Tumor Capillary Endothelial Cells Research Articles

Abstract 2649: An ex vivo 3D tumoroid model of fresh patient tissue (3D-EX) to assess the efficacy of anti-angiogenic compounds in renal cell carcinoma

Abstract Introduction: Renal Cell Carcinoma (RCC) is highly resistant to systemic chemotherapy; however, targeting pro-angiogenic pathways has shown significant clinical benefit. The development of targeted anti-angiogenetic agents has been hampered by the lack of clinically relevant models for screening. We have previously reported that the generation of 3D-tumoroids containing the unaltered tumor stroma could effectively be used to detect tumor response to small molecule inhibitors as well as antibody-based therapeutic agents. In this study we described a novel ex vivo platform to develop anti-angiogenic therapeutic strategies using fresh patient tumoroids of hepatocellular carcinoma and renal cell carcinoma. Materials and Methods: All fresh tumor samples were obtained with patient consent and relevant IRB approval. For the ex vivo assays, 3D tumoroids measuring 150 µm in size were treated with tyrosine kinase inhibitors (TKIs) sunitinib, sorafenib or axitinib. Treatment-mediated changes in endothelial cell viability was assessed by the confocal-based high-content real time imaging platform using fluorescent labeled anti-CD31 and anti-VEGFR2 antibodies, combined with custom image analysis algorithms. Additionally, treatment-mediated changes in tumor immune cell composition including CD4 and CD8 T-cells, Tregs, NK cells, macrophages, cell surface expression of checkpoint proteins as well as T-cell activation were evaluated by multiplex flow cytometry. Results: Our data shows that endothelial cells and capillary structures could clearly be visualized within3D tumoroids by confocal microscopy. Furthermore, we were able to quantify apoptotic cell death in endothelial cells induced by TKI inhibitors. Flow cytometry analysis demonstrated significant changes in T-cell activation upon treatment with TKIs that closely correlated with increased proinflammatory cytokine release. Observations found that the combination of anti-angiogenic treatments and immuno-modulatory agents significantly improved treatment responses. Conclusion: The ex vivo platform described in this study allowed assessment of the effect of anti-angiogenetic TKIs on tumor capillary endothelial cells as well as on tumor resident immune cell populations in intact RCC tumoroids of fresh patient tumor samples. We believe this clinically relevant approach can be used to identify the most effective anti-angiogenic and immunotherapeutic drugs and drug combinations in RCC and may improve personalized therapy for individual patients in clinical studies. Citation Format: Jared Ehrhart, Mibel M. Pabón, Stephen Iwanowycz, Zhisong Tong, Tina Pastoor, Soner Altiok. An ex vivo 3D tumoroid model of fresh patient tissue (3D-EX) to assess the efficacy of anti-angiogenic compounds in renal cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2649.

