Fibroblast growth factor 2 regulates endothelial cell sensitivity to sunitinib

An Endothelial Cell Is Not Simply an Endothelial Cell

Endothelial cells (ECs) are a multifaceted component of the vascular system with roles in immunity, maintaining tissue fluid balance, and vascular tone. Dysregulation or dysfunction of ECs can have far-reaching implications, leading pathologies ranging from cardiovascular diseases, such as hypertension and atherosclerosis, ischemia, chronic kidney disease, blood-brain barrier integrity, dementia, and tumor metastasis. Recent advancements in regenerative medicine have highlighted the potential of stem cell-derived ECs, particularly from induced pluripotent stem cells, to treat ischemic tissues, as well as models of vascular integrity. This review summarizes what is known in the generation of ECs with an emphasis on tissue-specific ECs and EC subphenotypes important in the development of targeted cell-based therapies for patient treatment.

Recovery of Therapeutically Ablated Engineered Blood-Vessel Networks on a Plug-and-Play Platform

Limiting the availability of key angiogenesis-promoting factors is a successful strategy to ablate tumor-supplying blood vessels or to reduce excessive vasculature in diabetic retinopathy. However, the efficacy of such anti-angiogenic therapies (AATs) varies with tumor type, and regrowth of vessels is observed upon termination of treatment. The ability to understand and develop AATs remains limited by a lack of robust in vitro systems for modeling the recovery of vascular networks. Here, complex 3D micro-capillary networks are engineered by sequentially seeding human bone marrow-derived mesenchymal stromal cells and human umbilical vein endothelial cells (ECs) on a previously established, synthetic plug-and-play hydrogel platform. In the tightly interconnected vascular networks that form this way, the two cell types share a basement membrane-like layer and can be maintained for several days of co-culture. Pre-formed networks degrade in the presence of bevacizumab. Upon treatment termination, vessel structures grow back to their original positions after replenishment with new ECs, which also integrate into unperturbed established networks. The data suggest that this plug-and-play platform enables the screening of drugs with blood-vessel inhibiting functions. It is believed that this platform could be of particular interest in studying resistance or recovery mechanisms to AAT treatment.

Mechanisms of tyrosine kinase inhibitor resistance in renal cell carcinoma

Renal cell carcinoma (RCC), the most prevalent type of kidney cancer, is a significant cause of cancer morbidity and mortality worldwide. Antiangiogenic tyrosine kinase inhibitors (TKIs), in combination with immune checkpoint inhibitors (ICIs), are among the first-line treatment options for patients with advanced RCC. These therapies target the vascular endothelial growth factor receptor (VEGFR) tyrosine kinase pathway and other kinases crucial to cancer proliferation, survival, and metastasis. TKIs have yielded substantial improvements in progression-free survival (PFS) and overall survival (OS) for patients with advanced RCC. However, nearly all patients eventually progress on these drugs as resistance develops. This review provides an overview of TKI resistance in RCC and explores different mechanisms of resistance, including upregulation of alternative proangiogenic pathways, epithelial-mesenchymal transition (EMT), decreased intracellular drug concentrations due to efflux pumps and lysosomal sequestration, alterations in the tumor microenvironment including bone marrow-derived cells (BMDCs) and tumor-associated fibroblasts (TAFs), and genetic factors such as single nucleotide polymorphisms (SNPs). A comprehensive understanding of these mechanisms opens the door to the development of innovative therapeutic approaches that can effectively overcome TKI resistance, thereby improving outcomes for patients with advanced RCC.

Candidate biomarkers for treatment benefit from sunitinib in patients with advanced renal cell carcinoma using mass spectrometry-based (phospho)proteomics

The tyrosine kinase inhibitor sunitinib is an effective first-line treatment for patients with advanced renal cell carcinoma (RCC). Hypothesizing that a functional read-out by mass spectrometry-based (phospho, p-)proteomics will identify predictive biomarkers for treatment outcome of sunitinib, tumor tissues of 26 RCC patients were analyzed. Eight patients had primary resistant (RES) and 18 sensitive (SENS) RCC. A 78 phosphosite signature (p < 0.05, fold-change > 2) was identified; 22 p-sites were upregulated in RES (unique in RES: BCAR3, NOP58, EIF4A2, GDI1) and 56 in SENS (35 unique). EIF4A1/EIF4A2 were differentially expressed in RES at the (p-)proteome and, in an independent cohort, transcriptome level. Inferred kinase activity of MAPK3 (p = 0.026) and EGFR (p = 0.045) as determined by INKA was higher in SENS. Posttranslational modifications signature enrichment analysis showed that different p-site-centric signatures were enriched (p < 0.05), of which FGF1 and prolactin pathways in RES and, in SENS, vanadate and thrombin treatment pathways, were most significant. In conclusion, the RCC (phospho)proteome revealed differential p-sites and kinase activities associated with sunitinib resistance and sensitivity. Independent validation is warranted to develop an assay for upfront identification of patients who are intrinsically resistant to sunitinib.

VEGF-B prevents excessive angiogenesis by inhibiting FGF2/FGFR1 pathway

Although VEGF-B was discovered as a VEGF-A homolog a long time ago, the angiogenic effect of VEGF-B remains poorly understood with limited and diverse findings from different groups. Notwithstanding, drugs that inhibit VEGF-B together with other VEGF family members are being used to treat patients with various neovascular diseases. It is therefore critical to have a better understanding of the angiogenic effect of VEGF-B and the underlying mechanisms. Using comprehensive in vitro and in vivo methods and models, we reveal here for the first time an unexpected and surprising function of VEGF-B as an endogenous inhibitor of angiogenesis by inhibiting the FGF2/FGFR1 pathway when the latter is abundantly expressed. Mechanistically, we unveil that VEGF-B binds to FGFR1, induces FGFR1/VEGFR1 complex formation, and suppresses FGF2-induced Erk activation, and inhibits FGF2-driven angiogenesis and tumor growth. Our work uncovers a previously unrecognized novel function of VEGF-B in tethering the FGF2/FGFR1 pathway. Given the anti-angiogenic nature of VEGF-B under conditions of high FGF2/FGFR1 levels, caution is warranted when modulating VEGF-B activity to treat neovascular diseases.

Primary and acquired resistance to first-line therapy for clear cell renal cell carcinoma

The introduction of first-line combinations had improved the outcomes for metastatic renal cell carcinoma (mRCC) compared to sunitinib. However, some patients either have inherent resistance or develop resistance as a result of the treatment. Depending on the kind of therapy employed, many factors underlie resistance to systemic therapy. Angiogenesis and the tumor immune microenvironment (TIME), nevertheless, are inextricably linked. Although angiogenesis and the manipulation of the tumor microenvironment are linked to hypoxia, which emerges as a hallmark of renal cell carcinoma (RCC) pathogenesis, it is only one of the potential elements involved in the distinctive intra- and inter-tumor heterogeneity of RCC that is still dynamic. We may be able to more correctly predict therapy response and comprehend the mechanisms underlying primary or acquired resistance by integrating tumor genetic and immunological markers. In order to provide tools for patient selection and to generate hypotheses for the development of new strategies to overcome resistance, we reviewed the most recent research on the mechanisms of primary and acquired resistance to immune checkpoint inhibitors (ICIs) and tyrosine kinase inhibitors (TKIs) that target the vascular endothelial growth factor receptor (VEGFR).We can choose patients' treatments and cancer preventive strategies using an evolutionary approach thanks to the few evolutionary trajectories that characterize ccRCC.

