Circulating tumor DNA tracking through driver mutations as a liquid biopsy-based biomarker for uveal melanoma.

BACKGROUND: Uveal melanoma (UM) is the most common intraocular tumor in adults. Despite good primary tumor control, up to 50% of patients develop metastasis, which is lethal. UM often presents asymptomatically and is usually diagnosed by clinical examination and imaging, making it one of the few cancer types diagnosed without a biopsy. Hence, alternative diagnostic tools are needed. Circulating tumor DNA (ctDNA) has shown potential as a liquid biopsy target for cancer screening and monitoring. The aim of this study was to evaluate the feasibility and clinical utility of ctDNA detection in UM using specific UM gene mutations. METHODS: We used the highly sensitive digital droplet PCR (ddPCR) assay to quantify UM driver mutations (GNAQ, GNA11, PLCß4 and CYSTLR2) in cell-free DNA (cfDNA). cfDNA was analyzed in six well established human UM cell lines with known mutational status. cfDNA was analyzed in the blood and aqueous humor of an UM rabbit model and in the blood of patients. Rabbits were inoculated with human UM cells into the suprachoroidal space, and mutated ctDNA was quantified from longitudinal peripheral blood and aqueous humor draws. Blood clinical specimens were obtained from primary UM patients (n = 14), patients presenting with choroidal nevi (n = 16) and healthy individuals (n = 15). RESULTS: The in vitro model validated the specificity and accuracy of ddPCR to detect mutated cfDNA from UM cell supernatant. In the rabbit model, plasma and aqueous humor levels of ctDNA correlated with tumor growth. Notably, the detection of ctDNA preceded clinical detection of the intraocular tumor. In human specimens, while we did not detect any trace of ctDNA in healthy controls, we detected ctDNA in all UM patients. We observed that UM patients had significantly higher levels of ctDNA than patients with nevi, with a strong correlation between ctDNA levels and malignancy. Noteworthy, in patients with nevi, the levels of ctDNA highly correlated with the presence of clinical risk factors. CONCLUSIONS: We report, for the first time, compelling evidence from in vitro assays, and in vivo animal model and clinical specimens for the potential of mutated ctDNA as a biomarker of UM progression. These findings pave the way towards the implementation of a liquid biopsy to detect and monitor UM tumors.

Trends in Radiation Practices for Female Ocular Oncologists in North America: A Collaborative Study of the International Society of Ocular Oncology.

BACKGROUND: The aim of this study was to determine the known radiation exposure, attitudes, and consequent risk modifications among female ocular oncologists in North America who routinely administer radioactive plaque brachytherapy treatment and are members of the International Society of Ocular Oncology. METHODS: Nineteen female ocular oncologists completed an anonymous 17-question radiation exposure survey. RESULTS: Eleven of the participants chose to routinely wear lead protection during surgery; 8 did not. Fifteen of 19 participants reported using an unloaded "nonactive" template to prepare for plaque implantation. During pregnancy, 11 of 13 participants continued to perform plaque brachytherapy. Eight of these 11 undertook measures to decrease radiation exposure self-reported as lead wear and other. The average reported anxiety regarding fertility was 2.1 (SD, 2.2) on a scale from 1 to 10. CONCLUSION: This study corroborates prior literature that surgeons' exposure to radiation during plaque brachytherapy is minimal. Nonetheless, there remains some anxiety regarding exposure risk to women, due to potential effects on fertility and fetal health. We found variability in exposure monitoring, required training, and precautions during pregnancy amongst this group of surgeons. Improved education and clearer pregnancy guidelines may equip female ocular oncologists with optimal knowledge regarding risk of radiation exposure.

Characterization of ocular and metastatic uveal melanoma in an animal model.