Reactive oxygen species in photodynamic therapy

Photosensitizer-mediated production of reactive oxygen species (ROS) plays a key role in photodynamic therapy (PDT). Reactive oxygen species mainly includes singlet oxygen, hydrogen peroxide, hydroxyl radical, superoxide anion radical and so on, among which singlet oxygen is the most important reactive oxygen species. In this paper, we firstly introduce the basic property of reactive oxygen species, generation and elimination of endogenous reactive oxygen species and generation mechanism of exogenous reactive oxygen species based on light, oxygen and photosensitizer. Next, we focus on the photosensitizers used to generate reactive oxygen species, factors that affect the yield of reactive oxygen species, and methods to increase the reactive oxygen species concentration at the tumor site. There are many factors that can affect the reactive oxygen species concentration at the tumor site, mainly among which are the singlet oxygen yield of the photosensitizer, the targeting of the photosensitizer, the oxygen concentration, and the illumination frequency. To achieve a good PDT effect, many photosensitizers or their nanoparticles with high singlet oxygen generation and good targeting ability are synthesized. Perfluorocarbon is used to deliver oxygen to overcome oxygen deficiency. Upconversion nanoparticles and two-photon absorption are very useful to solve the problem of weak penetration of short-wavelength light. New PDT methods are also introduced in the text, such as PDT combined photothermal therapy or chemotherapy. Then, we summarized various methods and technologies for reactive oxygen species detection, including direct detection of phosphorescence spectrophotometry, fluorescent probes and chemical probes for indirect detection, electron spin resonance, and positron emission tomography. The direct phosphorescence method mainly detects singlet oxygen based on the 1270 nm phosphorescence emission when singlet oxygen returns to the ground state. The first method to enhance the 1270 nm phosphor signal is to use a NIR photomultiplier tube (PMT) or an InGaAs linear array in combination with scanning of the excitation laser beam, and the second one is based on the use of a NIR camera with a filter. Because the lifetime of singlet oxygen is very short, time resolution is especially important. There are basically three main photon counting techniques: gated photon counting (GPC), multichannel scaling (MCS), and time-correlated single photon counting (TCSPC). In addition, singlet oxygen-sensitized delayed fluorescence (SOSDF) can also be used to detect singlet oxygen. Various new types of probes can specifically detect different types of reactive oxygen species, for example, 9, 10-anthracenedipropionic acid and MitoSOX can be used to detect singlet oxygen and superoxide anion in living cells respectively. The fluorescent probe itself does not have fluorescence, but reacts with reactive oxygen species to form an inner oxide, and emits strong fluorescence under the excitation of a certain wavelength of light. The difference of chemical probe is that it does not require light excitation because it can emit light spontaneously after reacted with reactive oxygen species. Electrons spin resonance (ESR) and positron emission tomography (PET) are also available to detect reactive oxygen species by using a probe. Finally, we discussed the mechanism of reactive oxygen species killing tumor cells, mainly in the following three aspects: (1) direct toxicity to tumor cells and induce their necrosis, apoptosis or autophagy; (2) damage on the tumor capillary endothelial cells and destruction of the microvasculature; (3) activation of an acute inflammatory response in host defense mechanisms. The effect of reactive oxygen species on the immune system and the apoptotic pathway of tumor cells from genes, proteins to the cell level were described in detail.

Targeted Alpha Therapy Trial in Bangladesh: Promise for Advanced MUC1 – Expressing Tumors

Introduction: Targeted alpha therapy (TAT) is a new experimental therapy that targets cancer cells and tumor capillary endothelial cells through intravenous injection of an alpha immuneconjugate (AIC). The AIC is formed by labeling the cancer targeting vector (monoclonal antibody) with alpha emitting radioisotopes using a bifunctionalchelator. The monoclonal antibody (MAb) is raised against antigens (e.g. MUC1) over-expressed on the surface of certain cancer cells. There are several centers notably in Europe, the US and Australia that are actively involved in TAT clinical trials of different cancers using a variety of techniques, alpha emitters and MAbs. Observations from their cumulative experience suggest that TAT is safe and effectivebut needs further trials for practical acceptance. Especially critical is the issue of maximum tolerance dose (MTD) which needs to be established for maximum target kill. Bangladesh has the infrastructure to conduct aTAT clinical trial and can significantly add to the growing pool of data for advanced treatment of cancers through collaborative involvement in targeted alpha therapy research.Objective: The aim of the article is to present a general overview of targeted alpha therapy and to discuss the feasibility of a TAT clinical trial in Bangladesh in the context of current cancer management situation in the country.Method: Literature review of significant publications was done to obtain an update of the current status of targeted alpha therapy. Relevant issues of TAT are presented for a theoretical basis of the technology. Next, the methodology of a proposed clinical trial is discussed, together with the practicability of its introduction in Bangladesh.Conclusion: Implementation of TAT clinical trial will help to develop an advanced technology and build- up skilled manpower in Bangladesh.It will optimize the key parameters of targeted alpha therapy, i e stability and specific activity of the alpha-conjugate and establish the maximum tolerance dose for the AIC. If the clinical trial is successful, it can change the prognosis of many end-stage cancers. Patients in Bangladesh with advanced MUCI expressing tumors of the breast, ovary, pancreas and prostate can have some measure of hope with stability of the disease.Bangladesh J. Nuclear Med. 19(1): 43-50, January 2016

Differential Effects of Tumor Secreted Factors on Mechanosensitivity, Capillary Branching, and Drug Responsiveness in PEG Hydrogels

