Mechanisms of resistance to anti-angiogenesis therapies

The adjunctive use of Leukocyte-Platelet Rich Fibrin (L-PRF) in the management of Medication Related Osteonecrosis of the Jaw (MRONJ): a retrospective observational study

PURPOSE

Medication related osteonecrosis of the jaw (MRONJ) is a risk for patients taking anti-resorptive or anti-angiogenic medications. The American Association of Oral and Maxillofacial Surgeons (AAMOS) has classified MRONJ in stages to reflect the severity of the disease and allows implementation of suitable treatment pathways. MRONJ risk is < 5% in cancer patients and < 0.05% in osteoporosis patients. Management is subdivided into operative and non-operative, with advances in the literature investigating adjuvants. Leukocyte-Platelet Rich Fibrin (L-PRF) is an autologous biomaterial consisting of leukocytes and platelets embedded within a fibrin matrix with the ability to release growth factors enabling angiogenesis, bone regeneration and soft tissue healing. This paper's aim is to investigate the effects of L-PRF in conjuction with surgical debridement for management of MRONJ.

METHODS

Twenty-two cases with established MRONJ were treated with either surgical intervention (Group A) or with surgical intervention and L-PRF (Group B), from 2016 to 2023 at Edinburgh Dental Institute (EDI). Treatments were deemed successful when the patients were asymptomatic, displayed complete soft tissue healing with the absence of infection/inflammation, fistula, or exposed bone.

RESULTS

All cases in Group B had healed in contrast to 54.5% not healed in Group A; p value < 0.05 indicating statistical significance.

CONCLUSION

The use of L-PRF as an adjuvant to surgical management of MRONJ is promising with its favourable functional capacity, simple application, and success of treatment outcomes.

Outcome after treatment with axitinib in children, young adults, and adults with renal cell carcinoma: a narrative review

Renal cell carcinoma (RCC) is a very rare type of renal cancer in children and young adults. When metastasized or recurrent, no standards of care are available, and outcome is still poor. The tyrosine kinase inhibitor axitinib is approved for treatment of RCC in adults, but its effects in children and young adults with RCC remains unclear. Due to the histological and biological differences between children and adults, it is difficult to extrapolate knowledge on treatments from the adult to the pediatric and young adult setting. This paper summarizes the clinical characteristics and outcomes of patients with RCC who were treated with axitinib, with the aim to gain insight in the clinical efficacy of this compound in this young patient group.

Efficacy and safety of TACE combined with tyrosine kinase inhibitors and camrelizumab for unresectable hepatocellular carcinoma: A systematic review and meta‑analysis

Transcatheter arterial chemoembolization (TACE) combined with tyrosine kinase inhibitors (TKIs) and camrelizumab (collectively: T-T-C) is a novel treatment strategy for unresectable hepatocellular carcinoma (HCC). The present systematic review and meta-analysis aimed to evaluate the efficacy and safety of T-T-C compared with TACE combined with TKIs only (T-T) in the treatment of patients with unresectable HCC. A systematic literature search was conducted on T-T and T-T-C using PubMed, Embase and the Cochrane Library. Data regarding the clinical outcome, including overall survival (OS), progression-free survival (PFS), tumor response and adverse events (AEs), were independently extracted and analyzed by two researchers using standardized protocols. In total, 7 cohort studies, including 1,798 patients (T-T-C, 838; T-T, 960), were included in the meta-analysis. The results of the present study demonstrated that the T-T-C group had significantly prolonged OS [hazard ratio (HR), 0.38; 95% confidence interval (CI), 0.29-0.50; I2=61.5%; P=0.016)] and PFS (HR, 0.37; 95% CI, 0.30-0.46; I2=44.5%; P=0.109), and showed significantly higher objective response rates [risk ratio (RR), 0.82; 95% CI, 0.69-0.96; I2=25.1%; P=0.237)] and slightly higher disease control rates without a significant difference (RR, 0.96; 95% CI, 0.89-1.03; I2=0.0%; P=0.969). In addition, grade 3/4 AEs were more common in the T-T group, including hypertension (RR, 1.15; 95% CI, 0.85-1.56), vomiting or nausea (RR, 0.88; 95% CI, 0.44-1.76) and pain (RR, 0.74; 95% CI, 0.45-1.21); however, these results were not statistically significant. In conclusion, compared with T-T combination therapy, T-T-C demonstrated a notable advantage in terms of OS, PFS, ORR and DCR in patients with unresectable HCC. For manageable AEs, although the results were not statistically significant, the incidence of AEs in the T-T group was higher than that in the T-T-C group in terms of event probability.

The ubiquitin-like protein FAT10 in hepatocellular carcinoma cells limits the efficacy of anti-VEGF therapy

INTRODUCTION

The efficacy of anti-vascular endothelial growth factor (VEGF) therapy is limited. However, the key factors involved in limiting the efficacy of anti-VEGF therapy and the underlying mechanisms remain unclear.

OBJECTIVES

To investigate the effects and mechanisms of human leukocyte antigen F locus-adjacent transcript 10 (FAT10), a ubiquitin-like protein, in limiting the efficacy of anti-VEGF therapy in hepatocellular carcinoma (HCC) cells.

METHODS

FAT10 was knocked out in HCC cells using the clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein 9 technology. Bevacizumab (BV), an anti-VEGF monoclonal antibody, was used to evaluate the efficacy of anti-VEGF therapy in vivo. Mechanisms of FAT10 action were assessed by RNA sequencing, glutathione S-transferase pulldown assays and in vivo ubiquitination assays.

RESULTS

FAT10 accelerated VEGF-independent angiogenesis in HCC cells which limited BV efficacy and BV-aggravated hypoxia and inflammation promoted FAT10 expression. FAT10 overexpression increased levels of proteins involved in several signaling pathways in HCC cells, resulting in upregulation of VEGF and multiple non-VEGF proangiogenic factors. Upregulation of multiple FAT10-mediated non-VEGF signals compensated for the inhibition of VEGF signaling by BV, enhancing VEGF-independent angiogenesis and promoting HCC growth.

CONCLUSIONS

Our preclinical findings identify FAT10 in HCC cells as a key factor limiting the efficacy of anti-VEGF therapy and elucidate its underlying mechanisms. This study provides new mechanistic insights into the development of antiangiogenic therapies.

Anti-angiogenic therapy using the multi-tyrosine kinase inhibitor Regorafenib enhances tumor progression in a transgenic mouse model of ß-cell carcinogenesis

BACKGROUND

Pancreatic neuroendocrine tumors (PNETs) represent a distinct hypervascularized tumor entity, often diagnosed at metastatic stage. Therapeutic efficacy of anti-angiogenic multi-kinase inhibitors is frequently limited by primary or acquired resistance in vivo. This study aimed to characterize the molecular mode of action as well as resistance mechanisms to the anti-angiogenic multi-tyrosine kinase inhibitor (TKI) Regorafenib in vitro and in vivo.

METHODS

In vitro, human and murine pancreatic neuroendocrine cell lines were comparatively treated with Regorafenib and other TKIs clinically used in PNETs. Effects on cell viability and proliferation were analyzed. In vivo, transgenic RIP1Tag2 mice were treated with Regorafenib at two different time periods during carcinogenesis and its impact on angiogenesis and tumor progression was evaluated.

RESULTS

Compared to the established TKI therapies with Sunitinib and Everolimus, Regorafenib showed the strongest effects on cell viability and proliferation in vitro, but was unable to induce apoptosis. Unexpectedly and in contrast to these in vitro findings, Regorafenib enhanced proliferation during early tumor development in RIP1Tag2 mice and had no significant effect in late tumor progression. In addition, invasiveness was increased at both time points. Mechanistically, we could identify an upregulation of the pro-survival protein Bcl-2, the induction of the COX2-PGE2-pathway as well as the infiltration of CSF1R positive immune cells into the tumors as potential resistance mechanisms following Regorafenib treatment.

DISCUSSION

Our data identify important tumor cell-autonomous and stroma-dependent mechanisms of resistance to antiangiogenic therapies.