PURPOSE: To characterize, in detail, tumor development, malignant cell dissemination, and metastasis in a 10-week animal model of uveal melanoma. METHODS: One million 92.1 human primary uveal melanoma cells were injected into the suprachoroidal space of the right eye of 27 immunosuppressed albino rabbits. Intraocular tumor growth was monitored weekly by fundoscopy and by ultrasonography at the end of the experiment. To document the progression of the disease, one animal per week was killed. The enucleated eyes, lungs, and livers were macroscopically examined and histopathologically studied by hematoxylin and eosin, periodic acid-Schiff, and immunohistochemistry. Mononuclear layers isolated from the rabbits' blood samples were cultured. RESULTS: Histopathology showed intraocular tumors in 89% of the animals. Tumor growth was found 1 week after cell inoculation, and by the end of the experiment large tumor masses were observed. Microscopic pulmonary metastatic foci were first observed 4 weeks after cell injection. By the end of the experiment, all the animals had metastasis to the lungs. Interestingly, 18% of the animals also had micrometastasis to the liver. Viable adherent uveal melanoma cells were successfully isolated from peripheral blood and grown in vitro. CONCLUSIONS: In this study, most rabbits developed intraocular tumors followed by lung metastasis, and some of these rabbits later developed liver micrometastases. This novel source of research material warrants a follow-up longer than 10 weeks to further explore the pathophysiologic bases of liver involvement commonly encountered in humans. The success in the isolation and culture of circulating malignant cells in this animal model suggests that it might be worthwhile to explore the application of this technique to the management of patients with primary uveal melanoma.

Cell proliferation profile of five human uveal melanoma cell lines of different metastatic potential.

OBJECTIVE: The aim of this study was to establish a proliferation profile of uveal melanoma cell lines, using different methods, and to compare it with their previously determined metastatic potential (MP). METHODS: Four human uveal melanoma and one transformed human uveal melanocytic cell line were ranked according to proliferation profiles. The proliferation profiles of the cell lines were compared to their MPs, which were previously determined from an immunosuppressed rabbit model. RESULTS: Ranking of the cell lines using pulse labeling with tritiated thymidine was similar to the MP of the cell lines. CONCLUSION: The correlation between the proliferative rate of the uveal melanoma cell lines and their previously determined MP resulted in the proposal of a new classification scheme: high proliferation/high MP, low proliferation/low MP, and high proliferation/no MP. High proliferative capacity of a cell line did not necessarily confer MP; therefore, further cellular functions/adaptations must be required for tumor cell dissemination, survival, and growth at a metastatic site.

The risk of other primary cancer in patients with uveal melanoma: a retrospective cohort study of a Canadian population.

BACKGROUND: The incidence of second primary malignant tumours has doubled during the last 2 decades. These tumours now represent the sixth most common group of cancers. Many authors have described the presence of multiple primary cancers in patients with uveal melanoma. However, no studies have been performed using Canadian data. The purpose of this study was to describe the occurrence of other primary cancers diagnosed before or after uveal melanoma and to calculate the incidence of subsequent primary cancer in a Canadian cohort with uveal melanoma. METHODS: We conducted a retrospective study of a cohort of patients with uveal melanoma diagnosed between 1990 and 2002 at a university-affiliated centre in Montreal. We reviewed medical records to identify patients in whom other, unrelated primary malignant disease had been diagnosed. We used the standardized incidence ratio to calculate the risk of development of a second, unrelated cancer following the diagnosis of uveal melanoma. RESULTS: A total of 129 cases of uveal melanoma were diagnosed. Eighteen patients (14%) also had a diagnosis of an unrelated primary cancer. In nine patients the other cancer had been diagnosed first, and in nine patients the other tumour had been diagnosed after the uveal melanoma. There was no increased risk of development of any particular form of cancer studied for females or males. INTERPRETATION: In our Canadian cohort, statistical analysis showed no increased risk of a second cancer, overall or by organ site, in male or female patients with uveal melanoma. As uveal melanoma is a rare type of cancer, analyses of a much larger cohort may be needed to accurately estimate the risk of development of a second primary cancer in patients with uveal melanoma.

Macrophage-derived soluble factor enhances melanoma inhibitory activity expression by uveal melanoma cells in vitro.

