Tumour-associated lymphangiogenesis in conjunctival malignant melanoma

New targets of nascent lymphatic vessels in ocular diseases

Recent advancements in the field of endothelial markers of lymphatic vessels and lymphangiogenic factors have shed light on the association between several ocular diseases and ocular nascent lymphatic vessels. The immune privilege of corneal tissue typically limits the formation of lymphatic vessels in a healthy eye. However, vessels in the eyes can potentially undergo lymphangiogenesis and be conditionally activated. It is evident that nascent lymphatic vessels in the eyes contribute to various ocular pathologies. Conversely, lymphatic vessels are present in the corneal limbus, ciliary body, lacrimal glands, optic nerve sheaths, and extraocular muscles, while a lymphatic vasculature-like system exists in the choroid, that can potentially cause several ocular pathologies. Moreover, numerous studies indicate that many ocular diseases can influence or activate nascent lymphatic vessels, ultimately affecting patient prognosis. By understanding the mechanisms underlying the onset, development, and regression of ocular nascent lymphatic vessels, as well as exploring related research on ocular diseases, this article aims to offer novel perspectives for the treatment of such conditions.

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.

New Therapeutic Approaches for Conjunctival Melanoma-What We Know So Far and Where Therapy Is Potentially Heading: Focus on Lymphatic Vessels and Dendritic Cells

Conjunctival melanoma (CM) accounts for 5% of all ocular melanomas and arises from malignantly transformed melanocytes in the conjunctival epithelium. Current therapies using surgical excision in combination with chemo- or cryotherapy still have high rates for recurrences and metastatic disease. Lately, novel signal transduction-targeted and immune checkpoint inhibitors like cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) inhibitors, programmed cell death protein-1 (PD-1) receptor inhibitors, BRAF- or MEK-inhibitors for systemic treatment of melanoma have improved the outcome even for unresectable cutaneous melanoma, improving patient survival dramatically. The use of these therapies is now also recommended for CM; however, the immunological background of CM is barely known, underlining the need for research to better understand the immunological basics when treating CM patients with immunomodulatory therapies. Immune checkpoint inhibitors activate tumor defense by interrupting inhibitory interactions between tumor cells and T lymphocytes at the so-called checkpoints. The tumor cells exploit these inhibitory targets on T-cells that are usually used by dendritic cells (DCs). DCs are antigen-presenting cells at the forefront of immune response induction. They contribute to immune tolerance and immune defense but in the case of tumor development, immune tolerance is often prevalent. Enhancing the immune response via DCs, interfering with the lymphatic pathways during immune cell migration and tumor development and specifically targeting tumor cells is a major therapeutic opportunity for many tumor entities including CM. This review summarizes the current knowledge on the function of lymphatic vessels in tumor growth and immune cell transport and continues to compare DC subsets in CM with related melanomas, such as cutaneous melanoma and mucosal melanoma.

Small but Challenging Conjunctival Melanoma: New Insights, Paradigms and Future Perspectives

Although its incidence has increased over the last decades, conjunctival melanoma (CM) remains a rare but challenging periocular malignancy. While there is currently no recognized standard of care, "no-touch" surgical excision followed by adjuvant treatments is usually recommended. Despite its small size, managing CM is challenging for clinicians. The first challenge is the high risk of tumour local recurrence that occurs in about one third of the patients. The management of locally advanced CM (≥T2) or multiple recurrences may require mutilating surgeries such as orbital exenteration (OE). The second challenge is the metastatic spread of CM that occurs in about one quarter of patients, regardless of whether complete surgical excision is performed or not. This highlights the infiltrative and highly aggressive behaviour of CM. Recently, attention has been directed towards the use of eye-sparing strategies to avoid OE. Initially, wide conservative surgeries followed by customized brachytherapy or radiotherapy have appeared as viable strategies. Nowadays, new biological insights into CM have revealed similarities with cutaneous melanoma. These new findings have allowed clinicians to reconsider the management of locally advanced CM with "medical" eye-sparing treatment as well as the management of metastatic spread. The aim of this review was to summarize the current and future perspectives of treatment for CM based on recent biological findings.

Current Management of Conjunctival Melanoma Part 2: Treatment and Future Directions

Conjunctival melanoma is a rare disease which requires tailored management in most cases. The mainstays of treatment can be classified as surgery, topical chemotherapy, radiotherapy, cryotherapy, and other emerging treatment modalities. Herein we review conventional approaches as well as more recently introduced treatment options, together with advances in molecular biology in this particular disease.

Conjunctival Melanoma Angiotropic Microsatellitosis: A Mechanism of Local Extravascular Migratory Metastasis

Purpose

To report a case of local metastasis of conjunctival melanoma, which may occur via extravascular migratory metastasis (EVMM), and discuss its clinical relevance in conjunctival melanoma tumor staging and possible management implications.

