Blood flow velocity in monocular retinoblastoma assessed by color Doppler

OBJECTIVE

To analyze the flow of retrobulbar vessels in retinoblastoma by color Doppler imaging.

METHODS

A prospective study of monocular retinoblastoma treated by enucleation between 2010 and 2014. The examination comprised fundoscopy, magnetic resonance imaging, ultrasonography and color Doppler imaging. The peak blood velocities in the central retinal artery and central retinal vein of tumor-containing eyes (tuCRAv and tuCRVv, respectively) were assessed. The velocities were compared with those for normal eyes (nlCRAv and nlCRVv) and correlated with clinical and pathological findings. Tumor dimensions in the pathological sections were compared with those in magnetic resonance imaging and ultrasonography and were correlated with tuCRAv and tuCRVv. In tumor-containing eyes, the resistivity index in the central retinal artery and the pulse index in the central retinal vein were studied in relation to all variables.

RESULTS

Eighteen patients were included. Comparisons between tuCRAv and nlCRAv and between tuCRVv and nlCRVv revealed higher velocities in tumor-containing eyes (p < 0.001 for both), with a greater effect in the central retinal artery than in the central retinal vein (p = 0.024). Magnetic resonance imaging and ultrasonography measurements were as reliable as pathology assessments (p = 0.675 and p = 0.375, respectively). A positive relationship was found between tuCRAv and the tumor volume (p = 0.027). The pulse index in the central retinal vein was lower in male patients (p = 0.017) and in eyes with optic nerve invasion (p = 0.0088).

CONCLUSIONS

TuCRAv and tuCRVv are higher in tumor-containing eyes than in normal eyes. Magnetic resonance imaging and ultrasonography measurements are reliable. The tumor volume is correlated with a higher tuCRAv and a reduced pulse in the central retinal vein is correlated with male sex and optic nerve invasion.

[HIF-1alpha, HPSE and VEGF promote malignant progression of retinoblastoma]

OBJECTIVE

To investigate the expression of heparanase (HPSE), hypoxia-inducible factor (HIF-1alpha) and their correlation with expression of vascular endothelial growth factor (VEGF) and microvessel density (MVD) in retinoblastoma.

METHODS

HIF-1alpha and VEGF were detected by SP immunohistochemical method in 34 cases of retinoblastoma and 10 cases of normal retina tissues. MVD was measured by anti-CD34. Eighteen samples of retinoblastoma tissues and ten samples of normal retina were examined for HPSE mRNA, HIF-1alpha mRNA, VEGF mRNA expression by RT-PCR. The correlation between HPSE, HIF-1alpha and VEGF expression, MVD and clinical and pathological characters were analyzed. The statistical methods are the measurement data using grouped quantitative data t test, variance analysis and q test; enumeration data compared with chi(2) test, Fisher test and rank sum test; correlation analysis using Spearman rank correlation analysis and the kappa test.

RESULTS

The positive expression rates of HIF-1alpha and VEGF were 58.8%, 64.7% higher in retinoblastoma than in normal retina's (chi(2) = 10.784, P < 0.05; chi(2) = 9.269, P < 0.05). Positive expression of HPSE, HIF-1alpha, VEGF mRNA were found in 55.6%, 44.4%, 72.2%. The expression of HIF-lalpha and VEGF in retinoblastoma were correlated with MVD (r = 0.664, P < 0.05; r = 0.590, P < 0.05). VEGF was correlated with HPSE and HIF-1alpha (Z = 2.350, P = 0.009; Z = 2.940, P = 0.002).

CONCLUSIONS

HPSE and HIF-1alpha can influence the expression of VEGF, an important angiogenesis factor. HPSE, HIF-1alpha and VEGF play a role in tumor angiogenesis and promote malignant progress of retinoblastoma.

