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Ana Carolina F. Tavares, Dominique DE Souza, Claudia Martins, Patrick T. Logan, Mohib W. Morcos, Miguel N. Burnier, Jr.; The Expression Of Dbc1 In Uveal Melanoma. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1450.
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The gene encoding DBC1, located on 8p21, is frequently deleted in breast cancer. DBC1 is supposed to act as a tumor suppressor gene by inhibiting the deacetylating activity of SIRT1 (considered a tumor promoter gene). However, the suggested function of DBC1 as a potential tumor suppressor has been challenged by observations of its respective down- and up- regulations in various cancers. Uveal Melanoma (UM) is the most common primary intra-ocular tumor in adults and 50% of patients develop metastasis. The aim of this study was to investigate the expression of DBC1 in primary UM patients and to correlate with clinico-pathological features.
Formalin-fixed, Paraffin-embedded sections from 20 UM specimens were immunostained with a rabbit anti-human monoclonal antibody (Abcam) using the Ventana Benchmark system. Sections of colon cancer were used as positive controls. UM staining was evaluated by the percentage of positive tumor cells and intensity of staining. Extent was graded as 0 (negative), 1 (0-25% of cells positive), 2 (25-50% of cells positive) and 3 (>50% of cells positive). Intensity was classified as 0 (negative), 1(mild), 2 (moderate), and 3(strong). The expression of DBC1 was correlated with clinicopathologic characteristics (age, tumor size, lymphocytic infiltration and metastasis) using the MedCalc Software.
Eighty percent (n=16) of the UM samples stained positive for DBC1. Expression of DBC1 was predominantly nuclear (90%). Regarding extent, 5 samples were classified as grade 1, 8 as grade 2 and 3 were grade 3. For intensity, 5 cases were grade 1, 8 were grade 2 and 3 were grade 3. All of the patients that had metastasis were positive for DBC1. Analysis or non-neoplastic structures showed positivity in the retina (n=14), RPE (n=4) and ciliary body (n=8). The expression of DBC1 did not correlate with any clinicopathological variables.
To the best of our knowledge, this is the first report that investigated the immunohistochemical expression of DBC1 in UM. All patients that developed metastasis were positive for DBC1, however a statistical correlation was not observed in this limited series. These results indicate that DBC1 is highly expressed UM, similar to gastric and breast carcinomas. Further studies with larger samples are needed in order to determine if there is a correlation between DBC1 and patient survival.
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