A Murine Model for Metastatic Conjunctival Melanoma

The novel role of lymphatic vessels in the pathogenesis of ocular diseases

Historically, the eye has been considered as an organ free of lymphatic vessels. In recent years, however, it became evident, that lymphatic vessels or lymphatic-like vessels contribute to several ocular pathologies at various peri- and intraocular locations. The aim of this review is to outline the pathogenetic role of ocular lymphatics, the respective molecular mechanisms and to discuss current and future therapeutic options based thereon. We will give an overview on the vascular anatomy of the healthy ocular surface and the molecular mechanisms contributing to corneal (lymph)angiogenic privilege. In addition, we present (i) current insights into the cellular and molecular mechanisms occurring during pathological neovascularization of the cornea triggered e.g. by inflammation or trauma, (ii) the role of lymphatic vessels in different ocular surface pathologies such as dry eye disease, corneal graft rejection, ocular graft versus host disease, allergy, and pterygium, (iii) the involvement of lymphatic vessels in ocular tumors and metastasis, and (iv) the novel role of the lymphatic-like structure of Schlemm's canal in glaucoma. Identification of the underlying molecular mechanisms and of novel modulators of lymphangiogenesis will contribute to the development of new therapeutic targets for the treatment of ocular diseases associated with pathological lymphangiogenesis in the future. The preclinical data presented here outline novel therapeutic concepts for promoting transplant survival, inhibiting metastasis of ocular tumors, reducing inflammation of the ocular surface, and treating glaucoma. Initial data from clinical trials suggest first success of novel treatment strategies to promote transplant survival based on pretransplant corneal lymphangioregression.

Targeting β-catenin using XAV939 nanoparticle promotes immunogenic cell death and suppresses conjunctival melanoma progression

Many tumors dysregulate Wnt/β-catenin pathway to promote stem-cell-like phenotype, tumorigenesis, immunosuppression, and resistance to targeted cancer immunotherapies. Therefore, targeting this pathway is a promising therapeutic approach to suppress tumor progression and elicit robust anti-tumor immunity. In this study, using a nanoparticle formulation for XAV939 (XAV-Np), a tankyrase inhibitor that promotes β-catenin degradation, we investigated the effect of β-catenin inhibition on melanoma cell viability, migration, and tumor progression using a mouse model of conjunctival melanoma. XAV-Nps were uniform and displayed near-spherical morphology with size stability for upto 5 days. We show that XAV-Np treatment of mouse melanoma cells significantly suppresses cell viability, tumor cell migration, and tumor spheroid formation compared to control nanoparticle (Con-Np) or free XAV939-treated groups. Further, we demonstrate that XAV-Np promotes immunogenic cell death (ICD) of tumor cells with a significant extracellular release or expression of ICD molecules, including high mobility group box 1 protein (HMGB1), calreticulin (CRT), and adenosine triphosphate (ATP). Finally, we show that local intra-tumoral delivery of XAV-Nps during conjunctival melanoma progression significantly suppresses tumor size and conjunctival melanoma progression compared to Con-Nps-treated animals. Collectively, our data suggest that selective inhibition of β-catenin in tumor cells using nanoparticle-based targeted delivery represents a novel approach to suppress tumor progression through increased tumor cell ICD.

The Use of Panitumumab-IRDye800CW in a Novel Murine Model for Conjunctival Squamous Cell Carcinoma

Purpose

Conjunctival squamous cell carcinoma (SCC) is a sight-threatening ocular surface malignancy with the primary treatment modality being surgical resection. To evaluate surgical imaging modalities to improve surgical resection, we established a novel murine model for conjunctival SCC to demonstrate the utility of panitumumab-IRDye800, a fluorescently labeled anti-epidermal growth factor receptor (EGFR) antibody.

Methods

NOD-scid IL2Rgamma^null (NSG) mice received subconjunctival injection of UM-SCC-1 or SCC-9, head and neck SCC cell lines. On tumor growth, mice were injected with Panitumumab-IRDye800CW, and imaged with a small animal imaging system and optical coherence tomography (OCT). Immunohistochemistry for SCC markers were used to confirm tumor origin.