[Relationship between vasculogenic mimicry and clinical pathological characters in retinoblastoma]

OBJECTIVE

To explore if vasculogenic mimicry (VM) exists in retinoblastoma (Rb) and to explore the clinical significance of VM.

METHODS

It was an experimental study. Sixty Rb specimens with complete clinical and prognostic data were collected. Periodic acid-Schif staining and immunohistochemical staining of CD34 were conducted to explore if VM exists in those Rb specimens. The expression of HIF-1alpha and VEGF were examined by immunohistochemical staining. The expression of CD34 endothelial antigen was used to label the neo-microvessels. Microvessel density (MVD) in retinoblastoma tissues was calculated.

RESULTS

In HE staining slides, VM was present in Rb specimens and was formed by tumor cells but not endothelial cells. Red blood cells were present in the VM. VM existed in 18.33% (11/60) of the Rb specimens. Low R-E graded Rb specimens exhibited a higher VM positive rate than that in the high R-E graded Rb (chi(2) = 8.861, P < 0.05). The positive rate of VM was 4.34% in differentiated type of Rb and was 22.02% in undifferentiated type of Rb (chi(2) = 4.872, P < 0.05). HIF-1alpha and VEGF expressions in Rb with VM were significantly greater than those in Rb without VM (P = 0.001). The density of endothelial vessels correlated with VM. The mean MVD was 49.77 +/- 2.05 in Rb without VM and 36.53 +/- 1.15 in Rb with VM (P < 0.05).

CONCLUSIONS

VM exists in Rb. Highly differentiated Rb exhibits more VM than that in less differentiated Rb. Expression of HIF-1alpha and VEGF is greater in Rb with VM, indicating that these factors may stimulate the occurrence of VM.

Retinoblastoma tumor vessel maturation impacts efficacy of vessel targeting in the LH(BETA)T(AG) mouse model

PURPOSE

The aim of this study was to quantify tumor cell proliferation and growth, analyze tumor blood vessel development, and determine the efficacy of antiangiogenic and angiostatic therapy in targeting mature vessels in retinal tumors of the LH(BETA)T(AG) mouse model for retinoblastoma.

METHODS

LH(BETA)T(AG) mouse retinas were analyzed at 4, 8, 12, and 16 weeks of age. Tumor burden was analyzed by histology; cell proliferation, vessel density, angiogenesis, and vessel maturation were detected by immunofluorescence. To assess the efficacy of mature vessel targeting, 16-week-old mice were treated with single subconjunctival injections of the selective vascular-targeting drug combretastatin A4 prodrug (CA4P) or anecortave acetate, and eyes were analyzed 1 day and 1 week after injection to determine microvessel density and the number of angiogenic and mature vessels.

RESULTS

Increased cell proliferation and angiogenesis were detected in the retinal inner nuclear layer (INL) before morphologic neoplastic changes were evident. As tumor size increased, angiogenesis diminished concomitantly with the appearance of mature vessels. Treatment with CA4P and anecortave acetate resulted in significant reductions in total vessel density. However, neither drug reduced the amount of alpha-smooth muscle actin (SMA)-positive, mature vessels.

CONCLUSIONS

Results of this study provide new insight into the relationship between tumor growth and blood vessel development in the LH(BETA)T(AG) mouse and establish the framework for defining the selective action of two vessel-targeting drugs against new blood vessels compared with mature blood vessels. These findings suggest a high potential value in targeting the process of angiogenesis in the treatment of children with retinoblastoma.