Solid cancers induce the formation of new blood vessels to promote growth and metastasis. Unlike the normal vascular networks, the tumor induced vasculatures exhibit abnormal shape and function. Past efforts have been focused on characterizing the altered growth factor signaling pathway in tumor capillary endothelial cells; however, the mechanical microenvironment of tumor also plays a significant role in regulating the formation of vascular patterns. Here, we used synthetic hydrogel based cell culture platforms to probe how activation of human umbilical endothelial cells (HUVECs) by tumor secreted factors alters the responses to matrix modulus and in turn the capillary network formation and drug sensitivity. Our study revealed that while in absence of activation, HUVECs prefer a substrate of appropriate stiffness for optimal capillary network formation; stimulation by tumor cells disrupts the mechano-responsive behavior of HUVECs. Additionally, the effect of vandetanib on reducing the capillary network was also investigated. The response of HUVECs to the anti-angiogenic agent was substrate modulus dependent displaying increased sensitivity on the compliant gels. Stimulation by tumor cells reduced the responsiveness to vandetanib, particularly when plated on stiffer gels.

Targeting potassium channels for increasing delivery of imaging agents and therapeutics to brain tumors

Every year in the US, 20,000 new primary and nearly 200,000 metastatic brain tumor cases are reported. The cerebral microvessels/capillaries that form the blood–brain barrier not only protect the brain from toxic agents in the blood but also pose a significant hindrance to the delivery of small and large therapeutic molecules. Different strategies have been employed to circumvent the physiological barrier posed by blood–brain tumor barrier (BTB). Studies in our laboratory have identified significant differences in the expression levels of certain genes and proteins between normal and brain tumor capillary endothelial cells (ECs). In this study, we validated the non-invasive and clinically relevant dynamic contrast enhancing-magnetic resonance imaging (DCE-MRI) method with invasive, clinically irrelevant but highly accurate quantitative autoradiography method using rat glioma model. We also showed that DCE-MRI metric of tissue vessel perfusion-permeability is sensitive to changes in blood vessel permeability following administration of calcium-activated potassium (BKCa) channel activator NS-1619. Our results show that human gliomas and brain tumor ECs that overexpress BKCa channels can be targeted for increased BTB permeability for MRI enhancing agents to brain tumors. We conclude that monitoring the outcome of increased MRI enhancing agents’ delivery to microsatellites and leading tumor edges in glioma patients would lead to beneficial clinical outcome.

TRPV4 channels regulate tumor angiogenesis through the modulation of Rho‐dependent tumor endothelial cell mechanosensitivity

Tumor vessels are characterized by abnormal morphology and patterning that cause vascular hyperpermeability and inefficient delivery of anti‐cancer agents. We have previously shown that tumor vessel malformations may arise from aberrant Rho‐mediated mechanosensitivity of tumor‐derived capillary endothelial (CE) cells to mechanical cues, in particular blood flow‐induced cyclic strain. Here, we demonstrate that the expression and function of TRPV4, a mechanosenstive ion channel required for CE cell reorientation, is significantly lower in tumor CE cells compared to normal CE cells. Overexpression of TRPV4 increased GSK1016790A‐induced calcium influx in tumor CE cells and restored their shape sensitivity to substrate elasticity. Further, TRPV4 overexpression resulted in the suppression of the endogenously high Rho that, we previously showed, is implicated in aberrant mechanosensitivity of tumor CE cells. Importantly, overexpression of TRPV4 alone normalized the aberrant capillary formation and abnormal migration by tumor‐derived CE cells in vitro. Finally, tumor xenograft experiments revealed that, compared to tumors in wild type mice, those in TRPV4 KO mice exhibit a greater degree of vascular abnormality, as demonstrated by increased vessel diameter and reduced pericyte coverage, as well as enhanced growth. This work, therefore, demonstrates the critical role of TRPV4 channels in tumor endothelial cell mechanosensitivity and offers a novel therapeutic target for normalizing tumor vessel malformations and improving cancer drug delivery.

ATP-binding cassette transporters in primary central nervous system lymphoma: Decreased expression of MDR1 P-glycoprotein and breast cancer resistance protein in tumor capillary endothelial cells

