Preferentially Expressed Antigen in Melanoma Immunohistochemistry Labeling in Uveal Melanomas

Utility of PRAME Immunohistochemistry in the Detection of Subtle Melanoma Microsatellites

ABSTRACT

Microsatellitosis is well established as a prognostic factor in malignant melanoma. Its identification leads to subsequent upstaging with implications for further management. We describe 6 cases in which immunohistochemical staining for PReferentially expressed Antigen in MElanoma facilitated detection of small foci of micrometastasis on scanning magnification, which may be potentially missed in routine sections.

Stereotactic radiotherapy for uveal melanoma: A case report

Uveal melanoma (UM) is the most common primary intraocular malignancy worldwide. Surgical intervention and radiation therapy (RT) are the primary treatment options. Given the complexity and cosmetic discomfort associated with eye enucleation, this method is less frequently used. As a result, RT, including photon therapy, proton therapy and brachytherapy, has become the treatment of choice. Traditionally, plaque brachytherapy has been the most commonly used in clinical practice. However, the question of which type of radiation therapy is the most effective, safe, commonly available and cost-effective remains open. The present study provided a follow-up analysis of a patient with UM who was treated using the image-guided volumetric modulated arc therapy (IG-VMAT) technique. A complete response without complications and symptom relief were noted one and a half years after treatment. The present findings suggest that photon external beam radiotherapy using the IG-VMAT technique may offer a viable and safe alternative for the management of UM. This approach potentially sidesteps the complex and morbid aspects of surgical intervention and plaque brachytherapy. Owing to the limited sample size, a more robust understanding of the efficacy and safety of this treatment will require the analysis of additional cases. Further research with a larger cohort is essential to validate these preliminary observations.

Characterisation of the protein expression of the emerging immunotherapy targets VISTA, LAG-3 and PRAME in primary uveal melanoma: insights from a southern French patient cohort

Uveal melanoma (UM) is the most common intraocular tumour in adults, with dismal prognosis once metastases develop, since therapeutic options for the metastatic disease are ineffective. Over the past decade, novel cancer therapies based on immunotherapy have changed the landscape of treatment of different forms of cancer leading to many hopes of improvement in patient overall survival (OS). VISTA, LAG-3 and PRAME are novel promising targets of immunotherapy that have recently gained attention in different solid tumours, but whose relevance in UM remained to be comprehensively evaluated until now. Here, we studied the protein expression of VISTA, LAG-3 and PRAME using immunohistochemistry in representative whole tissue sections from primary UM cases in a cohort of 30 patients from a single centre (Nice University Hospital, Nice, France). The expression of each of these markers was correlated with different clinical and pathological parameters, including onset of metastases and OS. We demonstrated the protein expression of VISTA and LAG-3 in small lymphocytes infiltrating the tumour, while no expression of the proteins was detected in UM cells. For PRAME, nuclear expression was observed in UM cells, but no expression in tumour infiltrating immune cells was identified. Increased levels of VISTA expression in tumour infiltrating lymphocytes (TILs) were associated with nuclear BAP1 expression and better prognosis. Higher levels of LAG-3 in TILs were associated with higher levels of CD8-positive TILs. PRAME nuclear positivity in melanoma cells was associated with epithelioid cell dominant (>90%) UM histological subtype, higher mitotic numbers and a higher percentage of chromosome 8q gain. This study proposes VISTA as a novel relevant immune checkpoint molecule in primary UM and contributes to confirm LAG-3 and PRAME as potentially important immunotherapy targets in the treatment of UM patients, helping to expand the number of immunotherapy candidate molecules that are relevant to modulate in this aggressive cancer.

Immunohistochemistry for PRAME in Dermatopathology

ABSTRACT

Preferentially expressed antigen in melanoma (PRAME) is a tumor-associated antigen first identified in a melanoma patient and found to be expressed in most melanomas as well as in variable levels in other malignant neoplasms of epithelial, mesenchymal, or hematolymphoid lineage. Detection of PRAME expression in formalin-fixed paraffin-embedded tissue is possible by immunohistochemistry (IHC) with commercially available monoclonal antibodies. In situ and invasive melanoma frequently show a diffuse pattern of nuclear PRAME immunoreactivity which contrasts with the infrequent and typically nondiffuse staining seen in nevi. In many challenging melanocytic tumors, results of PRAME IHC and other ancillary tests correlate well, but not always: The tests are not interchangeable. Most metastatic melanomas are positive for PRAME, whereas nodal nevi are not. Numerous studies on PRAME IHC have become available in the past few years with results supporting the value of PRAME IHC as an ancillary tool in the evaluation of melanocytic lesions and providing insights into limitations in sensitivity and specificity as well as possible pitfalls that need to be kept in mind by practicing pathologists.