VEGF-Targeted RNA Interference Suppresses Angiogenesis and Tumor Growth of Retinoblastoma

Vascular endothelial growth factor (VEGF) is one of the most important angiogenic growth factors for tumor angiogenesis which has been verified to be involved in neovascularization of retinoblastoma. Here, we sought to explore whether RNA interference (RNAi) targeting VEGF could inhibit retinoblastoma angiogenesis and tumor growth. Stable transfection of the two human retinoblastoma cell lines SO-RB50 and HXO-RB44 with VEGF-targeted small interfering RNA (siRNA) expression plasmid significantly inhibited VEGF expression determined by real-time polymerase chain reaction (PCR), enzyme-linked immunosorbent assay and Western blot, whereas the control transfection showed no effects. The chemically synthesized VEGF siRNA dramatically suppressed tumor angiogenesis (CD34 immunohistochemistry) and tumor growth in the SO-RB50 subcutaneous xenograft model. Significant downregulation of VEGF expression both on messenger RNA and protein levels in VEGF-siRNA-treated SO-RB50 subcutaneous xenograft was confirmed by real-time PCR and Western blot compared to control. Our data demonstrate the suppression function on angiogenesis and tumor growth of retinoblastoma by VEGF-targeted RNAi. This novel therapeutic strategy promises to play a part in the clinical management of retinoblastoma.

Involvement of RB gene family in tumor angiogenesis

Angiogenesis, the development of new blood vessels from pre-existing vessels, represents a fundamental step in tumor progression and metastatization. The induction of vasculature is required for growth of the tumor mass, to ensure an adequate supply of oxygen and metabolites to the tumor beyond a critical size. Tumor angiogenesis is a highly regulated process that is controlled physiologically by the tumor microenvironment and genetically by alteration of several oncogenes or tumor suppressor genes. We will focus on recent demonstrations regarding the involvement of the retinoblastoma family proteins (phosphorylated retinoblastoma (pRb), p107 and pRb2/p130) at different levels of the angiogenic process. pRb and its homologs can regulate the expression of pro- and antiangiogenic factors, such as the vascular endothelial growth factor, through an E2F-dependent mechanism. Moreover, pRb is able to modulate also the transcriptional activity of several angiogenesis-related factors like HIF-1, Id2 and Oct-1. pRb2/p130 is required for both differentiation and mobilization of bone marrow-derived endothelial cell precursors and endothelial sprouting from neighboring vessels. The involvement of the pRb pathway in the angiogenesis process has also been demonstrated by different cellular models expressing viral oncoproteins, like human papilloma virus. Moreover, some natural and synthetic compounds demonstrate their antiangiogenetic activity with a mechanism of action involving pRb. Finally, the possible prognostic value of immunohistochemical evaluation of pRb and/or pRb2/p130 expression can represent a useful tool for the characterization of the angiogenic phenotype of specific tumor histotypes.

Photodynamic therapy for vasoproliferative retinal tumors

PURPOSE

To report our experience with photodynamic therapy (PDT) with verteporfin for patients with vasoproliferative retinal tumors (VPRTs).

METHODS

Three patients with VPRTs who presented with macular exudative changes were treated with one session of PDT with 6 mg/m body surface area of verteporfin and a light dose of 100 J/cm at 689 nm delivered in 166 seconds. Biomicroscopy, fluorescein angiography, indocyanine green angiography, optical coherence tomography, and ultrasonography were performed before treatment and 1 month, 3 months, 6 months, and 1 year after treatment; visual acuity was measured using Early Treatment Diabetic Retinopathy Study criteria.

RESULTS

At the 1-year follow-up, all tumors responded with a reduction in size (mean height: pretreatment, 2.96 mm; posttreatment, 1.32 mm), and optical coherence tomography showed complete resolution of macular exudates. For all patients, fluorescein angiography evidenced reduction of leakage from the lesion, and indocyanine green angiography verified nonperfusion of the vascular channels. An improvement in visual acuity (average, 4.7 Early Treatment Diabetic Retinopathy Study letters) was observed. No retreatment was needed.

CONCLUSION

PDT may represent an effective and safe modality of treatment for VPRTs because of its selectivity. Our study supports the application of a light dose of 100 J/cm, although further studies with larger numbers of cases and longer follow-ups are required.

