Rapid angiogenesis onset after discontinuation of sunitinib treatment of renal cell carcinoma patients

Resistance, rebound, and recurrence regrowth patterns in pediatric low-grade glioma treated by MAPK inhibition: A modified Delphi approach to build international consensus-based definitions-International Pediatric Low-Grade Glioma Coalition

Pediatric low-grade glioma (pLGG) is the most common childhood brain tumor group. The natural history, when curative resection is not possible, is one of a chronic disease with periods of tumor stability and episodes of tumor progression. While there is a high overall survival rate, many patients experience significant and potentially lifelong morbidities. The majority of pLGGs have an underlying activation of the RAS/MAPK pathway due to mutational events, leading to the use of molecularly targeted therapies in clinical trials, with recent regulatory approval for the combination of BRAF and MEK inhibition for BRAFV600E mutated pLGG. Despite encouraging activity, tumor regrowth can occur during therapy due to drug resistance, off treatment as tumor recurrence, or as reported in some patients as a rapid rebound growth within 3 months of discontinuing targeted therapy. Definitions of these patterns of regrowth have not been well described in pLGG. For this reason, the International Pediatric Low-Grade Glioma Coalition, a global group of physicians and scientists, formed the Resistance, Rebound, and Recurrence (R3) working group to study resistance, rebound, and recurrence. A modified Delphi approach was undertaken to produce consensus-based definitions and recommendations for regrowth patterns in pLGG with specific reference to targeted therapies.

Milestones in tumor vascularization and its therapeutic targeting

Research into the mechanisms and manifestations of solid tumor vascularization was launched more than 50 years ago with the proposition and experimental demonstrations that angiogenesis is instrumental for tumor growth and was, therefore, a promising therapeutic target. The biological knowledge and therapeutic insights forthcoming have been remarkable, punctuated by new concepts, many of which were not foreseen in the early decades. This article presents a perspective on tumor vascularization and its therapeutic targeting but does not portray a historical timeline. Rather, we highlight eight conceptual milestones, integrating initial discoveries and recent progress and posing open questions for the future.

Avelumab Plus Intermittent Axitinib in Previously Untreated Patients with Metastatic Renal Cell Carcinoma. The Tide-A Phase 2 Study

BACKGROUND

Combinations of vascular endothelial growth factor receptor (VEGFR) tyrosine kinase inhibitors (TKIs) plus immune checkpoint inhibitor (ICI) against PD1/PD-L1 are the standard first-line therapy for patients with metastatic renal cell carcinoma (mRCC), irrespective of the prognostic class.

OBJECTIVE

To investigate the feasibility and safety of withdrawing VEGFR-TKI but continuing anti-PD1/PD-L1 in patients who achieve a response to their combination.

DESIGN, SETTING, AND PARTICIPANTS

This was a single-arm phase 2 trial in patients with treatment-naïve mRCC with prior nephrectomy, without symptomatic/bulky disease and no liver metastases.

INTERVENTION

Enrolled patients received axitinib + avelumab; after 36 wk of therapy those who achieved a tumour response interrupted axitinib and continued avelumab maintenance until disease progression.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The primary endpoint was the rate of patients without progression 8 wk after the axitinib interruption. The secondary endpoints were the median value for progression-free (mPFS) and overall (mOS) survival and the safety in the overall population.

RESULTS AND LIMITATIONS

Seventy-nine patients were enrolled and 75 were evaluated for efficacy. A total of 29 (38%) patients had axitinib withdrawn, as per the study design, with 72% of them having no progression after 8 wk and thus achieving the primary endpoint. The mPFS of the overall population was 24 mo, while the mOS was not reached. The objective response rate was 76% (12% complete response and 64% partial response), with 19% of patients having stable disease. In the patients who discontinued axitinib, the incidence of adverse events of any grade was 59% for grade 3 and 3% for grade 4. This study was limited by the lack of a comparative arm.

CONCLUSIONS

The TIDE-A study demonstrates that the withdrawal of VEGFR-TKI with ICI maintenance is feasible for selected mRCC patients with evidence of a response to the VEGFR-TKI + ICI combination employed in first-line therapy. Axitinib interruption with avelumab maintenance leads to decreased side effects and should be investigated further as a new strategy to delay tumour progression.

PATIENT SUMMARY

We evaluated whether certain patients with advanced kidney cancer treated with the fist-line combination of axitinib plus avelumab can interrupt the axitinib in case of a tumour response after 36 wk of therapy. We found that axitinib interruption improved the safety of the combination, while the maintenance with avelumab might delay tumour progression.

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.

The role of endothelial cell-pericyte interactions in vascularization and diseases

BACKGROUND

Endothelial cells (ECs) and pericytes (PCs) are crucial components of the vascular system, with ECs lining the inner layer of blood vessels and PCs surrounding capillaries to regulate blood flow and angiogenesis. Intercellular communication between ECs and PCs is vital for the formation, stability, and function of blood vessels. Various signaling pathways, such as the vascular endothelial growth factor/vascular endothelial growth factor receptor pathway and the platelet-derived growth factor-B/platelet-derived growth factor receptor-β pathway, play roles in communication between ECs and PCs. Dysfunctional communication between these cells is associated with various diseases, including vascular diseases, central nervous system disorders, and certain types of cancers.

AIM OF REVIEW

This review aimed to explore the diverse roles of ECs and PCs in the formation and reshaping of blood vessels. This review focused on the essential signaling pathways that facilitate communication between these cells and investigated how disruptions in these pathways may contribute to disease. Additionally, the review explored potential therapeutic targets, future research directions, and innovative approaches, such as investigating the impact of EC-PCs in novel systemic diseases, addressing resistance to antiangiogenic drugs, and developing novel antiangiogenic medications to enhance therapeutic efficacy.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Disordered EC-PC intercellular signaling plays a role in abnormal blood vessel formation, thus contributing to the progression of various diseases and the development of resistance to antiangiogenic drugs. Therefore, studies on EC-PC intercellular interactions have high clinical relevance.

Advanced in vitro models for renal cell carcinoma therapy design

Renal cell carcinoma (RCC) and its principal subtype, clear cell RCC, are the most diagnosed kidney cancer. Despite substantial improvement over the last decades, current pharmacological intervention still fails to achieve long-term therapeutic success. RCC is characterized by a high intra- and inter-tumoral heterogeneity and is heavily influenced by the crosstalk of the cells composing the tumor microenvironment, such as cancer-associated fibroblasts, endothelial cells and immune cells. Moreover, multiple physicochemical properties such as pH, interstitial pressure or oxygenation may also play an important role. These elements are often poorly recapitulated in in vitro models used for drug development. This inadequate recapitulation of the tumor is partially responsible for the current lack of an effective and curative treatment. Therefore, there are needs for more complex in vitro or ex vivo drug screening models. In this review, we discuss the current state-of-the-art of RCC models and suggest strategies for their further development.

Angiogenic signaling pathways and anti-angiogenic therapy for cancer

Angiogenesis, the formation of new blood vessels, is a complex and dynamic process regulated by various pro- and anti-angiogenic molecules, which plays a crucial role in tumor growth, invasion, and metastasis. With the advances in molecular and cellular biology, various biomolecules such as growth factors, chemokines, and adhesion factors involved in tumor angiogenesis has gradually been elucidated. Targeted therapeutic research based on these molecules has driven anti-angiogenic treatment to become a promising strategy in anti-tumor therapy. The most widely used anti-angiogenic agents include monoclonal antibodies and tyrosine kinase inhibitors (TKIs) targeting vascular endothelial growth factor (VEGF) pathway. However, the clinical benefit of this modality has still been limited due to several defects such as adverse events, acquired drug resistance, tumor recurrence, and lack of validated biomarkers, which impel further research on mechanisms of tumor angiogenesis, the development of multiple drugs and the combination therapy to figure out how to improve the therapeutic efficacy. Here, we broadly summarize various signaling pathways in tumor angiogenesis and discuss the development and current challenges of anti-angiogenic therapy. We also propose several new promising approaches to improve anti-angiogenic efficacy and provide a perspective for the development and research of anti-angiogenic therapy.

