Mario A. Economou

The Insulin-Like Growth Factor-I Receptor Inhibitor Picropodophyllin Causes Tumor Regression and Attenuates Mechanisms Involved in Invasion of Uveal Melanoma Cells

PURPOSE: Uveal melanoma has a high mortality rate due to a high incidence of metastasis (up to 50%), which preferentially occurs in the liver. Conventional chemotherapy, being the only therapeutic option today against metastatic uveal melanoma, has not proved to be effective. Therefore, new molecular targets important for malignant phenotype of uveal melanoma have to be found to design efficient pharmacologic agents. EXPERIMENTAL DESIGN: We previously reported data indicating that the insulin-like growth factor-1 receptor (IGF-IR) is a metastasis predictor as well as a therapeutic target for uveal melanoma. In the present study, we made use of the cyclolignan picropodophyllin (PPP), which is an inhibitor of the IGF-IR. RESULTS: We showed that PPP efficiently blocks growth and viability of uveal melanoma cells in cultures and causes tumor regression in xenografted mice. In addition, treatment with PPP inhibited several mechanisms involved in metastasis, including tumor cell adhesion to extracellular matrix proteins, activity and expression of matrix metalloproteinase 2, and cell migration as well as invasion through basement membranes and endothelial cell layers. Furthermore, PPP significantly delayed establishment of uveal melanoma tumors and drastically reduced the incidence of liver metastasis in mice. CONCLUSIONS: Our data suggest that IGF-IR is crucial for growth and survival as well as invasion and metastasis of uveal melanoma cells. Targeting this receptor may therefore comprise a strategy to treat ongoing disease (today incurable) as well as a strategy to prevent development of metastases in patients with primary disease.

Intratumoral forkhead box P3-positive regulatory T cells predict poor survival in cyclooxygenase-2–positive uveal melanoma

Forkhead box P3 (FOXP3)‐positive regulatory T cells (Tregs) are key mediators of peripheral tolerance and suppress efficient antitumor responses. Prostaglandin E2 (PGE2) produced by inducible cyclooxygenase‐2 (COX‐2) can lead to Treg induction. COX‐2 expression has been linked to tumorigenesis and growth in various malignancies. The objective of the current study was to investigate whether Tregs infiltrate uveal melanomas (UMs) and whether their prevalence is linked to COX‐2 expression and the prediction of overall survival (OS).

Oral picropodophyllin (PPP) is well tolerated in vivo and inhibits IGF-1R expression and growth of uveal melanoma.

PURPOSE The cyclolignan picropodophyllin (PPP) efficiently blocks the activity of insulinlike growth factor-1 receptor (IGF-1R) and inhibits the growth of uveal melanoma cells in vitro and in vivo. In this study, the authors investigated the efficiency of orally administered PPP on the growth of uveal melanoma xenografts. In addition, they focused on the effect of PPP on vascular endothelial growth factor (VEGF) in vivo and evaluated its effects in combination with other established antitumor agents in vitro. METHODS Four different uveal melanoma cell lines (OCM-1, OCM-3, OCM-8, 92-1) were treated with PPP alone and in combination with imatinib mesylate, cisplatin, 5-fluorouracil, and doxorubicin. Cell viability was determined by XTT assay. SCID mice that underwent xenografting with uveal melanoma cells were used to determine antitumor efficacy of oral PPP in vivo. Five mice were used per group. Tumor samples obtained from the in vivo experiments were analyzed for VEGF and IGF-1R expression by Western blotting. RESULTS PPP was found to be superior to the other antitumor agents in killing uveal melanoma cells in all four cell lines (IC50 < 0.05 microM). Oral PPP inhibited uveal melanoma growth in vivo in OCM-3 (P = 0.03) and OCM-8 (P = 0.01) xenografts and was well tolerated by the animals. PPP decreased VEGF expression in the OCM-1 (P = 0.006) and OCM-8 (P = 0.01) tumors. CONCLUSIONS Oral PPP was well tolerated in vivo, caused total growth inhibition of uveal melanoma xenografts, and decreased VEGF levels in the tumors.