Combretastatin A-4 prodrug in the treatment of a murine model of retinoblastoma

PURPOSE

To evaluate the effect of subconjunctival injections of combretastatin A-4 phosphate (CA-4P) prodrug treatment on tumor vasculature and growth in an animal model of hereditary retinoblastoma.

METHODS

Twenty-four, 12-week-old simian virus-40 T-antigen-positive mice received six subconjunctival CA-4P injections at doses of 0.5, 1.0, 1.5, and 2.0 mg delivered at 72-hour intervals to the right eye only. Six control animals received placebo treatment. All animals underwent serial ophthalmic evaluations and were euthanatized at 16 weeks of age, and eyes were obtained for histopathologic examination. Eyes were graded for presence or absence of tumor, delay of tumor growth, and intratumoral vascularity.

RESULTS

The use of subconjunctivally injected CA-4P prodrug induced an extensive, dose-dependent decrease in microvessel density and led to significant tumor reduction in treated eyes compared with the placebo control (P <0.001). No evidence of corneal, lenticular, choroidal, or retinal toxicity was observed by histopathologic evaluation.

CONCLUSIONS

Subconjunctival delivery of CA-4P is associated with extensive dose-dependent reduction in blood vessel count in this murine model of retinoblastoma. A combination treatment of retinoblastoma incorporating CA-4P may allow enhanced tumor reduction enabling a decrease in standard treatment doses of both chemotherapy and external beam radiotherapy.

The tyrp1-Tag/tyrp1-FGFR1-DN Bigenic Mouse

We describe herein a new transgenic mouse tumor model in which fibroblast growth factor (FGF) receptor activity is selectively inhibited. Tyrp1-Tag mice that develop early vascularized tumors of the retinal pigment epithelium were crossed with tyrp1-FGFR1-DN mice that express dominant-negative FGF receptors in the retinal pigment epithelium to generate bigenic mice. Initial angiogenesis-independent tumor growth progressed equally in tyrp1-Tag and bigenic mice with no significant differences in the number of dividing and apoptotic cells within the tumor. By contrast, at a later stage when tyrp1-Tag tumors rapidly expanded to fill the entire eye posterior chamber and migrate along the optic nerve toward the chiasma, bigenic tumors remained small and were poorly vascularized. Secondary tumors of small size developed in only 20% of bigenic mice by 1 month. Immunohistochemical analysis of secondary tumors from bigenic mice showed a reduction of angiogenesis and an increase in apoptosis in tumor cells. Tumor cells from bigenic mice expressed high levels of truncated FGF receptors and did not induce endothelial tube formation in vitro. All in all, this indicates that the tyrp1-Tag mouse may be a useful model to study selective tumor inhibition and the effect of antitumor therapy that targets a specific growth factor pathway. FGF receptors are required at the onset of tumor invasion and angiogenesis in ocular tumors and are good therapeutic targets in this model. The bigenic mouse may also constitute a useful model to answer more fundamental questions of cancer biology such as the mechanism of tumor escape.

Higher vessel densities in retinoblastoma with local invasive growth and metastasis

In this study, the importance of angiogenesis (the growth of new blood vessels from existing ones) for the growth of retinoblastoma was investigated by a retrospective immunohistochemical analysis. An individual vessel index for each tumor was determined using the endothelial-specific antibody CD 31 for vessel staining. The obtained data were correlated with clinical features, pathohistological characteristics, and the presence of metastasis. In 107 retinoblastomas collected between 1980 and 1990, we found no difference in the vessel densities between uni- and bilateral retinoblastomas (P = 0.41). However, tumors that had invaded the chorioid and/or the optic nerve statistically showed higher vessel densities than tumors without local invasive growth (P = 0.05 and P = 0.024). A tendency of higher vessel densities in retinoblastomas presenting with metastasis at the time of diagnosis was observed (P = 0.11). Based on this observation, we proceeded to examine all retinoblastomas presenting with metastasis at the time of diagnosis. These included patients that were treated between 1968 and 1993. The 18 investigated retinoblastomas had significantly higher vessel densities than all other retinoblastomas presenting without metastasis (P = 0.025). Our data indicate that in retinoblastoma, blood vessels are essential for local and systemic invasive growth. Therefore, an anti-angiogenic therapy could be considered in the multimodal therapy concept for retinoblastomas with invasive growth, both locally and systemically.