Unfolded protein response and angiogenesis in malignancies

Cellular stress, arising from accumulation of unfolded proteins, occurs frequently in rapidly proliferating cancer cells. This cellular stress, in turn, activates the unfolded protein response (UPR), an interconnected set of signal transduction pathways that alleviate the proteostatic stress. The UPR is implicated in cancer cell survival and proliferation through upregulation of pro-tumorigenic pathways that ultimately promote malignant metabolism and neoangiogenesis. Here, we reviewed mechanisms of signaling crosstalk between the UPR and angiogenesis pathways, as well as transmissible ER stress and the role in tumor growth and development. To characterize differences in UPR and UPR-mediated angiogenesis in malignancy, we employed a data mining approach using patient tumor data from The Cancer Genome Atlas (TCGA). The analysis of TCGA revealed differences in UPR between malignant samples versus their non-malignant counterparts.

Combining Sunitinib and Bevacizumab for the Management of Advanced Renal Cell Carcinoma: A Phase I/II Trial

BACKGROUND

Tyrosine kinase inhibitors remain a cornerstone in managing metastatic clear cell renal cell carcinoma (RCC). The 4 weeks on/2 weeks off intermittent sunitinib schedule could result in rebound angiogenesis and tumor progression in the 2-week rest period. We propose using bevacizumab during this period for continuous antiangiogenic effects.

METHOD

This was a phase I/II study of patients with advanced clear cell RCC. Sunitinib was given 50 mg daily on a 4-week on/2-week off schedule. Bevacizumab was given on day 29 of each sunitinib cycle. The bevacizumab starting dose was 5 mg/kg, and the dose was escalated to 10 mg if there was no dose-limiting toxicity. The primary endpoints were response rate and progression-free survival (PFS).

RESULTS

Twenty-five patients were recruited. The study was closed prematurely because of poor accrual. No dose-limiting toxicity was observed with 5 mg bevacizumab. One patient achieved a complete response, and 12 achieved a partial response (52% response rate). At a median follow-up of 42.2 months (95%, confidence interval (CI) 32.9 to 51.4), the median PFS duration was 16.5 months (95% CI 4.1-28.8), and the median overall survival time was 33.3 months (95% CI 19.4-47.3). Twenty-two patients (88%) had at least one grade 3 or 4 toxicity; the most common were thrombocytopenia (32%), lymphopenia (32%), hypertension (28%), and fatigue (24%).

CONCLUSION

Continuous angiogenesis blockade by adding bevacizumab to the sunitinib on/off regimen for advanced RCC yields significant antitumor activity with manageable increased toxicity.

Proinflammatory activity of VEGF-targeted treatment through reversal of tumor endothelial cell anergy

Purpose

Ongoing angiogenesis renders the tumor endothelium unresponsive to inflammatory cytokines and interferes with adhesion of leukocytes, resulting in escape from immunity. This process is referred to as tumor endothelial cell anergy. We aimed to investigate whether anti-angiogenic agents can overcome endothelial cell anergy and provide pro-inflammatory conditions.

Experimental design

Tissues of renal cell carcinoma (RCC) patients treated with VEGF pathway-targeted drugs and control tissues were subject to RNAseq and immunohistochemical profiling of the leukocyte infiltrate. Analysis of adhesion molecule regulation in cultured endothelial cells, in a preclinical model and in human tissues was performed and correlated to leukocyte infiltration.

Results

It is shown that treatment of RCC patients with the drugs sunitinib or bevacizumab overcomes tumor endothelial cell anergy. This treatment resulted in an augmented inflammatory state of the tumor, characterized by enhanced infiltration of all major leukocyte subsets, including T cells, regulatory T cells, macrophages of both M1- and M2-like phenotypes and activated dendritic cells. In vitro, exposure of angiogenic endothelial cells to anti-angiogenic drugs normalized ICAM-1 expression. In addition, a panel of tyrosine kinase inhibitors was shown to increase transendothelial migration of both non-adherent and monocytic leukocytes. In primary tumors of RCC patients, ICAM-1 expression was found to be significantly increased in both the sunitinib and bevacizumab-treated groups. Genomic analysis confirmed the correlation between increased immune cell infiltration and ICAM-1 expression upon VEGF-targeted treatment.

Conclusion

The results support the emerging concept that anti-angiogenic therapy can boost immunity and show how immunotherapy approaches can benefit from combination with anti-angiogenic compounds.

Stereotactic body radiotherapy and tyrosine kinase inhibitors in patients with oligometastatic renal cell carcinoma: a multi-institutional study

PURPOSE

Few studies have determined the viability of stereotactic body radiotherapy (SBRT) and tyrosine kinase inhibitors (TKIs) in the treatment of metastatic renal cell carcinoma (mRCC). We examined the results of RCC patients who had five or fewer lesions and were treated with TKI and SBRT.

METHODS

The clinical data of 42 patients with 96 metastases treated between 2011 and 2020 were retrospectively evaluated. The prognostic factors predicting overall survival (OS) and progression-free survival (PFS) were assessed in uni- and multivariable analyses.

RESULTS

Median follow-up and time between TKI therapy and SBRT were 62.3 and 3.7 months, respectively. The 2‑year OS and PFS rates were 58.0% and 51.3%, respectively, and 2‑year local control rate was 94.1% per SBRT-treated lesion. In univariable analysis, the time between TKI therapy and SBRT and treatment response were significant prognostic factors for OS and PFS. In multivariable analysis, a time between TKI therapy and SBRT of less than 3 months and complete response were significant predictors of better OS and PFS. Only 12 patients (28.6%) had a systemic treatment change at a median of 18.2 months after SBRT, mostly in patients with a non-complete treatment response after this therapy. Two patients (4.8%) experienced grade III toxicity, and all side effects observed during metastasis-directed therapy subsided over time.

CONCLUSION

We demonstrated that SBRT in combination with TKIs is an effective and safe treatment option for RCC patients with ≤ 5 metastases. However, distant metastasis was observed in 60% of the patients, indicating that distant disease control still has room for improvement.

Glycocalyx Acts as a Central Player in the Development of Tumor Microenvironment by Extracellular Vesicles for Angiogenesis and Metastasis

Simple Summary

The glycocalyx is a fluffy sugar coat covering the surface of all mammalian cells. While glycocalyx at endothelial cells is a barrier to tumor cell adhesion and transmigration, glycocalyx at tumor cells promotes tumor metastasis. Angiogenesis at primary tumors and the growth of tumor cells at metastatic sites are all affected by the tumor microenvironment, including the blood vasculature, extracellular matrix (ECM), and fibroblasts. Extracellular vesicles (EVs) secreted by the tumor cells and tumor-associated endothelial cells are also considered to be the components of the tumor microenvironment. They can modify tumor vasculature, ECM, and fibroblasts. But how the EVs are generated, secreted, and up taken by the endothelial and tumor cells in the development of the tumor microenvironment are unclear, especially after anti-angiogenic therapy (AAT). The objective of this short review is to summarize the role of the glycocalyx in EV biogenesis, secretion, and uptake, as well as the modulation of the glycocalyx by the EVs.

