Ahmadian Saman S, Dryden Ian J, Naranjo Andrea, Toland Angus, Cayrol Romain A, Born Donald E, Egbert Peter S, Brown Ryanne A, Mruthyunjaya Prithvi, Lin Jonathan H
Department of Pathology, Stanford University School of Medicine, Stanford, California, USA.
Department of Ophthalmology, Stanford University School of Medicine, Stanford, California, USA.
Ocul Oncol Pathol. 2022 Jun;8(2):133-140. doi: 10.1159/000524051. Epub 2022 Mar 11.
Uveal melanoma (UM) is the most common primary intraocular malignancy in adults, and despite treatment of the primary tumor, approximately 15%-50% of patients will develop metastatic disease. Based on gene expression profiling (GEPs), UM can be categorized as Class 1A (low metastatic risk), Class 1B (intermediate metastatic risk), or Class 2 (high metastatic risk). PReferentially expressed Antigen in MElanoma (PRAME) status is an independent prognostic UM biomarker and a potential target for immunotherapy in metastatic UM. PRAME expression status can be detected in tumors using reverse-transcription polymerase chain reaction (RT-PCR). More recently, immunohistochemistry (IHC) has been developed to detect PRAME protein expression. Here, we employed both techniques to evaluate PRAME expression in 18 UM enucleations.
Tumor material from the 18 UM patients who underwent enucleation was collected by fine-needle aspiration before or during enucleation and sent for GEP and PRAME analysis by RT-PCR. Histologic sections from these patients were stained with an anti-PRAME monoclonal antibody. We collected patient demographics and tumor characteristics and included this with our analysis of GEP class, PRAME status by RT-PCR, and PRAME status by IHC. PRAME IHC and RT-PCR results were compared.
Twelve males (12/18) and 6 females (6/18) with an average age of 60.6 years underwent enucleation for UM. TNM staging of the UM diagnosed Stage I in 2 patients (2/18), Stage II in 7 patients (7/18), Stage III in 8 patients (8/18), and Stage IV in 1 (1/18). GEP was Class 1A in 6 tumors (6/18), Class 1B in 6 tumors (6/18), and Class 2 in 6 tumors (6/18). PRAME IHC showed diffusely positive labeling of all UM cells in 2/18 enucleations; negative IHC labeling of UM cells in 9/18 enucleations; and IHC labeling of subsets of UM cells in 7/18 enucleations. Eleven of the 17 UMs tested for PRAME by both RT-PCR and IHC had consistent PRAME results. In the remaining 6/17 cases tested by both modalities, PRAME results were discordant between RT-PCR and IHC.
We find that PRAME IHC distinguishes PRAME-positive and PRAME-negative UM tumor cells. Interestingly, IHC reveals focal PRAME expression in subsets of tumor cells consistent with tumor heterogeneity. PRAME RT-PCR and IHC provide concordant results in most of our cases. We suggest that discordance in PRAME results could arise from spatial or temporal variation in PRAME expression between tumor cells. Further studies are required to determine the prognostic implications of PRAME IHC in UM.
葡萄膜黑色素瘤（UM）是成人中最常见的原发性眼内恶性肿瘤，尽管对原发性肿瘤进行了治疗，但仍有大约15%-50%的患者会发生转移性疾病。基于基因表达谱（GEP），UM可分为1A类（低转移风险）、1B类（中等转移风险）或2类（高转移风险）。黑色素瘤优先表达抗原（PRAME）状态是一种独立的UM预后生物标志物，也是转移性UM免疫治疗的潜在靶点。可使用逆转录聚合酶链反应（RT-PCR）在肿瘤中检测PRAME表达状态。最近，已开发出免疫组织化学（IHC）方法来检测PRAME蛋白表达。在此，我们采用这两种技术评估了18例UM眼球摘除标本中的PRAME表达。
收集18例行眼球摘除术的UM患者的肿瘤组织，在眼球摘除术前或术中通过细针穿刺获取，并送去进行GEP和RT-PCR检测PRAME。这些患者的组织切片用抗PRAME单克隆抗体染色。我们收集了患者的人口统计学资料和肿瘤特征，并将其纳入我们对GEP类别、RT-PCR检测的PRAME状态以及IHC检测的PRAME状态的分析中。比较了PRAME IHC和RT-PCR的结果。
12名男性（12/18）和6名女性（6/18）平均年龄60.6岁，因UM接受了眼球摘除术。所诊断的UM的TNM分期为：I期2例（2/18），II期7例（7/18），III期8例（8/18），IV期1例（1/18）。GEP显示6个肿瘤为1A类（6/18），6个肿瘤为1B类（6/18），6个肿瘤为2类（6/18）。PRAME IHC显示，在18例眼球摘除标本中有2例所有UM细胞弥漫性阳性标记；9例UM细胞IHC标记为阴性；7例UM细胞子集有IHC标记。在通过RT-PCR和IHC检测PRAME的17例UM中，11例的PRAME结果一致。在其余6/17例两种方法检测的病例中，RT-PCR和IHC的PRAME结果不一致。
我们发现PRAME IHC可区分PRAME阳性和PRAME阴性的UM肿瘤细胞。有趣的是，IHC揭示了肿瘤细胞亚群中PRAME的局灶性表达，这与肿瘤异质性一致。在我们的大多数病例中，PRAME RT-PCR和IHC提供了一致的结果。我们认为PRAME结果的不一致可能源于肿瘤细胞之间PRAME表达的空间或时间差异。需要进一步研究以确定PRAME IHC在UM中的预后意义。