Results

Seventy-five percent (N = 4) of the UM-SCC-1 group developed aggressive, rapidly growing tumors that were P40 and EGFR positive within two weeks of inoculation. The SCC-9 tumors failed to demonstrate any growth (N = 4). Ocular tumors demonstrated high fluorescence levels with a tumor to background ratio of 3.8.

Conclusions

Subconjunctival injections are an appropriate technique to create in vivo models for assessing treatment modalities and novel therapies in conjunctival SCC.

Translational Relevance

This model demonstrates Panitumumab-IRDye800CW's utility in the ophthalmic setting and suggests that clinical trials may be warranted.

IGF-1R is a molecular determinant for response to p53 reactivation therapy in conjunctival melanoma

As the p53 tumor suppressor is rarely mutated in conjunctival melanoma (CM), we investigated its activation as a potential therapeutic strategy. Preventing p53/Mdm2 interaction by Nutlin-3, the prototypical Mdm2 antagonist, or via direct siRNA Mdm2 depletion, increased p53 and inhibited viability in CM cell lines. The sensitivity to Nutlin-3 p53 reactivation with concomitant Mdm2 stabilization was higher than that achieved by siRNA, indicative of effects on alternative Mdm2 targets, identified as the cancer-protective IGF-1R. Nutlin-3 treatment increased the association between IGF-1R and β-arrestin1, the adaptor protein that brings Mdm2 to the IGF-1R, initiating receptor degradation in a ligand-dependent manner. Controlled expression of β-arrestin1 augmented inhibitory Nutlin-3 effects on CM survival through enhanced IGF-1R degradation. Yet, the effect of IGF-1R downregulation on cell proliferation is balanced by β-arrestin1-induced p53 inhibition. As mitomycin (MMC) is a well-established adjuvant treatment for CM, and it triggers p53 activation through genotoxic stress, we evaluated how these alternative p53-targeting strategies alter the cancer-relevant bioactivities of CM. In 2D and 3D in vitro models, Nutlin-3 or MMC alone, or in combination, reduces the overall cell tumor growth ~30%, with double treatment inhibition rate only marginally higher than single-drug regimens. However, histopathological evaluation of the 3D models revealed that Nutlin-3 was the most effective, causing necrotic areas inside spheroids and complete loss of nuclear staining for the proliferative marker Ki67. These findings were further validated in vivo; zebrafish xenografts demonstrate that Nutlin-3 alone has higher efficacy in restraining CM tumor cell growth and preventing metastasis. Combined, these results reveal that β-arrestin1 directs Mdm2 toward different substrates, thus balancing IGF-1R pro-tumorigenic and p53-tumor suppressive signals. This study defines a potent dual-hit strategy: simultaneous control of a tumor-promoter (IGF-1R) and tumor-suppressor (p53), which ultimately mitigates recurrent and metastatic potential, thus opening up targeted therapy to CM.

Process development and safety evaluation of ABCB5+ limbal stem cells as advanced-therapy medicinal product to treat limbal stem cell deficiency

Background

While therapeutic success of the limbal tissue or cell transplantation to treat severe cases of limbal stem cell (LSC) deficiency (LSCD) strongly depends on the percentage of LSCs within the transplanted cells, prospective LSC enrichment has been hampered by the intranuclear localization of the previously reported LSC marker p63. The recent identification of the ATP-binding cassette transporter ABCB5 as a plasma membrane-spanning marker of LSCs that are capable of restoring the cornea and the development of an antibody directed against an extracellular loop of the ABCB5 molecule stimulated us to develop a novel treatment strategy based on the utilization of in vitro expanded allogeneic ABCB5⁺ LSCs derived from human cadaveric limbal tissue.

