Tumor microvasculature with endothelial fenestrations in VHL null clear cell renal cell carcinomas as a potent target of anti-angiogenic therapy

Extracellular vesicles secreted from bone metastatic renal cell carcinoma promote angiogenesis and endothelial gap formation in bone marrow in a time-dependent manner in a preclinical mouse model

Introduction

Bone is a major metastatic site of renal cell carcinoma (RCC). Recently, it is well recognized that bone metastatic tumor cells remodel bone marrow vasculature. However, the precise mechanism underlying cell-cell communication between bone metastatic RCC and the cells in bone marrow remains unknown. Extracellular vesicles (EVs) reportedly play crucial roles in intercellular communication between metastatic tumor cells and bone marrow. Therefore, we conducted the current study to clarify the histological alteration in vascular endothelium in bone marrow induced by EVs secreted from bone metastatic RCC cells as well as association between angiogenesis in bone marrow and bone metastasis formation.

Materials and methods

We established a bone metastatic RCC cell line (786-O BM) by in vivo selection and observed phenotypic changes in tissues when EVs were intravenously injected into immunodeficient mice. Proteomic analysis was performed to identify the protein cargo of EVs that could contribute to histological changes in bone. Tissue exudative EVs (Te-EVs) from cancer tissues of patients with bone metastatic RCC (BM-EV) and those with locally advanced disease (LA-EV) were compared for in vitro function and protein cargo.

Results

Treatment of mice with EVs from 786-O BM promoted angiogenesis in the bone marrow in a time-dependent manner and increased the gaps of capillary endothelium. 786-O BM EVs also promoted tube formation in vitro. Proteomic analysis of EVs identified aminopeptidase N (APN) as a candidate protein that enhances angiogenesis. APN knockdown in 786-O BM resulted in reduced angiogenesis in vitro and in vivo. When parental 786-O cells were intracardially injected 12 weeks after treatment with786-O BM EVs, more bone metastasis developed compared to those treated with EVs from parental 786-O cells. In patient samples, BM-EVs contained higher APN compared to LA-EV. In addition, BM-EVs promoted tube formation in vitro compared to LA-EVs.

Conclusion

EVs from bone metastatic RCC promote angiogenesis and gap formation in capillary endothelium in bone marrow in a time-dependent manner.

Synergism between anti-angiogenic and immune checkpoint inhibitor drugs: A hypothesis

Hepatocellular cancer (HCC) and renal cell cancer (RCC) are singularly resistant to conventional chemotherapy drugs but therapies targeting the supporting stroma have significantly altered their management. Two recent trials combining anti-angiogenic (AA) agents with immune checkpoint inhibitors (ICIs)- the IMbrave150 and IMmotion151 - have reported impressive progress over targeted agents. It has been suggested that bevacizumab, by improving tissue perfusion, changes the immune suppressive tumour microenvironment to an immune stimulatory one where the ICIs can be more effective. This hypothesis proposes an alternative explanation: That bevacizumab, by increasing tissue hypoxia, amplifies the mutational burden of the tumour by stress-induced mutagenesis, creating a hypermutator profile, which is more vulnerable to the ICI drug, atezolizumab. Additionally, ICIs are known to cause hyperprogression in some tumours, and bevacizumab could provide further benefit by starving these rapidly proliferative tumours of blood supply and nutrients.