Melanoma inhibitory activity (MIA) is correlated with tumour progression and development of metastatic disease. Melanoma inhibitory activity, secreted by melanoma cells, is known to inhibit tumour cell attachment to the extracellular matrix enhancing their invasive potential. The regulatory pathways that lead to MIA expression have not yet been elucidated. It is well established that tumour cells and macrophages interact through soluble factors, preventing or enhancing tumour growth. The purpose of the present study was to determine whether soluble factor(s) derived from macrophages lead to the up-regulation of MIA production by human uveal melanoma cell lines (HUMCL) and whether MIA contributes to an increase in the invasive behaviour of HUMCL in vitro. Baseline MIA levels were measured by enzyme-linked immunosorbent assay in five HUMCL of known metastatic potential (92.1>SP6.5>OCM-1>MKT-BR>UW-1). Macrophage conditioned medium (MaCM) was placed on top of the HUMCL and MIA levels were measured at 6, 12, 24, and 36 h. The HUMCL were also seeded in a Matrigel chamber for 72 h and then cells invading the Matrigel were counted. The assay was repeated adding recombinant human MIA to the top layer of each well. All HUMCL expressed MIA at baseline (average of 31 ng/ml at 36 h). Following exposure to MaCM, MIA levels increased to an average of 45.2 ng/ml, with the 92.1 and SP6.5 cell lines expressing the highest MIA levels and UW-1 cell line expressing the lowest level. During the baseline invasion assay, the vast majority of cells (>95%) were found to adhere to the upper surface of the Matrigel. When MIA was added to the invasion chamber, no adhesion or invasion was observed. The results suggest, for the first time, that macrophages secrete a soluble factor(s) that may stimulate nearby melanoma cells to enhance their production of MIA in vitro. Furthermore, increased MIA production may, in turn, increase the invasive properties of the cells by modulating the attachment of HUMCL to the extracellular matrix.

Cyclooxygenase-2 expression in uveal melanoma: novel classification of mixed-cell-type tumours.

BACKGROUND: The expression of cyclooxygenase-2 (COX-2), an inducible prostaglandin (PG) synthase, has been investigated in various human malignant diseases, such as cutaneous melanoma. We investigated the expression of COX-2 in uveal melanoma and related the findings to prognostic factors. METHODS: In 40 cases of uveal melanoma, immunostaining for COX-2 was done. COX-2 expression was related to histopathological prognostic markers, such as cell type, the presence of lymphocytic infiltration and vascular closed loops in the tumour, and cytomorphometry results. RESULTS: COX-2 expression was found in 58% of the cases, and it correlated with markers of poor prognosis, such as epithelioid cell type and the presence of lymphocytic infiltration and vascular closed loops. The uveal melanomas expressing COX-2 had larger nuclei, as determined by cytomorphometry. INTERPRETATION: Whereas epithelioid tumours carry a worse prognosis than spindle cell tumours, until now it has not been possible to give a strong indication of prognosis in mixed-cell tumours. This study showed that mixed-cell tumours, representing the majority of uveal melanomas, may be further subclassified according to COX-2 expression, which serves as a marker of poor prognosis. The role of COX-2 in uveal melanoma should be further elucidated, and the use of COX-2 inhibitors warrants investigation as adjuvant treatment for this life-threatening malignant disease.

Benign ocular adnexal tumours of apocrine, eccrine or hair follicle origin.

BACKGROUND: The differential diagnosis of malignant eyelid tumours, particularly basal cell carcinoma (BCC), includes tumours of skin appendages. The incidence of these adnexal tumours has not been well established. This study aimed to determine the incidence and review the main clinicopathological features of benign tumours arising from skin appendages of the eyelid with apocrine, eccrine or hair follicle differentiation. METHODS: The histopathological diagnoses of 7751 ophthalmic specimens retrieved from 6967 patients between September 1993 and March 2002 at the Henry C. Witelson Ophthalmic Pathology Laboratory and Registry, McGill University, Montreal, were retrospectively reviewed. Clinical data and histopathological diagnoses were obtained for 228 benign adnexal tumours of apocrine, eccrine or hair follicle origin. New histopathological slides were made from the paraffin-embedded specimens and stained with hematoxylin-eosin and periodic acid-Schiffs reagent. RESULTS: Of the 228 benign adnexal tumours, 182 were diagnosed as apocrine or eccrine hydrocystoma (79.8%), 12 pilomatrixoma (5.3%), 12 syringoma (5.3%), 11 trichilemmoma (4.8%), 5 syringocystadenoma papilliferum (2.2%), 3 trichoepithelioma (1.3%) and 3 trichofolliculoma (1.3%). Discrepancies between clinical and histopathological diagnoses were noted in 22 cases (9.6%). INTERPRETATION: Benign tumours originating from skin appendages of the eyelid are rare and frequently have apocrine or eccrine differentiation. These tumours, particularly those originating from the hair follicle, should be considered in the differential diagnosis of BCC of the eyelid.