Targeting angiogenesis in oncology, ophthalmology and beyond

Angiogenesis is an essential process in normal development and in adult physiology, but can be disrupted in numerous diseases. The concept of targeting angiogenesis for treating diseases was proposed more than 50 years ago, and the first two drugs targeting vascular endothelial growth factor (VEGF), bevacizumab and pegaptanib, were approved in 2004 for the treatment of cancer and neovascular ophthalmic diseases, respectively. Since then, nearly 20 years of clinical experience with anti-angiogenic drugs (AADs) have demonstrated the importance of this therapeutic modality for these disorders. However, there is a need to improve clinical outcomes by enhancing therapeutic efficacy, overcoming drug resistance, defining surrogate markers, combining with other drugs and developing the next generation of therapeutics. In this Review, we examine emerging new targets, the development of new drugs and challenging issues such as the mode of action of AADs and elucidating mechanisms underlying clinical benefits; we also discuss possible future directions of the field.

Warburg effect in colorectal cancer: the emerging roles in tumor microenvironment and therapeutic implications

Colorectal cancer (CRC) is the third most common cancer and the second leading cause of cancer-related death worldwide. Countless CRC patients undergo disease progression. As a hallmark of cancer, Warburg effect promotes cancer metastasis and remodels the tumor microenvironment, including promoting angiogenesis, immune suppression, cancer-associated fibroblasts formation and drug resistance. Targeting Warburg metabolism would be a promising method for the treatment of CRC. In this review, we summarize information about the roles of Warburg effect in tumor microenvironment to elucidate the mechanisms governing Warburg effect in CRC and to identify novel targets for therapy.

The exploration of three different treatment models of osimertinib plus antiangiogenic agents in non‐small cell lung cancer: A real‐world study

Background

Real‐world application of osimertinib with antiangiogenic agents in non‐small cell lung cancer (NSCLC) is common, but the efficacy data are rarely reported.

Methods

To obtain an objective efficacy report of different real‐world treatment models of osimertinib and antiangiogenic agents.

Results

A total of 54 patients with NSCLC were enrolled into the study. Twelve (22.2%) who received a combination of antiangiogenic agents, when there was a trend of osimertinib resistance but did not reach imageology progressive disease (PD), were assigned to Group A, with a median overall survival (OS) and progression‐free survival (PFS) of 48.0 (95% CI, not reached) and 21.0 (95% CI: 16.7–25.3) months, respectively. Thirty (55.6%) who received a combination of antiangiogenic agents when there was imageology PD during treatment with osimertinib were assigned to Group B, with a median OS and PFS of 31.8 (95% CI: 26.6–37.1) and 9.2 (95% CI: 5.9–12.6) months, respectively. Twelve (22.2%) who received a combination of antiangiogenic agents at the initial treatment with osimertinib were assigned to Group C, with a median OS and PFS of 28.5 (95% CI: 15.2–41.8) and 15.3 (95% CI: 7.9–22.7) months, respectively. Patients in Group A achieved a significant prolonged median PFS (p < 0.001) compared with Groups B and C. Absence of epidermal growth factor receptor (EGFR) T790M mutations (p = 0.043; hazard ratio [HR] = 2.124, 95% CI: 1.023–4.413) and no previous antiangiogenic agent application (p = 0.012; HR = 0.362, 95% CI: 0.163–0.863) were the independent prognostic factors of OS.

Conclusion

The well‐timed action to combine antiangiogenic agents was when there was a trend of osimertinib resistance. The absence of EGFR T790M mutations and previous use of antiangiogenic agents were poor prognostic factors.

Genetic variants involved in the cGAS-STING pathway predict outcome in patients with metastatic colorectal cancer: Data from FIRE-3 and TRIBE trials

BACKGROUND

The activation of stimulator of interferon genes (STING) was reported to enhance cetuximab-mediated natural killer cell activation and dendritic cell maturation. Polymorphisms in genes in the cyclic GMP-AMP synthase (cGAS)-STING pathway may affect innate immune response. Therefore, we hypothesised that genetic variants in the cGAS-STING pathway may predict the efficacy of cetuximab-based treatment in patients with metastatic colorectal cancer.

METHODS

Genomic DNA from blood samples of patients enrolled in FIRE-3 (cetuximab arm, n = 129; bevacizumab arm, n = 107) and TRIBE (bevacizumab arm, n = 215) was genotyped using the OncoArray-500K bead chip panel. Seven selected single nucleotide polymorphisms in 3 genes (cGAS, STING and interferon B1 (IFNB1)) were analysed for the association with overall survival and progression-free survival.

RESULTS

In the cetuximab cohort, patients with STING rs1131769 any T allele showed significantly shorter overall survival (36.3 versus 56.1 months) than carriers of C/C in both univariate [hazard ratio (HR) = 2.08; 95% confidence interval (CI): 1.06-4.07; P = 0.03] and multivariate (HR = 2.98; 95% CI: 1.35-6.6; P = 0.0085) analyses; patients carrying IFNB1 rs1051922 G/A and A/A genotype showed a significantly shorter progression-free survival than carriers of G/G allele in both univariate (G/A versus G/G, 10.2 versus 14.1 months, HR = 1.84; 95% CI 1.23-2.76; A/A versus G/G, 10.7 versus 14.1 months, HR = 2.19; 95% CI 0.97-4.96; P = 0.0077) and multivariate analyses (G/A versus G/G, HR = 2; 95% CI 1.22-3.3; A/A versus G/G, HR = 2.19, 95% CI 0.92-5.26, P = 0.02). These associations were not observed in the bevacizumab arm of FIRE-3 or TRIBE.

CONCLUSION

These results suggest for the first time that germline polymorphisms in STING and IFNB1 genes may predict the outcomes of cetuximab-based treatment in patients with metastatic colorectal cancer.

From remodeling to quiescence: The transformation of the vascular network

The vascular system is essential for embryogenesis, healing, and homeostasis. Dysfunction or deregulated blood vessel function contributes to multiple diseases, including diabetic retinopathy, cancer, hypertension, or vascular malformations. A balance between the formation of new blood vessels, vascular remodeling, and vessel quiescence is fundamental for tissue growth and function. Whilst the major mechanisms contributing to the formation of new blood vessels have been well explored in recent years, vascular remodeling and quiescence remain poorly understood. In this review, we highlight the cellular and molecular mechanisms responsible for vessel remodeling and quiescence during angiogenesis. We further underline how impaired remodeling and/or destabilization of vessel networks can contribute to vascular pathologies. Finally, we speculate how addressing the molecular mechanisms of vascular remodeling and stabilization could help to treat vascular-related disorders.

The Anti-VEGF(R) Drug Discovery Legacy: Improving Attrition Rates by Breaking the Vicious Cycle of Angiogenesis in Cancer

Resistance to anti-vascular endothelial growth factor (VEGF) molecules causes lack of response and disease recurrence. Acquired resistance develops as a result of genetic/epigenetic changes conferring to the cancer cells a drug resistant phenotype. In addition to tumor cells, tumor endothelial cells also undergo epigenetic modifications involved in resistance to anti-angiogenic therapies. The association of multiple anti-angiogenic molecules or a combination of anti-angiogenic drugs with other treatment regimens have been indicated as alternative therapeutic strategies to overcome resistance to anti-angiogenic therapies. Alternative mechanisms of tumor vasculature, including intussusceptive microvascular growth (IMG), vasculogenic mimicry, and vascular co-option, are involved in resistance to anti-angiogenic therapies. The crosstalk between angiogenesis and immune cells explains the efficacy of combining anti-angiogenic drugs with immune check-point inhibitors. Collectively, in order to increase clinical benefits and overcome resistance to anti-angiogenesis therapies, pan-omics profiling is key.

Small molecules in targeted cancer therapy: advances, challenges, and future perspectives

Due to the advantages in efficacy and safety compared with traditional chemotherapy drugs, targeted therapeutic drugs have become mainstream cancer treatments. Since the first tyrosine kinase inhibitor imatinib was approved to enter the market by the US Food and Drug Administration (FDA) in 2001, an increasing number of small-molecule targeted drugs have been developed for the treatment of malignancies. By December 2020, 89 small-molecule targeted antitumor drugs have been approved by the US FDA and the National Medical Products Administration (NMPA) of China. Despite great progress, small-molecule targeted anti-cancer drugs still face many challenges, such as a low response rate and drug resistance. To better promote the development of targeted anti-cancer drugs, we conducted a comprehensive review of small-molecule targeted anti-cancer drugs according to the target classification. We present all the approved drugs as well as important drug candidates in clinical trials for each target, discuss the current challenges, and provide insights and perspectives for the research and development of anti-cancer drugs.

