Meng Ma1, Jie Dai1, Tianxiao Xu1, Sifan Yu1, Huan Yu1, Huan Tang1, Junya Yan1, Xiaowen Wu1, Jiayi Yu1, Zhihong Chi1, Lu Si1, Chuanliang Cui1, Xinan Sheng1, Yan Kong2, Jun Guo3. 1. Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Renal Cancer and Melanoma, Peking University Cancer Hospital and Institute, 52 Fucheng Road, Beijing, 100142, China. 2. Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Renal Cancer and Melanoma, Peking University Cancer Hospital and Institute, 52 Fucheng Road, Beijing, 100142, China. k-yan08@163.com. 3. Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Renal Cancer and Melanoma, Peking University Cancer Hospital and Institute, 52 Fucheng Road, Beijing, 100142, China. guoj307@126.com.
Abstract
PURPOSE: Mucosal melanoma is a relatively rare subtype of melanoma for which no clearly established therapeutic strategy exists. The genes of the mTOR signalling pathway have drawn great attention as key targets for cancer treatment, including melanoma. In this study, we aimed to investigate the mutation status of the upstream mTOR regulator TSC1 and evaluated its correlation with the clinicopathological features of mucosal melanoma. METHODS: We collected 91 mucosal melanoma samples for detecting TSC1 mutations. All the coding exons of TSC1 were amplified by PCR and subjected to Sanger sequencing. Expression level of TSC1 encoding protein (hamartin) was detected by immunohistochemistry. The activation of mTOR pathway was determined by evaluating the phosphorylation status of S6RP and 4E-BP1. RESULTS: The overall mutation frequency of TSC1 was found to be 17.6% (16/91 patients). TSC1 mutations were more inclined to occur in advanced mucosal melanoma (stages III and IV). In the 16 patients with TSC1 mutations, 14 different mutations were detected, affecting 11 different exons. TSC1 mutations were correlated with upregulation of S6RP phosphorylation but were unrelated to 4E-BP1 phosphorylation or hamartin expression. Mucosal melanoma patients with TSC1 mutations had a worse outcome than patients without TSC1 mutations (24.0 versus 34.0 months, P = 0.007). CONCLUSIONS: Our findings suggest that TSC1 mutations are frequent in mucosal melanoma. TSC1 mutations can activate the mTOR pathway through phospho-S6RP and might be a poor prognostic predictor of mucosal melanoma. Our data implicate the potential significance of TSC1 mutations for effective and specific drug therapy for mucosal melanoma.
PURPOSE:Mucosal melanoma is a relatively rare subtype of melanoma for which no clearly established therapeutic strategy exists. The genes of the mTOR signalling pathway have drawn great attention as key targets for cancer treatment, including melanoma. In this study, we aimed to investigate the mutation status of the upstream mTOR regulator TSC1 and evaluated its correlation with the clinicopathological features of mucosal melanoma. METHODS: We collected 91 mucosal melanoma samples for detecting TSC1 mutations. All the coding exons of TSC1 were amplified by PCR and subjected to Sanger sequencing. Expression level of TSC1 encoding protein (hamartin) was detected by immunohistochemistry. The activation of mTOR pathway was determined by evaluating the phosphorylation status of S6RP and 4E-BP1. RESULTS: The overall mutation frequency of TSC1 was found to be 17.6% (16/91 patients). TSC1 mutations were more inclined to occur in advanced mucosal melanoma (stages III and IV). In the 16 patients with TSC1 mutations, 14 different mutations were detected, affecting 11 different exons. TSC1 mutations were correlated with upregulation of S6RP phosphorylation but were unrelated to 4E-BP1 phosphorylation or hamartin expression. Mucosal melanomapatients with TSC1 mutations had a worse outcome than patients without TSC1 mutations (24.0 versus 34.0 months, P = 0.007). CONCLUSIONS: Our findings suggest that TSC1 mutations are frequent in mucosal melanoma. TSC1 mutations can activate the mTOR pathway through phospho-S6RP and might be a poor prognostic predictor of mucosal melanoma. Our data implicate the potential significance of TSC1 mutations for effective and specific drug therapy for mucosal melanoma.
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