Molecular mechanisms of resistance to tyrosine kinase inhibitor in clear cell renal cell carcinoma

Clear cell renal cell carcinoma (ccRCC) is the most common subtype of renal cell carcinoma (RCC). Loss of von Hippel-Lindau tumor suppressor gene is frequently observed in ccRCC and increases the expression of hypoxia-inducible factors and their targets, including epidermal growth factor, vascular endothelial growth factor, and platelet-derived growth factor. Tyrosine kinase inhibitors (TKIs) offer a survival benefit in metastatic renal cell carcinoma (mRCC). Recently, immune checkpoint inhibitors have been introduced in mRCC. Combination therapy with TKIs and immune checkpoint inhibitors significantly improved patient outcomes. Therefore, TKIs still play an essential role in mRCC treatment. However, the clinical utility of TKIs is compromised when primary and acquired resistance are encountered. The mechanism of resistance to TKI is not fully elucidated. Here, we comprehensively reviewed the molecular mechanisms of resistance to TKIs and a potential strategy to overcome this resistance. We outlined the involvement of angiogenesis, non-angiogenesis, epithelial-mesenchymal transition, activating bypass pathways, lysosomal sequestration, non-coding RNAs, epigenetic modifications and tumor microenvironment factors in the resistance to TKIs. Deep insight into the molecular mechanisms of resistance to TKIs will help to better understand the biology of RCC and can ultimately help in the development of more effective therapies.

Effect of Extracellular Signal-Regulated Protein Kinase 5 Inhibition in Clear Cell Renal Cell Carcinoma

(1) Background: Extracellular signal-regulating kinase 5 (ERK5) has been implicated in many cellular functions, including survival, proliferation, and vascularization. Our objectives were to examine the expression and effect of ERK5 in clear cell renal cell carcinoma (ccRCC). (2) Methods: The expressions of ERK5 and its regulating micro-RNA miR-143 were investigated using immunohistochemistry and quantitative reverse transcriptase PCR in surgical specimens of ccRCC patients. With invitro and in vivo studies, we used pharmacologic ERK5 inhibitor XMD8-92, RNA interference, pre-miR-143 transduction, Western blotting, MTS assay, apoptosis assay, and subcutaneous xenograft model. (3) Results: A strong ERK5 expression in surgical specimen was associated with high-grade (p = 0.01), high-recurrence free rate (p = 0.02), and high cancer-specific survival (p = 0.03). Expression levels of ERK5 and miR-143 expression level were correlated (p = 0.049). Pre-miR-143 transduction into ccRCC cell A498 suppressed ERK5 expression. ERK5 inhibition enhanced cyclin-dependent kinase inhibitor p21 expression and decreased anti-apoptotic molecules BCL2, resulting in decreased cell proliferation and survival both in ccRCC and endothelial cells. In the xenograft model, ERK5 inhibitor XMD8-92 suppressed tumor growth. (4) Conclusions: ERK5 is regulated by miR-143, and ERK5 inhibition is a promising target for ccRCC treatment.

New insights into antiangiogenic therapy resistance in cancer: Mechanisms and therapeutic aspects

Angiogenesis is a hallmark of cancer and is required for tumor growth and progression. Antiangiogenic therapy has been revolutionarily developing and was approved for the treatment of various types of cancer for nearly two decades, among which bevacizumab and sorafenib continue to be the two most frequently used antiangiogenic drugs. Although antiangiogenic therapy has brought substantial survival benefits to many cancer patients, resistance to antiangiogenic drugs frequently occurs during clinical treatment, leading to poor outcomes and treatment failure. Cumulative evidence has demonstrated that the intricate interplay among tumor cells, bone marrow-derived cells, and local stromal cells critically allows for tumor escape from antiangiogenic therapy. Currently, drug resistance has become the main challenge that hinders the therapeutic efficacies of antiangiogenic therapy. In this review, we describe and summarize the cellular and molecular mechanisms conferring tumor drug resistance to antiangiogenic therapy, which was predominantly associated with redundancy in angiogenic signaling molecules (e.g., VEGFs, GM-CSF, G-CSF, and IL17), alterations in biological processes of tumor cells (e.g., tumor invasiveness and metastasis, stemness, autophagy, metabolic reprogramming, vessel co-option, and vasculogenic mimicry), increased recruitment of bone marrow-derived cells (e.g., myeloid-derived suppressive cells, tumor-associated macrophages, and tumor-associated neutrophils), and changes in the biological functions and features of local stromal cells (e.g., pericytes, cancer-associated fibroblasts, and endothelial cells). We also review potential biomarkers to predict the response to antiangiogenic therapy in cancer patients, which mainly consist of imaging biomarkers, cellular and extracellular proteins, a certain type of bone marrow-derived cells, local stromal cell content (e.g., pericyte coverage) as well as serum or plasma biomarkers (e.g., non-coding RNAs). Finally, we highlight the recent advances in combination strategies with the aim of enhancing the response to antiangiogenic therapy in cancer patients and mouse models. This review introduces a comprehensive understanding of the mechanisms and biomarkers associated with the evasion of antiangiogenic therapy in cancer, providing an outlook for developing more effective approaches to promote the therapeutic efficacy of antiangiogenic therapy.

Cancer combination therapies by angiogenesis inhibitors; a comprehensive review

Abnormal vasculature is one of the most conspicuous traits of tumor tissue, largely contributing to tumor immune evasion. The deregulation mainly arises from the potentiated pro-angiogenic factors secretion and can also target immune cells' biological events, such as migration and activation. Owing to this fact, angiogenesis blockade therapy was established to fight cancer by eliminating the nutrient and oxygen supply to the malignant cells by impairing the vascular network. Given the dominant role of vascular-endothelium growth factor (VEGF) in the angiogenesis process, the well-known anti-angiogenic agents mainly depend on the targeting of its actions. However, cancer cells mainly show resistance to anti-angiogenic agents by several mechanisms, and also potentiated local invasiveness and also distant metastasis have been observed following their administration. Herein, we will focus on clinical developments of angiogenesis blockade therapy, more particular, in combination with other conventional treatments, such as immunotherapy, chemoradiotherapy, targeted therapy, and also cancer vaccines. Video abstract.

Capillary morphogenesis gene 2 (CMG2) mediates growth factor-induced angiogenesis by regulating endothelial cell chemotaxis

Anthrax protective antigen (PA) is a potent inhibitor of pathological angiogenesis with an unknown mechanism. In anthrax intoxication, PA interacts with capillary morphogenesis gene 2 (CMG2) and tumor endothelial marker 8 (TEM8). Here, we show that CMG2 mediates the antiangiogenic effects of PA and is required for growth-factor-induced chemotaxis. Using specific inhibitors of CMG2 and TEM8 interaction with natural ligand, as well as mice with the CMG2 or TEM8 transmembrane and intracellular domains disrupted, we demonstrate that inhibiting CMG2, but not TEM8 reduces growth-factor-induced angiogenesis in the cornea. Furthermore, the antiangiogenic effect of PA was abolished when the CMG2, but not the TEM8, gene was disrupted. Binding experiments demonstrated a broad ligand specificity for CMG2 among extracellular matrix (ECM) proteins. Ex vivo experiments demonstrated that CMG2 (but not TEM8) is required for PA activity in human dermal microvascular endothelial cell (HMVEC-d) network formation assays. Remarkably, blocking CMG2-ligand binding with PA or CRISPR knockout abolishes endothelial cell chemotaxis but not chemokinesis in microfluidic migration assays. These effects are phenocopied by Rho inhibition. Because CMG2 mediates the chemotactic response of endothelial cells to peptide growth factors in an ECM-dependent fashion, CMG2 is well-placed to integrate growth factor and ECM signals. Thus, CMG2 targeting is a novel way to inhibit angiogenesis.

