucial for tumor angiogenesis, its molecular mechanism is not well understood. Here we show that VEGFR-1 knockdown dramatically inhibits tumor growth. This inhibition is associated with significant decrease of tumor VEGF levels and tumor angiogenesis as well as an increased tumor necrosis. Moreover, we demonstrate that VEGF in CRCC tumors is mainly produced by tumor stromal cells instead of the tumor cells themselves. It has been shown that macrophages constitute a significant part of tumor stromal cells and produce a large amount of VEGF. We therefore examined the macrophage infiltration in the xenograft tumors. Remarkably, VEGFR-1 knockdown attenuates the tumor macrophages infiltration. To understand the mechanism, we investigated the impact of VEGFR-1 knockdown on the expression of monocyte chemoattractant protein-1 (MCP-1), one of the main chemoattractants for macrophages. Significantly, VEGFR-1 knockdown inhibits MCP-1 expression of CRCC cells. Taken together, these data indicate that VEGF/VEGFR-1 signaling plays an essential role in initiating tumor angiogenesis by regulating MCP-1 expression, which in turn, attracts macrophages infiltration and VEGF production. Thus, these studies suggest that blockade of VEGFR-1 function may provide a tumor-specific, VEGF-based therapeutic strategy for treatment of CRCC.

Endothelial-like cells derived directly from human tumor xenografts

Tumor-associated endothelial cells (TAECs) harboring various genomic abnormalities have been described in human cancers although their origins remain obscure. We generated 4 human cancer cell lines tagged with multiple markers, grew them as xenografts, and characterized their TAECs. Depending on their tumor of origin, 5-40% of TAECs reproducibly expressed all tags. Tagged TAECs (tTAECS) were morphologically, immunologically and functionally similar, although not identical, to normal endothelial cells (ECs) and contained only human chromosomes. tTAECs underwent a senescent-like proliferative arrest after several in vitro passages, but could be immortalized by telomerase, thus allowing us to show that the retention of the EC phenotype was of long-term duration. In contrast, nonimmortalized tTAECs could be propagated in vivo where they incorporated into the tumor neo-vasculature. Although consistent with previous reports that some tumor cells may undergo "vasculogenic mimicry" (VM), the tumor-derived endothelial-like cells described here appear distinctly different. Moreover, their properties and behaviors are more durable than expected for cells undergoing VM, are not the result of fusions between ECs and tumor cells, and are cell autonomous. These findings could have significant implications for therapies that target tumor angiogenesis.

111In-bevacizumab imaging of renal cell cancer and evaluation of neoadjuvant treatment with the vascular endothelial growth factor receptor inhibitor sorafenib

Clear cell renal cell cancer (ccRCC) prominently expresses vascular endothelial growth factor-A (VEGF-A), and new treatment strategies for renal cell cancer (RCC) aim at the inhibition of VEGF-VEGF receptor signaling. This study explores the ability of (111)In-bevacizumab scintigraphy to depict RCC and to evaluate response to neoadjuvant treatment with sorafenib, a VEGF receptor inhibitor.

METHODS

The ability to depict RCC with (111)In-bevacizumab scintigraphy was tested in 14 patients scheduled to undergo a tumor nephrectomy; of these, 9 RCC patients were treated in a neoadjuvant setting with sorafenib (400 mg orally twice a day). In the latter group, baseline and posttreatment (111)In-bevacizumab scans were compared. The intratumoral distribution of (111)In-bevacizumab was determined scintigraphically ex vivo in a 1-cm lamella of the resected tumorous kidney. Expression of VEGF-A, glucose transporter-1, carbonic anhydrase IX, α-smooth-muscle actin, and Ki67 was determined by immunohistochemistry and compared with the local concentration of (111)In-bevacizumab. Additionally, the VEGF-A content in tumor samples was determined quantitatively by enzyme-linked immunosorbent assay.

RESULTS

In all 5 non-neoadjuvant-treated patients, preferential accumulation of (111)In-bevacizumab was observed in the tumors. All ccRCC lesions with enhanced (111)In-bevacizumab targeting expressed high levels of VEGF-A. Treatment with sorafenib resulted in a significant decrease of (111)In-bevacizumab uptake in the tumor in the patients with ccRCC (mean change, -60.5%; range, +1.5% to -90.1%). The decrease in uptake was due to destruction of the tumor neovasculature, whereas the VEGF-A expression remained intact. In the patient with papillary RCC, limited uptake without change after sorafenib was observed.