Quantitative analysis of proliferation, apoptosis, and angiogenesis in retinoblastoma and their association with the clinicopathologic parameters

PURPOSE

Quantitative analyses of proliferation, apoptosis, and angiogenesis, which may be important for the prognosis of retinoblastoma, were performed and possible associations with some well-known clinicopathologic parameters were investigated.

METHODS

Fifty-three pathology specimens (43 enucleations, 10 exenterations) were evaluated by immunohistochemical methods. The proliferative index was detected by Ki67 antibody staining. The apoptotic index was calculated by the in situ terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) method, and angiogenesis was detected by CD34 antibody staining.

RESULTS

The mean proliferative index was 37.63+/-11.12, the mean apoptotic index was 2.67+/-1.18, and the microvessel density and mean vascular area were determined as 3.14+/-1.4 and 38.73+/-12.70, respectively. Statistical analysis showed that the proliferative index was directly proportional to the tumor dimensions (P=.001). In addition, the tumor dimensions were larger in cases where the apoptotic index was below 2.4% (P=.011). In cases where the apoptotic index was over 2.4%, no metastasis was observed and also a lower proliferative index was found (P=.014).

CONCLUSIONS

Proliferation appears to be more important than apoptosis and angiogenesis in determining the tumor dimensions. The apoptotic index may be an important predictor of metastasis, and may be useful in the follow-up of bilateral cases with 1 eye enucleated.

Tumour angiogenesis as a prognostic factor for disease dissemination in retinoblastoma

AIM

To evaluate tumour angiogenesis as a predictor of prognosis in retinoblastoma.

METHODS

This was a retrospective, non-randomised comparative clinicopathological study. The histopathology from 24 cases of Reese-Ellsworth (RE) group V unilateral retinoblastoma treated by enucleation alone was reviewed. Group I consisted of five patients (four RE group Vb and one group Va) who developed disseminated disease at a mean of 10.4 months after enucleation. The remaining 19 patients constitute group II (18 RE group Vb and 1 group Va), none of whom had developed metastatic disease with a mean follow up of 54 months. None of the 24 patients had evidence of extraocular disease at enucleation. The surgical specimens from patients with unilateral retinoblastoma treated by enucleation at Hospital do Cancer AC Camargo between January 1992 and December 1995 were identified, reviewed and the clinical data recorded. Two subsequent histological sections were prepared. One stained with haematoxylin and eosin for assessment of choroidal and optic nerve invasion, and the other for immunoreaction with an endothelium specific marker (antibody anti-CD 34). The main outcome measures were choroidal and/or optic nerve invasion and quantification of the tumour's relative vascular area (TRVA) obtained by Chalkley counting.

RESULTS

Choroidal invasion was present in three eyes of group I (all massive) and six eyes of group II (two focal and four massive). Optic nerve invasion was found in two eyes of group I (all post-laminar) and four eyes of group II (three prelaminar and one post-laminar). There was no statistical difference regarding choroidal or optic nerve between the two groups. The TRVA was the only independent variable found to predict disease dissemination (p = 0.008 by Cox analysis). A TRVA equal to or greater than 3.9% had 100% sensitivity and 79% specificity in predicting disease dissemination.

CONCLUSIONS

Quantification of angiogenesis, through measurement of the TRVA, can help to identify patients with retinoblastoma at high risk for disease dissemination after enucleation.

Retinal capillary hemangioma treatment by indocyanine green-mediated photothrombosis

PURPOSE

To describe the clinical, angiographic and optical coherence tomography (OCT) findings of a patient with a large retinal capillary hemangioma who was treated by indocyanine green-mediated photothrombosis. Interventional case report.