Ethanol and Cytokines in the Central Nervous System

The innate immune system plays a critical role in the ethanol-induced neuroimmune response in the brain. Ethanol initiates the innate immune response via activation of the innate immune receptors Toll-like receptors (TLRs, e.g., TLR4, TLR3, TLR7) and NOD-like receptors (inflammasome NLRs) leading to a release of a plethora of chemokines and cytokines and development of the innate immune response. Cytokines and chemokines can have pro- or anti-inflammatory properties through which they regulate the immune response. In this chapter, we will focus on key cytokines (e.g., IL-1, IL-6, TNF-α) and chemokines (e.g., MCP-1/CCL2) that mediate the ethanol-induced neuroimmune responses. In this regard, we will use IL-1β, as an example cytokine, to discuss the neuromodulatory properties of cytokines on cellular properties and synaptic transmission. We will discuss their involvement through a set of evidence: (1) changes in gene and protein expression following ethanol exposure, (2) association of gene polymorphisms (humans) and alterations in gene expression (animal models) with increased alcohol intake, and (3) modulation of alcohol-related behaviors by transgenic or pharmacological manipulations of chemokine and cytokine systems. Over the last years, our understanding of the molecular mechanisms mediating cytokine- and chemokine-dependent regulation of immune responses has advanced tremendously, and we review evidence pointing to cytokines and chemokines serving as neuromodulators and regulators of neurotransmission.

Nanotherapeutics to Modulate the Compromised Micro-Environment for Lung Cancers and Chronic Obstructive Pulmonary Disease

The use of nanomaterials to modulate the tumor microenvironment has great potential to advance outcomes in patients with lung cancer. Nanomaterials can be used to prolong the delivery time of therapeutics enabling their specific targeting to tumors while minimizing and potentially eliminating cytotoxic effects. Using nanomaterials to deliver small-molecule inhibitors for oncogene targeted therapy and cancer immunotherapy while concurrently enabling regeneration of the extracellular matrix could enhance our therapeutic reach and improve outcomes for patients with non-small cell lung cancer (NSCLC) and chronic obstructive pulmonary disease (COPD). The objective of this review is to highlight the role nanomedicines play in improving and reversing adverse outcomes in the tumor microenvironment for advancing treatments for targeting both diseases.

Exploring the Potential of Nanotherapeutics in Targeting Tumor Microenvironment for Cancer Therapy

Advanced research in the field of cancer biology clearly demonstrated the key role of tumor microenvironment (TME) in cancer development and metastasis particularly in solid tumors. Components of TME, being non-neoplastic in nature provide supportive and permissive conditions for the growth of cancer cells. Hence it is important to modify TME in cancer therapy and this would be achieved by better understanding of TME morphological features and functioning of stromal components. Nanotechnology based drug delivery offers various advantages such as prolonged circulation time, delivery of cargo at desired site, improved bioavailability, reduced toxicity etc. over conventional chemotherapeutics. Abnormal characteristic features of TME play a paradoxical role in nanoparticulate drug delivery. Leaky vasculature, acidic and hypoxic conditions of TME helps in the accumulation of tailored nanoparticles whereas high interstitial pressure and dense stroma restrict the extravasation, homogenous distribution of nanocarriers in TME. This review mainly discusses the potential of nanotherapeutics in targeting TME by briefly discussing stromal components, therapeutic opportunities and barriers offered by TME for nanoparticulate drug delivery. Updated information on TME remodeling strategies for improved drug delivery and specific targeting of individual stromal components are also outlined.

CCL2 as a potential therapeutic target for clear cell renal cell carcinoma

We previously reported that the pVHL‐atypical PKC‐JunB pathway contributed to promotion of cell invasiveness and angiogenesis in clear cell renal cell carcinoma (ccRCC), and we detected chemokine (C‐C motif) ligand‐2 (CCL2) as one of downstream effectors of JunB. CCL2 plays a critical role in tumorigenesis in other types of cancer, but its role in ccRCC remains unclear. In this study, we investigated the roles and therapeutic potential of CCL2 in ccRCC. Immunohistochemical analysis of CCL2 expression for ccRCC specimens showed that upregulation of CCL2 expression correlated with clinical stage, overall survival, and macrophage infiltration. For functional analysis of CCL2 in ccRCC cells, we generated subclones of WT8 cells that overexpressed CCL2 and subclones 786‐O cells in which CCL2 expression was knocked down. Although CCL2 expression did not affect cell proliferation in vitro, CCL2 overexpression enhanced and CCL2 knockdown suppressed tumor growth, angiogenesis, and macrophage infiltration in vivo. We then depleted macrophages from tumor xenografts by administration of clodronate liposomes to confirm the role of macrophages in ccRCC. Depletion of macrophages suppressed tumor growth and angiogenesis. To examine the effect of inhibiting CCL2 activity in ccRCC, we administered CCL2 neutralizing antibody to primary RCC xenografts established from patient surgical specimens. Inhibition of CCL2 activity resulted in significant suppression of tumor growth, angiogenesis, and macrophage infiltration. These results suggest that CCL2 is involved in angiogenesis and macrophage infiltration in ccRCC, and that CCL2 could be a potential therapeutic target for ccRCC.