Oxidative stress in cancer therapy: Friend or enemy?

Excessive cellular oxidative stress is widely perceived as a key factor in pathophysiological conditions and cancer development. Healthy cells use several mechanisms to maintain intracellular levels of reactive oxygen species (ROS) and overall redox homeostasis to avoid damage to DNA, proteins, and lipids. Cancer cells, in contrast, exhibit elevated ROS levels and upregulated protective antioxidant pathways. Counterintuitively, such elevated oxidative stress and enhanced antioxidant defence mechanisms in cancer cells provide a therapeutic opportunity for the development of drugs with different anticancer mechanisms of action (MoA). In this review, oxidative stress and the role of ROS in cells are described. The tumour-suppressive and tumour-promotive functions of ROS are discussed to compare these two different therapeutic strategies (increasing or decreasing ROS to fight cancer). Clinically approved drugs with demonstrated oxidative stress anticancer MoAs are highlighted before describing examples of metal-based anticancer drug candidates causing oxidative stress in cancer cells via novel MoAs.

Molecular Mechanisms of Resistance to Immunotherapy and Antiangiogenic Treatments in Clear Cell Renal Cell Carcinoma

Clear cell renal cell carcinoma (ccRCC) is the most common histological subtype arising from renal cell carcinomas. This tumor is characterized by a predominant angiogenic and immunogenic microenvironment that interplay with stromal, immune cells, and tumoral cells. Despite the obscure prognosis traditionally related to this entity, strategies including angiogenesis inhibition with tyrosine kinase inhibitors (TKIs), as well as the enhancement of the immune system with the inhibition of immune checkpoint proteins, such as PD-1/PDL-1 and CTLA-4, have revolutionized the treatment landscape. This approach has achieved a substantial improvement in life expectancy and quality of life from patients with advanced ccRCC. Unfortunately, not all patients benefit from this success as most patients will finally progress to these therapies and, even worse, approximately 5 to 30% of patients will primarily progress. In the last few years, preclinical and clinical research have been conducted to decode the biological basis underlying the resistance mechanisms regarding angiogenic and immune-based therapy. In this review, we summarize the insights of these molecular alterations to understand the resistance pathways related to the treatment with TKI and immune checkpoint inhibitors (ICIs). Moreover, we include additional information on novel approaches that are currently under research to overcome these resistance alterations in preclinical studies and early phase clinical trials.

Biological Significance and Targeting of the FGFR Axis in Cancer

The pleiotropic effects of fibroblast growth factors (FGFs), the widespread expression of all seven signalling FGF receptors (FGFRs) throughout the body, and the dramatic phenotypes shown by many FGF/R knockout mice, highlight the diversity, complexity and functional importance of FGFR signalling. The FGF/R axis is critical during normal tissue development, homeostasis and repair. Therefore, it is not surprising that substantial evidence also pinpoints the involvement of aberrant FGFR signalling in disease, including tumourigenesis. FGFR aberrations in cancer include mutations, gene fusions, and amplifications as well as corrupted autocrine/paracrine loops. Indeed, many clinical trials on cancer are focusing on targeting the FGF/FGFR axis, using selective FGFR inhibitors, nonselective FGFR tyrosine kinase inhibitors, ligand traps, and monoclonal antibodies and some have already been approved for the treatment of cancer patients. The heterogeneous tumour microenvironment and complexity of FGFR signalling may be some of the factors responsible for the resistance or poor response to therapy with FGFR axis-directed therapeutic agents. In the present review we will focus on the structure and function of FGF(R)s, their common irregularities in cancer and the therapeutic value of targeting their function in cancer.

The Immunotherapy Landscape in Renal Cell Carcinoma

The past 30 years have borne witness to a gradual evolution in the treatment landscape of advanced renal cell carcinoma (aRCC). Early immunotherapy approaches such as interferon-α and high-dose interleukin-2 (IL-2) therapy in this immunogenic tumor provided durable responses in only a minority of patients and came with toxic side effects. A growing understanding of the tumor biology elucidated pathways of tumorigenesis, which in turn revealed novel targets amenable to targeted therapies. Inhibition of angiogenesis and cell signaling emerged as cornerstones of treatment with the approval of bevacizumab and several pan-kinase and tyrosine kinase inhibitors. Though effective, their use has been limited by low rates of durable response, resistance, and side effects. The immunotherapy revolution of the past decade has led to immunotherapy-based combination regimens such as ipilimumab plus nivolumab, pembrolizumab plus axitinib, and avelumab plus axitinib, displacing single agent anti-angiogenic therapy in the first-line setting by demonstrating durable responses and improved survival over sunitinib. These immunotherapy-based combinations define first-line standard of care for aRCC today. The pipeline of second-line agents for consideration in patients who have disease progression despite immunotherapy regimens is robust but still in early stages of development.

Role of bFGF in Acquired Resistance upon Anti-VEGF Therapy in Cancer

Anti-angiogenic approaches targeting the vascular endothelial growth factor (VEGF) signaling pathway have been a significant research focus during the past decades and are well established in clinical practice. Despite the expectations, their benefit is ephemeral in several diseases, including specific cancers. One of the most prominent side effects of the current, VEGF-based, anti-angiogenic treatments remains the development of resistance, mostly due to the upregulation and compensatory mechanisms of other growth factors, with the basic fibroblast growth factor (bFGF) being at the top of the list. Over the past decade, several anti-angiogenic approaches targeting simultaneously different growth factors and their signaling pathways have been developed and some have reached the clinical practice. In the present review, we summarize the knowledge regarding resistance mechanisms upon anti-angiogenic treatment, mainly focusing on bFGF. We discuss its role in acquired resistance upon prolonged anti-angiogenic treatment in different tumor settings, outline the reported resistance mechanisms leading to bFGF upregulation, and summarize the efforts and outcome of combined anti-angiogenic approaches to date.

Endothelial Cells as Tools to Model Tissue Microenvironment in Hypoxia-Dependent Pathologies

Endothelial cells (ECs) lining the blood vessels are important players in many biological phenomena but are crucial in hypoxia-dependent diseases where their deregulation contributes to pathology. On the other hand, processes mediated by ECs, such as angiogenesis, vessel permeability, interactions with cells and factors circulating in the blood, maintain homeostasis of the organism. Understanding the diversity and heterogeneity of ECs in different tissues and during various biological processes is crucial in biomedical research to properly develop our knowledge on many diseases, including cancer. Here, we review the most important aspects related to ECs’ heterogeneity and list the available in vitro tools to study different angiogenesis-related pathologies. We focus on the relationship between functions of ECs and their organo-specificity but also point to how the microenvironment, mainly hypoxia, shapes their activity. We believe that taking into account the specific features of ECs that are relevant to the object of the study (organ or disease state), especially in a simplified in vitro setting, is important to truly depict the biology of endothelium and its consequences. This is possible in many instances with the use of proper in vitro tools as alternative methods to animal testing.