Galectins in the Pathogenesis of Common Retinal Disease

Diseases of the retina are major causes of visual impairment and blindness in developed countries and, due to an ageing population, their prevalence is continually rising. The lack of effective therapies and the limitations of those currently in use highlight the importance of continued research into the pathogenesis of these diseases. Vascular endothelial growth factor (VEGF) plays a major role in driving vascular dysfunction in retinal disease and has therefore become a key therapeutic target. Recent evidence also points to a potentially similarly important role of galectins, a family of β-galactoside-binding proteins. Indeed, they have been implicated in regulating fundamental processes, including vascular hyperpermeability, angiogenesis, neuroinflammation, and oxidative stress, all of which also play a prominent role in retinopathies. Here, we review direct evidence for pathological roles of galectins in retinal disease. In addition, we extrapolate potential roles of galectins in the retina from evidence in cancer, immune and neuro-biology. We conclude that there is value in increasing understanding of galectin function in retinal biology, in particular in the context of the retinal vasculature and microglia. With greater insight, recent clinical developments of galectin-targeting drugs could potentially also be of benefit to the clinical management of many blinding diseases.

Combination of Immune Checkpoint Inhibitors and Anti-Angiogenic Agents in Brain Metastases From Non-Small Cell Lung Cancer

Brain metastases remain a critical issue in the management of non-small cell lung cancer (NSCLC) because of the high frequency and poor prognosis, with survival rates often measured in just months. The local treatment approach remains the current standard of care, but management of multiple asymptomatic brain metastases always involves systemic therapy. Given that anti-angiogenic agents and immune checkpoint inhibitors (ICIs) both target the tumor microenvironment (TME), this combination therapy has become a promising strategy in clinical practice. Increasing number of preclinical and clinical studies have shown remarkable anti-tumor activity of the combination therapy, but the efficacy in brain metastases is unclear due to the strict selection criteria adopted in most clinical trials. This review briefly summarizes the potential synergistic anti-tumor effect and clinical development of the combination of anti-angiogenic agents and ICIs in NSCLC brain metastases, and discusses the existing challenges and problems.

Efficient differentiation of human embryonic stem cells to retinal pigment epithelium under defined conditions

Age-related macular degeneration (AMD) is a highly prevalent form of blindness caused by loss death of cells of the retinal pigment epithelium (RPE). Transplantation of pluripotent stem cell (PSC)-derived RPE cells is considered a promising therapy to regenerate cell function and vision.

OBJECTIVE

The objective of this study is to develop a rapid directed differentiation method for production of RPE cells from PSC which is rapid, efficient, and fully defined and produces cells suitable for clinical use.

DESIGN

A protocol for cell growth and differentiation from hESCs was developed to induce differentiation through screening small molecules which regulated a primary stage of differentiation to the eyefield progenitor, and then, a subsequent set of molecules to drive differentiation to RPE cells. Methods for cell plating and maintenance have been optimized to give a homogeneous population of cells in a short 14-day period, followed by a procedure to support maturation of cell function.

RESULTS

We show here the efficient production of RPE cells from human embryonic stem cells (hESCs) using small molecules in a feeder-free system using xeno-free/defined medium. Flow cytometry at day 14 showed ~ 90% of cells expressed the RPE markers MITF and PMEL17. Temporal gene analysis confirmed differentiation through defined cell intermediates. Mature hESC-RPE cell monolayers exhibited key morphological, molecular, and functional characteristics of the endogenous RPE.

CONCLUSION

This study identifies a novel cell differentiation process for rapid and efficient production of retinal RPE cells directly from hESCs. The described protocol has utility for clinical-grade cell production for human therapy to treat AMD.

Angiogenesis in the progression from liver fibrosis to cirrhosis and hepatocelluar carcinoma

Introduction: Persistent inflammation and hypoxia are strong stimulus for pathological angiogenesis and vascular remodeling, and are also the most important elements resulting in liver fibrosis. Sustained inflammatory process stimulates fibrosis to the end-point of cirrhosis and sinusoidal portal hypertension is an important feature of cirrhosis. Neovascularization plays a pivotal role in collateral circulation formation of portal vein, mesenteric congestion, and high perfusion. Imbalance of hepatic artery and portal vein blood flow leads to the increase of hepatic artery inflow, which is beneficial to the formation of nodules. Angiogenesis contributes to progression from liver fibrosis to cirrhosis and hepatocellular carcinoma (HCC) and anti-angiogenesis therapy can improve liver fibrosis, reduce portal pressure, and prolong overall survival of patients with HCC. Areas covers: This paper will try to address the difference of the morphological characteristics and mechanisms of neovascularization in the process from liver fibrosis to cirrhosis and HCC and further compare the different efficacy of anti-angiogenesis therapy in these three stages. Expert opinion: More in-depth understanding of the role of angiogenesis factors and the relationship between angiogenesis and other aspects of the pathogenesis and transformation may be the key to enabling future progress in the treatment of patients with liver fibrosis, cirrhosis, and HCC.

Plk1, upregulated by HIF-2, mediates metastasis and drug resistance of clear cell renal cell carcinoma

Polo-like kinase 1 (Plk1) expression is inversely correlated with survival advantages in many cancers. However, molecular mechanisms that underlie Plk1 expression are poorly understood. Here, we uncover a hypoxia-regulated mechanism of Plk1-mediated cancer metastasis and drug resistance. We demonstrated that a HIF-2-dependent regulatory pathway drives Plk1 expression in clear cell renal cell carcinoma (ccRCC). Mechanistically, HIF-2 transcriptionally targets the hypoxia response element of the Plk1 promoter. In ccRCC patients, high expression of Plk1 was correlated to poor disease-free survival and overall survival. Loss-of-function of Plk1 in vivo markedly attenuated ccRCC growth and metastasis. High Plk1 expression conferred a resistant phenotype of ccRCC to targeted therapeutics such as sunitinib, in vitro, in vivo, and in metastatic ccRCC patients. Importantly, high Plk1 expression was defined in a subpopulation of ccRCC patients that are refractory to current therapies. Hence, we propose a therapeutic paradigm for improving outcomes of ccRCC patients.

Neuropilin 1 and Neuropilin 2 gene invalidation or pharmacological inhibition reveals their relevance for the treatment of metastatic renal cell carcinoma

Background

Despite the improvement of relapse-free survival mediated by anti-angiogenic drugs like sunitinib (Sutent®), or by combinations of anti-angiogenic drugs with immunotherapy, metastatic clear cell Renal Cell Carcinoma (mccRCC) remain incurable. Hence, new relevant treatments are urgently needed. The VEGFs coreceptors, Neuropilins 1, 2 (NRP1, 2) are expressed on several tumor cells including ccRCC. We analyzed the role of the VEGFs/NRPs signaling in ccRCC aggressiveness and evaluated the relevance to target this pathway.

Methods

We correlated the NRP1, 2 levels to patients’ survival using online available data base. Human and mouse ccRCC cells were knocked-out for the NRP1 and NRP2 genes by a CRISPR/Cas9 method. The number of metabolically active cells was evaluated by XTT assays. Migration ability was determined by wound closure experiments and invasion ability by using Boyden chamber coated with collagen. Production of VEGFA and VEGFC was evaluated by ELISA. Experimental ccRCC were generated in immuno-competent/deficient mice. The effects of a competitive inhibitor of NRP1, 2, NRPa-308, was tested in vitro and in vivo with the above-mentioned tests and on experimental ccRCC. NRPa-308 docking was performed on both NRPs.

Results

Knock-out of the NRP1 and NRP2 genes inhibited cell metabolism and migration and stimulated the expression of VEGFA or VEGFC, respectively. NRPa-308 presented a higher affinity for NRP2 than for NRP1. It decreased cell metabolism and migration/invasion more efficiently than sunitinib and the commercially available NRP inhibitor EG00229. NRPa-308 presented a robust inhibition of experimental ccRCC growth in immunocompetent and immunodeficient mice. Such inhibition was associated with decreased expression of several pro-tumoral factors. Analysis of the TCGA database showed that the NRP2 pathway, more than the NRP1 pathway correlates with tumor aggressiveness only in metastatic patients.

Conclusions

Our study strongly suggests that inhibiting NRPs is a relevant treatment for mccRCC patients in therapeutic impasses and NRPa-308 represents a relevant hit.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-01832-x.

Implications of flavonoids as potential modulators of cancer neovascularity

PURPOSE

The formation of new blood vessels from previous ones, angiogenesis, is critical in tissue repair, expansion or remodeling in physiological processes and in various pathologies including cancer. Despite that, the development of anti-angiogenic drugs has great potential as the treatment of cancer faces many problems such as development of the resistance to treatment or an improperly selected therapy approach. An evaluation of predictive markers in personalized medicine could significantly improve treatment outcomes in many patients.