Most tumors in the central nervous system are drug resistant partly because of the presence of the blood-brain barrier (BBB) between circulating blood and tumor tissues. Primary central nervous system lymphoma (PCNSL) is one of the exceptions, as it is highly sensitive to high-dose methotrexate (MTX)-based chemotherapy. The aim of this study was to evaluate the BBB function of tumor capillary endothelial cells in PCNSL. Expression of three major drug efflux transporters that belong to the ATP-binding cassette (ABC) superfamily, P-glycoprotein encoded by the human multidrug resistance gene (MDR1 Pgp; ABCB1), breast cancer resistance protein (BCRP; ABCG2), and multidrug resistance-associated protein 1 (MRP1; ABCC1), was evaluated. Immunohistochemistry was performed in capillary endothelial cells of 30 tumor areas from 22 PCNSL cases and compared with that of 30 gliomas. The microenvironment around tumor capillaries was assessed by examining the distribution of astrocytes and by counting the number of macrophages and T-cells, the principal cytokine producers. In PCNSL, expression of MDR1 Pgp and BCRP in tumor capillary endothelial cells was decreased in 63 and 93% of tumor areas examined, respectively, and these reduction levels differed significantly from those of gliomas (P<0.05). When the PCNSLs were further segregated by way of infiltration of tumor cells into three patterns (dense, perivascular and sparse), decreased MDR1 Pgp and BCRP in tumor capillary endothelial cells were much more prominent in dense and perivascular patterns. In all tumors and non-tumor areas of the brain, MRP1 was undetected on capillary endothelial cells. Assessment of the microenvironment around the tumor capillaries suggested that dissociation from astrocytes and infiltration of macrophages and T-cells was involved in the down-regulation of MDR1 Pgp and BCRP in capillary endothelial cells. In conclusion, we report that expression of the major ABC transporters of the BBB, MDR1 Pgp and BCRP, decreases in tumor capillary endothelial cells of PCNSL. Thus, decreased expression may permit delivery of chemotherapeutic agents to the tumor tissues.

Identification of proteins differentially expressed between capillary endothelial cells of hepatocellular carcinoma and normal liver in an orthotopic rat tumor model using 2-D DIGE

Hepatocellular carcinoma (HCC) is one of the deadliest cancers with few treatment options. It is a hypervascular tumor in which angiogenesis plays a critical role in its progression. Tumor capillary endothelial cells (TECs) in HCC are known to originate from liver sinusoid endothelial cells, which then go through a capillarization process to become morphologically as well as functionally different TECs. In this work, we investigated proteins differentially expressed between freshly isolated TECs and sinusoid endothelial cells from well-formed rat HCC using 2-D DIGE coupled with MALDI-TOF/TOF MS. Thirty-eight unique proteins were identified to be differentially expressed more than twofold between the two endothelial cell types. Amongst the differentially expressed proteins, two novel endothelial markers, EH domain-containing protein 3 and galectin-3, were confirmed by Western blot and immunohistochemistry in both rat and human HCC samples. We showed that EH domain-containing protein 3 is significantly down-regulated in TECs, but galectin-3 is up-regulated. We propose possible roles of these two proteins in tumor vessel development in HCC.

Reduction of angiocidin expression in human umbilical vein endothelial cells via siRNA silencing inhibits angiogenesis

Angiocidin, a protein over-expressed in many different solid tumors and tumor capillary endothelial cells inhibits angiogenesis and tumor growth [Zhou, J., et al., 2004. Cloning and characterization of angiocidin, a tumor cell binding protein for thrombospondin-1. J Cell Biochem. 92, 125–146]. Since several splice variants of angiocidin have distinct biochemical functions in membrane transport and protein degradation, we sought to evaluate the function of endogenously expressed angiocidin in human umbilical vein endothelial (HUVE) cells using siRNA. We observed a 90% reduction of the target mRNA levels after 24 h. Endogenous angiocidin protein expression was reduced by 80% after three days, as evaluated by Western blot analysis. We also found that anti-angiocidin siRNA down-regulated 90% of the protein expression of matrix metalloproteinase 2 (MMP-2) and 50% of its gelatinolytic activity. Reduction of endogenous angiocidin completely inhibited endothelial cord formation on Matrigel. Cells expressing low levels of angiocidin grew more slowly, were less invasive and less adhesive than control cells. Consistent with the reported function of one of the angiocidin analogues S5a, we found that the expression of polyubiquitinated proteins was higher in anti-angiocidin siRNA-treated cells as compared to normal and control siRNA-treated cells. These results suggest that endogenous angiocidin and its homologues promote endothelial cell invasion, adhesion, and angiogenesis through mechanisms involving polyubiquitin-dependent protein degradation and MMP-2 expression.

Modulation of brain tumor capillaries for enhanced drug delivery selectively to brain tumor.