Alphastatin-C a new inhibitor of endothelial cell activation is a pro-arteriogenic agent in vivo and retards B16-F10 melanoma growth in a preclinical model

Most characterized angiogenic modulators are proteolytic fragments of structural plasma and/or matrix components. Herein, we have identified a novel anti-angiogenic peptide generated by the in vitro hydrolysis of the C-terminal moiety of the fibrinogen alpha chain, produced by the snake venom metalloprotease bothropasin (SVMP), a hemorrhagic proteinase in Bothrops jararaca venom. The 14-amino acids peptide (alphastatin-C) is a potent antagonist of basic fibroblast growth factor, induced endothelial cell (HUVEC-CS) proliferation, migration and capillary tube formation in matrigel. It also inhibits cell adhesion to fibronectin. The basis of the antagonism between bFGF and alphastatin-C is elucidated by the inhibition of various bFGF induced signaling pathways and their molecular components modification, whenever the combination of the stimuli is provided, in comparison to the treatment with bFGF only. To corroborate to the potential therapeutic use of alphastatin-C, we have chosen to perform in vivo assays in two distinct angiogenic settings. In chick model, alphastatin-C inhibits chorioallantoic membrane angiogenesis. In mouse, it efficiently reduces tumor number and volume in a melanoma model, due to the impairment of tumor neovascularization in treated mice. In contrast, we show that the alphastatin-C peptide induces arteriogenesis, increasing pial collateral density in neonate mice. alphastatin-C is an efficient new antiangiogenic FGF-associated agent in vitro, it is an inhibitor of embryonic and tumor vascularization in vivo while, it is an arteriogenic agent. The results also suggest that SVMPs can be used as in vitro biochemical tools to process plasma and/or matrix macromolecular components unraveling new angiostatic peptides.

In vitro 3D Systems to Model Tumor Angiogenesis and Interactions With Stromal Cells

In vitro 3D culture systems provide promising tools for screening novel therapies and understanding drug resistance mechanisms in cancer because they are adapted for high throughput analysis. One of the main current challenges is to reproducibly culture patient samples containing cancer and stromal cells to faithfully recapitulate tumor microenvironment and move toward efficient personalized medicine. Tumors are composed of heterogeneous cell populations and characterized by chaotic vascularization in a remodeled microenvironment. Indeed, tumor angiogenesis occurs in a complex stroma containing immune cells and cancer-associated fibroblasts that secrete important amounts of cytokines, growth factors, extracellular vesicles, and extracellular matrix (ECM). This process leads to the formation of inflated, tortuous, and permeable capillaries that display deficient basement membrane (BM) and perivascular coverage. These abnormal capillaries affect responses to anti-cancer therapies such as anti-angiogenic, radio-, and immunotherapies. Current pre-clinical models are limited for investigating interactions between tumor cells and vascularization during tumor progression as well as mechanisms that lead to drug resistance. In vitro approaches developed for vascularization are either the result of engineered cell lining or based on physiological processes including vasculogenesis and sprouting angiogenesis. They allow investigation of paracrine and direct interactions between endothelial and tumor and/or stromal cells, as well as impact of biochemical and biophysical cues of the microenvironment, using either natural matrix components or functionalized synthetic hydrogels. In addition, microfluidic devices provide access to modeling the impact of shear stress and interstitial flow and growth factor gradients. In this review, we will describe the state of the art co-culture models of vascularized micro-tumors in order to study tumor progression and metastatic dissemination including intravasation and/or extravasation processes.

FGFR1 is associated with c-MYC and proangiogenic molecules in metastatic renal cell carcinoma under anti-angiogenic therapy

AIMS

This study aimed to investigate the clinicopathological significance of FGFR1 and c-MYC expression, particularly in relation to angiogenesis in clear cell renal cell carcinoma (CCRCC).

METHODS AND RESULTS

Immunohistochemistry and fluorescence in-situ hybridisation were conducted with tissue microarrays from 91 metastatic CCRCC patients who received VEGF receptor tyrosine kinase inhibitors (VEGFR-TKIs). The expression of angiogenic molecules, FGFR1 and c-MYC, and tumoral vascular density (TVD) and mRNA expression and TVD of 533 CCRCCs in The Cancer Genome Atlas (TCGA) were analysed. FGFR1, pFGFR1 and c-MYC expression was observed in 29.1, 74.4 and 30.8% of tumours, respectively. FGFR1^high was an independent worse prognostic factor for overall (HR = 1.871, P = 0.032) and progression-free (HR = 1.976, P = 0.016) survival. FGFR1^high was significantly related to VEGFR-TKI responsiveness (P = 0.011). The presence of FGFR1^high /c-MYC^high showed a positive correlation with proangiogenic markers, including VEGF (P = 0.018) and HIF-1α (P < 0.0001). FGFR1^high /c-MYC^high tumours showed higher TVDs together with higher VEGFR2 and PDGFR-β expression (both P < 0.0001). FGFR1 and c-MYC expression was also positively correlated with the expression of hypoxia-related and proangiogenic-related genes in the TCGA data.

CONCLUSIONS

FGFR1 and c-MYC may be involved in tumour angiogenesis and FGFR1 may represent a promising therapeutic target in metastatic CCRCC.

Metastasis-associated fibroblasts promote angiogenesis in metastasized pancreatic cancer via the CXCL8 and the CCL2 axes

The characteristic desmoplastic stroma of pancreatic ductal adenocarcinoma (PDAC) is a key contributor to its lethality. This stromal microenvironment is populated by cancer-associated fibroblasts (CAFs) that interact with cancer cells to drive progression and chemo-resistance. Research has focused on CAFs in the primary tumour but not in metastases, calling into question the role of analogous metastasis-associated fibroblasts (MAFs). We infer a role of MAFs in murine hepatic metastases following untargeted treatment with the anti-angiogenic drug sunitinib in vivo. Treated metastases were smaller and had fewer stromal cells, but were able to maintain angiogenesis and metastasis formation in the liver. Furthermore, sunitinib was ineffective at reducing MAFs alongside other stromal cells. We speculate that cancer cells interact with MAFs to maintain angiogenesis and tumour progression. Thus, we tested interactions between metastatic pancreatic cancer cells and fibroblasts using in vitro co-culture systems. Co-cultures enhanced fibroblast proliferation and induced angiogenesis. We identify carcinoma-educated fibroblasts as the source of angiogenesis via secretions of CXCL8 (aka IL-8) and CCL2 (aka MCP-1). Overall, we demonstrate that metastasis-associated fibroblasts have potential as a therapeutic target and highlight the CXCL8 and CCL2 axes for further investigation.

Vessel co-option and resistance to anti-angiogenic therapy

Vessel co-option is a non-angiogenic mechanism of tumour vascularisation in which cancer cells utilise pre-existing blood vessels instead of inducing new blood vessel formation. Vessel co-option has been observed across a range of different tumour types, in both primary cancers and metastatic disease. Importantly, vessel co-option is now implicated as a major mechanism that mediates resistance to conventional anti-angiogenic drugs and this may help to explain the limited efficacy of this therapeutic approach in certain clinical settings. This includes the use of anti-angiogenic drugs to treat advanced-stage/metastatic disease, treatment in the adjuvant setting and the treatment of primary disease. In this article, we review the available evidence linking vessel co-option with resistance to anti-angiogenic therapy in numerous tumour types, including breast, colorectal, lung and pancreatic cancer, glioblastoma, melanoma, hepatocellular carcinoma, and renal cell carcinoma. The finding that vessel co-option is a significant mechanism of resistance to anti-angiogenic therapy may have important implications for the future of anti-cancer therapy, including (a) predicting response to anti-angiogenic drugs, (b) the need to develop therapies that target both angiogenesis and vessel co-option in tumours, and (c) predicting the response to other therapeutic modalities, including immunotherapy.