Methods

We developed and validated a Good Manufacturing Practice- and European Pharmacopeia-conform production and quality-control process, by which ABCB5⁺ LSCs are derived from human corneal rims, expanded ex vivo, isolated as homogenous cell population, and manufactured as an advanced-therapy medicinal product (ATMP). This product was tested in a preclinical study program investigating the cells’ engraftment potential, biodistribution behavior, and safety.

Results

ABCB5⁺ LSCs were reliably expanded and manufactured as an ATMP that contains comparably high percentages of cells expressing transcription factors critical for LSC stemness maintenance (p63) and corneal epithelial differentiation (PAX6). Preclinical studies confirmed local engraftment potential of the cells and gave no signals of toxicity and tumorgenicity. These findings were sufficient for the product to be approved by the German Paul Ehrlich Institute and the U.S. Food & Drug Administration to be tested in an international multicenter phase I/IIa clinical trial (NCT03549299) to evaluate the safety and therapeutic efficacy in patients with LSCD.

Conclusion

Building upon these data in conjunction with the previously shown cornea-restoring capacity of human ABCB5⁺ LSCs in animal models of LSCD, we provide an advanced allogeneic LSC-based treatment strategy that shows promise for replenishment of the patient’s LSC pool, recreation of a functional barrier against invading conjunctival cells and restoration of a transparent, avascular cornea.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02272-2.

In-vivo imaging for assessing tumor growth in mouse models of ocular melanoma

Uveal melanoma (UM) and conjunctival melanoma (CM) are ocular malignancies that give rise to life-threatening metastases. Although local disease can often be treated successfully, it is often associated with significant vision impairment and treatments are often not effective against metastatic disease. Novel treatment modalities that preserve vision may enable elimination of small tumors and may prevent subsequent metastatic spread. Very few mouse models of metastatic CM and UM are available for research and for development of novel therapies. One of the challenges is to follow tumor growth in-vivo and to determine the right size for treatment, mainly of the posterior, choroidal melanoma. Hence, the purpose of this study was to establish a simple, noninvasive imaging tool that will simplify visualization and tumor follow-up in mouse models of CM and UM. Tumors were induced by inoculation of murine B16LS9 cells into the sub-conjunctival or the choroidal space of a C57BL/6 mouse eye under a surgical microscope. Five to ten days following injection, tumor size was assessed by Phoenix MicronIV™ image-guided Optical Coherence Tomography (OCT) imaging, which included a real-time camera view and OCT scan of the conjunctiva and the retina. In addition, tumor size was evaluated by ultrasound and histopathological examination of eye sections. Tumor growth was observed 5-9 days following sub-conjunctival or sub-retinal injection of seven-thousand or seventy-thousand cells, respectively. A clear tumor mass was detected at these regions using the MicronIV™ imaging system camera and OCT scans. Histology of eye sections confirmed the presence of tumor tissue. OCT allowed an accurate measurement of tumor size in the UM model and a qualitative assessment of tumor size in the CM model. Moreover, OCT enabled assessing the success rate of the choroidal tumor induction and importantly, predicted final tumor size already on the day of cell inoculation. In conclusion, by using a simple, non-invasive imaging tool, we were able to follow intraocular tumor growth of both CM and UM, and to define, already at the time of cell inoculation, a grading scale to evaluate tumor size. This tool may be utilized for evaluation of new mouse models for CM and UM, as well as for testing new therapies for these diseases.

Chemokine Receptor Expression Pattern Correlates to Progression of Conjunctival Melanocytic Lesions

Purpose

Chemokines play a role in the progression and metastatic spread of both cutaneous and uveal melanomas. The aim of this study was to examine the prognostic value of expression of chemokine receptors CCR7, CXCR4, and CCR10 in conjunctival melanocytic lesions.

Methods

In total, 44 conjunctival nevi, 21 cases of primary acquired melanosis (PAM) with atypia and 35 conjunctival melanomas, were included. After immunohistochemical staining for CCR7, CXCR4, and CCR10 the immunoreactive score (IRS) was determined. The findings were correlated for association with melanoma and development of metastasis. For mechanistic evaluation, we used a mouse melanoma metastasis model using two human conjunctival melanoma cell lines, CM2005.1 and CRMM1.