METHODS

This comprehensive review emphasizes the anticancer potential of flavonoids mediated by their anti-angiogenic efficacy evaluated in current preclinical and clinical cancer research.

RESULTS AND CONCLUSION

Flavonoids are important groups of phytochemicals present in common diet. Flavonoids show significant anticancer effects. The anti-angiogenic effects of flavonoids are currently a widely discussed topic of preclinical cancer research. Flavonoids are able to regulate the process of tumor angiogenesis through modulation of signaling molecules such as VEGF, MMPs, ILs, HIF or others. However, the evaluation of the anti-angiogenic potential of flavonoids within the clinical studies is not frequently discussed and is still of significant scientific interest.

Realizing Cancer Precision Medicine by Integrating Systems Biology and Nanomaterial Engineering

Many clinical trials for cancer precision medicine have yielded unsatisfactory results due to challenges such as drug resistance and low efficacy. Drug resistance is often caused by the complex compensatory regulation within the biomolecular network in a cancer cell. Recently, systems biological studies have modeled and simulated such complex networks to unravel the hidden mechanisms of drug resistance and identify promising new drug targets or combinatorial or sequential treatments for overcoming resistance to anticancer drugs. However, many of the identified targets or treatments present major difficulties for drug development and clinical application. Nanocarriers represent a path forward for developing therapies with these "undruggable" targets or those that require precise combinatorial or sequential application, for which conventional drug delivery mechanisms are unsuitable. Conversely, a challenge in nanomedicine has been low efficacy due to heterogeneity of cancers in patients. This problem can also be resolved through systems biological approaches by identifying personalized targets for individual patients or promoting the drug responses. Therefore, integration of systems biology and nanomaterial engineering will enable the clinical application of cancer precision medicine to overcome both drug resistance of conventional treatments and low efficacy of nanomedicine due to patient heterogeneity.

Anti-angiogenic Agents in Combination With Immune Checkpoint Inhibitors: A Promising Strategy for Cancer Treatment

Advances in cancer immunity have promoted a major breakthrough in the field of cancer therapy. This is mainly associated with the successful development of immune checkpoint inhibitors (ICIs) for multiple types of human tumors. Blockade with different ICIs, including programmed cell death 1 (PD-1), programmed cell death-ligand 1 (PD-L1), and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) inhibitors, may activate the immune system of the host against malignant cells. However, only a subgroup of patients with cancer would benefit from immune checkpoint blockade. Some patients experience primary resistance to initial immunotherapy, and a majority eventually develop acquired resistance to ICIs. However, the mechanisms involved in the development of drug resistance to immune checkpoint blockade remain unclear. Recent studies supported that combination of ICIs and anti-angiogenic agents could be a promising therapeutic strategy for overcoming the low efficacy of ICIs. Moreover, through their direct anti-cancer effect by inhibiting tumor growth and metastasis, anti-angiogenic drugs reprogram the tumor milieu from an immunosuppressive to an immune permissive microenvironment. Activated immunity by immune checkpoint blockade also facilitates anti-angiogenesis by downregulating the expression of vascular endothelial growth factor and alleviating hypoxia condition. Many clinical trials showed an improved anti-cancer efficacy and prolonged survival following the addition of anti-angiogenic agents to ICIs. This review summarizes the current understanding and clinical development of combination therapy with immune checkpoint blockade and anti-angiogenic strategy.

Artemisinin and its derivatives: a promising cancer therapy

The world is experiencing a cancer epidemic and an increase in the prevalence of the disease. Cancer remains a major killer, accounting for more than half a million deaths annually. There is a wide range of natural products that have the potential to treat this disease. One of these products is artemisinin; a natural product from Artemisia plant. The Nobel Prize for Medicine was awarded in 2015 for the discovery of artemisinin in recognition of the drug's efficacy. Artemisinin produces highly reactive free radicals by the breakdown of two oxygen atoms that kill cancerous cells. These cells sequester iron and accumulate as much as 1000 times in comparison with normal cells. Generally, chemotherapy is toxic to both cancerous cells and normal cells, while no significant cytotoxicity from artemisinin to normal cells has been found in more than 4000 case studies, which makes it far different than conventional chemotherapy. The pleiotropic response of artemisinin in cancer cells is responsible for growth inhibition by multiple ways including inhibition of angiogenesis, apoptosis, cell cycle arrest, disruption of cell migration, and modulation of nuclear receptor responsiveness. It is very encouraging that artemisinin and its derivatives are anticipated to be a novel class of broad-spectrum antitumor agents based on efficacy and safety. This review aims to highlight these achievements and propose potential strategies to develop artemisinin and its derivatives as a new class of cancer therapeutic agents.

Apatinib as targeted therapy for advanced bone and soft tissue sarcoma: a dilemma of reversing multidrug resistance while suffering drug resistance itself

Bone and soft tissue sarcomas are rare malignant tumors originated from mesenchymal tissues. They harbor more than 50 distinct subtypes and differ in pathological features and clinical courses. Despite the significant improvements in modern multi-modality treatment, the outcomes and overall survival rates remain poor for patients with advanced, refractory, metastatic, or relapsed diseases. The growth and metastasis of bone and soft tissue sarcoma largely depend on angiogenesis, and VEGF/VEGFR pathway is considered as the most prominent player in angiogenesis. Therefore, blockade of VEGF/VEGFR pathways is a promising therapeutic strategy to retard neovascularization. Several VEGFR inhibitors have been developed and revealed their favorable anti-neoplastic effects in various cancers, but such desirable anti-tumor effects are not obtained in advanced sarcomas because of multiple reasons, such as drug tolerance, short duration of response, and severe adverse effects. Fortunately, preclinical and clinical studies have indicated that apatinib is a novel promising VEGFR2 inhibitor showing potent anti-angiogenic and anti-neoplastic activities in advanced sarcomas. Especially, apatinib has showed notable characteristics in multidrug resistance reversal, tumor regression, vascular normalization, immunosuppression alleviation, and enhancement of chemotherapeutic and radiotherapeutic effects. However, apatinib also gets struck in dilemma of reversing multidrug resistance of chemotherapeutic agents while suffering drug resistance itself, and several difficulties should be tackled before full use of apatinib. In this review, we discuss the outstanding characteristics and main predicaments of apatinib as targeted therapy in advanced sarcomas. Bone and soft tissue sarcomas are rare but malignant tumors originated from mesenchymal tissues. They harbor more than 100 distinct subtypes and differ in features of pathologies and clinical courses. Despite the significant improvements in modern multi-modality treatment, the outcomes and overall survival rates remain poor for patients with advanced, refractory, metastatic, or relapsed lesions. The growth and metastasis of bone and soft tissue sarcoma largely depend on angiogenesis and VEGF/VEGFR pathways play a pivotal role in angiogenesis. Therefore, blockade of VEGF/VEGFR pathways is a promising therapeutic strategy. Several VEGFR inhibitors have been developed and verified in clinical trials but with unfavorable outcomes. Fortunately, preclinical studies and clinical trials have indicated that apatinib is a novel promising VEGFR2 inhibitor showing potent anti-angiogenic and anti-neoplastic activities in advanced sarcomas. Actually, apatinib has showed notable characteristics in multidrug resistance reversal, tumor regression, vascular normalization, immunosuppression alleviation, enhancement of chemotherapeutic and radiotherapeutic effects. However, apatinib also gets struck in dilemma of reversing multidrug resistance of chemotherapeutic agents while suffering drug resistance itself, and several difficulties should be tackled before full use of apatinib. In this review, we discuss the outstanding characteristics and main predicaments of apatinib as targeted therapy in advanced sarcomas.

The Role of Kinase Signaling in Resistance to Bevacizumab Therapy for Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is the most malignant primary brain tumor and is characterized by vascular hyperplasia, necrosis, and high cell proliferation. Despite current standard therapies, including surgical resection and chemoradiotherapy, GBM patients survive for only about 15 months after diagnosis. Recently, the U.S. Food and Drug Administration (FDA) has approved an antiangiogenesis medication for recurrent GBM-bevacizumab-which has improved progression-free survival in GBM patients. Although bevacizumab has resulted in significant early clinical benefit, it inescapably predisposes tumor to relapse that can be represented as an infiltrative phenotype. Fundamentally, bevacizumab antagonizes the vascular endothelial growth factor A (VEGF_A), which is consistently released on both endothelial cells (ECs) and GBM cells. Actually, VEGF_A inhibition on the ECs leads to the suppression of vascular progression, permeability, and the vasogenic edema. However, the consequence of the VEGF_A pathway blockage on the GBM cells remains controversial. Nevertheless, a piece of evidence supports the relationship between bevacizumab application and compensatory activation of kinase signaling within GBM cells, leading to a tumor cell invasion known as the main mechanism of bevacizumab-induced tumor resistance. A complete understanding of kinase responses associated with tumor invasion in bevacizumab-resistant GBMs offers new therapeutic opportunities. Thus, this study aimed at presenting a brief overview of preclinical and clinical data of the tumor invasion and resistance induced by bevacizumab administration in GBMs, with a focus on the kinase responses during treatment. The novel therapeutic strategies to overcome this resistance by targeting protein kinases have also been summarized.

