Molecular Profiling of Uveal Melanoma Patients

Although uveal melanoma represents only 5% of all melanomas, it is the most common primary intraocular malignancy of the adult eye. Approximately 50% of patients will develop metastases which are resistant to medical interventions. There is a great need for improved therapy as the prognosis is poor for advanced-stage disease. Our study was undertaken to investigate the presence of novel therapeutic targets. Methods: We analyzed 49 uveal melanoma patients with immunohistochemistry for 23 markers including cKIT, PDGFR, cMET, PTEN and IGF1R. Furthermore, microarray analysis was performed on 29 samples using the Illumina platform. We also investigated FISH amplification of EGFR and mutational analysis of cKIT, BRAF, KRAS and NRAS on a smaller patient subset. Results: Overexpression of KIT at the protein and RNA level was 74% (28 out of 38) and 45% (13 out of 29), respectively. Expression of cKIT did not correlate with gain-of-function cKIT mutations in any of the 34 samples tested. In our study, MET was overexpressed in 15 out of 17 cases at the RNA level and IGF1R was high in 4 out of 6 patients indicating poor prognosis. PTEN expression by IHC was present in 90% (36 out of 40) patients, indicating the PI3K pathway is not activated in the majority of uveal melanoma patients. BRAF was wild-type in all 42 patients tested. Similarly, no KRAS or NRAS mutations were detected. Protein and RNA expression of PDGFR were low in our patients. MGMT was lost in 16 out of 40 patients at the protein level and 10 out of 29 patients at the RNA level. EGFR expression, copy number and protein levels were low in the patients tested. Conclusions: Our data on cKIT suggests that it is a promising target in uveal melanoma. Low expression of MGMT in about a third of our patients may indicate the likelihood of favorable response to alkylating agents like dacarbazine or temozolomide. There are currently several clinical trials investigating various cKIT inhibitors, as well as temozolomide in advanced uveal melanoma patients. Our findings highlight the importance of molecular profiling uveal melanoma patients. Microarray was also utilized to interrogate the tumor. In all, 88 biomarkers were analyzed by this methodology in 29 tumors. Table 2 and Table 3 (shown below) are graphical illustrations showing the twenty biomarkers with the highest relative overexpression and the twenty biomarkers with the highest relative underexpression, sorted by percentage (from highest to lowest). Overexpressed biomarkers worth mentioning in Table 2 include MET (88.2%), KIT (44.8%), ERCC1 (41.4%), GART (41.4%), SPARC (41.4%), PDGFRB (34.5%), and RRM2B (34.5%). Some of these results are associated with potential benefit to agents like sunitinib (KIT), pemetrexed (GART), and nab-paclitaxel (SPARC), while others are associated with a lack of clinical benefit to agents like cisplatin/carboplatin (ERCC1). By contrast, biomarkers worth mentioning in Table 3 include EGFR (55.2%), TOP2A (51.7%), PDGFRA (48.3%), RRM1 (48.3%), MGMT (34.5%), and TYMS (34.5%). Some of these results are associated with benefit to fluorouracil (TYMS) and temozolomide/ dacarbazine (MGMT). Fluorescent in-situ hybridization (FISH) was also performed, either by reflexing from PTEN or HER2 IHC results or by physician request. Results in Table 4 show that ALK, cMYC, EGFR, HER2, and TOP2A showed no amplification. Note how EGFR by FISH results indicate a lack of clinical benefit to anti-EGFR-targeted therapy, in keeping with EGFR by microarray.