METHODS

An 18-year-old male patient was treated at a tertiary referral center with a novel laser-dye procedure that uses low-irradiance 810-nm laser and intravenous indocyanine green injection and was prospectively evaluated with fluorescein and indocyanine green angiography, as well as OCT.

RESULTS

Vision improved from 20/125 to 20/32 + 1 at 1-year follow-up. Fundus photography showed marked reduction of a 3 disk diameters retinal capillary hemangioma. Both fluorescein and indocyanine green angiography demonstrated reduced tumor perfusion and narrowing of the lesion feeder and draining vessels as early as 5 days after indocyanine green-mediated photothrombosis; OCT showed immediate decrease in retinal elevation and complete resolution of subretinal fluid within 2 months of treatment. Minimal laser-induced effects were noted in the vicinity of the tumor.

CONCLUSIONS

Photothrombosis using low-intensity, 810-nm light to direct laser energy continuously at the tumor after intravenous indocyanine green infusion was effective in restoring macular architecture and improving vision in a patient with a large peripheral retinal capillary hemangioma by means of substantial occlusion of the tumor vasculature and resolution of subretinal fluid.

Expression of vascular endothelial growth factor (VEGF) and its receptors is regulated in eyes with intra-ocular tumours

The immunolocalization and gene expression of vascular endothelial growth factor (VEGF) and its cognate tyrosine kinase receptors, Flt-1 and KDR, has been studied in ocular melanomas and retinoblastomas using in situ hybridization and immunohistochemistry. Tumour-related alterations in VEGF/VEGF-receptor expression have also been examined in separate and uninvolved iris, retina and choroid of the same eyes. Although VEGF immunoreactivity in the normal retina was virtually absent, low-level VEGF expression was evident in the ganglion cell-bodies, Müller cells and in a distinct population of amacrine cells. VEGF gene expression was absent in the iris and choroid of normal eyes. In tumour-bearing eyes, high levels of VEGF protein and gene expression were observed within the vascularized regions of the tumours, while the adjacent retina and choroid showed increased VEGF levels when compared with normals. Flt-1 and KDR gene expression and immunolocalization occurred in VEGF-expressing ganglion, Müller and amacrine cells in normal eyes. Within the intra-ocular tumours, VEGF-receptor gene expression and protein was evident in the endothelial cells and also in cells close to the vessels, while in the adjacent retina, Flt-1 and KDR levels were elevated over normal, especially in the blood vessels. Flt-1 and KDR were both observed at elevated levels in the choroid and iris blood vessels. This study suggests that VEGF, Flt-1 and KDR are expressed by neural, glial and vascular elements within normal human retina. Intra-ocular tumours demonstrate a high level of VEGF and VEGF-receptor expression; within uninvolved, spatially separate retina, choroid and iris in the same eyes, expression is also elevated, especially within the vasculature. Retinal vascular endothelia may respond to high intra-ocular levels of VEGF by increasing expression of their VEGF receptors, a phenomenon which could have relevance to neoplasm-related ocular neovascularization.

[Anatomicopathological studies in retinoblastoma]

For a fifteen-years period it has been examined fourteen cases with retinoblastoma, twelve of them have been undifferentiated forms and two cases differentiated forms in rosette, in undifferentiated retinoblastoma has been observed low size cells with poor cytoplasm and big nucleus that occupied near the whole cell; the nucleus to cytoplasm ratio is increased. The cellular density is irregular and most important perivascular. The tumoral parenchyma is condensed in perivascular areas, the tumoral stroma is poor, amorphous or mucinous. The necrosis areas are frequently but very import out in undifferentiated retinoblastoma. The tumoral vascularity is increased. In some cases occur melanin pigment that belong to the pigment epithelium without the existence of tumoral proliferation.