Abstract
High basal or induced expression of the tripartite motif protein, TRIM16, leads to reduce cell growth and migration of neuroblastoma and skin squamous cell carcinoma cells. However, the role of TRIM16 in melanoma is currently unknown. TRIM16 protein levels were markedly reduced in human melanoma cell lines, compared with normal human epidermal melanocytes due to both DNA methylation and reduced protein stability. TRIM16 knockdown strongly increased cell migration in normal human epidermal melanocytes, while TRIM16 overexpression reduced cell migration and proliferation of melanoma cells in an interferon beta 1 (IFNβ1)-dependent manner. Chromatin immunoprecipitation assays revealed TRIM16 directly bound the IFNβ1 gene promoter. Low level TRIM16 expression in 91 melanoma patient samples, strongly correlated with lymph node metastasis, and, predicted poor patient prognosis in a separate cohort of 170 melanoma patients with lymph node metastasis. The BRAF inhibitor, vemurafenib, increased TRIM16 protein levels in melanoma cells in vitro, and induced growth arrest in BRAF-mutant melanoma cells in a TRIM16-dependent manner. High levels of TRIM16 in melanoma tissues from patients treated with Vemurafenib correlated with clinical response. Our data, for the first time, demonstrates TRIM16 is a marker of cell migration and metastasis, and a novel treatment target in melanoma.
Highlights
Melanoma is an aggressive malignancy which is responsible for 80% of skin cancer deaths [1]
We define an important role for TRIM16 expression in the early stages of melanomagenesis as an inhibitor of cell growth and migration through its effects on the melanoma cell expression of the inflammatory cytokine, IFNβ1
TRIM16 expression was markedly repressed in metastases compared with localized melanoma, suggesting that a low TRIM16 expression level in apparently localized melanoma may predict a high subsequent risk of distant metastases, our findings have significant diagnostic and therapeutic implications
Summary
Melanoma is an aggressive malignancy which is responsible for 80% of skin cancer deaths [1]. While surgical excision can cure localized disease, metastatic melanoma treated with conventional therapies has a median survival of only 6–9 months historically [2, 3]. Metastatic melanoma is highly resistant to traditional cytotoxic chemotherapies [3, 4]. New targeted melanoma treatments, such as BRAF inhibitors, vemurafenib (PLX4032) and dabrafenib (GSK2118436) [5, 6] offer higher patient response rates due to specific BRAFV600 www.impactjournals.com/oncotarget targeting [4, 5]. Combination of dabrafenib and trametinib is the standard of care for BRAFV600 patients, with 50% of patients experiencing a progression free survival of 9–10 months [8]
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