Melanoma is the deadliest form of skin cancer and its incidence is rising rapidly. Our long-term objective is to determine the mechanisms leading to aberrant growth of human melanomas. Mutations in the serine/threonine kinase, B-RAF, are found in approximately 50-70% of melanomas and mutant B-RAF is required for proliferation and tumorigenicity of melanomas. Mutant B-RAF signaling in human melanoma cells elevates activation of the MEK-ERK1/2 pathway and regulates two key G1 cell cycle proteins: cyclin D1 and p27Kip1. Our preliminary data indicate that mutant B-RAF signaling and cyclin D1 regulate p27Kip1 via expression of Skp2 F- box protein, a component of a Skp1/Cullin/F-box (SCF) ubiquitin ligase complex that mediates p27Kip1 degradation. Specifically, mutant B-RAF and cyclin D1 regulate the expression of Cks1, a co-factor for Skp2 that regulates Skp2 protein stability. B-RAF mutations are also found in common acquired and dysplastic nevi melanocytes and sustained B-RAF signaling mediates a cell cycle arrest concomitant with down-regulation of ERK1/2 activation observed in nevi. MKP3, a phosphatase that inactivates ERK1/2, is proteasomally down-regulated in melanoma cells. In this proposal, we seek to further elucidate cell cycle control in melanoma and melanocytes by studying mutant B-RAF-regulated signaling events.
Aim 1 will analyze Cks1 levels in human tissue samples, B-RAF depleted melanoma cells in a 3-D skin reconstruct model, and following modulation of E2F transcription factors.
Aim 2 will determine the mechanism underlying Skp2 effects on melanoma cell cycle progression in 3-D and 2-D systems.
In Aim 3, we will determine whether MKP3 inhibits mutant B-RAF signaling in melanocytes and seek to identify the E3 ubiquitin ligase that regulates MKP3 protein turnover. The lack of effective drugs and treatments for melanoma underscores the need to identify new targets in melanoma. At the completion of our experiments, we aim to have identified new targets for therapeutic intervention to prevent aberrant melanoma cell proliferation.

Public Health Relevance

Malignant melanoma is the deadliest form of skin cancer and its incidence rate is rapidly rising in the United States. Our studies analyze the effects of the most common gene mutation found in melanoma on cancerous growth. We expect to uncover new targets for therapeutic intervention to prevent aberrant melanoma cell growth.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
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Tumor Cell Biology Study Section (TCB)
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Snyderwine, Elizabeth G
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Thomas Jefferson University
Schools of Medicine
United States
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Hartsough, Edward J; Aplin, Andrew E (2016) Of Mice and Melanoma: PDX System for Modeling Personalized Medicine. Clin Cancer Res 22:1550-2
Hartsough, Edward; Shao, Yongping; Aplin, Andrew E (2014) Resistance to RAF inhibitors revisited. J Invest Dermatol 134:319-325
Abel, Ethan V; Basile, Kevin J; Kugel 3rd, Curtis H et al. (2013) Melanoma adapts to RAF/MEK inhibitors through FOXD3-mediated upregulation of ERBB3. J Clin Invest 123:2155-68
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Zhou, Hong; Ekmekcioglu, Suhendan; Marks, John W et al. (2013) The TWEAK receptor Fn14 is a therapeutic target in melanoma: immunotoxins targeting Fn14 receptor for malignant melanoma treatment. J Invest Dermatol 133:1052-62
Basile, K J; Abel, E V; Aplin, A E (2012) Adaptive upregulation of FOXD3 and resistance to PLX4032/4720-induced cell death in mutant B-RAF melanoma cells. Oncogene 31:2471-9
Kaplan, Fred M; Kugel 3rd, Curtis H; Dadpey, Neda et al. (2012) SHOC2 and CRAF mediate ERK1/2 reactivation in mutant NRAS-mediated resistance to RAF inhibitor. J Biol Chem 287:41797-807
Shao, Y; Aplin, A E (2012) ERK2 phosphorylation of serine 77 regulates Bmf pro-apoptotic activity. Cell Death Dis 3:e253
Weiss, Michele B; Abel, Ethan V; Mayberry, Melanie M et al. (2012) TWIST1 is an ERK1/2 effector that promotes invasion and regulates MMP-1 expression in human melanoma cells. Cancer Res 72:6382-92
Shao, Y; Aplin, A E (2012) BH3-only protein silencing contributes to acquired resistance to PLX4720 in human melanoma. Cell Death Differ 19:2029-39

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