Methods

Retrospective chart review of a single clinical case with clinicopathologic correlation.

Results

A 65-year-old male referred due to local recurrence of conjunctival melanoma at the caruncle was successfully treated after two excisional procedures with negative sentinel lymph node biopsies. Forty-eight months after initial presentation, the patient developed a nodular lesion representing local recurrence in the ipsilateral upper tarsal conjunctiva, distant from the primary tumor site. Histopathology showed nodules in the substantia propria in the absence of primary acquired melanosis. The tumor cells were found along the extravascular surface without intralymphatic or intravascular tumor cells consistent with local metastasis. One possible mechanism is angiotropic microsatellitosis leading to local EVMM. Additional neck CT imaging showed no lymphadenopathy.

Conclusion

EVMM via angiotropic microsatellitosis is another possible mechanism of noncontiguous local recurrence of conjunctival melanoma. Angiotropic microsatellitosis may represent a high-risk finding possibly related to increased melanoma-related mortality.

Absence of Intraocular Lymphatic Vessels in Uveal Melanomas with Extrascleral Growth

The aim of this study was to investigate the presence of intraocular lymphatic vessels in patients with uveal melanomas and extrascleral extension using a panel of lymphatic markers. The following immunohistochemical markers were analyzed: lymphatic vessel endothelial hyaluronic acid receptor-1 (LYVE-1), podoplanin (D2-40), prospero-related homeobox gene-1 (Prox-1), pan-endothelial marker cluster of differentiation 31 (CD31), and blood vessel endothelium-specific CD34. Lymphatic vessels were defined as a combination of staining of the following positive markers: LYVE-1, D2-40, Prox-1, and CD31; and no staining of the negative marker CD34. In total, 456 patients were enucleated; 16 of the 46 uveal melanomas with extrascleral extension were contained in stored paraffin tissue. Two samples of the 16 uveal melanomas showed focal positive intraocular vascular staining for LYVE-1 and co-expression of CD31 and CD34. Due to the lack of Prox-1 and D2-40, and positive expression of CD34, these cannot be classified as lymphatic vessels. In one case recruitment of an extraocular, intratumoral lymphatic vascular structure was observed in the periphery of the subconjunctival extrascleral extension. Intraocular lymphatic vessels are absent in uveal melanomas with extrascleral extension; however, we provide proof for recruitment of intratumoral lymphatics by uveal melanomas with extraocular extension from subconjunctival lymphatics that may explain the rare cases of regional lymphatic spread. A panel of antibodies is necessary to detect lymphatic vessels with high specificity.

Immunohistochemical profiling including beta-catenin in conjunctival melanocytic lesions

Conjunctival melanocytic lesions encompass a group of clinically diverse, benign to malignant, neoplasms that may contain overlapping histopathological features, making definitive diagnosis challenging in some cases. In this series, we compared multiple immunohistochemical (IHC) markers in 11 conjunctival nevi, 10 primary acquired melanosis (PAM) lesions, and 11 conjunctival melanomas. Immunostains included the melanocytic markers HMB-45 and Melan-A, as well as the proliferative marker Ki-67. Loss of beta-catenin expression has been associated with more aggressive clinical disease in cutaneous melanoma, but its status in conjunctival melanocytic lesions is not known, therefore we incorporated beta-catenin immunohistochemical staining in our study. In this series, conjunctival melanomas had a higher Ki-67 proliferative index and HMB-45 immunoreactivity than did PAM lesions and conjunctival nevi (P<0.001). Melan-A was highly expressed in all 3 groups. Beta-catenin was more strongly expressed in melanomas and nevi than in PAM (P<0.001). There was high inter-grader reliability (Kappa=0.53). Overall, IHC labeling of HMB-45 and Ki-67 is increased in conjunctival melanomas compared to PAM or conjunctival nevi. Beta-catenin, an IHC marker previously unstudied in conjunctival melanocytic lesions, is not preferentially expressed in benign lesions and may play a different role in conjunctival atypia than it does in cutaneous melanoma.

[Adjuvant therapy and interdisciplinary follow-up care of conjunctival melanoma]

BACKGROUND

Despite microscopically controlled tumor excision, malignant melanomas of the conjunctiva have a propensity for local recurrence, lymphatic spread and distant metastases.

OBJECTIVES

This review outlines the options of adjuvant therapy as well as the structure of interdisciplinary follow-up care for patients with conjunctival melanoma.

METHODS

The study provides a PubMed literature review and own clinical results.