Inhibition of VEGF secretion and experimental choroidal neovascularization by picropodophyllin (PPP), an inhibitor of the insulin-like growth factor-1 receptor.

INTRODUCTION Choroidal neovascularization (CNV) is a debilitating complication of age-related macular degeneration (AMD) and a leading cause of vision loss. Along with other angiogenic factors such as vascular endothelial growth factor (VEGF), insulin-like growth factor (IGF)-1 and its receptor, IGF-1R, have been implicated in CNV. PURPOSE A prior study has shown that the cyclolignan picropodophyllin (PPP) efficiently blocks the insulin-like growth factor-1 receptor (IGF-1R) activity and causes cell death in uveal melanoma cell lines and in an in vivo model. In this study we investigated the effect of PPP on VEGF expression, both in vitro and in vivo, and whether this effect has antiangiogenic consequences in a murine CNV model. METHODS C57BL/6J mice with laser-induced CNVs were treated with PPP. Effects on CNV area were assayed by image analysis. VEGF levels in the choroid and retinal pigment epithelial cells (ARPE-19) were measured by Western blot or ELISA. Transcriptional activation of the VEGF promoter was determined by luciferase reporter gene assay. RESULTS Mice treated with PPP, administered intraperitoneally or orally, showed a 22% to 32% (P = 0.002) decrease in CNV area. Furthermore, VEGF levels in the choroid were significantly reduced. In cultured ARPE-19 cells, IGF-1 was shown to increase VEGF secretion. This increase was completely blocked by PPP. PPP reduced the level of transcriptional activity of the VEGF promoter. CONCLUSIONS PPP reduces IGF-1-dependent VEGF expression and CNV in vivo. Accordingly, IGF-1R inhibitors may be useful tools in the treatment of conditions associated with CNV, including neovascular AMD.

Expression and prognostic significance of iNOS in uveal melanoma

Uveal melanoma (UM) is the most common primary intraocular tumor in adults. Disease metastasis occurs in half of the patients and is uniformly fatal despite systemic therapy. Inducible nitric oxide synthase (iNOS) is associated with disease progression in various malignancies including cutaneous melanoma. In this retrospective cohort, we examined the prognostic value of iNOS in UM by performing immunohistochemistry on paraffin‐embedded sections of primary tumors (90 patients) and matched primary and metastatic hepatic tumors (19 patients) with complete histopathological and clinical data. We show that iNOS is expressed in UM (57% of the patients) and high iNOS levels significantly (p = 0.04; hazard ratio (HR) = 2.3) predict disease‐specific survival (DSS) as assessed by Kaplan‐Meier analysis and univariate Coxs proportional hazards regression model. Furthermore, high iNOS expression in the UM primary tissue was significantly associated with metastatic disease and vice versa. Expression of iNOS in hepatic metastases significantly (p = 0.02) predicted a shortened survival as assessed by Kaplan‐Meier analysis. However, iNOS did not appear to be a significant (p = 0.16; HR = 1.9) factor in the multivariate Coxs regression analysis performed together with the clinical parameters tumor diameter, tumor cell type, and tumor location in which only tumor diameter predicted DSS. In conclusion, iNOS predicts DSS in UM and may play a role in disease progression but it is not an independent prognostic factor.

Oral picropodophyllin (PPP) is well tolerated in vivo and inhibits IGF‐1R expression and growth of uveal melanoma

Purpose:  The cyclolignan picropodophyllin (PPP) efficiently blocks the activity of insulin‐like growth factor‐1 receptor (IGF‐1R) and inhibits growth of uveal melanoma cells in vitro and in vivo. In this study, we aimed to investigate the efficiency of orally administered PPP on growth of uveal melanoma xenografts. Further, we focused on the effect of PPP on vascular endothelial growth factor (VEGF) in vivo and evaluated its effects in combination with other established anti‐tumor agents in vitro.

