Molecular profiling of uveal melanoma patients.

Abstract

10630 Background: 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 stages. Our study was undertaken to investigate the presence of novel therapeutic targets. Methods: We analyzed 49 uveal melanoma patients with immunohistochemistry for 16 markers including cKIT, PDGFR, cMET, PTEN and IGF1R. Further, microarray analysis was performed on 29 samples using the Illumina platform. We also investigated 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 wildtype 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 dacarbazine and 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.