Ras Cancer Therapeutics: 5 Promising Targets · The Ras GTPase plays an important role in multiple...
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The Ras GTPase plays an important role in mulple signal transducon pathways involved in normal cell growth and differenaon as well as several forms of cancer 1,2 . The three isoforms of Ras, H-Ras, N-Ras, and K-Ras, were idenfied over 30 years ago for their oncogenic acvaon in human tumors 1,2 . Aberrant Ras signaling has been idenfied in more than 30% of all human cancers with the most common being lung, colon, and pancreac cancers 1,3 . In parcular, K-Ras has been idenfied as the most important Ras protein in cancer research, correlated with over 21% of human cancers 4 . Despite extensive research on these proteins, no effecve Ras inhibitor has been idenfied, earning K-Ras the reputaon of an undruggable protein. Many efforts in the past have been unsuccessful, but recent advances in the field have lead to new hope in developing a direct therapeuc inhibitor to Ras protein as well as indirect inhibitors targeng GEFs, GAPs, downstream proteins, and post-translaonal modificaons (Fig. 1). Here we briefly highlight several of the targets that show promise for Ras cancer therapeucs. 1. Targeng Mutant K-Ras Directly Mutant vs wildtype K-Ras selecvity has proved challenging since mutaons are distal from the effector binding sites 1 . The recent discovery of an allosteric switch II pocket (S-IIP) in a K-Ras mutant (G12C) provided a new target for K-Ras inhibion 5 . Soon aſter, the development of small molecules that bind to this mutant cysteine were found to disrupt SOS-mediated nucleode exchange, thus inhibing mutant K-Ras and giving new hope to direct K-Ras therapies via small molecules 5 . To read more regarding SOS and Ras inhibion, please refer to the July 2014 newsleer "New small molecule inhibitors to control Ras signaling via Sos/K-Ras binding" found here: www.cytoskeleton.com/blog/kras-sos- inhibitor-news. 2. Targeng GEFs and GAPs SOS, RasGRF, and RasGRP are the three classes of GEFs that mammals express that are typically regarded as the acvators of Ras 6 . Despite GEF-mediated Ras acvaon, mutaons in GEFs are surprisingly uncommon in cancer. On the other hand, GAPs, including classes NF1, p120GAP/RASA1, SynGAP/RASA5, GAP1 family, DAB2IP, and GAPVD1, have been associated with several Ras-linked cancers 6,7,8 (Fig. 1). For more about the role of GEFs/ GAPs in tumorigenesis, please refer to the recent review by Dr. Anne Hennig et al 6 . 3. Targeng Downstream Proteins Mitogen-acvated protein kinase (MAPK) kinase (MEK), a protein in the MAPK pathway downstream of Ras acvaon, is targeted by the FDA approved drug tramenib (Mekinist TM ), which has been shown to be clinically acve in some paents 9 . However, maintaining the necessary amount of acve drug in the bloodstream without serious side effects has been challenging 9 . Another pathway downstream of Ras acvaon is the Merlin/ Hippo protein kinase pathway which regulates the acvity of the pro-growth transcriponal co-acvator YAP. Acvaon of this pathway restricts cell proliferaon and promotes apoptosis and this pathway is crical for Ras-dependent cancers 10-12 . Merlin regulates the Hippo pathway as its loss results in inacvaon of the Hippo pathway 10 . The site of Merlin's suppression of tumorigenesis remains unclear with papers supporng both a membrane and nuclear localizaon. However, a recent paper suggests that rather than suppressing tumorigenesis via the Hippo pathway at the plasma membrane, Merlin acts by inhibing the E3 ubiquin ligase complex CRL4 DCAF1 interacon with Hippo pathway serine/threonine kinases LATS1/2 in the nucleus 13 . Nuclear-localized Merlin interacts with CRL4 DCAF1 , prevenng this complex from ubiquinang LATS kinases which can then phosphorylate YAP, inacvang it and triggering YAP's Ras Cancer Therapeutics: 5 Promising Targets News Publications Research Tools MAY 2015 www.cytoskeleton.com CYTOSKELETON NEWS NEWS FROM CYTOSKELETON INC. Meetings 3rd International Meeting of the German Society for Cell Biology on Actin Dynamics May 2-5, 2015 Regensburg, Germany Fibronectin, Integrins, & Related Molecules (GRS) May 9-10, 2015 Lucca (Barga), Italy Pint of Science May 18-20, 2015 Philadelphia, PA, USA Front Range Cytoskeleton Meeting May 29th, 2015 Boulder, CO Cytoskeleton Products Actin Proteins Activation Assays Antibodies ECM Proteins ELISA Kits G-LISA® Kits Pull-down Assays Motor Proteins Small G-Proteins Tubulin & FtsZ Proteins Contact Us P: 1 (303) 322.2254 F: 1 (303) 322.2257 E: [email protected] W: cytoskeleton.com this issue Ras Cancer Therapeutics: 5 Promising Targets Related Publications Research Tools P i Ras GDP Ras GTP Active Inactive GDP GTP GAP GEF Ras GEFs RasGRP RasGRF1 SOS Ras GAPs NF1-SPREAD p120 GAP SynGAP GAP1 Family DAB2IP GAPVD1 Figure 1: Ras GTPase cycle depicng select GAPs and GEFs involved in Ras Acvaon.
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Transcript of Ras Cancer Therapeutics: 5 Promising Targets · The Ras GTPase plays an important role in multiple...