Abstract

Angiogenesis in tumor growth and progression involves a series of complex changes in the tumor microenvironment. Extracellular vesicles (EVs) are important components of the tumor microenvironment, which can be classified as exosomes, apoptotic vesicles, and matrix vesicles according to their origins and properties. The EVs that share many common biological properties are important factors for the microenvironmental modification and play a vital role in tumor growth and progression. For example, vascular endothelial growth factor (VEGF) exosomes, which carry VEGF, participate in the tolerance of anti-angiogenic therapy (AAT). The glycocalyx is a mucopolysaccharide structure consisting of glycoproteins, proteoglycans, and glycosaminoglycans. Both endothelial and tumor cells have glycocalyx at their surfaces. Glycocalyx at both cells mediates the secretion and uptake of EVs. On the other hand, many components carried by EVs can modify the glycocalyx, which finally facilitates the development of the tumor microenvironment. In this short review, we first summarize the role of EVs in the development of the tumor microenvironment. Then we review how the glycocalyx is associated with the tumor microenvironment and how it is modulated by the EVs, and finally, we review the role of the glycocalyx in the synthesis, release, and uptake of EVs that affect tumor microenvironments. This review aims to provide a basis for the mechanistic study of AAT and new clues to address the challenges in AAT tolerance, tumor angiogenesis and metastasis.

Increased Angiogenesis and Lymphangiogenesis in Adenomyosis Visualized by Multiplex Immunohistochemistry

There is evidence for increased angiogenesis in the (ectopic) endometrium of adenomyosis patients under the influence of vascular endothelial growth factor (VEGF). VEGF stimulates both angiogenesis and lymph-angiogenesis. However, information on lymph vessels in the (ectopic) endometrium of adenomyosis patients is lacking. In this retrospective matched case-control study, multiplex immunohistochemistry was performed on thirty-eight paraffin embedded specimens from premenopausal women who had undergone a hysterectomy at the Amsterdam UMC between 2001 and 2018 to investigate the evidence for (lymph) angiogenesis in the (ectopic) endometrium or myometrium of patients with adenomyosis versus controls with unrelated pathologies. Baseline characteristics of both groups were comparable. In the proliferative phase, the blood and lymph vessel densities were, respectively, higher in the ectopic and eutopic endometrium of patients with adenomyosis than in the endometrium of controls. The relative number of blood vessels without α-smooth muscle actinin (α SMA) was higher in the eutopic and ectopic endometrium of adenomyosis patients versus controls. The level of VEGF staining intensity was highest in the myometrium but did not differ between patients with adenomyosis or controls. The results indicate increased angiogenesis and lymphangiogenesis in the (ectopic) endometrium affected by adenomyosis. The clinical relevance of our findings should be confirmed in prospective clinical studies.

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.

Vorolanib, a novel tyrosine receptor kinase receptor inhibitor with potent preclinical anti-angiogenic and anti-tumor activity

Vorolanib (CM082) is a multi-targeted tyrosine kinase receptor inhibitor with a short half-life and limited tissue accumulation that has been shown to reduce choroidal neovascularization in rats. In this preclinical study, vorolanib demonstrated competitive binding and inhibitory activities with KDR, PDGFRβ, FLT3, and C-Kit, and inhibited RET and AMPKα1 more weakly than sunitinib, indicating more stringent kinase selectivity. Vorolanib inhibited vascular endothelial growth factor (VEGF)-induced proliferation of human umbilical vein endothelial cells (HUVECs) and HUVEC tube formation in vitro. In mouse xenograft models, vorolanib inhibited tumor growth of MV-4-11, A549, 786-O, HT-29, BxPC-3, and A375 cells in a dose-dependent fashion. Complete tumor regression was achieved in the MV-4-11 xenograft model. No significant toxicities were observed in vorolanib groups, whereas a significant negative impact on body weights was observed in the sunitinib group at a dose of 40 mg/kg qd. Overall, vorolanib is a novel multi-kinase receptor inhibitor with potent preclinical anti-angiogenic and anti-tumor activity that is potentially less toxic than other similar kinase inhibitors.

Combination of Anti-Angiogenics and Checkpoint Inhibitors for Renal Cell Carcinoma: Is the Whole Greater Than the Sum of Its Parts?

Simple Summary

Checkpoint inhibitors and anti-angiogenic therapies are treatments that slow the progression of renal cell carcinoma, the most common type of kidney cancer. Checkpoint inhibitors and anti-angiogenic therapies work in different ways. Checkpoint inhibitors help to prevent tumors from hiding from the body’s immune system, while anti-angiogenic therapies slow the development of blood vessels that tumours need to help them to grow. Studies have shown that treatment with combination checkpoint inhibitor plus anti-angiogenic therapy can achieve better outcomes for patients with renal cell carcinoma than treatment with anti-angiogenic therapy alone. In this review, we consider how combination checkpoint inhibitor plus anti-angiogenic therapy works, and we review the current literature to identify evidence to inform clinicians as to the most effective way to use these different types of drugs, either one after the other, or together, for maximum patient benefit.

Abstract

Anti-angiogenic agents, such as vascular endothelial growth factor (VEGF) receptor tyrosine kinase inhibitors and anti-VEGF antibodies, and immune checkpoint inhibitors (CPIs) are standard treatments for advanced renal cell carcinoma (aRCC). In the past, these agents were administered as sequential monotherapies. Recently, combinations of anti-angiogenic agents and CPIs have been approved for the treatment of aRCC, based on evidence that they provide superior efficacy when compared with sunitinib monotherapy. Here we explore the possible mechanisms of action of these combinations, including a review of relevant preclinical data and clinical evidence in patients with aRCC. We also ask whether the benefit is additive or synergistic, and, thus, whether concomitant administration is preferred over sequential monotherapy. Further research is needed to understand how combinations of anti-angiogenic agents with CPIs compare with CPI monotherapy or combination therapy (e.g., nivolumab and ipilimumab), and whether the long-term benefit observed in a subset of patients treated with CPI combinations will also be realised in patients treated with an anti-angiogenic therapy and a CPI. Additional research is also needed to establish whether other elements of the tumour microenvironment also need to be targeted to optimise treatment efficacy, and to identify biomarkers of response to inform personalised treatment using combination therapies.

Continued versus Interrupted Targeted Therapy during Metastasis-Directed Stereotactic Radiotherapy: A Retrospective Multi-Center Safety and Efficacy Analysis

Simple Summary

The increasing use of targeted therapy (TT) has resulted in prolonged disease control and survival in many metastatic cancers. In parallel, stereotactic radiotherapy (SRT) is increasingly performed in patients receiving TT to obtain a durable control of resistant metastases, and thereby to prolong the time to disseminated disease progression and switch of systemic therapy. The aim of this study was to analyze the safety and efficacy of SRT combined with TT in metastatic cancer patients and to assess the influence of continuous vs. interrupted TT during metastasis-directed SRT. The data of 454 SRTs in 158 patients from the international multicenter database (TOaSTT) on metastatic cancer patients treated with SRT and concurrent TT (within 30 days) were analyzed. We found that there was no significant difference in survival, progression, or severe toxicity, whether TT was interrupted during SRT or not. Although any-grade acute and late SRT-related toxicity occurred in 63 (40%) and 52 (33%) patients, severe SRT-related toxicity rates were low (3% and 4%, respectively). The highest toxicity rates were observed for the combination of SRT and EGFRi or BRAF/MEKi, and any grade of toxicity was significantly increased when EGFRi or BRAF/MEKi were continued during SRT. However, this did not account for severe toxicity.