Revascularization after angiogenesis inhibition favors new sprouting over abandoned vessel reuse

Inhibiting pathologic angiogenesis can halt disease progression, but such inhibition may offer only a temporary benefit, followed by tissue revascularization after treatment stoppage. This revascularization, however, occurs by largely unknown phenotypic changes in pathologic vessels. To investigate the dynamics of vessel reconfiguration during revascularization, we developed a model of reversible murine corneal angiogenesis permitting longitudinal examination of the same vasculature. Following 30 days of angiogenesis inhibition, two types of vascular structure were evident: partially regressed persistent vessels that were degenerate and barely functional, and fully regressed, non-functional empty basement membrane sleeves (ebms). While persistent vessels maintained a limited flow and retained collagen IV+ basement membrane, CD31+ endothelial cells (EC), and α-SMA+ pericytes, ebms were acellular and expressed only collagen IV. Upon terminating angiogenesis inhibition, transmission electron microscopy and live imaging revealed that revascularization ensued by a rapid reversal of EC degeneracy in persistent vessels, facilitating their phenotypic normalization, vasodilation, increased flow, and subsequent new angiogenic sprouting. Conversely, ebms were irreversibly sealed from the circulation by excess collagen IV deposition that inhibited EC migration and prevented their reuse. Fully and partially regressed vessels therefore have opposing roles during revascularization, where fully regressed vessels inhibit new sprouting while partially regressed persistent vessels rapidly reactivate and serve as the source of continued pathologic angiogenesis.

Phase II randomised discontinuation trial of brivanib in patients with advanced solid tumours

BACKGROUND

Brivanib is a selective inhibitor of vascular endothelial growth factor and fibroblast growth factor (FGF) signalling. We performed a phase II randomised discontinuation trial of brivanib in 7 tumour types (soft-tissue sarcomas [STS], ovarian cancer, breast cancer, pancreatic cancer, non-small-cell lung cancer [NSCLC], gastric/esophageal cancer and transitional cell carcinoma [TCC]).

PATIENTS AND METHODS

During a 12-week open-label lead-in period, patients received brivanib 800 mg daily and were evaluated for FGF2 status by immunohistochemistry. Patients with stable disease at week 12 were randomised to brivanib or placebo. A study steering committee evaluated week 12 response to determine if enrolment in a tumour type would continue. The primary objective was progression-free survival (PFS) for brivanib versus placebo in patients with FGF2-positive tumours.

RESULTS

A total of 595 patients were treated, and stable disease was observed at the week 12 randomisation point in all tumour types. Closure decisions were made for breast cancer, pancreatic cancer, NSCLC, gastric cancer and TCC. Criteria for expansion were met for STS and ovarian cancer. In 53 randomised patients with STS and FGF2-positive tumours, the median PFS was 2.8 months for brivanib and 1.4 months for placebo (hazard ratio [HR]: 0.58, p = 0.08). For all randomised patients with sarcomas, the median PFS was 2.8 months (95% confidence interval [CI]: 1.4-4.0) for those treated with brivanib compared with 1.4 months (95% CI: 1.3-1.6) for placebo (HR = 0.64, 95% CI: 0.38-1.07; p = 0.09). In the 36 randomised patients with ovarian cancer and FGF2-positive tumours, the median PFS was 4.0 (95% CI: 2.6-4.2) months for brivanib and 2.0 months (95% CI: 1.2-2.7) for placebo (HR: 0.56, 95% CI: 0.26-1.22). For all randomised patients with ovarian cancer, the median PFS in those randomised to brivanib was 4.0 months (95% CI: 2.6-4.2) and was 2.0 months (95% CI: 1.2-2.7) in those randomised to placebo (HR = 0.54, 95% CI: 0.25-1.17; p = 0.11).

CONCLUSION

Brivanib demonstrated activity in STS and ovarian cancer with an acceptable safety profile. FGF2 expression, as defined in the protocol, is not a predictive biomarker of the efficacy of brivanib.

Vimentin Overexpressions Induced by Cell Hypoxia Promote Vasculogenic Mimicry by Renal Cell Carcinoma Cells

Vasculogenic mimicry (VM), the novel approach for tumor cells to obtain blood supply, was reported to be involved in antiangiogenic resistance and poor prognosis in renal cell carcinoma (RCC). However, the molecular mechanisms underlying VM formed by RCC cells are still not clearly depicted. In the present study, we found that OS-RC-2 acquired the VM forming ability accompanied with the increased expressions of Vimentin and AXL and decreased expression of E-Cadherin by CoCl₂ treatment. Downregulation of Vimentin by siRNA severely impaired the capability of OS-RC-2 and 786-O to form VM structures induced by cell hypoxia in vitro. Moreover, knockdown of Vimentin inhibited cell migration and invasion, which could be prompted by hypoxia induction in RCC cells. In our clear cell RCC tissues, we found that VM was positively correlated with Vimentin overexpression and both predicted poor prognosis. In conclusion, Vimentin plays an important role in hypoxia induced VM formation of RCC cells and targeted Vimentin might be beneficial for RCC therapy.

Resistance to Systemic Therapies in Clear Cell Renal Cell Carcinoma: Mechanisms and Management Strategies

Renal cell carcinoma (RCC) is the most common form of kidney cancer. It is categorized into various subtypes, with clear cell RCC (ccRCC) representing about 85% of all RCC tumors. The lack of sensitivity to chemotherapy and radiation therapy prompted research efforts into novel treatment options. The development of targeted therapeutics, including multi-targeted tyrosine kinase inhibitors (TKI) and mTOR inhibitors, has been a major breakthrough in ccRCC therapy. More recently, other therapeutic strategies, including immune checkpoint inhibitors, have emerged as effective treatment options against advanced ccRCC. Furthermore, recent advances in disease biology, tumor microenvironment, and mechanisms of resistance formed the basis for attempts to combine targeted therapies with newer generation immunotherapies to take advantage of possible synergy. This review focuses on the current status of basic, translational, and clinical studies on mechanisms of resistance to systemic therapies in ccRCC. Mol Cancer Ther; 17(7); 1355-64. ©2018 AACR.

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.

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.

Discontinuous Schedule of Bevacizumab in Colorectal Cancer Induces Accelerated Tumor Growth and Phenotypic Changes

Antiangiogenics administration in colorectal cancer patients seemed promising therapeutic approach. Inspite of early encouraging results, it however gave only modest clinical benefits. When AAG was administered with discontinuous schedule, the disease showed acceleration in certain cases. Though resistance to AAG has been extensively studied, it is not documented for discontinuous schedules. To simulate clinical situations, we subjected a patient-derived CRC subcutaneous xenograft in mice to three different protocols: 1) AAG (bevacizumab) treatment for 30 days (group A) (group B was the control), 2) bevacizumab treatment for 50 days (group C) and bevacizumab for 30 days and 20 without treatment (group D), and 3) bevacizumab treatment for 70 days (group E) and 70 days treatment with a drug-break period between day 30 and 50 (group F). The tumor growth was monitored, and at sacrifice, the vascularity of tumors was measured and the proangiogenic factors quantified. Tumor phenotype was studied by quantifying cancer stem cells. Interrupting bevacizumab during treatment accelerated tumor growth and revascularization. A significant increase of proangiogenic factors was observed when therapy was stopped. On withdrawal of bevacizumab, as also after the drug-break period, the plasmatic VEGF increased significantly. Similarly, a notable increase of CSCs after the withdrawal and drug-break period of bevacizumab was observed (P<.01). The present study indicates that bevacizumab treatment needs to be maintained because discontinuous schedules tend to trigger tumor regrowth, and increase tumor resistance and CSC heterogeneity.

