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.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
3R01CA125103-06S1
Application #
8727713
Study Section
Tumor Cell Biology Study Section (TCB)
Program Officer
Snyderwine, Elizabeth G
Project Start
2008-08-01
Project End
2014-05-31
Budget Start
2012-06-01
Budget End
2014-05-31
Support Year
6
Fiscal Year
2013
Total Cost
$58,707
Indirect Cost
$20,709
Name
Thomas Jefferson University
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
053284659
City
Philadelphia
State
PA
Country
United States
Zip Code
19107
Hartsough, Edward; Shao, Yongping; Aplin, Andrew E (2014) Resistance to RAF inhibitors revisited. J Invest Dermatol 134:319-25
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
Basile, Kevin J; Abel, Ethan V; Dadpey, Neda et al. (2013) In vivo MAPK reporting reveals the heterogeneity in tumoral selection of resistance to RAF inhibitors. Cancer Res 73:7101-10
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
Shao, Y; Aplin, A E (2012) ERK2 phosphorylation of serine 77 regulates Bmf pro-apoptotic activity. Cell Death Dis 3:e253
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
Katiyar, Pragati; Aplin, Andrew E (2011) FOXD3 regulates migration properties and Rnd3 expression in melanoma cells. Mol Cancer Res 9:545-52
Kaplan, F M; Shao, Y; Mayberry, M M et al. (2011) Hyperactivation of MEK-ERK1/2 signaling and resistance to apoptosis induced by the oncogenic B-RAF inhibitor, PLX4720, in mutant N-RAS melanoma cells. Oncogene 30:366-71
Klein, R Matthew; Higgins, Paul J (2011) A switch in RND3-RHOA signaling is critical for melanoma cell invasion following mutant-BRAF inhibition. Mol Cancer 10:114
Aplin, Andrew E; Kaplan, Fred M; Shao, Yongping (2011) Mechanisms of resistance to RAF inhibitors in melanoma. J Invest Dermatol 131:1817-20

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