Results

All tested chemokines showed a significantly higher expression in conjunctival melanoma than conjunctival nevi. There was a statistically significant difference between the IRS in nevi and PAM with atypia for nuclear IRS in CCR10 (P = 0.03) and both nuclear and cytoplasmic IRS in CXCR4 (P < 0.01 and P = 0.03, respectively); this was also true evaluating the groups PAM with atypia and melanoma all together (P < 0.01). Furthermore, a trend for lower IRS was seen in cases of melanoma without metastasis, with a suggestive pattern of a higher IRS in cases that did develop metastases, supported for CXCR4 using the mouse melanoma metastasis model.

Conclusions

Expression of specific chemokines changes during the progression and metastatic spread of conjunctival melanocytic lesions. Differential chemokine profiles may hold prognostic value for patients with conjunctival melanomas and might be considered as a therapeutic target.

Conjunctival melanoma and electrochemotherapy: preliminary results using 2D and 3D cell culture models in vitro

Purpose

To investigate the cytotoxic effect of bleomycin, mitomycin C (MMC) and Fluorouracil (5‐FU) in combination with electroporation (EP) on human conjunctival melanoma (CM) and normal conjunctival cell lines using 2D and 3D cell culture systems in vitro.

Methods

Two CM (CRMM1, CRMM2) and one normal conjunctival epithelial cell line (HCjE‐Gi) were treated with various EP conditions and increasing concentrations of 5‐FU, MMC and bleomycin. Cell survival was assessed by MTT viability assay. All cell lines were seeded to create spheroids and were treated with bleomycin on day 3 and day 8 combined with EP. Spheroids were collected, fixed in buffered formalin and subsequently paraffin embedded for histological assessment of the effects of the treatment on cell viability.

Results

CM cell lines were resistant to electroporation alone and showed a reduction in cell number only when treated with 1000 Volts/cm and 8 pulses. HCjE‐Gi cells showed higher sensitivity to electric pulses over 750 Volts/cm. MMC and 5‐FU demonstrated a higher cytotoxicity for the HCjE‐Gi cell line. The CM cell lines were resistant to MMC and 5‐FU. Bleomycin (1 μg/ml) alone had no significant effect on the HCjE‐Gi even when combined with EP conditions ≥750 Volts/cm. In contrast, it significantly (p ‐, paired t‐test) reduced cell viability in the CM cell lines. Spheroids treated with bleomycin and EP showed a reduction in tumour mass and proliferation rates after treatment.

Conclusion

Our in vitro study using 2D and 3D models indicates that the application of EP may effectively enhance chemotherapy with bleomycin in CM. This may offer new viable perspectives for CM treatment.

Proceedings of the Association for Research in Vision and Ophthalmology and Champalimaud Foundation Ocular Oncogenesis and Oncology Conference

The 2018 Ocular Oncogenesis and Oncology Conference was held through a partnership of the Association for Research in Vision and Ophthalmology (ARVO) and the Champalimaud Foundation. Twenty-one experts from international ocular oncology centers, from the Champalimaud Clinical Centre and the Champalimaud Foundation Cancer Research Program, and from patient advocacy organizations, delivered lectures on subjects that ranged from global ocular oncology, to basic research in mechanisms of ocular malignancy, to clinical research in ocular cancers, and to anticipated future developments in the area. The scientific program of the conference covered a broad range of ocular tumors-including uveal melanoma, retinoblastoma, ocular surface tumors, and adnexal and intraocular lymphomas-and pathogenesis and management were deliberated in the context of the broader systemic cancer discipline. In considering the latest basic and clinical research developments in ocular oncogenesis and oncology, and providing the opportunity for cross-talk between ocular cancer biologists, systemic cancer biologists, ocular oncologists, systemic oncologists, patients, and patient advocates, the forum generated new knowledge and novel insights for the field. This report summarizes the content of the invited talks at the 2018 ARVO-Champalimaud Foundation Ocular Oncogenesis and Oncology Conference.