Lenvatinib in the management of metastatic renal cell carcinoma: a promising combination therapy?

INTRODUCTION

To date, results of combination therapy studies have shown no meaningful clinical benefit over monotherapy and an unacceptably high degree of toxicity in the treatment of metastatic renal cell carcinoma (RCC), with the exception of a combination of immune-checkpoint inhibitors and the association of lenvatinib with everolimus. Lenvatinib is a potent multi-targeted tyrosine kinase inhibitor that targets VEGFR pathways. Everolimus inhibits primarily mTORC1 complex, a downstream effecter of the intracellular PI3K/AKT/mTOR pathway. The association of these two drugs was demonstrated to enhance the inhibitory activity against VEGF and FGF-induced angiogenesis by a vertical inhibition of angiogenic signaling pathways, suggesting a synergistic activity. Areas covered: In this review we summarize the lenvatinib pharmacokinetics, pharmacodynamics, characteristics and the main clinical trial that showed lenvatinib activity in advanced RCC. Expert opinion: Lenvatinib plus everolimus showed promising results in a phase II trial, leading to FDA approval of this combination. Their synergic action on inhibiting the VEGF/VEGFR, FGF (a compensatory mechanism to VEGFR inhibition) and mTOR pathway could be a potential mechanism to overcome treatment resistance. Given that the activity of lenvatinib as an immune-regulator in tumor microenvironment has been demonstrated in cell lines, novel combinations, in particular with immune-checkpoint inhibitors, are under development.

Everolimus affects vasculogenic mimicry in renal carcinoma resistant to sunitinib

Angiogenesis is hallmark of clear cell renal cell carcinogenesis. Anti-angiogenic therapies have been successful in improving disease outcome; however, most patients treated with anti-angiogenic agents will eventually progress. In this study we report that clear cell renal cell carcinoma was associated with vasculogenic mimicry in both mice and human with tumor cells expressing endothelial markers in the vicinity of tumor vessels. We show that vasculogenic mimicry was efficiently targeted by sunitinib but eventually associated with tumor resistance and a more aggressive phenotype both in vitro and in vivo. Re-challenging these resistant tumors in mice, we showed that second-line treatment with everolimus particularly affected vasculogenic mimicry and tumor cell differentiation compared to sorafenib and axitinib. Finally, our results highlighted the phenotypic and genotypic changes at the tumor cell and microenvironment levels during sunitinib response and progression and the subsequent improvement second-line therapies bring to the current renal cell carcinoma treatment paradigm.

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.

Fibroblast growth factor-mediated crosstalk in cancer etiology and treatment

It is becoming increasingly evident that multiple cell types within the tumor work together to drive tumour progression and impact on both the response to therapy and the dissemination of tumour cells throughout the body. Fibroblast growth factor signalling (FGF) is perturbed in a number of tumors, serving to drive tumor cell proliferation and migration, but also has a central role in orchestrating the plethora of cells that comprise the tumor microenvironment. This review focuses on how this family of signalling molecules can influence the interactions between tumor cells and their surrounding environment. Unraveling the complexities of FGF signalling between the distinct cell types of a tumor may identify additional opportunities for FGF-targeted compounds in therapy and could help combat drug resistance. Developmental Dynamics 246:493-501, 2017. © 2017 Wiley Periodicals, Inc.

Targeting of tumor growth and angiogenesis underlies the enhanced antitumor activity of lenvatinib in combination with everolimus

The combination of lenvatinib, a multiple receptor tyrosine kinase inhibitor, plus everolimus, a mammalian target of rapamycin (mTOR) inhibitor, significantly improved clinical outcomes versus everolimus monotherapy in a phase II clinical study of metastatic renal cell carcinoma (RCC). We investigated potential mechanisms underlying the antitumor activity of the combination treatment in preclinical RCC models. Lenvatinib plus everolimus showed greater antitumor activity than either monotherapy in three human RCC xenograft mouse models (A‐498, Caki‐1, and Caki‐2). In particular, the combination led to tumor regression in the A‐498 and Caki‐1 models. In the A‐498 model, everolimus showed antiproliferative activity, whereas lenvatinib showed anti‐angiogenic effects. The anti‐angiogenic activity was potentiated by the lenvatinib plus everolimus combination in Caki‐1 xenografts, in which fibroblast growth factor (FGF)‐driven angiogenesis may contribute to tumor growth. The combination showed mostly additive activity in vascular endothelial growth factor (VEGF)‐activated, and synergistic activity against FGF‐activated endothelial cells, in cell proliferation and tube formation assays, as well as strongly suppressed mTOR‐S6K‐S6 signaling. Enhanced antitumor activities of the combination versus each monotherapy were also observed in mice bearing human pancreatic KP‐1 xenografts overexpressing VEGF or FGF. Our results indicated that simultaneous targeting of tumor cell growth and angiogenesis by lenvatinib plus everolimus resulted in enhanced antitumor activity. The enhanced inhibition of both VEGF and FGF signaling pathways by the combination underlies its superior anti‐angiogenic activity in human RCC xenograft models.

FGFR a promising druggable target in cancer: Molecular biology and new drugs

INTRODUCTION

The Fibroblast Growth Factor Receptor (FGFR) family consists of Tyrosine Kinase Receptors (TKR) involved in several biological functions. Recently, alterations of FGFR have been reported to be important for progression and development of several cancers. In this setting, different studies are trying to evaluate the efficacy of different therapies targeting FGFR.

AREAS COVERED

This review summarizes the current status of treatments targeting FGFR, focusing on the trials that are evaluating the FGFR profile as inclusion criteria: Multi-Target, Pan-FGFR Inhibitors and anti-FGF (Fibroblast Growth Factor)/FGFR Monoclonal Antibodies.

EXPERT OPINION

Most of the TKR share intracellular signaling pathways; therefore, cancer cells tend to overcome the inhibition of one tyrosine kinase receptor by activating another. The future of TKI (Tyrosine Kinase Inhibitor) therapy will potentially come from multi-targeted TKIs that target different TKR simultaneously. It is crucial to understand the interaction of the FGF-FGFR axis with other known driver TKRs. Based on this, it is possible to develop therapeutic strategies targeting multiple connected TKRs at once. One correct step in this direction is the reassessment of multi target inhibitors considering the FGFR status of the tumor. Another opportunity arises from assessing the use of FGFR TKI on patients harboring FGFR alterations.

Sunitinib Treatment Enhances Metastasis of Innately Drug-Resistant Breast Tumors

Antiangiogenic therapies have failed to confer survival benefits in patients with metastatic breast cancer (mBC). However, to date, there has not been an inquiry into the roles for acquired versus innate drug resistance in this setting. In this study, we report roles for these distinct phenotypes in determining therapeutic response in a murine model of mBC resistance to the antiangiogenic tyrosine kinase inhibitor sunitinib. Using tumor measurement and vascular patterning approaches, we differentiated tumors displaying innate versus acquired resistance. Bioluminescent imaging of tumor metastases to the liver, lungs, and spleen revealed that sunitinib administration enhances metastasis, but only in tumors displaying innate resistance to therapy. Transcriptomic analysis of tumors displaying acquired versus innate resistance allowed the identification of specific biomarkers, many of which have a role in angiogenesis. In particular, aquaporin-1 upregulation occurred in acquired resistance, mTOR in innate resistance, and pleiotrophin in both settings, suggesting their utility as candidate diagnostics to predict drug response or to design tactics to circumvent resistance. Our results unravel specific features of antiangiogenic resistance, with potential therapeutic implications. Cancer Res; 77(4); 1008-20. ©2016 AACR.