Abstract

The increasing use of targeted therapy (TT) has resulted in prolonged disease control and survival in many metastatic cancers. In parallel, stereotactic radiotherapy (SRT) is increasingly performed in patients receiving TT to obtain a durable control of resistant metastases, and thereby to prolong the time to disseminated disease progression and switch of systemic therapy. The aims of this study were to analyze the safety and efficacy of SRT combined with TT in metastatic cancer patients and to assess the influence of continuous vs. interrupted TT during metastasis-directed SRT. The data of 454 SRTs in 158 patients from the international multicenter database (TOaSTT) on metastatic cancer patients treated with SRT and concurrent TT (within 30 days) were analyzed using Kaplan–Meier and log rank testing. Toxicity was defined by the CTCAE v4.03 criteria. The median FU was 19.9 mo (range 1–102 mo); 1y OS, PFS and LC were 59%, 24% and 84%, respectively. Median TTS was 25.5 mo (95% CI 11–40). TT was started before SRT in 77% of patients. TT was interrupted during SRT in 44% of patients, with a median interruption of 7 (range 1–42) days. There was no significant difference in OS or PFS whether TT was temporarily interrupted during SRT or not. Any-grade acute and late SRT-related toxicity occurred in 63 (40%) and 52 (33%) patients, respectively. The highest toxicity rates were observed for the combination of SRT and EGFRi or BRAF/MEKi, and any-grade toxicity was significantly increased when EGFRi (p = 0.016) or BRAF/MEKi (p = 0.009) were continued during SRT. Severe (≥grade 3) acute and late SRT-related toxicity were observed in 5 (3%) and 7 (4%) patients, respectively, most frequently in patients treated with EGFRi or BRAF/MEKi and in the intracranial cohort. There was no significant difference in severe toxicity whether TT was interrupted before and after SRT or not. In conclusion, SRT and continuous vs. interrupted TT in metastatic cancer patients did not influence OS or PFS. Overall, severe toxicity of combined treatment was rare; a potentially increased toxicity after SRT and continuous treatment with EGFR inhibitors or BRAF(±MEK) inhibitors requires further evaluation.

Second-line treatment in renal cell carcinoma: clinical experience and decision making

Currently, conventional treatments for metastatic RCC (mRCC) include immune-based combination regimens and/or targeted therapies, the latter mainly acting on angiogenesis, a key element of the process of tumor growth and spread. Although these agents proved able to improve patients’ outcomes, drug resistance and disease progression are still experienced by a substantial number of VEGFR-TKIs-treated mRCC patients. Following the inhibition of the VEGF/VEGFRs axis, two strategies have emerged: either specifically targeting resistance pathways, at the same time continuing to inhibit angiogenesis, or using a completely different approach aimed at re-activating the immune system through the use of inhibitors of specific negative immune checkpoints. These two approaches, practically represented by the use of either cabozantinib or nivolumab, seem to remain a rational therapeutic approach also when first-line immune-based combinations are used. The objective of this study is to design a preferential therapeutic pathway for the second-line treatment of mRCC. The procedure applied in this project was a group discussion, based on the Nominal Group Technique (NGT) method in a meeting session, aimed at defining the therapeutic choice for the second-line treatment of mRCC. The NGT process defined the most relevant parameters that, according to the interviewed panelists, clinicians should consider for the selection of the second-line therapy in the context of advanced renal cell carcinoma of mRCC. The algorithm developed for the treatment selection as a result of this process should thus be considered by clinicians as reference for therapy selection.

When the MET receptor kicks in to resist targeted therapies

Although targeted therapies have increased the life expectancy of patients with druggable molecular alterations directly involved in tumor development, the efficacy of these therapies is limited by acquired resistances leading to treatment failure. Most targeted therapies, including ones exploiting therapeutic antibodies and kinase inhibitors, are directed against receptor tyrosine kinases (RTKs) or major signaling hubs. Resistances to these therapies arise when inhibition of these targets is bypassed through activation of alternative signaling pathways. In recent years, activation of the receptor tyrosine kinase MET has been shown to promote resistance to various targeted therapies. This casts MET as important actor in resistance. In this review, we describe how the MET receptor triggers resistance to targeted therapies against RTKs such as EGFR, VEGFR, and HER2 and against signaling hubs such as BRAF. We also describe how MET can be its own resistance factor, as illustrated by on-target resistance of lung tumors harboring activating mutations causing MET exon 14 skipping. Interestingly, investigation of all these situations reveals functional physiological relationships between MET and the target of the therapy to which the cancer becomes resistant, suggesting that resistance stems from preexisting mechanisms. Identification of MET as a resistance factor opens the way to co-treatment strategies that are being tested in current clinical trials.

Survival After Combining Stereotactic Body Radiation Therapy and Tyrosine Kinase Inhibitors in Patients With Metastatic Renal Cell Carcinoma

Background

Stereotactic body radiation therapy (SBRT) and tyrosine kinase inhibitors (TKIs) are effective treatments for metastatic renal cell carcinoma, but data on combining these two modalities are scarce. We aimed to investigate the survival outcomes of SBRT plus TKIs.

Methods

Data of patients treated with TKIs from December 2007 to June 2019 were collected. Patients received SBRT plus TKIs (TKI + SBRT group) or TKIs alone (TKI alone group). Local control (LC), time to change of systemic therapy (TTS), and overall survival (OS) were assessed.

Results

A total of 190 patients were included, and 85 patients received TKI + SBRT. The 2-year LC rate was 92.8%. The median OS in the TKI + SBRT group was significantly longer than that of the TKI alone group (63.2 vs 29.8 months; P < 0.001). In multivariate analysis, IMDC intermediate (HR 1.96; 95% CI 1.10-3.48; P = 0.022) and poor risk (HR 2.43; 95% CI 1.25-4.75; P = 0.009), oligometastasis (HR 0.41; 95% CI 0.26-0.65; P < 0.001), and the addition of SBRT (HR 0.48; 95% CI 0.31-0.75; P = 0.001) were prognostic factors for OS. Patients with oligometastasis (P = 0.009) and those with IMDC favorable (P = 0.044) or intermediate (P = 0.002) risk had significantly longer OS with TKI + SBRT. The median TTS were 21.5, 6.4, and 9.0 months in patients receiving SBRT before first-line TKI failure, SBRT after first-line TKI failure, and first-line TKI alone (P < 0.001). Five patients (5.9%) experienced SBRT-related grade 3 toxicities.

Conclusions

Combining SBRT with TKIs is tolerable and associated with longer OS in selected patients, such as those with oligometastasis and favorable or intermediate risk.

Resistance Mechanisms of Anti-angiogenic Therapy and Exosomes-Mediated Revascularization in Cancer

Anti-angiogenic therapies (AATs) have been widely used for cancer treatment. But the beneficial effects of AATs are short, because AAT-induced tumor revascularization facilitates the tumor relapse. In this mini-review, we described different forms of tumor neovascularization and revascularization including sprouting angiogenesis, vessel co-option, intussusceptive angiogenesis, and vasculogenic mimicry, all of which are closely mediated by vascular endothelial growth factor (VEGF), angiopoietins, matrix metalloproteinases, and exosomes. We also summarized the current findings for the resistance mechanisms of AATs including enhancement in pro-angiogenic cytokines, heterogeneity in tumor-associated endothelial cells (ECs), crosstalk between tumor cells and ECs, masking of extracellular vesicles, matrix stiffness and contributions from fibroblasts, macrophages and adipocytes in the tumor microenvironment. We highlighted the revascularization following AATs, particularly the role of exosome stimulating factors such as hypoxia and miRNA, and that of exosomal cargos such as cytokines, miRNAs, lncRNAs, and circRNAs from the tumor ECs in angiogenesis and revascularization. Finally, we proposed that renormalization of tumor ECs would be a more efficient cancer therapy than the current AATs.