Immunohistochemical expression of PRAME is a marker of poor prognosis in uveal melanoma: A clinico-pathologic and immunohistochemical study on a series of 85 cases

PReferentially expressed Antigen in Melanoma (PRAME) is a cancer testis antigen, first isolated in tumor-reactive T-cell clones from a metastatic melanoma patient. It has been widely studied in skin pathology as an immunohistochemical marker capable of distinguishing between benign nevi and malignant melanomas. PRAME has been found to be also expressed in non-melanocytic tumors, including lung, breast, kidney and ovarian cancer. However, less is known about the diagnostic and/or prognostic role of this protein in uveal melanoma (UM); few studies have reported that PRAME expression seems to give to UM patients an additional metastatic risk beyond the other already-known prognostic parameters. In the present retrospective study, we aimed to correlate PRAME immunoreactivity to other clinico-pathologic features and follow-up data on a large series of 85 cases (45 non-metastasizing and 40 metastasizing tumors) of primary UM. A statistically significant correlation was found between PRAME expression and higher metastatic risk and lower metastasis-free survival. We propose to include PRAME in the immunohistochemical panel of UM as an easily usable marker capable of predicting higher metastatic risk and stratifying patients' outcome.

Prognostic Value of BAP1 and Preferentially Expressed Antigen in Melanoma (PRAME) Immunohistochemistry in Uveal Melanomas

Uveal melanoma (UM) is the most common primary intraocular tumor in adults, and despite excellent local control, more than 50% of patients develop and die from metastatic disease. Loss of BAP1 nuclear staining, a surrogate marker of BAP1 mutation, and preferentially expressed antigen in melanoma (PRAME) messenger RNA overexpression, as assessed using qPCR, have previously been shown to correlate with increased metastasis rate in UM. In this study, we demonstrated that UM could be successfully risk-stratified using a combination of BAP1 and PRAME immunohistochemical (IHC) stains. We retrospectively reviewed 318 UM cases with sufficient tissue and performed BAP1 and PRAME IHC to stratify them as BAP1+/PRAME- (group 1, n = 135), BAP1+/PRAME+ (group 2, n = 43), BAP1-/PRAME- (group 3, n = 94), and BAP1-/PRAME+ (group 4, n = 46). Increasing the study risk group on the basis of loss of BAP1 expression and positive PRAME staining was associated with a higher rate of metastasis and disease-specific death and lower metastasis-free survival (MFS) and disease-specific survival (DSS). Among tumors with loss of BAP1 staining, PRAME positivity was associated with shorter MFS (P = .018) and showed a trend toward shorter DSS (P = .061). Among tumors with retained BAP1 staining, PRAME positivity was associated with shorter MFS and DSS (P = .001 and P = .021, respectively). In summary, a combination of BAP1 and PRAME IHC can be used for risk stratification of UMs.

Diagnostic utility of immunohistochemistry in concordance with mRNA analysis of PRAME in the stratification of high-risk uveal melanoma patients

Existing clinical indicators for metastatic risk classification and patient treatment of uveal melanoma (UM) in the Asian population are limited. Preferentially expressed antigen in melanoma (PRAME) has gained attention in the prognosis of cancers and considered as a potential biomarker in many tumors including UM. Therefore, this study investigated the expression of PRAME and its association with loss of nuclear BAP1 (nBAP1) as well as its correlation with clinicopathological parameters and patient outcome. Immunohistochemical expression of PRAME and BAP1 proteins were assessed in 66 prospective cases of UM. mRNA expression level was measured by quantitative real-time PCR. Kaplan-Meier curves and Cox proportional hazard models were used to analyze the correlation of protein expression with clinicopathological parameters, metastasis-free survival and overall survival. Nuclear PRAME (nPRAME) expression and loss of nBAP1 were observed in 24 and 62% cases, respectively. PRAME mRNA expression level was found to be upregulated in 64% (7/11) of metastatic patients. mRNA and immunoexpression of nPRAME were statistically significant with many clinicopathological high-risk factors. On univariate and multivariate analyses, high mitotic activity, extraocular invasion and presence of nPRAME expression were statistically significant (p < 0.05). On Kaplan-Meier survival analysis, patients expressing PRAME had significantly reduced metastasis-free survival (MFS) and overall survival (OS). MFS and OS were also reduced in patients expressing PRAME along with loss of nBAP1. Our data show that nPRAME expression, in combination with loss of nBAP1, could be a useful predictive biomarker in the therapeutic management of UM patients at high risk.