Lenvatinib therapy for the treatment of patients with advanced renal cell carcinoma

Despite advances in metastatic renal cell carcinoma (mRCC) treatments, patients eventually progress and develop resistance to therapies targeting a single pathway. Lenvatinib inhibits VEGFR1–3, FGFR1–4, PDGFRβ, RET and KIT proto-oncogenes. In a randomized, Phase II trial evaluating patients with mRCC who had progressed after one prior VEGF-targeted therapy, progression-free survival was significantly improved with lenvatinib alone or in combination with everolimus versus everolimus alone. This review summarizes the clinical development of lenvatinib in mRCC, and how simultaneous targeting of multiple pathways involved in carcinogenesis and/or therapeutic resistance may improve patient outcomes. Lenvatinib plus everolimus may be a promising second-line treatment in patients with mRCC.

MEK inhibition abrogates sunitinib resistance in a renal cell carcinoma patient-derived xenograft model

Background:

Renal cell carcinoma (RCC) patients treated with tyrosine kinase inhibitors (TKI) typically respond initially, but usually develop resistance to therapy. We utilised transcriptome analysis to identify gene expression changes during development of sunitinib resistance in a RCC patient-derived xenograft (PDX) model.

Methods:

RCC tumours were harvested during pre-treatment, response and escape phases. Direct anti-proliferative effects of sunitinib plus MEK inhibitor were assessed. Activation status (phosphorylation) of MEK1/2 and ERK1/2 was determined, myeloid-derived suppressor cells (MDSC) sub-fractions were quantitated and G-CSF was measured by ELISA.

Results:

During the response phase, tumours exhibited 91% reduction in volume, characterised by decreased expression of cell survival genes. After 4-week treatment, tumours developed resistance to sunitinib, associated with increased expression of pro-angiogenic and cell survival genes. During tumour escape, cellular movement, inflammatory response and immune cell trafficking genes were induced, along with intra-tumoural accumulation of MDSC. In this PDX model, either continuous treatment with sunitinib plus MEK inhibitor PD-0325901, or switching from sunitinib to PD-0325901 was effective. The combination of PD-0325901 with TKI suppressed intra-tumoural phospho-MEK1/2, phospho-ERK1/2 and MDSC.

Conclusions:

Continuous treatment with sunitinib alone did not maintain anti-tumour response; addition of MEK inhibitor abrogated resistance, leading to improved anti-tumour efficacy.

Leishmania major Infection-Induced VEGF-A/VEGFR-2 Signaling Promotes Lymphangiogenesis That Controls Disease

Cutaneous leishmaniasis causes a spectrum of diseases from self-healing to severe nonhealing lesions. Defining the factors contributing to lesion resolution may help in developing new therapies for those patients with chronic disease. We found that infection with Leishmania major increases the expression of vascular endothelial growth factor-A and vascular endothelial growth factor receptor (VEGFR)-2 and is associated with significant changes in the blood and lymphatic vasculature at the site of infection. Ab blockade of VEGFR-2 during infection led to a reduction in lymphatic endothelial cell proliferation and simultaneously increased lesion size without altering the parasite burden. These data show that L. major infection initiates enhanced vascular endothelial growth factor-A/VEGFR-2 signaling and suggest that VEGFR-2-dependent lymphangiogenesis is a mechanism that restricts tissue inflammation in leishmaniasis.

The prospect of precision therapy for renal cell carcinoma

The therapeutic landscape of renal cell carcinoma (RCC) has greatly expanded in the last decade. From being a malignancy orphan of effective therapies, kidney cancer has become today a tumor with several treatment options. Renal cell carcinoma (RCC) is a metabolic disease, being characterized by the dysregulation of metabolic pathways involved in oxygen sensing (VHL/HIF pathway alterations and the subsequent up-regulation of HIF-responsive genes such as VEGF, PDGF, EGF, and glucose transporters GLUT1 and GLUT4, which justify the RCC reliance on aerobic glycolysis), energy sensing (fumarate hydratase-deficient, succinate dehydrogenase-deficient RCC, mutations of HGF/MET pathway resulting in the metabolic Warburg shift marked by RCC increased dependence on aerobic glycolysis and the pentose phosphate shunt, augmented lipogenesis, and reduced AMPK and Krebs cycle activity) and/or nutrient sensing cascade (deregulation of AMPK-TSC1/2-mTOR and PI3K-Akt-mTOR pathways). In this complex scenario it is important to find prognostic and predictive factors that can help in decision making in the treatment of mRCC.

Fibroblast Growth Factor Receptor-Dependent and -Independent Paracrine Signaling by Sunitinib-Resistant Renal Cell Carcinoma

Antiangiogenic therapies, such as sunitinib, have revolutionized renal cell carcinoma (RCC) treatment. However, a precarious understanding of how resistance emerges and a lack of tractable experimental systems hinder progress. We evaluated the potential of primary RCC cultures (derived from tumors and tumor grafts) to signal to endothelial cells (EC) and fibroblasts in vitro and to stimulate angiogenesis ex vivo in chorioallantoic membrane (CAM) assays. From 65 patients, 27 primary cultures, including several from patients with sunitinib-resistant RCC, were established. RCC cells supported EC survival in coculture assays and induced angiogenesis in CAM assays. RCC-induced EC survival was sensitive to sunitinib in half of the tumors and was refractory in tumors from resistant patients. Sunitinib sensitivity correlated with vascular endothelial growth factor (VEGF) production. RCC induced paracrine extracellular signal-regulated kinase (ERK) activation in EC which was inhibited by sunitinib in sensitive but not in resistant tumors. As determined by fibroblast growth factor receptor substrate 2 (FRS2) phosphorylation in fibroblasts, RCC broadly induced low-level fibroblast growth factor receptor (FGFR) signaling. Whereas ERK activation in EC was uniformly inhibited by combined VEGF/platelet-derived growth factor (PDGF)/FGF receptor inhibitors, paracrine ERK activation in fibroblasts was blocked in only a fraction of tumors. Our data show that RCC activates EC through VEGF-dependent and -independent pathways, that sunitinib sensitivity correlates with VEGF-mediated ERK activation, and that combined inhibition of VEGF/PDGF/FGF receptors is sufficient to inhibit mitogenic signaling in EC but not in fibroblasts.

Uronyl 2-O sulfotransferase potentiates Fgf2-induced cell migration

Fibroblast growth factor 2 (Fgf2) is involved in several biological functions. Fgf2 requires glycosaminoglycans, like chondroitin and dermatan sulfates (hereafter denoted CS/DS) as co-receptors. CS/DS are linear polysaccharides composed of repeating disaccharide units [-4GlcUAb1-3-GalNAc-b1-] and [-4IdoUAa1-3-GalNAc-b1-],which can be sulfated. Uronyl 2-O-sulfotransferase (Ust)introduces sulfation at the C2 of IdoUA and GlcUA resulting inover-sulfated units. Here, we investigated the role of Ust-mediated CS/DS 2-O sulfation in Fgf2-induced cell migration. We found that CHO-K1 cells overexpressing Ust contain significantly more CS/DS2-O sulfated units, whereas Ust knockdown abolished CS/DS 2-O sulfation. These structural differences in CS/DS resulted in altered Fgf2 binding and increased phosphorylation of ERK1/2 (also known as MAPK3 and MAPK1, respectively). As a functional consequence of CS/DS 2-O sulfation and altered Fgf2 binding, cell migration and paxillin activation were increased. Inhibition of sulfation, knockdown of Ust and inhibition of FgfR resulted in reduced migration. Similarly, in 3T3 cells Fgf2 treatment increased migration, which was abolished by Ust knockdown. The proteoglycan controlling the CHO migration was syndecan 1. Knockdown of Sdc1 in CHO-K1 cells overexpressing Ust abolished cell migration.We conclude that the presence of distinctly sulfated CS/DS can tune the Fgf2 effect on cell migration.