The insulin‐like growth factor‐I receptor inhibitor picropodophyllin causes tumor regression and attenuates mechanisms involved in invasion of uveal melanoma cells

Purpose:  Uveal melanoma has a high mortality rate due to a high incidence of metastasis (up to 50%) which preferentially occurs in the liver. Conventional chemotherapy being the only therapeutic option today against metastatic uveal melanoma, has not proved to be effective. Therefore, new molecular targets important for malignant phenotype of uveal melanoma have to be found to design efficient pharmacologic agents.

Inhibition of VEGF secretion and experimental choroidal neovascularization by picropodophyllin (PPP), an inhibitor of the insulin-like growth factor-1 receptor

Introduction:  Choroidal neovascularization (CNV) is a debilitating complication of age‐related macular degeneration (AMD) and a leading cause of vision loss. Along with other angiogenic factors like vascular endothelial growth factor (VEGF), insulin‐like growth factor (IGF‐1) and its receptor, IGF‐1R, have been implicated in CNV.

Nuclear HER3 is associated with favorable overall survival in uveal melanoma.

HER3 is a member of the epidermal growth factor receptor (EGFR) family and is expressed in several types of cancer. Both the cytoplasmic and nuclear appearances of the receptor have been reported. Here, we investigate the expression and subcellular distribution of HER3 in uveal melanoma (UM) cells and tissues and its potential impact on clinical outcome of patients. Paraffin‐embedded samples from 128 consecutive UM patients, enucleated without alternative treatment on UM diagnosis, were evaluated for HER3 using immunohistochemistry. Immunoreactivity was scored for frequency, intensity of positive cells, and subcellular distribution. The results were correlated with the established clinicopathological parameters using univariate and multivariate statistical analyses. HER3 expression was shown in 70% of the cases (89/128). This contrasts with the other EGFR family receptors (EGFR, HER2 and HER4) that are infrequently expressed in UM. Surprisingly, HER3 was found to be localized solely in the cell nuclei in 56 cases. The remaining 33 HER3 positive cases showed diffuse distribution (cytoplasmic ± nuclear). Nuclear HER3 was independently correlated with a more favorable overall survival (p = 0.043 and hazard ratio = 0.618) compared to cases with diffuse and/or no HER3. Nuclear localization of HER3 was also confirmed in fresh UM material and in UM cell lines. In conclusion, HER3 is frequently localized solely in the cell nuclei in UM and as such it predicts a more favorable overall survival.

JARID1B Protein Expression and Prognostic Implications in Uveal Melanoma

PURPOSE It has been suggested recently that stem cell marker expression of jumonji AT-rich interactive domain 1B (JARID1B) is required for continuous tumor growth and maintenance in human cutaneous melanoma cells. The aim of this study is to determine whether JARID1B is also expressed in uveal melanoma (UM) and whether JARID1B marks an expanded cancer stem cell pool in poor prognosis UM. Based on the available data, this is the first time JARID1B expression in UM has been studied. METHODS A total of 121 consecutive patients diagnosed with UM and who underwent enucleation were included in the study. Immunohistochemical staining with JARID1B antibodies was performed and immunoreactivity was assessed. Correlations of JARID1B expression with established clinicopathological parameters and overall survival (OS) were evaluated in univariate and multivariate analyses. RESULTS JARID1B positive expression, as defined by >0% staining, was present in 55% of UMs and invariably in ciliary body epithelium. The correlation between JARID1B negative expression and JARID1B expression >5% inside the tumor tissue and OS was borderline statistically significant based on LogRank test at 5% significance level (P = 0.06). There were significantly more JARID1B positive cells in tumors with extrascleral extension than in tumors with no or minimal intrascleral invasion (P < 0.01, Mann-Whitney test). CONCLUSIONS This study demonstrates that JARID1B is expressed by UM cells. Despite that JARID1B was highly expressed in UM, a statistically significant association (P < 0.05) between JARID1B expression and OS could not be obtained. However, a P-value of 0.06 could suggest that high JARID1B expression is correlated with lower survival; thus, a follow up study with a greater patient sample is recommended. In addition, samples of tumors characterized by high invasiveness showed a higher JARID1B expression. Furthermore, this study substantiates the presence of progenitor cells in the ciliary body epithelium.