Kidney cancer PDOXs reveal patient-specific pro-malignant effects of antiangiogenics and its molecular traits

An open debate in antiangiogenic therapies is about their consequence on tumor invasiveness and metastasis, which is undoubtedly relevant for patients currently treated with antiangiogenics, such as renal cell carcinoma patients. To address, this we developed an extensive series of 27 patient biopsy‐derived orthotopic xenograft models (Ren‐PDOX) that represent inter‐patient heterogeneity. In specific tumors, antiangiogenics produced increased invasiveness and metastatic dissemination, while in others aggressiveness remained unchanged. Mechanistically, species‐discriminative RNA sequencing identified a tumor cell‐specific differential expression profile associated with tumor progression and aggressivity in TCGA RCC patients. Gene filtering using an invasion‐annotated patient series pinpointed two candidate genes, of which ALDH1A3 differentiated the pro‐invasive subtype of Ren‐PDOXs. Validation in an independent series of 15 antiangiogenic‐treated patients confirmed that pre‐treatment ALDH1A3 can significantly discriminate patients with pro‐aggressive response upon treatment. Overall, results confirm that effects of antiangiogenic drugs on tumor invasion and metastasis are heterogeneous and may profoundly affect the natural progression of tumors and promote malignancy. Furthermore, we identify a specific molecular biomarker that could be used to select patients that better benefit from treatment.

Synergizing sunitinib and radiofrequency ablation to treat hepatocellular cancer by triggering the antitumor immune response

Background

Minimally invasive radiofrequency ablation (RFA) is used as a first-line treatment option for hepatocellular cancer (HCC) with the weaknesses of incomplete ablation, tumor recurrence, and inferior outcomes. To overcome this limitation, we proposed to develop sunitinib-RFA integrated therapy with a potential of activating anti-HCC immune response.

Methods

Using our unique murine model, we developed a novel RFA platform with a modified human cardiac RF generator. Therapeutic efficacy of sunitinib–RFA combined treatment in HCC was tested in this platform. Tumor progression was monitored by MRI; tumor necrosis and apoptosis were detected by H&E and terminal deoxynucleotidyl transferase dUTP nick end labeling; immune reaction was defined by flow cytometry; and signaling molecules were examined with real-time PCR (qPCR), western blot, and immunohistochemical staining.

Results

A significantly reduced tumor growth and extended lift span were observed in the mice receiving combined treatment with RFA and sunitinib. This combined treatment significantly increased the frequency of CD8⁺ T cell, memory CD8⁺ T cell, and dendritic cells (DCs); decreased the frequency of regulatory T cells; and activated tumor-specific antigen (TSA) immune response in tumor microenvironment. We found that RFA caused PD-1 upregulation in tumor-infiltrated T cells by boosting hepatocyte growth factor (HGF) expression, which was suppressed by sunitinib treatment. We have also demonstrated that sunitinib suppressed VEGF’s effect in enhancing PD-L1 expression in DCs and attenuated heat-sink effect. The results indicate that RFA induced tumor destruction and release of in situ TSAs which can activate a tumoricidal immune response in sunitinib-treated mice, significantly improving anti-HCC therapeutic efficacy.

Conclusions

Sunitinib enables RFA-released in situ TSA to ignite an effective anti-tumor immune response by suppressing HGF and VEGF signaling pathways. Sunitinib–RFA as a synergistic therapeutic approach significantly suppresses HCC growth.

A Phase I Open-Label Clinical Trial Evaluating the Therapeutic Vaccine hVEGF26-104/RFASE in Patients with Advanced Solid Malignancies

LESSONS LEARNED

The novel therapeutic vaccine hVEGF_26-104 /RFASE was found to be safe and well tolerated in patients with cancer. hVEGF_26-104 /RFASE failed to induce seroconversion against native hVEGF₁₆₅ and, accordingly, neither a decrease in circulating vascular endothelial growth factor (VEGF) levels nor clinical benefit was observed. Remarkably, hVEGF_26-104 /RFASE induced VEGF₁₆₅ -neutralizing antibodies in a nonhuman primate model. The absence of seroconversion in human calls for caution in the interpretation of efficacy of human vaccines in nonhuman primates.

BACKGROUND

Targeting vascular endothelial growth factor-A (VEGF) is a well-established anticancer therapy. We designed a first-in-human clinical trial to investigate the safety and immunogenicity of the novel vaccine hVEGF_26-104 /RFASE.

METHODS

Patients with advanced solid malignancies with no standard treatment options available were eligible for this phase I study with a 3+3 dose-escalation design. On days 0, 14, and 28, patients received intramuscular hVEGF_26-104 , a truncated synthetic three-dimensional (3D)-structured peptide mimic covering the amino acids 26-104 of the human VEGF₁₆₅ isoform, emulsified in the novel adjuvant Raffinose Fatty Acid Sulphate Ester (RFASE), a sulpholipopolysaccharide. Objectives were to determine safety, induction of VEGF-neutralizing antibodies, and the maximum tolerated dose. Blood was sampled to measure VEGF levels and antibody titers.

RESULTS

Eighteen of 27 enrolled patients received three immunizations in six different dose-levels up to 1,000 μg hVEGF_26-104 and 40 mg RFASE. No dose-limiting toxicity was observed. Although in four patients an antibody titer against hVEGF_26-104 was induced (highest titer: 2.77 ¹⁰ log), neither a reduction in VEGF levels nor neutralizing antibodies against native VEGF₁₆₅ were detected.

CONCLUSION

Despite having an attractive safety profile, hVEGF_26-104 /RFASE was not able to elicit seroconversions against native VEGF₁₆₅ and, consequently, did not decrease circulating VEGF levels. Deficient RFASE adjuvant activity, as well as dominant immunoreactivity toward neoepitopes, may have impeded hVEGF_26-104 /RFASE's efficacy in humans.

Angiogenesis in gynecological cancers and the options for anti-angiogenesis therapy

Angiogenesis is required in cancer, including gynecological cancers, for the growth of primary tumors and secondary metastases. Development of anti-angiogenesis therapy in gynecological cancers and improvement of its efficacy have been a major focus of fundamental and clinical research. However, survival benefits of current anti-angiogenic agents, such as bevacizumab, in patients with gynecological cancer, are modest. Therefore, a better understanding of angiogenesis and the tumor microenvironment in gynecological cancers is urgently needed to develop more effective anti-angiogenic therapies, either or not in combination with other therapeutic approaches. We describe the molecular aspects of (tumor) blood vessel formation and the tumor microenvironment and provide an extensive clinical overview of current anti-angiogenic therapies for gynecological cancers. We discuss the different phenotypes of angiogenic endothelial cells as potential therapeutic targets, strategies aimed at intervention in their metabolism, and approaches targeting their (inflammatory) tumor microenvironment.

Integrating Phenotypic Search and Phosphoproteomic Profiling of Active Kinases for Optimization of Drug Mixtures for RCC Treatment

Combined application of multiple therapeutic agents presents the possibility of enhanced efficacy and reduced development of resistance. Definition of the most appropriate combination for any given disease phenotype is challenged by the vast number of theoretically possible combinations of drugs and doses, making extensive empirical testing a virtually impossible task. We have used the streamlined-feedback system control (s-FSC) technique, a phenotypic approach, which converges to optimized drug combinations (ODC) within a few experimental steps. Phosphoproteomics analysis coupled to kinase activity analysis using the novel INKA (integrative inferred kinase activity) pipeline was performed to evaluate ODC mechanisms in a panel of renal cell carcinoma (RCC) cell lines. We identified different ODC with up to 95% effectivity for each RCC cell line, with low doses (ED_5-25) of individual drugs. Global phosphoproteomics analysis demonstrated inhibition of relevant kinases, and targeting remaining active kinases with additional compounds improved efficacy. In addition, we identified a common RCC ODC, based on kinase activity data, to be effective in all RCC cell lines under study. Combining s-FSC with a phosphoproteomic profiling approach provides valuable insight in targetable kinase activity and allows for the identification of superior drug combinations for the treatment of RCC.

