Tumor blood vessels supply nutrients and oxygen to tumor cells for their growth and provide routes for them to enter circulation. Thus, angiogenesis, the formation of new blood vessels, is essential for tumor progression and metastasis. Tumor endothelial cells (TECs) that cover the inner surfaces of tumor blood vessels reportedly show phenotypes distinct from those of their normal counterparts. As examples, TECs show cytogenetic abnormalities, resistance to anticancer drugs, activated proliferation and migration, and specific gene expression patterns. TECs contain stem-like cell populations, which means that the origin of TECs is heterogeneous. In addition, since some abnormal phenotypes in TECs are induced by factors in the tumor microenvironment, such as hypoxia and tumor cell-derived factors, phenotypic diversity in TECs may be caused in part by intratumoral heterogeneity. Recent studies have identified that the interaction of tumor cells and TECs by juxtacrine and paracrine signaling contributes to tumor malignancy. Understanding TEC abnormality and heterogeneity is important for treatment of cancers. This review provides an overview of the diversity of TECs and discusses the interaction between TECs and tumor cells in the tumor microenvironment.

Background: Tumor endothelial cells (TECs) perform tumor angiogenesis, which is essential for tumor growth and metastasis. Tumor cells produce large amounts of lactic acid from glycolysis; however, the mechanism underlying the survival of TECs to enable tumor angiogenesis under high lactic acid conditions in tumors remains poorly understood.Methodology: The metabolomes of TECs and normal endothelial cells (NECs) were analyzed by capillary electrophoresis time-of-flight mass spectrometry. The expressions of pH regulators in TECs and NECs were determined by quantitative reverse transcription-PCR. Cell proliferation was measured by the MTS assay. Western blotting and ELISA were used to validate monocarboxylate transporter 1 and carbonic anhydrase 2 (CAII) protein expression within the cells, respectively. Human tumor xenograft models were used to access the effect of CA inhibition on tumor angiogenesis. Immunohistochemical staining was used to observe CAII expression, quantify tumor microvasculature, microvessel pericyte coverage, and hypoxia.Results: The present study shows that, unlike NECs, TECs proliferate in lactic acidic. TECs showed an upregulated CAII expression both in vitro and in vivo. CAII knockdown decreased TEC survival under lactic acidosis and nutrient-replete conditions. Vascular endothelial growth factor A and vascular endothelial growth factor receptor signaling induced CAII expression in NECs. CAII inhibition with acetazolamide minimally reduced tumor angiogenesis in vivo. However, matured blood vessel number increased after acetazolamide treatment, similar to bevacizumab treatment. Additionally, acetazolamide-treated mice showed decreased lung metastasis.Conclusion: These findings suggest that due to their effect on blood vessel maturity, pH regulators like CAII are promising targets of antiangiogenic therapy.Graphical

Going from bench to bedside is a simplified description of translational research, with the ultimate goal being to improve the health status of mankind. Tumor endothelial cells (TECs) perform angiogenesis to support the growth, establishment, and dissemination of tumors to distant organs. TECs have various features that distinguish them from normal endothelial cells, which include alterations in gene expression patterns, higher angiogenic and metabolic activities, and drug resistance tendencies. The special characteristics of TECs enhance the vulnerability of tumor blood vessels toward antiangiogenic therapeutic strategies. Therefore, apart from being a viable therapeutic target, TECs would act as a better mediator between the bench (i.e., angiogenesis research) and the bedside (i.e., clinical application of drugs discovered through research). Exploitation of TEC characteristics could reveal unidentified strategies of enhancing and monitoring antiangiogenic therapy in the treatment of cancer, which are discussed in this review.

Tumor blood vessels play important roles in tumor progression and metastasis. Targeting tumor endothelial cells (TECs) is one of the strategies for cancer therapy. We previously reported that biglycan, a small leucine‐rich proteoglycan, is highly expressed in TECs. TECs utilize biglycan in an autocrine manner for migration and angiogenesis. Furthermore, TEC‐derived biglycan stimulates tumor cell migration in a paracrine manner leading to tumor cell intravasation and metastasis. In this study, we explored the therapeutic effect of biglycan inhibition in the TECs of renal cell carcinoma using an in vivo siRNA delivery system known as a multifunctional envelope‐type nanodevice (MEND), which contains a unique pH‐sensitive cationic lipid. To specifically deliver MEND into TECs, we incorporated cyclo(Arg–Gly–Asp–D–Phe–Lys) (cRGD) into MEND because α_Vβ₃ integrin, a receptor for cRGD, is selective and highly expressed in TECs. We developed RGD‐MEND‐encapsulating siRNA against biglycan. First, we confirmed that MEND was delivered into OS‐RC‐2 tumor‐derived TECs and induced in vitro RNAi‐mediated gene silencing. MEND was then injected intravenously into OS‐RC‐2 tumor‐bearing mice. Flow cytometry analysis demonstrated that MEND was specifically delivered into TECs. Quantitative RT‐PCR indicated that biglycan was knocked down by biglycan siRNA‐containing MEND. Finally, we analyzed the therapeutic effect of biglycan silencing by MEND in TECs. Tumor growth was inhibited by biglycan siRNA‐containing MEND. Tumor microenvironmental factors such as fibrosis were also normalized using biglycan inhibition in TECs. Biglycan in TECs can be a novel target for cancer treatment.

During the past 2 decades, in order to improve perioperative and oncological outcomes, a minimally invasive approach, neoadjuvant chemotherapy (NAC), and an enhanced postoperative recovery program after surgery have been introduced into routine clinical practice of radical cystectomy (RC). Our aim was to examine the differences in clinical practice and postoperative complications after RC by comparing our previous and current cohorts. A retrospective multi-institutional study. We collected all complications within 90 days after surgery between 2011 and 2017 (current cohort), and categorized them according to a standardized methodology. Then, we compared the outcomes with those in our previous study (previous cohort, 1997-2010). A multivariate logistic regression model was utilized to determine predictors of complications in the current cohort. A total of 838 patients were newly collected (current cohort), and 919 from the previous cohort were included in the subsequent analyses. In the current cohort, the rate of performing NAC was significantly higher (13% vs. 4%, respectively, P < 0.0001), and 26% (222/838) underwent laparoscopic RC (LRC, without robotic assistance: n = 210, with robotic assistance: n = 12). There was no significant difference in the overall complication [69% (580/838) vs. 68% (629/919), respectively, P = 0.7284] or major complication (Grades 3-5) [25% (211/838) vs. 22% (201/919), respectively, P = 0.1022] rates between the 2 cohorts. In both cohorts, the most frequent categories were infectious, gastrointestinal, wound-related, and genitourinary. In the current cohort, the performance status (odds ratio, OR = 2.11, P = 0.0013) and operative time (OR = 1.003, P = 0.0016) remained significant predictors of major complications. NAC was not associated with any or major complications. Surgical complications related to RC still remain significant problems, despite the recent improvements in surgical techniques and perioperative care. NAC did not increase the complications.