RESULTS

In conjunctival melanoma complete tumor excision using a minimal touch technique should always be combined with adjuvant therapy, such as cryotherapy, radiotherapy, topical chemotherapy and/or immunotherapy. For locally circumscribed lesions of the bulbar conjunctiva adjuvant brachytherapy can be supplemented and for non-bulbar, extensive, diffuse or multilocular tumor growth, complementary adjuvant topical mitomycin C therapy or proton radiotherapy can be used. Novel adjuvant approaches include topical interferon alpha-2b immunotherapy, topical vascular endothelial growth factor (VEGF) inhibitors or in cases of BRAF mutations personalized therapy using selective BRAF inhibitors or in combination with mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinase (ERK), MAPK/ERK (MEK) inhibitors. All patients should be integrated into an interdisciplinary follow-up care program including quarter yearly checkups in the first 5 years and psycho-oncological healthcare.

CONCLUSION

Following microscopically controlled tumor excision, adjuvant treatment using cryotherapy, radiotherapy, topical chemotherapy and/or immunotherapy as well as interdisciplinary follow-up care are mandatory for the modern management of patients with conjunctival melanoma.

Lymphangiogenic and Chemotactic Factors in Conjunctival Melanoma

PURPOSE

The aim of this study was to evaluate expression patterns of known lymphangiogenic growth factors and chemokines in conjunctival melanoma, and to describe patterns of lymphatic vessel growth in these tumors.

METHODS

This was a retrospective chart review comprising 5 participants (6 tumor specimens) and the main outcome measures were expression of growth factors, chemokines, and their receptors known to be important in tumor lymphangiogenesis as well as patterns of lymphatic vessel growth on immunohistochemical sections.

RESULTS

Tumor cells in all specimens expressed lymphangiogenic growth factors VEGFC, VEGFD, and their receptor VEGFR3. Chemotactic factors CXCL12 and CCL21 and their receptors, CXCR4 and CCL21, were also expressed in tumor cells and lymphatic endothelial cells. Staining was most intense for these proteins at the invasive tumor edge, suggesting increased lymphangiogenic activity at this location. In addition, lymphatic vessels clustered near the invasive edge of the tumors.

CONCLUSIONS

VEGFC, VEGFD, and VEGR3 are diffusely expressed by conjunctival melanoma cells, most intensely at the invasive tumor edge. CXCL12, CXCR4, CCL21, and CCR7 were also most intensely expressed at the invasive edge, where the highest density of lymphatic vessels was also observed. These expression patterns suggest that these mediators of tumor-associated lymphangiogenesis warrant further investigation as potential therapeutic targets in conjunctival melanoma.

Antilymphangiogenic therapy to promote transplant survival and to reduce cancer metastasis: what can we learn from the eye?

The lymphatic vasculature is - amongst other tasks - essentially involved in inflammation, (auto)immunity, graft rejection and cancer metastasis. The eye is mainly devoid of lymphatic vessels except for its adnexa, the conjunctiva and the limbus. However, several pathologic conditions can result in the secondary ingrowth of lymphatic vessels into physiologically alymphatic parts of the eye such as the cornea or the inner eye. Therefore, the cornea has served as an excellent in vivo model system to study lymphangiogenesis, and findings from such studies have substantially contributed to the understanding of central principles of lymphangiogenesis also with relevance outside the eye. Grafting experiments at the cornea have been extensively used to analyze the role of lymphangiogenesis in transplant immunology. In this regard, we recently demonstrated the crucial role of lymphatic vessels in mediating corneal allograft rejection and could show that antilymphangiogenic therapy increases graft survival. In the field of cancer research, we recently detected tumor-associated lymphangiogenesis in the most common malignant tumors of the eye, such as conjunctival carcinoma and melanoma, and ciliochoroidal melanoma with extraocular extension. These neolymphatics correlate with an increased risk of local recurrence, metastasis and tumor related death, and may offer potential therapeutic targets for the treatment of these tumors. This review will focus on corneal and tumor-associated ocular lymphangiogenesis. First, we will describe common experimentally used corneal lymphangiogenesis models and will recapitulate recent findings regarding the involvement of lymphatic vessels in corneal diseases and transplant immunology. The second part of this article will summarize findings about the participation of tumor-associated lymphangiogenesis in ocular malignancies and their implications for the development of future therapeutic strategies.

Identification of microRNAs associated with lymphangiogenesis in human gastric cancer

PURPOSE

Lymphatic metastasis is a primary cause of gastric cancer-related death, yet factors governing tumor cell lymphatic metastasis have not been fully elucidated. MicroRNAs (miRNAs) are a recently discovered class of regulatory, non-coding RNAs, some of which are involved in gastric cancer progression. However, little is known about which miRNA contributes to the lymphatic metastasis in human gastric cancer. This prompted us to find the significant miRNAs associated with lymphangiogenesis in human gastric cancer.

