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The RAS/mitogen activated protein (MAP) kinase pathway in melanoma biology and therapeutics.

ABSTRACT: An effective treatment for metastatic melanoma remains one of the most elusive goals in all of oncology. Several generations of therapeutic trials have yet to yield any agents that can significantly prolong survival for widespread disease. Despite this disheartening history, our understanding of the biology and molecular genetics of melanoma hold the promise of a new era of molecular targets. One pathway that appears to be universally activated in and critically needed for melanoma growth is the Ras/mitogen activated protein (MAP) kinase signaling cascade. Since the enzymatic functions of the signaling partners are well characterized, this pathway offers many potential "druggable" candidates including Braf, Mek and Ras itself. In this review, we describe this pathway in the context of melanoma tumorigenesis and discuss some of the current relevant pharmacologic treatments and clinical trials.

SUBMITTER: Jarell AD

PROVIDER: S-EPMC2721285 | biostudies-literature | 2007 Dec

REPOSITORIES: biostudies-literature

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The RAS/mitogen activated protein (MAP) kinase pathway in melanoma biology and therapeutics.

Jarell Abel D AD Lawrence Donald D Tsao Hensin H

Biologics : targets & therapy 20071201 4

An effective treatment for metastatic melanoma remains one of the most elusive goals in all of oncology. Several generations of therapeutic trials have yet to yield any agents that can significantly prolong survival for widespread disease. Despite this disheartening history, our understanding of the biology and molecular genetics of melanoma hold the promise of a new era of molecular targets. One pathway that appears to be universally activated in and critically needed for melanoma growth is the ...[more]

PMID: 19707310

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Project description:The BRAF-MKK1/2-ERK1/2 pathway is constitutively activated in response to oncogenic mutations of BRAF in many cancer types, including melanoma. Although small molecules that inhibit oncogenic BRAF and MAP kinase kinase (MKK)1/2 have been successful in clinical settings, resistance invariably develops. High affinity inhibitors of ERK1/2 have been shown in preclinical studies to bypass the resistance of melanoma and colon cancer cells to BRAF and MKK1/2 inhibitors, and are thus promising additions to current treatment protocols. But still unknown is how molecular responses to ERK1/2 inhibitors compare with inhibitors currently in clinical use. Here, we employ quantitative phosphoproteomics to evaluate changes in phosphorylation in response to the ERK inhibitors, SCH772984 and GDC0994, and compare these to the clinically used MKK1/2 inhibitor, trametinib. Combined with previous studies measuring phosphoproteomic responses to the MKK1/2 inhibitor, selumetinib, and the BRAF inhibitor, vemurafenib, the outcomes reveal key insights into pathway organization, phosphorylation specificity and off-target effects of these inhibitors. The results demonstrate linearity in signaling from BRAF to MKK1/2 and from MKK1/2 to ERK1/2. They identify likely targets of direct phosphorylation by ERK1/2, as well as inhibitor off-targets, including an off-target regulation of the p38α mitogen activated protein kinase (MAPK) pathway by the MKK1/2 inhibitor, trametinib, at concentrations used in the literature but higher than in vivo drug concentrations. In addition, several known phosphorylation targets of ERK1/2 are insensitive to MKK or ERK inhibitors, revealing variability in canonical pathway responses between different cell systems. By comparing multiple inhibitors targeted to multiple tiers of protein kinases in the MAPK pathway, we gain insight into regulation and new targets of the oncogenic BRAF driver pathway in cancer cells, and a useful approach for evaluating the specificity of drugs and drug candidates.

Project description:Kinase inhibition in the mitogen activated protein kinase (MAPK) pathway is a standard therapy for cancer patients with activating BRAF mutations. However, the anti-tumorigenic effect and clinical benefit are only transient, and tumors are prone to treatment resistance and relapse. To elucidate mechanistic insights into drug resistance, we have established an in vitro cellular model of MAPK inhibitor resistance in malignant melanoma.The cellular model evolved in response to clinical dosage of the BRAF inhibitor, vemurafenib, PLX4032. We conducted transcriptomic expression profiling using RNA-Seq and RT-qPCR arrays. Pathways of melanogenesis, MAPK signaling, cell cycle, and metabolism were significantly enriched among the set of differentially expressed genes of vemurafenib-resistant cells vs control. The underlying mechanism of treatment resistance and pathway rewiring was uncovered to be based on non-genomic adaptation and validated in two distinct melanoma models, SK-MEL-28 and A375. Both cell lines have activating BRAF mutations and display metastatic potential.Downregulation of dual specific phosphatases, tumor suppressors, and negative MAPK regulators reengages mitogenic signaling. Upregulation of growth factors, cytokines, and cognate receptors triggers signaling pathways circumventing BRAF blockage. Further, changes in amino acid and one-carbon metabolism support cellular proliferation despite MAPK inhibitor treatment. In addition, treatment-resistant cells upregulate pigmentation and melanogenesis, pathways which partially overlap with MAPK signaling. Upstream regulator analysis discovered significant perturbation in oncogenic forkhead box and hypoxia inducible factor family transcription factors.The established cellular models offer mechanistic insight into cellular changes and therapeutic targets under inhibitor resistance in malignant melanoma. At a systems biology level, the MAPK pathway undergoes major rewiring while acquiring inhibitor resistance. The outcome of this transcriptional plasticity is selection for a set of transcriptional master regulators, which circumvent upstream targeted kinases and provide alternative routes of mitogenic activation. A fine-woven network of redundant signals maintains similar effector genes allowing for tumor cell survival and malignant progression in therapy-resistant cancer.

Dataset Information

The RAS/mitogen activated protein (MAP) kinase pathway in melanoma biology and therapeutics.

Publications

The RAS/mitogen activated protein (MAP) kinase pathway in melanoma biology and therapeutics.

Similar Datasets

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