Characterization of a conjunctival melanoma cell line CM-AS16, newly-established from a metastatic Han Chinese patient

Conjunctival melanoma (CM) is associated with metastases formation, can be fatal, and occurs in all different races. While cell lines are essential for experimental research, all available CM cell lines are derived from Caucasian patients. Furthermore, they are not derived from metastases. We aimed to establish a new CM cell line from a parotid metastasis in a Han Chinese patient and to depict its characteristics. The novel cell line, CM-AS16, was obtained from a surgical parotid sample and determined as a unique one with short tandem repeat (STR) analysis. It has been successively sub-cultured in vitro for more than 100 passages and exhibits rapid proliferation and migration. Chromosome analysis shows abundant chromosome aberrations, while whole exome sequencing (WES) reveals a typical NRAS mutation (Q61R). In vivo tumor growth was successfully established in a NOD/SCID mice model, and the immunophenotypes, such as HMB45, Melan A, S100, SOX10 and Ki67, manifested similar between the original tumor and the xenograft by immunohistochemistry. A MEK inhibitor binimetinib prominently suppressed in vitro cell growth by inhibiting ERK1/2 phosphorylation. In addition, monoclonal cells were used to demonstrate the drug sensitivity of different cells. In conclusion, the first cell line, CM-AS16, that is derived from a CM in a Han Chinese patient has highly malignant characteristics and a typical NRAS mutation. It may be used as a tool for further exploration of the molecular mechanisms of CM.

Kinome-wide transcriptional profiling of uveal melanoma reveals new vulnerabilities to targeted therapeutics

Metastatic uveal melanoma (UM) is invariably fatal, usually within a year of diagnosis. There are currently no effective therapies, and clinical studies employing kinase inhibitors have so far demonstrated limited success. This is despite common activating mutations in GNAQ/11 genes, which trigger signalling pathways that might predispose tumours to a variety of targeted drugs. In this study, we have profiled kinome expression network dynamics in various human ocular melanomas. We uncovered a shared transcriptional profile in human primary UM samples and across a variety of experimental cell-based models. The poor overall response of UM cells to FDA-approved kinase inhibitors contrasted with much higher sensitivity to the bromodomain inhibitor JQ1, a broad transcriptional repressor. Mechanistically, we identified a repressed FOXM1-dependent kinase subnetwork in JQ1-exposed cells that contained multiple cell cycle-regulated protein kinases. Consistently, we demonstrated vulnerability of UM cells to inhibitors of mitotic protein kinases within this network, including the investigational PLK1 inhibitor BI6727. We conclude that analysis of kinome-wide signalling network dynamics has the potential to reveal actionable drug targets and inhibitors of potential therapeutic benefit for UM patients.

Targeting of the MAPK and AKT pathways in conjunctival melanoma shows potential synergy

PURPOSE

Conjunctival melanoma (CM) is a rare but lethal form of cancer. Similar to cutaneous melanoma, CM frequently carries activating mutations in BRAF and NRAS. We studied whether CM as well as conjunctival benign and premalignant melanocytic lesions express targets in the mitogen-activated protein kinase (MAPK) and AKT pathways, and whether specific inhibitors can suppress CM growth in vitro.

METHODS

131 conjunctival lesions obtained from 129 patients were collected. The presence of BRAF V600E mutation and expression of phosphorylated (p)-ERK and p-AKT were assessed by immunohistochemistry. We studied cell proliferation, phosphorylation, cell cycling and apoptosis in three CM cell lines using two BRAF inhibitors (Vemurafenib and Dabrafenib), a MEK inhibitor (MEK162) and an AKT inhibitor (MK2206).