CONCLUSION

RCC lesions were clearly delineated with (111)In-bevacizumab scintigraphy. Neoadjuvant treatment with sorafenib resulted in a significant decrease of (111)In-bevacizumab uptake in RCC. (111)In-bevacizumab scintigraphy can be an attractive biomarker for response and needs further study.

Soluble isoforms of vascular endothelial growth factor are predictors of response to sunitinib in metastatic renal cell carcinomas

BACKGROUND

Angiogenesis is the target of several agents in the treatment of malignancies, including renal cell carcinoma (RCC). There is a real need for surrogate biomarkers that can predict selection of patients who may benefit from antiangiogenic therapies, prediction of disease outcome and which may improve the knowledge regarding mechanism of action of these treatments. Tyrosine kinase inhibitors (TKI) have proven efficacy in metastatic RCC (mRCC). However, the molecular mechanisms underlying the clinical response to these drugs remain unclear.

METHODOLOGY/PRINCIPAL FINDINGS

The present study aimed to identify molecular biomarkers associated with the response to sunitinib, a Tyrosine kinase inhibitor. To evaluate this relationship, primary tumors from 23 metastatic RCC patients treated by sunitinib were analyzed for a panel of 16 biomarkers involved in tumor pathways targeted by sunitinib, using real-time quantitative reverse-transcriptase PCR. Nine of the 23 patients (39%) responded to sunitinib. Among transcripts analyzed, only the levels of vascular endothelial growth factor (VEGF) soluble isoforms (VEGF(121) and VEGF(165)) were associated with the response to sunitinib (P = 0.04 for both). Furthermore, the ratio of VEGF soluble isoforms (VEGF(121)/VEGF(165)) was significantly associated with prognosis (P = 0.02).

CONCLUSIONS

This preliminary study provides a promising tool that might help in the management of metastatic RCC, and could be extended to other tumors treated by TKI.

mTOR in renal cell cancer: modulator of tumor biology and therapeutic target

Elucidation of the crucial role of the PI3K/Akt/mTOR pathway in the pathogenesis of cancer has led to the development of various drugs targeting this signaling cascade at distinct levels. mTOR, a serine/threonine kinase plays a pivotal role in coupling growth stimuli to cell cycle progression. There are two distinct macromolecular complexes of mTOR: mTORC1, which is rapamycin-sensitive and contains raptor; and mTORC2, which is rapamycin-insensitive and contains rictor. However, in recent preclinical studies a sustained exposure of cancer cells to rapamycin has been shown to inhibit the function of both mTORC1 and mTORC2 complexes. Downstream targets of these complexes, which involve HIF-1alpha and HIF-2alpha, cyclin D1 and PKC-alpha, are responsible for the activation of various intracellular processes leading to the activation of cell proliferation, and induction of angiogenesis, metastasis or chemoresistance. Since the biology of renal cell cancer (RCC) is tightly controlled by mTOR, targeted inhibition of mTOR function appeared to be a promising therapeutic approach for RCC patients. To date, results of two, large, Phase III clinical trials evaluating the efficacy of rapamycin derivatives (i.e., temsirolimus and everolimus) in the treatment of RCC have been published. First-line temsirolimus (CCI-779) administered to metastatic, poor-prognosis RCC patients significantly prolonged overall and progression-free survival when compared with IFN-alpha. Treatment of metastatic RCC patients refractory to tyrosine kinase inhibitors with everolimus (RAD-001) significantly prolonged progression-free survival when compared with placebo. Therapeutic strategies based on mTOR inhibition in RCC demonstrated a significant clinical activity. However, there are still patients refractory to mTOR inhibitors. Various molecular mechanisms of resistance to rapalogues have been identified and will have to be targeted simultaneously with mTOR in order to achieve a complete inhibition of signaling pathways crucial for the pathogenesis of RCC. Such clinical trials evaluating a combination of mTOR inhibitors with other targeted therapies are ongoing.

Prognostic models and algorithms in renal cell carcinoma

Although surgical treatment is curative for localized renal cell carcinoma (RCC), 25% of patients present with locally advanced or disseminated disease, and disease will recur systemically in another 20% to 30% of those who have localized disease at presentation. Many clinical, histologic, and molecular factors have been identified that place patients who have localized RCC at greater risk for recurrence and those who have metastatic disease at risk for progression or death. This article reviews the major prognostic factors for RCC and the most commonly used algorithms developed for use before or after nephrectomy and before initiation of systemic therapy. These RCC nomograms allow more accurate counseling of patients regarding their likely clinical course and facilitate treatment planning.