Cyclooxygenase-2 blockade can improve efficacy of VEGF-targeting drugs

Anti-angiogenic therapies were approved for different cancers. However, significant primary and secondary resistance hampers efficacy in several tumor types including breast cancer. Thus, we need to develop clinically applicable strategies to enhance efficacy of anti-angiogenic drugs.

We report that anti-angiogenic therapies can induce upregulation of cyclooxygenase-2 (Cox-2) and of its product prostaglandin E2 (PGE₂) in breast cancer models. Upon Cox-2 inhibition PGE₂ levels were normalized and efficacy of anti-vascular endothelial growth factor receptor 2 (anti-VEGFR-2) antibodies and sunitinib was enhanced. Interestingly, both treatments exerted additive anti-angiogenic effects. Following Cox-2 inhibition, we observed reduced infiltration of tumors with cancer-associated fibroblasts (CAFs) and lower levels of pro-angiogenic factors active besides the VEGF axis including hepatocyte growth factor (HGF) and basic fibroblast growth factor (FGF2). Mechanistic studies indicated that Cox-2 inhibition reduced PGE₂-induced migration and proliferation of CAFs via inhibiting phosphorylation of Akt.

Hence, Cox-2 inhibition can increase efficacy of anti-angiogenic treatments and our findings might pave the road for clinical investigations of concomitant blockade of Cox-2 and VEGF-signaling.

Improving outcomes in metastatic clear cell renal cell carcinoma by sequencing therapy

Targeted agents have substantially improved outcomes in metastatic clear cell renal cell carcinoma. However, due to multiple mechanisms of evasive resistance, almost all patients progress at some point and may require subsequent therapies. Various agents have been explored after failure of first-line treatment in randomized clinical trials. However, so far few questions about the optimal sequence have been answered. Both everolimus and axitinib have been considered standard of care after failure of first-line VEGF-TKI; sorafenib has been proposed as an additional option. In clinical practice, several factors may influence the choice of subsequent treatment: these include considerations on appropriate drug exposure in first-line, gained insights on prognostic and predictive factors as well as mechanisms of resistance. Once the decision in second-line has been made and treatment has been initiated, treating physicians may already be challenged by the question of what to offer in third- and later lines. Treatment beyond second-line treatment isn't supported by strong evidence, and at this stage of disease, retrospective reports on rechallenge may help to guide decisions. In addition, local treatment approaches including metastasectomy and stereotactic radiosurgery may help to optimize outcomes in all treatment lines.

Targeting fibroblast growth factor receptor (FGFR) pathway in renal cell carcinoma

Fibroblast growth factor receptor (FGFR) pathway is involved in driving vascular endothelial growth factor (VEGF)-independent tumor angiogenesis, as a compensatory mechanism to escape VEGF-targeted therapies. Therefore, targeting FGF/FGFR axis seems to be a promising strategy in order to inhibit tumor angiogenesis and reduce resistance to VEGF receptor-tyrosine kinase inhibitors. This editorial is focused on the role of FGF/FGFR pathway in renal cell carcinoma and on the ongoing trials of emerging agents targeting this axis.

Prognostic tissue biomarker exploration for patients with metastatic renal cell carcinoma receiving vascular endothelial growth factor receptor tyrosine kinase inhibitors

In metastatic renal cell carcinoma (mRCC), the prognostic role of several tumor tissue biomarkers has been evaluated, but the results were controversial. This study aims to verify the prognostic importance of selected tumor tissue biomarkers in patients with mRCC. The clinicopathological features, immunohistochemical staining and scoring for select tissue biomarkers, treatment, and outcome of patients with mRCC treated with vascular endothelial growth factor receptor (VEGFR) tyrosine kinase inhibitors (TKIs) between July 2006 and March 2011 at Asan Medical Center in Seoul, South Korea, were reviewed. In total, 123 patients met the inclusion criteria. Most patients had clear-cell carcinoma (107 patients, 87.0 %). First-line VEGFR TKIs were sunitinib (97 patients, 78.9 %), sorafenib (23 patients, 18.7 %), and pazopanib (3 patients, 2.4 %). With a median follow-up period of 60.0 months (95 % confidence interval (CI), 56.3-63.6), median overall survival (OS) and progression-free survival (PFS) were 25.6 months (95 % CI, 19.2-32.0) and 12.2 months (95 % CI, 8.1-16.3), respectively. In the multivariable analysis for OS, carbonic anhydrase IX (CAIX; 47.5 % or less vs. more than 47.5 %, p = 0.014), sarcomatoid change (40 % or less vs. more than 40 %, p < 0.001), tumor necrosis (20 % or less vs. more than 20 %, p = 0.006), and Heng's risk group (good vs. intermediate vs. poor, p = 0.011) were identified as independent prognostic factors. In the multivariable analysis for PFS, CAIX (p < 0.001), phosphatase and tensin homolog (PTEN; 45 % or less vs. more than 45 %, p = 0.004), sarcomatoid change (p = 0.002), and tumor necrosis (p = 0.001) were identified as independent factors affecting PFS. CAIX and PTEN had prognostic importance for mRCC patients receiving first-line VEGFR TKI. Future validation and mechanistic studies are required.

Preclinical Evidence That Trametinib Enhances the Response to Antiangiogenic Tyrosine Kinase Inhibitors in Renal Cell Carcinoma

Sunitinib and pazopanib are antiangiogenic tyrosine kinase inhibitors (TKI) used to treat metastatic renal cell carcinoma (RCC). However, the ability of these drugs to extend progression-free and overall survival in this patient population is limited by drug resistance. It is possible that treatment outcomes in RCC patients could be improved by rationally combining TKIs with other agents. Here, we address whether inhibition of the Ras-Raf-MEK-ERK1/2 pathway is a rational means to improve the response to TKIs in RCC. Using a xenograft model of RCC, we found that tumors that are resistant to sunitinib have a significantly increased angiogenic response compared with tumors that are sensitive to sunitinib in vivo. We also observed significantly increased levels of phosphorylated ERK1/2 in the vasculature of resistant tumors, when compared with sensitive tumors. These data suggested that the Ras-Raf-MEK-ERK1/2 pathway, an important driver of angiogenesis in endothelial cells, remains active in the vasculature of TKI-resistant tumors. Using an in vitro angiogenesis assay, we identified that the MEK inhibitor (MEKI) trametinib has potent antiangiogenic activity. We then show that, when trametinib is combined with a TKI in vivo, more effective suppression of tumor growth and tumor angiogenesis is achieved than when either drug is utilized alone. In conclusion, we provide preclinical evidence that combining a TKI, such as sunitinib or pazopanib, with a MEKI, such as trametinib, is a rational and efficacious treatment regimen for RCC.