METHODS

We screened vascular endothelial growth factor C (VEGF-C) expression in several gastric cancer cell lines as well as in the immortalized human gastric mucosal cell line GES-1, by real-time reverse transcriptase PCR (qRT-PCR). The gastric cancer cell lines MKN-45 and SGC-7901, which have commonly been cultured with human lymphatic endothelial cells (HLECs) in vitro, promoted tube formation of HLECs following transformation with a VEGF-C expression vector. Using microarrays, we identified a panel of differentially expressed miRNAs in HLECs that had been co-cultured with VEGF-C-transformed gastric cancer cells compared with non-transformed gastric cancer cells. A subset of miRNAs was further validated using qRT-PCR.

RESULTS

We found altered expression of miRNAs in HLECs co-cultured with lymphangiogenesis-inducing VEGF-C-transformed gastric cancer cells, with 47 up-regulated and 42 down-regulated miRNAs. These findings were confirmed by qRT-PCR of selected miRNAs. Furthermore, several miRNAs were differentially expressed in patients with positive lymphatic metastasis of the primary gastric tumor. Up-regulated miRNAs included miR-648, miR-5002-3p, miR-4754, miR-4760-5p, miR-4491, miR-4252, miR-5007-3p, and miR-647; and down-regulated miRNAs included miR-3178, miR-593-5p, miR-4485, miR-135a-3p, miR-17, miR-1469, and miR-124-5p.

CONCLUSIONS

Several lymphangiogenesis-related miRNAs are significantly altered during lymphatic metastasis of gastric cancer.

Novel anti(lymph)angiogenic treatment strategies for corneal and ocular surface diseases

The cornea is one of the few tissues which actively maintain an avascular state, i.e. the absence of blood and lymphatic vessels (corneal [lymph]angiogenic privilege). Nonetheless do several diseases interfere with this privilege and cause pathologic corneal hem- and lymphangiogenesis. The ingrowths of pathologic blood and lymphatic vessels into the cornea not only reduce transparency and thereby visual acuity up to blindness, but also significantly increases the rate of graft rejections after subsequent corneal transplantation. Therefore great interest exists in new strategies to target pathologic corneal (lymph)angiogenesis to promote graft survival. This review gives an overview on the vascular anatomy of the normal ocular surface, on the molecular mechanisms contributing to the corneal (lymph)angiogenic privilege and on the cellular and molecular mechanisms occurring during pathological neovascularization of the cornea. In addition we summarize the current preclinical and clinical evidence for three novel treatment strategies against ocular surface diseases based on targeting pathologic (lymph)angiogenesis: (a) modulation of the immune responses after (corneal) transplantation by targeting pathologic (lymph)angiogenesis prior to and after transplantation, (b) novel concepts against metastasis and recurrence of ocular surface tumors such as malignant melanoma of the conjunctiva by anti(lymph)angiogenic therapy and (c) new ideas on how to target ocular surface inflammatory diseases such as dry eye by targeting conjunctival and corneal lymphatic vessels. Based on compelling preclinical evidence and early data from clinical trials the novel therapeutic concepts of promoting graft survival, inhibiting tumor metastasis and dampening ocular surface inflammation and dry eye disease by targeting (lymph)angiogenesis are on their way to translation into the clinic.

Histologic features of conjunctival melanoma predictive of metastasis and death (an American Ophthalmological thesis)

PURPOSE

In conjunctival melanoma, tumor thickness and nonlimbal location are associated with poor prognosis. However, other established high-risk features for cutaneous melanoma, including ulceration, mitotic figures, epithelioid cell type, and lymphovascular invasion, have not previously been studied extensively for their prognostic value in conjunctival melanoma. We examined the hypothesis that these features also predict regional nodal metastasis and death in conjunctival melanoma.

METHODS

The medical records of 44 of 46 consecutive conjunctival melanoma patients treated between June 2003 and December 2009 were retrospectively reviewed; tumor tissue was not available for the two excluded patients. Demographic and clinicopathologic features, including tumor location, tumor thickness, ulceration, mitotic rate, histology, lymphovascular invasion, and microsatellitosis, were reviewed. Outcome measures included regional nodal metastasis, distant metastasis, and death.

RESULTS

Twenty-six women and 18 men had a median age of 62 years. Regional nodal metastasis occurred in 7 patients (16%) and distant metastasis in 9 (20%). Median follow-up was 40 months. At last follow-up, 10 patients (23%) had died of disease. Tumor thickness>2.0 mm, ulceration, and mitotic figure>1/mm2 predicted regional nodal metastasis and death from disease. In addition to these three histologic features, vascular invasion, epithelioid cell type, and microsatellitosis significantly predicted death from disease. Tumor location (bulbar vs nonbulbar) was not correlated with regional nodal metastasis or death.

CONCLUSIONS

In conjunctival melanoma, as in cutaneous melanoma, thicker tumor, ulceration, and higher mitotic rate are correlated with regional nodal metastasis. In addition, lymphovascular invasion, epithelioid cell type, and microsatellitosis are correlated with melanoma-related death.