RESULTS

The BRAF V600E mutation was present in 19% of nevi and 26% of melanomas, but not in primary acquired melanosis (PAM). Nuclear and cytoplasmic p-ERK and p-AKT were expressed in all conjunctival lesions. Both BRAF inhibitors suppressed growth of both BRAF mutant CM cell lines, but only one induced cell death. MEK162 and MK2206 inhibited proliferation of CM cells in a dose-dependent manner, and the combination of these two drugs led to synergistic growth inhibition and cell death in all CM cell lines.

CONCLUSION

ERK and AKT are constitutively activated in conjunctival nevi, PAM and melanoma. While BRAF inhibitors prohibited cell growth, they were not always cytotoxic. Combining MEK and AKT inhibitors led to more growth inhibition and cell death in CM cells. The combination may benefit patients suffering from metastatic conjunctival melanoma.

Satellite in transit metastases in rapidly fatal conjunctival melanoma: implications for angiotropism and extravascular migratory metastasis (description of a murine model for conjunctival melanoma)

Little information is currently available concerning loco-regional metastases such as satellite and in transit metastases and their natural history in conjunctival melanoma as compared to cutaneous melanoma. Angiotropism, a marker of extravascular migration of melanoma cells along vascular channels, often appears responsible for microscopic satellite, satellite and in transit metastases development in cutaneous melanoma. In addition, diffuse tissue microscopic satellites are correlated with widespread melanoma dissemination and death. Herein we report rapid conjunctival melanoma progression and a fatal outcome in four of five patients following recurrence as satellite in transit metastases. Five patients aged 31, 60, 63, 56, and 67 years developed primary conjunctival melanoma, histologically characterised by tumour thicknesses of 4, 4, 1.1, 3, and 2 mm. Two or more conjunctival melanomas manifested ulceration, significant mitotic rates, necrosis, angiotropism, and intralesional transformation. The conjunctival melanoma recurred in a matter of months as one or more discrete satellite in transit lesions in the vicinity of the primary melanoma. Histological examination revealed well-defined micronodules containing atypical melanocytes in the subepithelial connective tissue stroma. All lesions were extravascular and most appeared angiotropic. Four of five patients subsequently developed parotid or other loco-regional nodal disease and rapidly ensuing widespread metastases and death. The time course from diagnosis to the demise of the patients averaged about 13 (range 7-20) months. Our findings suggest that satellite in transit metastases constitute an important new risk marker for possible rapid metastatic disease progression and death in patients with conjunctival melanoma. This finding appears to take on even greater significance if such lesions develop rapidly, i.e., in a matter of weeks or months following diagnosis of primary conjunctival melanoma, and if the primary melanoma manifests additional high-risk features. Additional studies are underway in order to further elucidate the mechanism of these metastases.

Expression of Multidrug Resistance Transporter ABCB5 in a Murine Model of Human Conjunctival Melanoma

Conjunctival melanoma (CM) is a rare ocular malignancy with a high tendency to reoccur locally and with a high risk of metastatic disease. Metastases are often unresponsive to conventional treatment. Recently, an animal model was set up using human CM cells. Orthotopic xenografts from human CM were created by subconjunctival injection of three different CM cell lines into NOD.Cg-Prkdc^scid IL2rg^tm1Wjl /SzJ (NSG) mice. Subconjunctival injection of cultured CM cells led to excellent subconjunctival growth, but no metastases were found. When single-cell suspensions were obtained from the subconjunctival xenografts and passaged in vivo, all mice developed metastases. As recent findings indicate that cancer stem cells are linked to tumor recurrences, we used this new murine model to determine the expression of the stem cell marker ABCB5 during tumor progression. Expression of the ABCB5 protein was determined in three cell lines and during different stages of tumor development as observed in our model. All three cell lines contained a subpopulation of cells positive for ABCB5. During tumor development, expression of ABCB5 increased during phases of tumor expansion. Furthermore, expression of ABCB5 was increased in metastases. Using this model for CM, we were able to initiate metastatic spread and determine the expression of the stem cell marker ABCB5 during different stages of tumor development, identifying ABCB5 as a potential novel therapeutic target. This study illustrates the potential of our newly established murine model.