Identification of low-dose multidrug combinations for sunitinib-naive and pre-treated renal cell carcinoma

Background

Combinations of drugs can improve the efficacy of cancer treatment, enable the reduction of side effects and the occurrence of acquired drug resistance.

Methods

We approached this challenge mathematically by using the validated technology called the Therapeutically Guided Multidrug Optimization (TGMO) method. In a set of genetically distinct human renal cell carcinoma (RCC) cell lines, either treated chronically with sunitinib (−ST) or sunitinib-naive, we identified cell line-specific low-dose-optimised drug combinations (ODC).

Results

Six cell-type-specific low-dose drug combinations for three sunitinib-naive as well as three sunitinib pre-treated cells were established. These ODCs effectively inhibited the RCC cell metabolic activity while being ineffective in non-cancerous cells. Based on a single screening test and three searches, starting with ten drugs, we identified highly efficacious drug mixtures containing four drugs. All ODCs contained AZD4547 (FGFR signalling pathway inhibitor) and pictilisib (pan-phosphatidylinositol 3-kinase inhibitor), but varied in the third and fourth drug. ODC treatment significantly decreased cell metabolic activity (up to 70%) and induced apoptosis, independent of the pretreatment with sunitinib. The ODCs outperformed sunitinib, the standard care for RCC. Moreover, short-term starvation potentiated the ODC activity. The translation of the 2D-based results to 3D heterotypic co-culture models revealed significant inhibition of the spheroid growth (up to 95%).

Conclusion

We demonstrate a promising low-dose drug combination development to obtain drug combinations effective in naive as well as resistant tumours. Nevertheless, we emphasise the need for further mechanistic investigation and preclinical development.

Angiogenesis in Breast Cancer Progression, Diagnosis, and Treatment

Angiogenesis is a significant event in a wide range of healthy and diseased conditions. This process frequently involves vasodilation and an increase in vascular permeability. Numerous players referred to as angiogenic factors, work in tandem to facilitate the outgrowth of endothelial cells (EC) and the consequent vascularity. Conversely, angiogenic factors could also feature in pathological conditions. Angiogenesis is a critical factor in the development of tumors and metastases in numerous cancers. An increased level of angiogenesis is associated with decreased survival in breast cancer patients. Therefore, a good understanding of the angiogenic mechanism holds a promise of providing effective treatments for breast cancer progression, thereby enhancing patients' survival. Disrupting the initiation and progression of this process by targeting angiogenic factors such as vascular endothelial growth factor (Vegf)-one of the most potent member of the VEGF family- or by targeting transcription factors, such as Hypoxia-Inducible Factors (HIFs) that act as angiogenic regulators, have been considered potential treatment options for several types of cancers. The objective of this review is to highlight the mechanism of angiogenesis in diseases, specifically its role in the progression of malignancy in breast cancer, as well as to highlight the undergoing research in the development of angiogenesis-targeting therapies.

Survival Outcomes After Adding Stereotactic Body Radiotherapy to Metastatic Renal Cell Carcinoma Patients Treated With Tyrosine Kinase Inhibitors

OBJECTIVE

Long-lasting control is rarely achieved with tyrosine kinase inhibitors (TKI) alone in metastatic renal cell carcinoma (mRCC). Our study aimed to investigate the survival outcomes of adding stereotactic body radiotherapy (SBRT) to TKI in mRCC.

MATERIALS AND METHODS

From September 2015 to September 2018, 56 patients treated with TKI received SBRT for 103 unresectable lesions. A total of 24 and 32 patients were irradiated before and after TKI failure, respectively. Overall survival (OS) was calculated from metastases. Progression-free survival (PFS) was calculated from SBRT.

RESULTS

Overall, 10, 32, and 12 patients had International Metastatic Renal Cell Carcinoma Database Consortium favorable, intermediate, and poor risk. Median follow-up was 21.7 months (range, 5.1 to 110.6 mo). Median OS was 61.2 months. The median PFS was 11.5 months, while the 2-year LC rate was 94%. Sixteen (34%) lesions achieved complete response (CR) in patients irradiated before TKI failure, whereas only 4 (7%) lesions yielded CR in those irradiated after TKI failure (P=0.001). The median PFS in CR group was significantly longer than that of non-CR group (18.9 vs. 7.1 mo; P=0.003). The 5-year OS in CR group was 86%, compared with 48% in non-CR group (P=0.010). Four (7%) patients experienced Grade 3 toxicity.

CONCLUSIONS

Adding SBRT to TKI is safe and seems to improve survival in mRCC. Patients irradiated before TKI failure have higher CR rate, and the favorable local response might turn into survival benefit.

A Transient Pseudosenescent Secretome Promotes Tumor Growth after Antiangiogenic Therapy Withdrawal

VEGF receptor tyrosine kinase inhibitors (VEGFR TKIs) approved to treat multiple cancer types can promote metastatic disease in certain limited preclinical settings. Here, we show that stopping VEGFR TKI treatment after resistance can lead to rebound tumor growth that is driven by cellular changes resembling senescence-associated secretory phenotypes (SASPs) known to promote cancer progression. A SASP-mimicking antiangiogenic therapy-induced secretome (ATIS) was found to persist during short withdrawal periods, and blockade of known SASP regulators, including mTOR and IL-6, could blunt rebound effects. Critically, senescence hallmarks ultimately reversed after long drug withdrawal periods, suggesting that the transition to a permanent growth-arrested senescent state was incomplete and the hijacking of SASP machinery ultimately transient. These findings may account for the highly diverse and reversible cytokine changes observed in VEGF inhibitor-treated patients, and suggest senescence-targeted therapies ("senotherapeutics")-particularly those that block SASP regulation-may improve outcomes in patients after VEGFR TKI failure.

Colorectal Cancer Growth Retardation through Induction of Apoptosis, Using an Optimized Synergistic Cocktail of Axitinib, Erlotinib, and Dasatinib

Patients with advanced colorectal cancer (CRC) still depend on chemotherapy regimens that are associated with significant limitations, including resistance and toxicity. The contribution of tyrosine kinase inhibitors (TKIs) to the prolongation of survival in these patients is limited, hampering clinical implementation. It is suggested that an optimal combination of appropriate TKIs can outperform treatment strategies that contain chemotherapy. We have previously identified a strongly synergistic drug combination (SDC), consisting of axitinib, erlotinib, and dasatinib that is active in renal cell carcinoma cells. In this study, we investigated the activity of this SDC in different CRC cell lines (SW620, HT29, and DLD-1) in more detail. SDC treatment significantly and synergistically decreased cell metabolic activity and induced apoptosis. The translation of the in-vitro-based results to in vivo conditions revealed significant CRC tumor growth inhibition, as evaluated in the chicken chorioallantoic membrane (CAM) model. Phosphoproteomics analysis of the tested cell lines revealed expression profiles that explained the observed activity. In conclusion, we demonstrate promising activity of an optimized mixture of axitinib, erlotinib, and dasatinib in CRC cells, and suggest further translational development of this drug mixture.

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.