Autocrine MCP-1/CCR2 signaling stimulates proliferation and migration of renal carcinoma cells

The chemokine monocyte chemoattractant protein-1 [MCP-1; also known as chemokine (C-C motif) ligand 2] is an important mediator of monocyte recruitment during inflammatory processes. Pathologically high expression levels of MCP-1 by tumor cells have been observed in a variety of cancer types. In the majority of cases, high MCP-1 expression is associated with a poor prognosis, as infiltration of the tumor with inflammatory monocytes promotes tumor progression and metastasis. MCP-1 is also expressed in renal cell carcinoma (RCC). In the present study, the function and the regulation of MCP-1 was investigated in two RCC cell lines, CaKi-1 and 786-O. In both cell lines, expression of MCP-1 was significantly enhanced compared with non-cancerous control cells. As expected, secretion of MCP-1 into the medium facilitated the recruitment of peripheral blood monocytes via the chemokine (C-C motif) receptor type 2 (CCR2). As expression of CCR2 was also detected in 786-O and CaKi-1 cells, the effect of autocrine MCP-1/CCR2 signaling was evaluated in these cells. In proliferation assays, administration of an MCP-1 neutralizing antibody or of a CCR2 antagonist to CaKi-1 and 786-O cells significantly decreased cell growth; supplementation of the growth medium with recombinant human MCP-1 had no additional effect on proliferation. The migration ability of RCC cells was impaired by MCP-1 neutralization or pharmacological CCR2 inhibition, while it was stimulated by the addition of recombinant human MCP-1, compared with untreated control cells. Finally, substantial differences in the regulation of MCP-1 expression were observed between RCC cell lines. In CaKi-1 cells, expression of MCP-1 appears to be largely mediated by the transcription factor nuclear factor of activated T cells 5, while in 786-O cells, deletion of the tumor suppressor gene Von-Hippel-Lindau appeared to be responsible for MCP-1 upregulation, as suggested by previous studies. Taken together, the results of the current study indicate that expression of MCP-1 in RCC cells promotes tumor progression and metastasis not only by paracrine, but also by autocrine, MCP-1/CCR2 signaling events, enhancing cell proliferation and migration ability. Therefore, the present findings suggest the MCP-1/CCR2 axis is a potential target for future therapeutic strategies in the treatment of metastatic RCC.

The genetic basis of intradural spinal tumors and its impact on clinical treatment

Genetic alterations in the cells of intradural spinal tumors can have a significant impact on the treatment options, counseling, and prognosis for patients. Although surgery is the primary therapy for most intradural tumors, radiochemothera-peutic modalities and targeted interventions play an ever-evolving role in treating aggressive cancers and in addressing cancer recurrence in long-term survivors. Recent studies have helped delineate specific genetic and molecular differences between intradural spinal tumors and their intracranial counterparts and have also identified significant variation in therapeutic effects on these tumors. This review discusses the genetic and molecular alterations in the most common intradural spinal tumors in both adult and pediatrie patients, including nerve sheath tumors (that is, neurofibroma and schwannoma), meningioma, ependymoma, astrocytoma (that is, low-grade glioma, anaplastic astrocytoma, and glioblastoma), hemangioblastoma, and medulloblastoma. It also examines the genetics of metastatic tumors to the spinal cord, arising either from the CNS or from systemic sources. Importantly, the impact of this knowledge on therapeutic options and its application to clinical practice are discussed.