Necrosis in the Tumor Microenvironment and Its Role in Cancer Recurrence

Cancer recurrence is one of the most imminent problems in the current world of medicine, and it is responsible for most of the cancer-related death rates worldwide. Long-term administration of anticancer cytotoxic drugs may act as a double-edged sword, as necrosis may lead to renewed cancer progression and treatment resistance. The lack of nutrients, coupled with the induced hypoxia, triggers cell death and secretion of signals that affect the tumor niche. Many efforts have been made to better understand the contribution of hypoxia and metabolic stress to cancer progression and resistance, but mostly with respect to inflammation. Here we provide an overview of the direct anticancer effects of necrotic signals, which are not necessarily mediated by inflammation and the role of DAMPs (damage-associated molecular patterns) on the formation of a pro-cancerous environment.

Endothelial nitric oxide synthase c.-813C>T predicts for proteinuria in metastatic breast cancer patients treated with bevacizumab-based chemotherapy

PURPOSE

To investigate the association between single nucleotide polymorphisms (SNPs) in endothelial nitric oxide synthase (eNOS) and interleukin-8 (IL-8) genes and risk of developing bevacizumab-related adverse events in metastatic breast cancer (mBC) patients.

PATIENTS AND METHODS

mBC patients candidate to receive bevacizumab-based chemotherapy were enrolled in this pharmacogenetic study. eNOS c.-813C>T and c.894G>T, and IL-8 c.-251A>T were analyzed by real time PCR on genomic DNA extracted from peripheral blood. Univariate analysis was performed to test the association between each SNP and treatment-related toxicities.

RESULTS

Seventy-six mBC patients were enrolled in the present study. Patients carrying the homozygous variant eNOS c.-813TT genotype showed a statistically significant occurrence of any grade proteinuria when compared to CT or CC genotypes (p = 0.004). No significant association of proteinuria with IL-8 SNP or hypertension with selected eNOS and IL-8 SNPs was found.

CONCLUSIONS

These findings suggest an association between the eNOS c.-813C>T polymorphism and the development of proteinuria in mBC patients receiving a bevacizumab-based chemotherapy.

Comparison of the Therapeutic Efficacies of Topical Rivoceranib and Topical Bevacizumab in a Murine Model of Corneal Neovascularization

Background and Objectives: Corneal neovasculariziation (CNV) is a serious vision-threatening complication; however, all therapeutics have their clinical limitations. The aim of this study is to investigate the efficacy of topical rivoceranib compared with topical bevacizumab in a murine model of corneal neovascularization (CNV). Materials and Methods: Murine CNV was induced by means of total de-epithelization and alkali burn. Mice were divided into five groups according to topical treatment: untreated control, phosphate-buffered saline (PBS), 0.1% and 0.5% rivoceranib, and 0.5% bevacizumab. CNV area and index were measured 7 and 14 days after treatment. After corneal tissues were excised at day 14, the blood and lymphatic vessels were quantified by cluster of differentiation 31 (CD31) and lymphatic vessel endothelial hyaluronan receptor 1 (LYVE1) immunofluorescence, respectively. Results: After 14 days, treatment groups with 0.1% and 0.5% rivoceranib and 0.5% bevacizumab showed a decrease in CNV area and index compared with the untreated and PBS groups (all p < 0.01). Blood and lymphatic vascularization significantly decreased in the 0.5% rivoceranib and 0.5% bevacizumab groups, as measured by CD31 and LYVE1 immunofluorescence. There was no significant difference of vascularization between the 0.5% rivoceranib and bevacizumab groups. Conclusions: Topical application of rivoceranib could effectively decrease CNV equivalent to topical bevacizumab in a murine model.

Synergy Between Low Dose Metronomic Chemotherapy and the pH-centered Approach Against Cancer

Low dose metronomic chemotherapy (MC) is becoming a mainstream treatment for cancer in veterinary medicine. Its mechanism of action is anti-angiogenesis by lowering vascular endothelial growth factor (VEGF) and increasing trombospondin-1 (TSP1). It has also been adopted as a compassionate treatment in very advanced human cancer. However, one of the main limitations of this therapy is its short-term effectiveness: 6 to 12 months, after which resistance develops. pH-centered cancer treatment (pHT) has been proposed as a complementary therapy in cancer, but it has not been adopted or tested as a mainstream protocol, in spite of existing evidence of its advantages and benefits. Many of the factors directly or indirectly involved in MC and anti-angiogenic treatment resistance are appropriately antagonized by pHT. This led to the testing of an association between these two treatments. Preliminary evidence indicates that the association of MC and pHT has the ability to reduce anti-angiogenic treatment limitations and develop synergistic anti-cancer effects. This review will describe each of these treatments and will analyze the fundamentals of their synergy.

KRAS Mutations Predict Response and Outcome in Advanced Lung Adenocarcinoma Patients Receiving First-Line Bevacizumab and Platinum-Based Chemotherapy

Bevacizumab, combined with platinum-based chemotherapy, has been widely used in the treatment of advanced-stage lung adenocarcinoma (LADC). Although KRAS (V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog) mutation is the most common genetic alteration in human LADC and its role in promoting angiogenesis has been well established, its prognostic and predictive role in the above setting remains unclear. The association between KRAS exon 2 mutational status and clinicopathological variables including progression-free survival and overall survival (PFS and OS, respectively) was retrospectively analyzed in 501 Caucasian stage IIIB-IV LADC patients receiving first-line platinum-based chemotherapy (CHT) with or without bevacizumab (BEV). EGFR (epidermal growth factor receptor)-mutant cases were excluded. Of 247 BEV/CHT and 254 CHT patients, 95 (38.5%) and 75 (29.5%) had mutations in KRAS, respectively. KRAS mutation was associated with smoking (p = 0.008) and female gender (p = 0.002) in the BEV/CHT group. We found no difference in OS between patients with KRAS-mutant versus KRAS wild-type tumors in the CHT-alone group (p = 0.6771). Notably, patients with KRAS-mutant tumors demonstrated significantly shorter PFS (p = 0.0255) and OS (p = 0.0186) in response to BEV/CHT compared to KRAS wild-type patients. KRAS mutation was an independent predictor of shorter PFS (hazard ratio, 0.597; p = 0.011) and OS (hazard ratio, 0.645; p = 0.012) in the BEV/CHT group. G12D KRAS-mutant patients receiving BEV/CHT showed significantly shorter PFS (3.7 months versus 8.27 months in the G12/13x group; p = 0.0032) and OS (7.2 months versus 16.1 months in the G12/13x group; p = 0.0144). In this single-center, retrospective study, KRAS-mutant LADC patients receiving BEV/CHT treatment exhibited inferior PFS and OS compared to those with KRAS wild-type advanced LADC. G12D mutations may define a subset of KRAS-mutant LADC patients unsuitable for antiangiogenic therapy with BEV.

Significance of cyclooxygenase-2, prostaglandin E2 and CD133 levels in sunitinib-resistant renal cell carcinoma

The current study investigated the mechanism underlying sunitinib resistance. The parental human renal cell carcinoma (RCC) cell line 786-O was continuously exposed to various doses of sunitinib to obtain sunitinib-resistant cells (786-O/S). Cell proliferation and colony formation assays were performed to assess the survival of 786-O/S cells. The half-inhibitory concentration for the drug-resistant cells was calculated. 786-O/S cells demonstrated notably morphological changes compared with parental cells. Compared with 786-O cells, 786-O/S cells exhibited stronger proliferative and colony-forming abilities. Western blot analysis was performed to measure the levels of cyclooxygenase 2 (COX-2) and prostaglandin E2 (PGE2). Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to detect the expression of COX-2 and cluster of differentiation (CD) 133 in both 786-O and 786-O/S cells. Following incubation of the two cell lines with celecoxib, a COX-2 inhibitor, RT-qPCR was performed to detect the expression of COX-2 and CD133, and western blot analysis was used to assess the expression of CD133. The results revealed that the levels of COX-2 and PGE2 were significantly higher in 786-O/S cells compared with 786-O cells (P<0.01). Similarly, the expression of CD133 was 24-fold higher in 786-O/S compared with the parental cells (P<0.01). When celecoxib was incubated with the two cell lines, the expression of COX-2 and CD133 decreased significantly (P<0.0001). In summary, the results indicate that activation of the COX-2-PGE2 pathway in RCC leads to the development of sunitinib resistance and may serve an important role in the maintenance of the characteristics of stem cells that are closely associated with drug resistance.