Gold nanoparticles and angiogenesis: molecular mechanisms and biomedical applications

Angiogenesis is the formation of new blood vessels from pre-existing vessels. It is a highly regulated process as determined by the interplay between pro-angiogenic and anti-angiogenic factors. Under certain conditions the balance between angiogenesis stimulators and inhibitors is altered, which results in a shift from physiological to pathological angiogenesis. Therefore, the goal of therapeutic targeting of angiogenic process is to normalize vasculature in target tissues by enhancing angiogenesis in disease conditions of reduced vascularity and blood flow, such as tissue ischemia, or alternatively to inhibit excessive and abnormal angiogenesis in disorders like cancer. Gold nanoparticles (AuNPs) are special particles that are generated by nanotechnology and composed of an inorganic core containing gold which is encircled by an organic monolayer. The ability of AuNPs to alter vasculature has captured recent attention in medical literature as potential therapeutic agents for the management of pathologic angiogenesis. This review provides an overview of the effects of AuNPs on angiogenesis and the molecular mechanisms and biomedical applications associated with their effects. In addition, the main synthesis methods, physical properties, uptake mechanisms, and toxicity of AuNPs are briefly summarized.

Pazopanib in advanced soft tissue sarcomas

Pazopanib is the first and only tyrosine kinase inhibitor currently approved for the treatment of multiple histological subtypes of soft tissue sarcoma (STS). Initially developed as a small molecule inhibitor of vascular endothelial growth factor receptors, preclinical work indicates that pazopanib exerts an anticancer effect through the inhibition of both angiogenic and oncogenic signaling pathways. Following the establishment of optimal dosing and safety profiles in early phase studies and approval for the treatment of advanced renal cell carcinoma, pazopanib was investigated in STS. A landmark phase III randomized study demonstrated improved progression-free survival with pazopanib compared to that with placebo in pretreated patients with STS of various subtypes. The efficacy of pazopanib in specific STS subtypes has been further described in real-world-based case series in both mixed and subtype-specific STS cohorts. At present, there are no clinically validated predictive biomarkers for use in selecting patients with advanced STS for pazopanib therapy, limiting the clinical effectiveness and cost-effectiveness of the drug. In this review, we summarize the preclinical and clinical data for pazopanib, outline the evidence base for its effect in STS and explore reported studies that have investigated putative biomarkers.

Epithelial-mesenchymal transition as a mechanism of resistance to tyrosine kinase inhibitors in clear cell renal cell carcinoma

Tyrosine kinase inhibitors (TKIs) are widely accepted as treatment for metastatic clear cell renal cell carcinoma (ccRCC). However, most patients eventually experience disease progression despite TKI treatment, even if the initial response is favorable. To define the underlying mechanism of TKI resistance, 10 TKI-treated metastatic ccRCC cases in which tumor samples were harvested before treatment and immediately after disease progression were examined. Gene expression profiles and copy number variations of matched pre- and post-treatment tumor samples were investigated. Altered biologic characteristics were confirmed in sunitinib-resistant ccRCC cell lines, which were generated by long-term treatment with sunitinib-containing media. Gene transcript levels related to the cell cycle and epithelial-mesenchymal transition (EMT) were significantly upregulated in the treated tumor samples compared with the pre-treatment samples. The mitotic count and sarcomatoid component were significantly increased in treated tumor samples. Alteration of EMT-related genes was also demonstrated in a sunitinib-resistant ccRCC cell line that showed enhanced migration and invasion compared to the parent cell line. siRNA-induced inhibition of EMT-related gene expression significantly suppressed the migration and invasion capacity of TKI-resistant cell lines. The present study shows that both ccRCC cases that progressed after TKI treatment and sunitinib-resistant ccRCC cell lines demonstrated alteration of EMT-related gene expression and enhancement of EMT-related behavior. These results suggest that EMT may explain the aggressive behavior of TKI-resistant ccRCC.

Targeting Tumor Vascular CD99 Inhibits Tumor Growth

CD99 (MIC2; single-chain type-1 glycoprotein) is a heavily O-glycosylated transmembrane protein (32 kDa) present on leukocytes and activated endothelium. Expression of CD99 on endothelium is important in lymphocyte diapedesis. CD99 is a diagnostic marker for Ewing's Sarcoma (EWS), as it is highly expressed by these tumors. It has been reported that CD99 can affect the migration, invasion and metastasis of tumor cells. Our results show that CD99 is also highly expressed in the tumor vasculature of most solid tumors. Furthermore, we found that in vitro CD99 expression in cultured endothelial cells is induced by starvation. Targeting of murine CD99 by a conjugate vaccine, which induced antibodies against CD99 in mice, resulted in inhibition of tumor growth in both a tumor model with high CD99 (Os-P0109 osteosarcoma) and low CD99 (CT26 colon carcinoma) expression. We demonstrated that vaccination against CD99 is safe, since no toxicity was observed in mice with high antibody titers against CD99 in their sera during a period of almost 11 months. Targeting of CD99 in humans is more complicated due to the fact that the human and mouse CD99 protein are not identical. We are the first to show that growth factor activated endothelial cells express a distinct human CD99 isoform. We conclude that our observations provide an opportunity for specific targeting of CD99 isoforms in human tumor vasculature.

Precision treatment in colorectal cancer: Now and the future

Until recently, a one‐drug‐fits‐all model was applied to every patient diagnosed with the same condition. But not every condition is the same, and this has led to many cases of ineffective treatment. Pharmacogenetics is increasingly used to stratify patients for precision medicine treatments, for instance, the UGT1A1*28 polymorphism as a dosage indicator for the use of irinotecan as well as epidermal growth factor receptor (EGFR) immunohistochemistry and KRAS Proto‐Oncogene (KRAS) exon 2 mutation tests for determining the likelihood of treatment response to cetuximab or panitumumab treatment in metastatic colorectal cancer (CRC). The other molecular subtypes, such as KRAS exon 3/4, B‐Raf Proto‐Oncogene, NRAF, PIK3CA, and PETN, were also reported as potential new pharmacogenetic targets for the current and the newly discovered anticancer drugs. In addition to next‐generation sequencing (NGS), primary tumor cells for in vivo and in vitro drug screening, imaging biomarker 3′‐Deoxy‐3′‐18F‐fluorothymidine positron emission tomography, and circulating tumor DNA (ctDNA) detection methods are being developed and may represent the future direction of precision medicine. This review will discuss the current environment of precision medicine, including clinically approved targeted therapies, the latest potential therapeutic agents, and the ongoing pharmacogenetic trials for CRC patients.

Targeting angiogenesis in metastatic renal cell carcinoma

INTRODUCTION

Renal cell carcinoma (RCC), and particularly its clear cell histological subtype, is commonly characterized by genetic alterations in the Von Hippel Lindau (VHL) tumor suppressor gene, leading to a typically exasperated angiogenesis. However, other biological and genetic peculiarities contribute to differentiate this malignancy from other solid tumors, including its immunogenicity. Areas covered: This review focuses on the present and future role of antiangiogenic drugs, administered either alone (as it has been in the past few years), or in combination with other agents (e.g. immune checkpoint inhibitors), in the treatment of metastatic RCC. Expert commentary: Due to its peculiar pathogenesis, it is unrealistic to expect to be able to get rid of antiangiogenic agents for the treatment of this disease; however, we do expect that combinations of VEGF/VEGFRs-targeting agents with immune checkpoint inhibitors will gradually replace antiangiogenic monotherapies as the standard of care, at least in the first line setting of metastatic RCC patients. Biomarkers discovery remains the highest priority in order to further improve the percentage of patients benefitting of our treatment.

Oncofoetal insulin receptor isoform A marks the tumour endothelium; an underestimated pathway during tumour angiogenesis and angiostatic treatment

Background

In a genomic screen for determinants of the tumour vasculature, we identified insulin receptor (INSR) to mark the tumour endothelium. As a functional role for insulin/INSR in cancer has been suggested and markers of the tumour endothelium may be attractive therapeutic targets, we investigated the role of INSR in angiogenesis.