Role of IL13RA2 in Sunitinib Resistance in Clear Cell Renal Cell Carcinoma

Vascular endothelial growth factor (VEGF) and mammalian target of rapamycin are well-known therapeutic targets for renal cell carcinoma (RCC). Sunitinib is an agent that targets VEGF receptors and is considered to be a standard treatment for metastatic or unresectable clear cell RCC (ccRCC). However, ccRCC eventually develops resistance to sunitinib in most cases, and the mechanisms underlying this resistance are not fully elucidated. In the present study, we established unique primary xenograft models, KURC1 (Kyoto University Renal Cancer 1) and KURC2, from freshly isolated ccRCC specimens. The KURC1 xenograft initially responded to sunitinib treatment, however finally acquired resistance. KURC2 retained sensitivity to sunitinib for over 6 months. Comparing gene expression profiles between the two xenograft models with different sensitivity to sunitinib, we identified interleukin 13 receptor alpha 2 (IL13RA2) as a candidate molecule associated with the acquired sunitinib-resistance in ccRCC. And patients with high IL13RA2 expression in immunohistochemistry in primary ccRCC tumor tends to have sunitinib-resistant metastatic site. Next, we showed that sunitinib-sensitive 786-O cells acquired resistance in vivo when IL13RA2 was overexpressed. Conversely, shRNA-mediated knockdown of IL13RA2 successfully overcame the sunitinib-resistance in Caki-1 cells. Histopathological analyses revealed that IL13RA2 repressed sunitinib-induced apoptosis without increasing tumor vasculature in vivo. To our knowledge, this is a novel mechanism of developing resistance to sunitinib in a certain population of ccRCC, and these results indicate that IL13RA2 could be one of potential target to overcome sunitinib resistance.

Modulation of the tumor microenvironment for cancer treatment: a biomaterials approach

Tumors are complex tissues that consist of stromal cells, such as fibroblasts, immune cells and mesenchymal stem cells, as well as non-cellular components, in addition to neoplastic cells. Increasingly, there is evidence to suggest that these non-neoplastic cell components support cancer initiation, progression and metastasis and that their ablation or reprogramming can inhibit tumor growth. Our understanding of the activities of different parts of the tumor stroma in advancing cancer has been improved by the use of scaffold and matrix-based 3D systems originally developed for regenerative medicine. Additionally, drug delivery systems made from synthetic and natural biomaterials deliver drugs to kill stromal cells or reprogram the microenvironment for tumor inhibition. In this article, we review the impact of 3D tumor models in increasing our understanding of tumorigenesis. We also discuss how different drug delivery systems aid in the reprogramming of tumor stroma for cancer treatment.

Vascularity of primary and metastatic renal cell carcinoma specimens

Purpose

Anti-angiogenic therapies are among the most commonly used drugs in renal cell carcinoma. Tumor vascularity, defined by microvessel area, may be associated with response to these drugs. Clinical studies suggest that metastatic sites are more responsive than primary tumors. Our purpose was to characterize microvessel area (MVA) in matched primary and metastatic samples and in samples of different histologies.

Methods

We employed a method of automated, quantitative analysis of in situ tumor components to identify the area of CD-34 staining endothelial cells within renal cell carcinoma tumors. MVA was assessed in corresponding primary and metastatic samples from 34 patients, as well as in 334 primary nephrectomy specimens with variable histologies.

Results

MVA measurements from different parts of the same tumor correlated well (R = 0.75), indicating that MVA was fairly uniform within a tumor. While MVA was slightly higher in primary tumors than corresponding metastatic sites, the difference was not statistically significant (P = 0.1). MVA in paired primary and metastatic samples correlated moderately well (R = 0.36). MVA was higher in clear cell than papillary histology and oncocytomas (P < 0.0001 and P = 0.018, respectively).