Phase II trial of levocetirizine with capecitabine and bevacizumab to overcome the resistance of antiangiogenic therapies in refractory metastatic colorectal cancer

Background

Despite the clinical success of vascular endothelial growth factor (VEGF) blockade in metastatic colorectal cancers (mCRC), resistance to anti-angiogenic drugs invariably develops. IL-8 and other cytokines have been implicated in development of resistance to anti-angiogenic therapy. Levocetirizine is a second generation H1 antihistamine with anti-inflammatory and IL-8 suppression properties. We conducted a phase II trial combining levocetirizine with capecitabine and bevacizumab to potentially overcome anti-angiogenic therapy resistance in patients with refractory mCRC.

Methods

This was a single-center open-label prospective trial in refractory mCRC patients. Treatment consisted of oral capecitabine 850 mg/m² twice daily administered as 7 days on and 7 days off, intravenous (IV) bevacizumab 5 mg/kg every 14 days and oral levocetirizine 5 mg daily. The primary end point was progression free survival (PFS) and secondary endpoints included objective response rate (ORR) and tolerability. An exploratory endpoint included correlation of PFS with cytokine levels. A sample size of 36 evaluable patients could identify a median PFS of 3.4 months at a 0.05 significance level. To examine cytokine changes related to levocetirizine treatment, patients were randomized to Arm A where levocetirizine was started 7 days after starting chemotherapy and to Arm B where levocetirizine was started 7 days prior to chemotherapy. Cytokine levels were measured at baseline and with each cycle of chemotherapy (up to three cycles).

Results

Forty-seven patients were enrolled in the trial to have 36 evaluable patients. Arm A enrolled 23 patients and Arm B enrolled 24 patients. Fifty percent of patients had progressive disease and 62% of patients had stable disease in each arm as best response. There was no demonstrable difference in PFS between the two arms (log-rank test P=0.83). Median time to progression was 3.4 months in Arm A and 3.5 months in Arm B.

Conclusions

Median PFS in the trial was comparable to and appeared to be better than other regimens used in the refractory setting (e.g., median PFS of 1.9 months for regorafenib). Cytokine measurement with IL-8 levels did not show any correlation with progression free survival but patients with stable disease showed overall lower levels of IL-8 as compared to patients with progressive disease in the cytokine analysis.

Chrysin inhibit human melanoma A375.S2 cell migration and invasion via affecting MAPK signaling and NF-κB signaling pathway in vitro

Numerous evidences have shown that chrysin induced cytotoxic effects via induced cell cycle arrest and induction of cell apoptosis in human cancer cell lines, however, no information showed that chrysin inhibited skin cancer cell migration and invasion. In this study, we investigated anti-metastasis mechanisms of chrysin in human melanoma cancer A375.S2 cells in vitro. Under sub-lethal concentrations of chrysin (0, 5, 10, and 15 μM) which inhibits cell mobility, migration and invasion of A375.S2 cells that were assayed by wound healing and Transwell filter. That chrysin inhibited MMP-2 activity in A375.S2 cells was investigated by gelatin zymography assay. Western blotting was used to examine protein expression and results indicated that chrysin inhibited the expression of GRB2, SOS-1, PKC, p-AKT (Thr308), NF-κBp65, and NF-κBp50 at 24 and 48 hours treatment, but only at 10-15 μM of chrysin decreased Ras, PI3K, p-c-Jun, and Snail only at 48 hours treatment and only decrease p-AKT(Ser473) at 24 hours treatment. Furthermore, chrysin (5-15 μM) decreased the expression of uPA, N-cadherin and MMP-1 at 24 and 48 hours treatment but only decreased MMP-2 and VEGF at 48 hours treatment at 10-15 μM and 5-15 μM of chrysin, respectively, however, increased E-cadherin at 5-15 μM treatment. Results of confocal laser microscopy systems indicated that chrysin inhibited expression of NF-κBp65 in A375.S2 cells. Based on these observations, we suggest that chrysin can be used in anti-metastasis of human melanoma cells in the future.

Inhibition of the amino-acid transporter LAT1 demonstrates anti-neoplastic activity in medulloblastoma

Most cases of medulloblastoma (MB) occur in young children. While the overall survival rate can be relatively high, current treatments combining surgery, chemo- and radiotherapy are very destructive for patient development and quality of life. Moreover, aggressive forms and recurrences of MB cannot be controlled by classical therapies. Therefore, new therapeutic approaches yielding good efficacy and low toxicity for healthy tissues are required to improve patient outcome. Cancer cells sustain their proliferation by optimizing their nutrient uptake capacities. The L-type amino acid transporter 1 (LAT1) is an essential amino acid carrier overexpressed in aggressive human cancers that was described as a potential therapeutic target. In this study, we investigated the therapeutic potential of JPH203, a LAT1-specific pharmacological inhibitor, on two independent MB cell lines belonging to subgroups 3 (HD-MB03) and Shh (DAOY). We show that while displaying low toxicity towards normal cerebral cells, JPH203 disrupts AA homeostasis, mTORC1 activity, proliferation and survival in MB cells. Moreover, we demonstrate that a long-term treatment with JPH203 does not lead to resistance in MB cells. Therefore, this study suggests that targeting LAT1 with JPH203 is a promising therapeutic approach for MB treatment.

Recent advances on anti-angiogenesis receptor tyrosine kinase inhibitors in cancer therapy

Angiogenesis has always been the topic of major scientific interest in the field of malignant tumors. Nowadays, targeting angiogenesis has achieved success in various carcinomas by several mechanisms, including the use of anti-angiogenic small molecule receptor tyrosine kinase inhibitors (TKIs). The development of TKIs targeting pro-angiogenic receptors, mainly vascular endothelial growth factor receptor (VEGFR) family, have significantly improved the outcome of certain types of cancers, like renal cell carcinoma, hepatocellular carcinoma, and colorectal carcinoma. However, the general response rate is not very satisfactory. The particular toxicity profile and resistance to anti-angiogenic targeted agents are unavoidable, and no specific marker is available to screen responsive patients to TKIs for precision therapy. To date, about 11 anti-angiogenic TKIs with different binding capacities to angiogenic receptor tyrosine kinase have been approved for the treatment of patients with advanced cancers. This review presents all approved anti-angiogenic small molecule receptor TKIs so far with an emphasis on their indications and clinical efficacy. We also discuss the combination between TKIs and immune checkpoint blockade inhibitors based on the most recent exciting outcome in immunotherapy.

Challenges facing antiangiogenesis therapy: The significant role of hypoxia-inducible factor and MET in development of resistance to anti-vascular endothelial growth factor-targeted therapies

It is now fully recognized that along with multiple physiological functions, angiogenesis is also involved in the fundamental process and pathobiology of several disorders including cancer. Recent studies have fully established the role of angiogenesis in cancer progression as well as invasion and metastasis. Consequently, many therapeutic agents such as monoclonal antibodies targeting angiogenesis pathway have been introduced in clinic with the hope for improving the outcomes of cancer therapy. Bevacizumab (Avastin®) was the first anti-vascular endothelial growth factor (VEGF) targeting monoclonal antibody developed with this purpose and soon received its accelerated US Food and Drug Administration (FDA) approval for treatment of patients with metastatic breast cancer in 2008. However, the failure to meet expecting results in different follow-up studies, forced FDA to remove bevacizumab approval for metastatic breast cancer. Investigations have now revealed that while suppressing VEGF pathway initially decreases tumor progression rate and vasculature density, activation of several interrelated pathways and signaling molecules following VEGF blockade compensate the insufficiency of VEGF and initially blocked angiogenesis, explaining in part the failure observed with bevacizumab single therapy. In present review, we introduce some of the main pathways and signaling molecules involved in angiogenesis and then propose how their interconnection may result in development of resistance to bevacizumab.

