Crystal Structures of MEK1 Binary and Ternary Complexes with Nucleotides and Inhibitors

Fischmann, Thierry O.; Smith, Catherine K.; Mayhood, Todd; Myers, Joseph E.; Reichert, Paul; Mannarino, Anthony P.; Carr, Donna; Zhu, Haiyuan; Wong, Jesse K.; Yang, Rong-Sheng; Le, Hung V.; Madison, Vincent

doi:10.1021/bi801898e

Cited by 159 publications

(153 citation statements)

References 62 publications

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“…These studies identified the MEK1 P124L mutation in a metastatic focus that progressed in the context of otherwise stable disease on AZD6244. The proline residue at codon 124 is uniquely positioned such that it may exert an indirect influence on helix C conformation while also interfacing directly with helix A, a negative regulatory motif whose crystal structure was recently solved (15). We speculate that mutation of this proline may disrupt a key regulatory interaction between helix A and the rest of the kinase, while simultaneously altering helix C indirectly through loss of a turn motif proximal to this segment.…”

Section: Discussionmentioning

confidence: 94%

“…Numerous candidate MEK1 resistance alleles identified in vitro reside outside of the drug binding pocket, localizing to regions such as the C-terminal kinase domain or the interface between helix A and the core kinase domain (15). Notably, several such secondary mutations correspond closely to missense germline variants that are observed in CFC syndrome (28).…”

Section: Discussionmentioning

confidence: 99%

“…1 B and E) suggests a resistance mechanism that involves upregulation of intrinsic MEK1 kinase activity. Toward this end, the Q56P and P124S mutations closely mimic T55P and P124L, respectively-two germline variants observed in patients with cardio-facio-cutaneous (CFC) syndrome (15,16) that confer aberrant MEK activation. The D67N mutation, which was identified in the CI-1040 mutagenesis screen (Fig.…”

Section: Comprehensive Identification Of Mek1 Resistance Mutations Inmentioning

confidence: 99%

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MEK1 mutations confer resistance to MEK and B-RAF inhibition

Emery

Vijayendran

Zipser

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

577

509

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Genetic alterations that activate the mitogen-activated protein kinase (MAP kinase) pathway occur commonly in cancer. For example, the majority of melanomas harbor mutations in the BRAF oncogene, which are predicted to confer enhanced sensitivity to pharmacologic MAP kinase inhibition (e.g., RAF or MEK inhibitors). We investigated the clinical relevance of MEK dependency in melanoma by massively parallel sequencing of resistant clones generated from a MEK1 random mutagenesis screen in vitro, as well as tumors obtained from relapsed patients following treatment with AZD6244, an allosteric MEK inhibitor. Most mutations conferring resistance to MEK inhibition in vitro populated the allosteric drug binding pocket or ␣-helix C and showed robust (Ϸ100-fold) resistance to allosteric MEK inhibition. Other mutations affected MEK1 codons located within or abutting the Nterminal negative regulatory helix (helix A), which also undergo gain-of-function germline mutations in cardio-facio-cutaneous (CFC) syndrome. One such mutation, MEK1(P124L), was identified in a resistant metastatic focus that emerged in a melanoma patient treated with AZD6244. Both MEK1(P124L) and MEK1(Q56P), which disrupts helix A, conferred cross-resistance to PLX4720, a selective B-RAF inhibitor. However, exposing BRAF-mutant melanoma cells to AZD6244 and PLX4720 in combination prevented emergence of resistant clones. These results affirm the importance of MEK dependency in BRAF-mutant melanoma and suggest novel mechanisms of resistance to MEK and B-RAF inhibitors that may have important clinical implications.BRAF ͉ drug resistance ͉ MAP kinase ͉ melanoma A pproximately one-third of all cancers harbor genetic alterations that aberrantly upregulate mitogen-activated protein kinase (MAPK)-dependent signal transduction (1). In the MAPK pathway, RAS oncoproteins activate RAF, MEK, and ERK kinases to direct key cell proliferative and survival signals. When rendered constitutively active by genetic mutation, the MAP kinase pathway is believed to confer ''oncogene dependency'' (2), an excessive reliance on its dysregulated activity for tumor viability. Therefore, protein kinases within this signaling cascade offer promising targets for novel anticancer therapeutics.In melanoma, uncontrolled MAP kinase pathway activity is nearly ubiquitous and occurs most commonly through gain-offunction mutations involving codon 600 of the B-RAF kinase (3) (BRAF V600E ; 50-70% of cases). Considerable preclinical evidence has associated the BRAF V600E mutation with heightened sensitivity to pharmacologic inhibition of RAF or MEK kinases (4, 5). Although early clinical trials of RAF and MEK inhibitors failed to show a substantial benefit (6, 7), recent phase I studies of selective RAF inhibitors have shown promising results in patients with BRAF-mutant tumors (8, 9). Thus, optimizing therapeutic efficacy while avoiding or bypassing the emergence of resistance to MAP kinase pathway inhibition will likely gain increasing importance in melanoma and other MAP kinasedriven cancers.He...