The blood-brain tumor barrier (BTB) significantly impedes delivery of most hydrophilic molecules to brain tumors. Several promising strategies, however, have been developed to overcome this problem. We discuss several drug delivery methods to brain tumor, including intracerebroventricular, convection enhanced delivery, BBB/BTB disruption, and BTB permeability modulation, which was developed in our laboratory. Using immunolocalization, immunoblotting, and potentiometric studies, we found that brain tumor capillary endothelial cells overexpress certain unique protein markers that are absent or barely detectable in normal capillary endothelial cells. We biochemically modulated these markers to sustain and enhance drug delivery, including molecules of varying sizes, selectively to tumors in rat syngeneic and xenograft brain tumor models. We also demonstrated that the cellular mechanism for vasomodulator-mediated BTB permeability increase is due to accelerated formation of pinocytotic vesicles that transport therapeutic molecules across the BTB. Other methods to deliver drugs across the BTB are effective but have severe drawbacks. Our strategy targets BTB-specific proteins to increase antineoplastic drug delivery selectively to brain tumors with few or no side effects, thus increasing the possibility of improving brain tumor treatment.

Protease-activated receptor (PAR)-1 and PAR-2 participate in the cell growth of alveolar capillary endothelium in primary lung adenocarcinomas.

Cell growth can be induced via elicitation of protease-activated receptors (PAR) with serine proteases such as thrombin and trypsin. To understand whether PAR are involved in tumor vessel formation in the neoplastic cell-bearing alveolar walls, immunohistochemical and reverse transcriptase-polymerase chain reaction analyses were performed using the lung tissues from 16 patients with primary lung adenocarcinomas. In microdissected tumor alveolar walls, the expressions of PAR-1 and PAR-2 mRNA were increased by 10-fold (P < 0.05) and 16-fold (P < 0.01), respectively, as compared with normal alveolar walls. Confocal microscopy revealed that tumor capillary endothelial cells in alveolar walls lost thrombomodulin expression. Instead, the expression of PAR-2 often became obvious at the normal border. Both PAR-1 and PAR-2 were expressed in the microvessel endothelial cells in tumors. Trypsin mRNA was expressed in 7 of the 16 cancer cell-bearing tissue specimens in contrast to 1 of the 14 normal alveolar walls. Immunohistochemically, trypsin was positive in the neoplastic cells from 10 patients and in lung adenocarcinoma cell lines (A549, HLC-1, LC-2, and PC-14). An in vitro assay showed a significant increase in idoxuridine (IdU) or bromodeoxyuridine uptake in human pulmonary artery endothelial cells and human umbilical cord vein endothelial cells after treatments with alpha-thrombin or activating peptides; SFLLRN for PAR-1 and SLIGKV for PAR-2, respectively. Thus, proliferation of alveolar capillary endothelial cells is initialized in part by PAR activation with serum thrombin and neoplastic cell-released trypsin. These results suggest a synergistic effect of PAR with vascular endothelial growth factor in alveolar angiogenesis.

Correlation between bradykinin-induced blood–tumor barrier permeability and B2 receptor expression in experimental brain tumors

Localization of B2 receptors in brain tumor cells and microvessel endothelial cells of the brain tumors was investigated to study the differential sensitivity of brain tumors to bradykinin. The present study shows that B2 receptor expression levels vary in cultured RG2, C6 and 9L glioma cells as well as in the intracerebral tumors established with these cell lines in rats. The double immunohistochemical data indicate that B2 receptors are localized to tumor cells and not to the tumor capillaries. Immunostaining and Western blot analysis for B2 receptor showed that the B2 receptor expression was in the order C6>RG2>9L. The permeability studies on RG2, C6 and 9L tumors in rats showed that C6 tumor had the highest increase (178%) in Ki (unidirectional transport across blood–brain barrier (BBB)/blood–tumor barrier (BTB)), while 9L tumor had the least increase of Ki (35%) over the control group, following intracarotid infusion of bradykinin. We found a positive correlation (r = 0.965, p<0.001) between B2 receptor levels and bradykinin-induced increase in BTB permeability. We conclude that B2 receptors are localized to tumor cells and not to normal or tumor capillary endothelial cells. C6 tumor with highest B2 receptor expression was most responsive to bradykinin, while RG2 and 9L tumors with lower B2 receptor expression level were less sensitive to bradykinin with regard to BTB permeability.