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.

Targeting the Tie2-αvβ3 integrin axis with bi-specific reagents for the inhibition of angiogenesis

BACKGROUND

Increased activity of the receptor tyrosine kinase Tie2 has been implicated in the promotion of pathological angiogenesis. This activity is mainly mediated through angiopoietin (Ang)1- and Ang2-dependent activation of integrins by Tie2, rendering the Ang/Tie2/integrin axis an attractive putative target for cancer therapeutics.

RESULTS

To target this axis, we developed single domain, non-immunoglobulin high-affinity bi-specific protein inhibitors against both Tie2 and αvβ3 integrin. We have previously engineered the Ang2-binding domain of Tie2 (Ang2-BD) as a Tie2 inhibitor. Here, we engineered an exposed loop in Ang2-BD to generate variants that include an integrin-binding Arg-Gly-Asp (RGD) motif and used flow cytometry screening of a yeast-displayed Ang2-BD RGD loop library to identify the integrin antagonists. The bi-specific antagonists targeting both Tie2 and αvβ3 integrin inhibited adhesion and proliferation of endothelial cells cultured together with the αvβ3 integrin ligand vitronectin, as well as endothelial cell invasion and tube formation. The bi-specific reagents inhibited downstream signaling by Tie2 intracellularly in response to its agonist Ang1 more effectively than the wild-type Ang2 BD that binds Tie2 alone.

CONCLUSIONS

Collectively, this study-the first to describe inhibitors targeting all the known functions resulting from Tie2/integrin αvβ3 cross-talk-has created new tools for studying Tie2- and integrin αvβ3-dependent molecular pathways and provides the basis for the rational and combinatorial engineering of ligand-Tie2 and ligand-integrin αvβ3 receptor interactions. Given the roles of these pathways in cancer angiogenesis and metastasis, this proof of principle study paves the route to create novel Tie2/integrin αvβ3-targeting proteins for clinical use as imaging and therapeutic agents.

Antiangiogenic therapy: Markers of response, "normalization" and resistance

Currently in cancer treatment, one premise is to use antiangiogenic therapies in association with chemotherapy or radiotherapy to augment their efficacy by benefiting from the vascular "normalization" induced by antiangiogenic therapy. This concept defines the time during which the tumor blood vessels adopt normal-like morphology and functionality, i.e. the blood vessels become more mature, the perfusion augments and hypoxia decreases. To date, there is such a diversity of treatment protocols where the type of antiangiogenic to adopt, its dose and duration of administration are different, that knowing when and how to treat is problematic. In this review, we analyzed thoroughly preclinical and clinical studies that use antiangiogenic treatments to benefit from the "normalization" and showed that the effects depend on the type of antiangiogenic administrated (anti-VEGF, anti-VEGFR, Multi-Kinase Inhibitor) and on the duration of treatment. Finally, biomarkers of "normalization" and resistance that could be used in the clinic are presented.

Starvation tactics using natural compounds for advanced cancers: pharmacodynamics, clinical efficacy, and predictive biomarkers

The high mortality associated with oncological diseases is mostly due to tumors in advanced stages, and their management is a major challenge in modern oncology. Angiogenesis is a defined hallmark of cancer and predisposes to metastatic invasion and dissemination and is therefore an important druggable target for cancer drug discovery. Recently, because of drug resistance and poor prognosis, new anticancer drugs from natural sources targeting tumor vessels have attracted more attention and have been used in several randomized and controlled clinical trials as therapeutic options. Here, we outline and discuss potential natural compounds as salvage treatment for advanced cancers from recent and ongoing clinical trials and real-world studies. We also discuss predictive biomarkers for patients' selection to optimize the use of these potential anticancer drugs.

Choroidal pericytes promote subretinal fibrosis after experimental photocoagulation

Subretinal fibrosis results in local destruction of retinal structures and permanent vision loss, representing the end stage of neovascular age-related macular degeneration (AMD). Histological examination of fibrotic specimens from AMD patients has uncovered a wide range of cellular and acellular components. However, their origins and roles in fibrosis remain largely unexplored. Using a laser-induced photocoagulation model with collagen 1α1-GFP reporter mice, we demonstrate, by cell-lineage tracing, that pericytes associating with choroidal microvasculature are activated upon injury and infiltrate into the subretinal space as significant components of fibrotic lesions. In contrast to their choroidal precursors, infiltrating pericytes acquire stellate-like structures, upregulate expression of fibrogenic molecules and colocalize with extracellular fibrotic scar. Collectively, our results identify the choroidal perivascular niche as a novel source of subretinal fibrosis after photocoagulation, and suggest that collagen 1-expressing pericytes are potential targets for therapeutic intervention to suppress subretinal fibrosis and preserve vision.

Treatment response assessment with (R)-[11CPAQ PET in the MMTV-PyMT mouse model of breast cancer

Background

The goal of the study was to assess the potential of the vascular endothelial growth factor receptor (VEGFR)-2-targeting carbon-11 labeled (R)-N-(4-bromo-2-fluorophenyl)-6-methoxy-7-((1-methyl-3-piperidinyl)methoxy)-4-quinazolineamine ((R)-[¹¹C]PAQ) as a positron emission tomography (PET) imaging biomarker for evaluation of the efficacy of anticancer drugs in preclinical models.

Methods

MMTV-PyMT mice were treated with vehicle alone (VEH), murine anti-VEGFA antibody (B20-4.1.1), and paclitaxel (PTX) in combination or as single agents. The treatment response was measured with (R)-[¹¹C]PAQ PET as standardized uptake value (SUV)_mean, SUV_max relative changes at the baseline (day 0) and follow-up (day 4) time points, and magnetic resonance imaging (MRI)-derived PyMT mammary tumor volume (TV) changes. Expression of Ki67, VEGFR-2, and CD31 in tumor tissue was determined by immunohistochemistry (IHC). Non-parametric statistical tests were used to evaluate the relation between (R)-[¹¹C]PAQ radiotracer uptake and therapy response biomarkers.

Results

The (R)-[¹¹C]PAQ SUV_max in tumors was significantly reduced after 4 days in the B20-4.1.1/PTX combinational and B20-4.1.1 monotherapy groups (p < 0.0005 and p < 0.003, respectively). No significant change was observed in the PTX monotherapy group. There was a significant difference in the SUV_max change between the VEH group and B20-4.1.1/PTX combinational group, as well as between the VEH group and the B20-4.1.1 monotherapy group (p < 0.05). MRI revealed significant decreases in TV in the B20-4.1.1/PTX treatment group (p < 0.005) but not the other therapy groups. A positive trend was observed between the (R)-[¹¹C]PAQ SUV_max change and TV reduction in the B20-4.1.1/PTX group. Statistical testing showed a significant difference in the blood vessel density between the B20-4.1.1/PTX combinational group and the VEH group (p < 0.05) but no significant difference in the Ki67 positive signal between treatment groups.

Conclusions

The results of this study are promising. However, additional studies are necessary before (R)-[¹¹C]PAQ can be approved as a predictive radiotracer for cancer therapy response.

Emerging Roles of Vascular Cell Adhesion Molecule-1 (VCAM-1) in Immunological Disorders and Cancer

Tumor necrosis factor alpha (TNFα) is a pro-inflammatory cytokine that triggers the expression of inflammatory molecules, including other cytokines and cell adhesion molecules. TNFα induces the expression of intercellular cell adhesion molecule-1 and vascular cell adhesion molecule-1 (VCAM-1). VCAM-1 was originally identified as a cell adhesion molecule that helps regulate inflammation-associated vascular adhesion and the transendothelial migration of leukocytes, such as macrophages and T cells. Recent evidence suggests that VCAM-1 is closely associated with the progression of various immunological disorders, including rheumatoid arthritis, asthma, transplant rejection, and cancer. This review covers the role and relevance of VCAM-1 in inflammation, and also highlights the emerging potential of VCAM-1 as a novel therapeutic target in immunological disorders and cancer.

Potential lymphangiogenesis therapies: Learning from current antiangiogenesis therapies-A review

In recent years, lymphangiogenesis, the process of lymphatic vessel formation from existing lymph vessels, has been demonstrated to have a significant role in diverse pathologies, including cancer metastasis, organ graft rejection, and lymphedema. Our understanding of the mechanisms of lymphangiogenesis has advanced on the heels of studies demonstrating vascular endothelial growth factor C as a central pro-lymphangiogenic regulator and others identifying multiple lymphatic endothelial biomarkers. Despite these breakthroughs and a growing appreciation of the signaling events that govern the lymphangiogenic process, there are no FDA-approved drugs that target lymphangiogenesis. In this review, we reflect on the lessons available from the development of antiangiogenic therapies (26 FDA-approved drugs to date), review current lymphangiogenesis research including nanotechnology in therapeutic drug delivery and imaging, and discuss molecules in the lymphangiogenic pathway that are promising therapeutic targets.