Conclusions

Lack of significant differences MVA in matched primary and metastatic samples suggests that both types of tumors should respond to anti-angiogenic drugs. This should be confirmed on additional cohorts. Given the small cohort, future predictive biomarker studies entailing MVA measurements should include specimens from both sites. Clear cell carcinomas are more vascular than other histologic subtypes, which may explain the higher response rates to anti-angiogenic therapies in clear cell tumors.

Establishment of phosphatidylinositol 3-kinase inhibitor-resistant cancer cell lines and therapeutic strategies for overcoming the resistance

Acquired resistance is a major obstacle for conventional cancer chemotherapy, and also for some of the targeted therapies approved to date. Long-term treatment using protein tyrosine kinase inhibitors (TKIs), such as gefitinib and imatinib, gives rise to resistant cancer cells carrying a drug-resistant gatekeeper mutation in the kinase domain of the respective target genes, EGFR and BCR-ABL. As for the phosphatidylinositol 3-kinase inhibitors (PI3Kis), little is known about their acquired resistance, although some are undergoing clinical trials. To address this issue, we exposed 11 human cancer cell lines to ZSTK474, a PI3Ki we developed previously, for a period of more than 1 year in vitro. Consequently, we established ZSTK474-resistant cells from four of the 11 cancer cell lines tested. The acquired resistance was not only to ZSTK474 but also to other PI3Kis. None of the PI3Ki-resistant cells, however, contained any mutation in the kinase domain of the PIK3CA gene. Instead, we found that insulin-like growth factor 1 receptor (IGF1R) was overexpressed in all four resistant cells. Interestingly, targeted knockdown of IGF1R expression using specific siRNAs or inhibition of IGF1R using IGF1R-TKIs reversed the acquired PI3Ki resistance. These results suggest that long-term treatment with PI3Kis may cause acquired resistance, and targeting IGF1R is a promising strategy to overcome the resistance.

Tumor microvasculature with endothelial fenestrations in VHL null clear cell renal cell carcinomas as a potent target of anti-angiogenic therapy

Vascular endothelial growth factor (VEGF)-targeted therapies show significant antitumor effects for advanced clear cell renal cell carcinomas (CC-RCCs). Previous studies using VEGF inhibitors in mice models revealed that VEGF-dependent capillaries were characterized by the existence of endothelial fenestrations (EFs). In this study, we revealed that capillaries with abundant EFs did exist, particularly in CC-RCCs harboring VHL mutation. This finding was recapitulated in mice xenograft models, in which tumors from VHL null cells showed more abundant EFs compared to those from VHL wild-type cells. Importantly, treatment with bevacizumab resulted in a significant decrease of tumor size established from VHL null cells. Additionally, a significant reduction of EFs and microvessel density was observed in VHL null tumors. Indeed, xenograft from 786-O/mock (pRC3) cells developed four times more abundant EFs than that from 786-O/VHL (WT8). However, introduction of the constitutively active form of hypoxia-inducible factor (HIF)-2α to WT8 cells failed to either augment the number of EFs or restore the sensitivity to bevacizumab in mice xenograft, irrespective of the equivalent production of VEGF to 786-O/mock cells. These results indicated that HIF-2α independent factors also play significant roles in the development of abundant EFs. In fact, several angiogenesis-related genes including CCL2 were upregulated in 786-O cells in a HIF-2α independent manner. Treatment with CCL2 neutralizing antibody caused significant reduction of capillaries with EFs in 786-O xenograft, indicating that they were also sensitive to CCL2 inhibition as well as VEGF. Collectively, these results strongly indicated that capillaries with distinctive phenotype developed in VHL null CC-RCCs are potent targets for anti-angiogenic therapy.