Methods

In a genomic screen for determinants of the tumour vasculature we identified insulin receptor to mark the tumour endothelium.

Results

The current report demonstrates the following: (i) the heavy overexpression of INSR on angiogenic vasculature in human tumours and the correlation to short survival, (ii) that INSR expression in the tumour vasculature is mainly representing the short oncofoetal and non-metabolic isoform INSR-A, (iii) the angiogenic activity of insulin on endothelial cells (EC) in vitro and in vivo, (iv) suppression of proliferation and sprouting of EC in vitro after antibody targeting or siRNA knockdown, and (v) inhibition of in vivo angiogenesis in the chicken chorioallantoic membrane (CAM) by anti-INSR antibodies. We additionally show, using preclinical mouse as well as patient data, that treatment with the inhibitor sunitinib significantly reduces the expression of INSR-A.

Conclusions

The current study underscores the oncogenic impact of INSR and suggests that targeting the INSR-A isoform should be considered in therapeutic settings.

Combined treatment with apatinib and docetaxel in A549 xenograft mice and its cellular pharmacokinetic basis

Apatinib, a small-molecule inhibitor of VEGFR-2, has attracted much attention due to its encouraging anticancer activity in third-line clinical treatment for many malignancies, including non-small cell lung cancer (NSCLC). Its usage in second-line therapy with chemotherapeutic drugs is still under exploration. In this study we investigated the antitumor effect of apatinib combined with docetaxel against NSCLC and its cellular pharmacokinetic basis. A549 xenograft nude mice were treated with apatinib (100 mg/kg every day for 20 days) combined with docetaxel (8 mg/kg, ip, every four days for 5 times). Apatinib significantly enhanced the antitumor effect of docetaxel and alleviated docetaxel-induced liver damage as well as decreased serum transaminases (ALT and AST). LC-MS/MS analysis revealed that apatinib treatment significantly increased the docetaxel concentration in tumors (up to 1.77 times) without enhancing the docetaxel concentration in the serum, heart, liver, lung and kidney. Furthermore, apatinib decreased docetaxel-induced upregulation of P-glycoprotein in tumors. The effects of apatinib on the uptake, efflux and subcellular distribution of docetaxel were investigated in A549 and A549/DTX (docetaxel-resistant) cells in vitro. A cellular pharmacokinetic study revealed that apatinib significantly increased cellular/subcellular accumulation (especially in the cytosol) and decreased the efflux of docetaxel in A549/DTX cells through P-gp, while apatinib exerted no significant effect on the cellular pharmacokinetics of docetaxel in A549 cells. Consequently, the IC₅₀ value of docetaxel in A549/DTX cells was more significantly decreased by apatinib than that in A549 cells. These results demonstrate that apatinib has potential for application in second-line therapy combined with docetaxel for NSCLC patients, especially for docetaxel-resistant or multidrug-resistant patients.

Targeted Silencing of Kim-1 Inhibits the Growth of Clear Cell Renal Cell Carcinoma Cell Line 786-0 In Vitro and In Vivo

To investigate the effect of Kim-1 on 786-0 cells in vivo and in vitro, several experiments such as quantitative real-time PCR, Western blot, MTT, colony formation, and flow cytometry were performed to evaluate the biological behavior of 786-0 cells treated with Kim-1 siRNA. Furthermore, the tumor xenograft model was applied to BALB/c nude mice to assess the effect of Kim-1 silencing. Lentivirus-mediated RNAi effectively silenced Kim-1 in 786-0 cells. Kim-1 knockdown significantly inhibited the proliferation and colony formation ability of 786-0 cells (p < 0.01). The cell cycle of 786-0 cells was arrested in the G0/G1 phase (p < 0.01). Early and late apoptosis were significantly increased in the Kim-1 siRNA cells (p < 0.01). In addition, growth of 786-0 cells was significantly inhibited in the Kim-1-silenced mice. In conclusion, knockdown of Kim-1 inhibits the growth of 786-0 cells in vitro and in vivo, indicating that Kim-1 could be used as a potential target for clear cell renal cell carcinoma therapy.

Consensus guidelines for the use and interpretation of angiogenesis assays

The formation of new blood vessels, or angiogenesis, is a complex process that plays important roles in growth and development, tissue and organ regeneration, as well as numerous pathological conditions. Angiogenesis undergoes multiple discrete steps that can be individually evaluated and quantified by a large number of bioassays. These independent assessments hold advantages but also have limitations. This article describes in vivo, ex vivo, and in vitro bioassays that are available for the evaluation of angiogenesis and highlights critical aspects that are relevant for their execution and proper interpretation. As such, this collaborative work is the first edition of consensus guidelines on angiogenesis bioassays to serve for current and future reference.

Dynamic 18F-FLT PET imaging of spatiotemporal changes in tumor cell proliferation and vasculature reveals the mechanistic actions of anti-angiogenic therapy

Anti-angiogenic therapies target tumor vasculature and tumor cells, thus a concurrent assessment of these targets would lead to a greater understanding of therapeutic resistance and facilitate development of improved therapeutic strategies. We utilize dynamic 3'-deoxy-3'-¹⁸F-fluorothymidine positron emission tomography (¹⁸F-FLT PET) scanning to concurrently assess changes in tumor cell proliferation and vasculature during anti-angiogenic therapy, providing insight into how these therapies may be used effectively with combination chemotherapy. Thirty-three patients with advanced solid malignancies underwent treatment with vascular endothelial growth factor receptor inhibitor (VEGFR-TKI) axitinib on an intermittent schedule (two-weeks-on/one-week-off). Patients had up to three dynamic ¹⁸F-FLT PET/CT scans: at baseline, after two weeks of continuous VEGFR-TKI treatment, and following a one week treatment break. ¹⁸F-FLT kinetics were analyzed using a two-tissue compartment kinetic model. Kinetic parameters V _b and K ₁ were extracted to quantify changes in tumor vasculature and the ¹⁸F-FLT flux constant K _i was calculated to quantify changes in tumor cell proliferation. Two weeks of continuous axitinib exposure led to decreases in V _b (median -21%, P  =  0.07), K ₁ (median -39%, P  <  0.01), and K _i (median -37%, P  <  0.01), corresponding to diminished tumor vasculature and cell proliferation that may antagonize treatment with concurrent chemotherapy. Axitinib treatment breaks led to significant increases in V _b (median  +42%, P  <  0.01), K ₁ (median  +46%, P  <  0.01), and K _i (median  +39%, P  <  0.01) that is suggestive of an optimal time to schedule synergistic chemotherapy. Significant negative correlations (rho  ⩽  -0.70, P  <  0.01) were found between changes in tumor vasculature during axitinib exposure weeks and changes in tumor vasculature during treatment breaks. Imaging with dynamic ¹⁸F-FLT PET revealed new insights relating to the interplay of vascular and proliferative pharmacodynamics of axitinib therapy, facilitating a greater understanding of the mechanistic actions of VEGFR-TKIs. Increases in tumor vasculature and cell proliferation during VEGFR-TKI treatment breaks, suggests this period is an optimal time to schedule synergistic chemotherapy and warrants further investigation.

Targeting the renin-angiotensin system to improve cancer treatment: Implications for immunotherapy

Renin-angiotensin system (RAS) inhibitors (RASi)-widely prescribed for the treatment of cardiovascular diseases-have considerable potential in oncology. The RAS plays a crucial role in cancer biology and affects tumor growth and dissemination directly and indirectly by remodeling the tumor microenvironment. We review clinical data on the benefit of RASi in primary and metastatic tumors and propose that, by activating immunostimulatory pathways, these inhibitors can enhance immunotherapy of cancer.