Inhibition of VEGF-dependent angiogenesis and tumor angiogenesis by an optimized antibody targeting CLEC14a

The C‐type lectin‐like domain of CLEC14a (CLEC14a‐C‐type lectin‐like domain [CTLD]) is a key domain that mediates endothelial cell–cell contacts in angiogenesis. However, the role of CLEC14a‐CTLD in pathological angiogenesis has not yet been clearly elucidated. In this study, through complementarity‐determining region grafting, consecutive deglycosylation, and functional isolation, we generated a novel anti‐angiogenic human monoclonal antibody that specifically targets CLEC14a‐CTLD and that shows improved stability and homogeneity relative to the parental antibody. We found that this antibody directly inhibits CLEC14a‐CTLD‐mediated endothelial cell–cell contact and simultaneously downregulates expression of CLEC14a on the surface of endothelial cells. Using various in vitro and in vivo functional assays, we demonstrated that this antibody effectively suppresses vascular endothelial growth factor (VEGF)‐dependent angiogenesis and tumor angiogenesis of SNU182 human hepatocellular carcinoma, CFPAC‐1 human pancreatic cancer, and U87 human glioma cells. Furthermore, we also found that this antibody significantly inhibits tumor angiogenesis of HCT116 and bevacizumab‐adapted HCT116 human colorectal cancer cells. These findings suggest that antibody targeting of CLEC14a‐CTLD has the potential to suppress VEGF‐dependent angiogenesis and tumor angiogenesis and that CLEC14a‐CTLD may be a novel anti‐angiogenic target for VEGF‐dependent angiogenesis and tumor angiogenesis.

Bevacizumab Injection in Patients with Neovascular Age-Related Macular Degeneration Increases Angiogenic Biomarkers

Purpose

To evaluate the expression of 19 angiogenic biomarkers in the aqueous humor before and after intravitreal bevacizumab injection (IVB) in eyes with neovascular age-related macular degeneration (AMD).

Design

Prospective, noncomparative, interventional case series.

Participants

Twenty-three eyes of 23 treatment-naïve patients with choroidal neovascularization (CNV) secondary to neovascular AMD.

Methods

Eyes were diagnosed with CNV secondary to neovascular AMD and were treated with 3 monthly IVBs. Aqueous humor samples were obtained by anterior chamber paracentesis at baseline and immediately before each intravitreal bevacizumab injection.

Main Outcome Measures

Aqueous humor levels of 19 angiogenic biomarkers (angiopoietin 2, bone morphogenetic protein 9 [BMP-9], epidermal growth factor [EGF], endoglin, endothelin 1, fibroblast growth factor [FGF]-1 and FGF-2, follistatin, granulocyte colony-stimulating factor [GCSF], heparin-binding EGF-like growth factor [HB-EGF], hepatocyte growth factor [HGF], interleukin 8, leptin, placental growth factor [PLGF], vascular endothelial growth factor [VEGF]-A, VEGF-C, VEGF-D, and tissue inhibitor of metalloproteinases [TIMP]-1 and TIMP-2) were measured. Best-corrected visual acuity (BCVA), spectral-domain OCT parameters, and intraocular pressure also were evaluated.

Results

Baseline aqueous VEGF-A expression was elevated in all study eyes before treatment initiation. A statistically significant decrease of VEGF-A was observed at the 1- and 2-month follow-ups. A statistically significant increased concentration was observed in 7 biomarkers: VEGF-C, angiopoietin 2, endothelin 1, follistatin, HB-EGF, HGF, and interleukin 8. The other 11 study biomarker levels (VEGF-D, BMP-9, EGF, endoglin, FGF-1, FGF-2, GCSF, leptin, PLGF, TIMP-1, and TIMP-2) did not show any significant difference during follow-up. The BCVA statistically improved significantly at 2 months. Spectral-domain OCT parameters improved significantly at all follow-ups. Mean intraocular pressure values were not statistically different during the study period.

Conclusions

Despite a decrease in VEGF-A, the aqueous levels of VEGF-C, angiopoietin 2, endothelin 1, follistatin, HB-EGF, HGF, and interleukin 8 increased significantly after intravitreal injection of bevacizumab. These upregulated angiogenic biomarkers may represent new therapeutic targets in exudative AMD.

A randomized Phase III trial of neoadjuvant recombinant human endostatin, docetaxel and epirubicin as first-line therapy for patients with breast cancer (CBCRT01)

To further assess the efficacy and safety of recombinant human endostatin (rh-endostatin), a Phase III, multicenter, prospective, randomized, controlled clinical trial was conducted. Patients to be treated with neoadjuvant docetaxel and epirubicin (DE) or DE plus rh-endostatin (DEE) were eligible for this trial. The primary endpoint was clinical/pathological response. Secondary endpoints included adverse events and quality of life (QOL). Finally, 803 patients were enrolled and randomly assigned to receive DE (n = 402) or DEE (n = 401) regimen. After three cycles of neoadjuvant therapy, "complete response" achieved in 14.2% of patients in DEE group versus 6.7% in DE group, "partial response" achieved in 76.8% versus 71.1%, while "stable disease" in 6.0% versus 18.9%, "progressive disease" in 3.0% versus 3.2% of patients. The rate of objective response in DEE and DE group was 91.0% and 77.9%, respectively (p < 0.001). In spite of a relatively higher pathological complete response achieved following the combination therapy, no significant difference was found between two arms. Adverse events were mostly of Grades 1-2. No significant difference in adverse event and QOL was found between the two arms. In conclusion, the combination of chemotherapy and rh-endostatin achieved better outcomes than chemotherapy alone, and thus can be considered as a promising therapeutic strategy for breast cancer.

Vitamin D derivatives potentiate the anticancer and anti-angiogenic activity of tyrosine kinase inhibitors in combination with cytostatic drugs in an A549 non-small cell lung cancer model

Numerous in vitro and in vivo studies have demonstrated that calcitriol [1,25(OH)₂D₃] and different vitamin D analogs possess antineoplastic activity, regulating proliferation, differentiation and apoptosis, as well as angiogenesis. Vitamin D compounds have been shown to exert synergistic effects when used in combination with different agents used in anticancer therapies in different cancer models. The aim of this study was to evaluate the mechanisms of the cooperation of the vitamin D compounds [1,24(OH)₂D₃ (PRI-2191) and 1,25(OH)₂D₃] with tyrosine kinase inhibitors (imatinib and sunitinib) together with cytostatics (cisplatin and docetaxel) in an A549 non-small cell lung cancer model. The cytotoxic effects of the test compounds used in different combinations were evaluated on A549 lung cancer cells, as well as on human lung microvascular endothelial cells (HLMECs). The effects of such combinations on the cell cycle and cell death were also determined. In addition, changes in the expression of proteins involved in cell cycle regulation, angiogenesis and the action of vitamin D were analyzed. Moreover, the effects of 1,24(OH)₂D₃ on the anticancer activity of sunitinib and sunitinib in combination with docetaxel were examined in an A549 lung cancer model in vivo. Experiments aiming at evaluating the cytotoxicity of the combinations of the test agents revealed that imatinib and sunitinib together with cisplatin or docetaxel exerted potent anti-proliferative effects in vitro on A549 lung cancer cells and in HLMECs; however, 1,24(OH)₂D₃ and 1,25(OH)₂D₃ enhanced the cytotoxic effects only in the endothelial cells. Among the test agents, sunitinib and cisplatin decreased the secretion of vascular endothelial growth factor (VEGF)-A from the A549 lung cancer cells. The decrease in the VEGF-A level following incubation with cisplatin correlated with a higher p53 protein expression, while no such correlation was observed following treatment of the A549 cells with sunitinib. Sunitinib together with docetaxel and 1,24(OH)₂D₃ exhibited a more potent anticancer activity in the A549 lung cancer model compared to double combinations and to treatment with the compounds alone. The observed anticancer activity may be the result of the influence of the test agents on the process of tumor angiogenesis, for example, through the downregulation of VEGF-A expression in tumor and also on the induction of cell death inside the tumor.