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Section: Discussionmentioning

confidence: 94%

Section: Discussionmentioning

confidence: 99%

Section: Comprehensive Identification Of Mek1 Resistance Mutations Inmentioning

confidence: 99%

See 1 more Smart Citation

MEK1 mutations confer resistance to MEK and B-RAF inhibition

Emery

Vijayendran

Zipser

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

577

509

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“…Why ERK inhibitors remain effective in the context of upstream oncogene amplification, although MEK inhibitors become less potent, is not entirely clear. We hypothesize that this phenomenon may be related to the fact that activation of MEK by these upstream oncogenes may change the steady-state conformation of MEK in a way that limits the accessibility of the allosteric binding pocket to MEK inhibitors (40). The ERK inhibitor described here is ATP competitive and may be less sensitive to altered conformation dynamics of activated ERK in the context of upstream oncogene amplification.…”

Section: Discussionmentioning

confidence: 93%

ERK Inhibition Overcomes Acquired Resistance to MEK Inhibitors

Hatzivassiliou¹,

Liu²,

O’Brien³

et al. 2012

Molecular Cancer Therapeutics

191

155

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The RAS/RAF/MEK pathway is activated in more than 30% of human cancers, most commonly via mutation in the K-ras oncogene and also via mutations in BRAF. Several allosteric mitogen-activated protein/ extracellular signal-regulated kinase (MEK) inhibitors, aimed at treating tumors with RAS/RAF pathway alterations, are in clinical development. However, acquired resistance to these inhibitors has been documented both in preclinical and clinical samples. To identify strategies to overcome this resistance, we have derived three independent MEK inhibitor-resistant cell lines. Resistance to allosteric MEK inhibitors in these cell lines was consistently linked to acquired mutations in the allosteric binding pocket of MEK. In one cell line, concurrent amplification of mutant K-ras was observed in conjunction with MEK allosteric pocket mutations. Clonal analysis showed that both resistance mechanisms occur in the same cell and contribute to enhanced resistance. Importantly, in all cases the MEK-resistant cell lines retained their addiction to the mitogenactivated protein kinase (MAPK) pathway, as evidenced by their sensitivity to a selective inhibitor of the ERK1/2 kinases. These data suggest that tumors with acquired MEK inhibitor resistance remain dependent on the MAPK pathway and are therefore sensitive to inhibitors that act downstream of the mutated MEK target. Importantly, we show that dual inhibition of MEK and ERK by small molecule inhibitors was synergistic and acted to both inhibit the emergence of resistance, as well as to overcome acquired resistance to MEK inhibitors. Therefore, our data provide a rationale for cotargeting multiple nodes within the MAPK signaling cascade in K-ras mutant tumors to maximize therapeutic benefit for patients.

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“…4C). PD325901 is an important control in this experiment because it binds to the same site on MEK 46 with a~100-fold lower IC 50 . 47 Taken together, these data indicate that U0126 inhibits mitochondrial function and stimulates aerobic glycolysis by a MEK-independent mechanism.…”

Section: U0126 Inhibits Resveratrol Induced Apoptosismentioning

confidence: 99%

A metabolic perturbation by U0126 identifies a role for glutamine in resveratrol-induced cell death

Freeman

Kim

Lisanti

et al. 2011

Cancer Biology & Therapy

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Recent evidence has identified substantial overlap between metabolic and oncogenic biochemical pathways, suggesting novel approaches to cancer intervention. For example, cholesterol lowering statins and the antidiabetes medication metformin both act as chemopreventive agents in prostate and other cancers. The natural compound resveratrol has similar properties: increasing insulin sensitivity, suppressing adipogenesis, and inducing apoptotic death of cancer cells in vitro. However, in vivo tumor xenografts acquire resistance to resveratrol by an unknown mechanism, while mouse models of metabolic disorders respond more consistently to the compound. Here we demonstrate that castrationresistant human prostate cancer C4-2 cells are more sensitive to resveratrol-induced apoptosis than isogenic androgendependent LNCaP cells. The MEK inhibitor U0126 antagonized resveratrol-induced apoptosis in C4-2 cells, but this effect was not seen with other MEK inhibitors. U0126 was found to inhibit mitochondrial function and shift cells to aerobic glycolysis independently of MEK. Mitochondrial activity of U0126 arose through decomposition, producing both mitochondrial fluorescence and cyanide, a known inhibitor of complex IV. Applying U0126 mitochondrial inhibition to C4-2 cell apoptosis, we tested the possibility that glutamine supplementation of citric acid cycle intermediate aketoglutarate may be involved. Suppression of the conversion of glutamate to a-ketoglutarate antagonized resveratrolinduced death in C4-2 cells. A similar effect was also seen by reducing extracellular glutamine concentration in the culture medium, suggesting that resveratrol-induced death is dependent on glutamine metabolism, a process frequently dysregulated in cancer. Further work on resveratrol and metabolism in cancer is warranted to ascertain if the glutamine dependence has clinical implications.

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Crystal Structures of MEK1 Binary and Ternary Complexes with Nucleotides and Inhibitors

Cited by 159 publications

References 62 publications

MEK1 mutations confer resistance to MEK and B-RAF inhibition

MEK1 mutations confer resistance to MEK and B-RAF inhibition

ERK Inhibition Overcomes Acquired Resistance to MEK Inhibitors

A metabolic perturbation by U0126 identifies a role for glutamine in resveratrol-induced cell death

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