The Ras GTPase plays an important role in multiple signal transduction pathways involved in normal cell growth and differentiation as well as several forms of cancer1,2. The three isoforms of Ras, H-Ras, N-Ras, and K-Ras, were identified over 30 years ago for their oncogenic activation in human tumors1,2. Aberrant Ras signaling has been identified in more than 30% of all human cancers with the most common being lung, colon, and pancreatic cancers1,3. In particular, K-Ras has been identified as the most important Ras protein in cancer research, correlated with over 21% of human cancers4. Despite extensive research on these proteins, no effective Ras inhibitor has been identified, earning K-Ras the reputation of an undruggable protein. Many efforts in the past have been unsuccessful, but recent advances in the field have lead to new hope in developing a direct therapeutic inhibitor to Ras protein as well as indirect inhibitors targeting GEFs, GAPs, downstream proteins, and post-translational modifications (Fig. 1). Here we briefly highlight several of the targets that show promise for Ras cancer therapeutics.
1. Targeting Mutant K-Ras DirectlyMutant vs wildtype K-Ras selectivity has proved challenging since mutations are distal from the effector binding sites1. The recent discovery of an allosteric switch II pocket (S-IIP) in a K-Ras mutant (G12C) provided a new target for K-Ras inhibition5. Soon after, the development of small molecules that bind to this mutant cysteine were found to disrupt SOS-mediated nucleotide exchange, thus inhibiting mutant K-Ras and giving new hope to direct K-Ras therapies via small molecules5. To read more regarding SOS and Ras inhibition, please refer to the July 2014 newsletter "New small molecule inhibitors to control Ras signaling via Sos/K-Ras binding" found here: www.cytoskeleton.com/blog/kras-sos-inhibitor-news.
2. Targeting GEFs and GAPsSOS, RasGRF, and RasGRP are the three classes of GEFs that mammals express that are typically regarded as the activators of Ras6. Despite GEF-mediated Ras activation, mutations in GEFs are surprisingly uncommon in cancer. On the other hand, GAPs, including classes NF1, p120GAP/RASA1, SynGAP/RASA5, GAP1 family, DAB2IP, and GAPVD1, have been associated with several
Ras-linked cancers6,7,8 (Fig. 1). For more about the role of GEFs/GAPs in tumorigenesis, please refer to the recent review by Dr. Anne Hennig et al6.
3. Targeting Downstream ProteinsMitogen-activated protein kinase (MAPK) kinase (MEK), a protein in the MAPK pathway downstream of Ras activation, is targeted by the FDA approved drug trametinib (MekinistTM), which has been shown to be clinically active in some patients9. However, maintaining the necessary amount of active drug in the bloodstream without serious side effects has been challenging9.
Another pathway downstream of Ras activation is the Merlin/Hippo protein kinase pathway which regulates the activity of the pro-growth transcriptional co-activator YAP. Activation of this pathway restricts cell proliferation and promotes apoptosis and this pathway is critical for Ras-dependent cancers10-12. Merlin regulates the Hippo pathway as its loss results in inactivation of the Hippo pathway10. The site of Merlin's suppression of tumorigenesis remains unclear with papers supporting both a membrane and nuclear localization. However, a recent paper suggests that rather than suppressing tumorigenesis via the Hippo pathway at the plasma membrane, Merlin acts by inhibiting the E3 ubiquitin ligase complex CRL4DCAF1 interaction with Hippo pathway serine/threonine kinases LATS1/2 in the nucleus13. Nuclear-localized Merlin interacts with CRL4DCAF1, preventing this complex from ubiquitinating LATS kinases which can then phosphorylate YAP, inactivating it and triggering YAP's
Ras Cancer Therapeutics: 5 Promising Targets
New
s Publications
Research Tools
MAY2015
www.cytoskeleton.com
CYTOSKELETON NEWSN E W S F R O M C Y T O S K E L E T O N I N C .
Meetings3rd International Meeting of the German Society for Cell Biology on Actin DynamicsMay 2-5, 2015Regensburg, Germany
Fibronectin, Integrins, & Related Molecules (GRS)May 9-10, 2015Lucca (Barga), Italy
Pint of ScienceMay 18-20, 2015Philadelphia, PA, USA
Front Range Cytoskeleton MeetingMay 29th, 2015Boulder, CO
Cytoskeleton ProductsActin ProteinsActivation AssaysAntibodiesECM ProteinsELISA KitsG-LISA® KitsPull-down AssaysMotor ProteinsSmall G-ProteinsTubulin & FtsZ Proteins
Contact UsP: 1 (303) 322.2254
F: 1 (303) 322.2257
W: cytoskeleton.com
this issueRas Cancer Therapeutics: 5 Promising Targets
Related PublicationsResearch Tools
Pi
RasGDP
RasGTP
Active
Inactive
GDP
GTP
GAP GEF
Ras GEFsRasGRP
RasGRF1SOS
Ras GAPsNF1-SPREAD
p120 GAPSynGAP
GAP1 FamilyDAB2IP
GAPVD1
Figure 1: Ras GTPase cycle depicting select GAPs and GEFs involved in Ras Activation.
ReferencesContinued from Page 1
www.cytoskeleton.com
SMALL G-PROTEIN PRODUCTS
accumulation in the cytoplasm10. However, if YAP is active (unphosphorylated), it partners with TEAD transcription factors to increase expression of mutant and wild-type Ras proteins10,13. A more detailed review of YAP1 and the Hippo Pathway can be found in our April 2015 newsletter found here: www.cytoskeleton.com/yap1-ras-oncogenic-review-detail 4. Targeting Post-translational ModificationsRas proteins undergo several post-translational modifications, including proteolytic cleavage by RCE1, farnesylation, carboxymethylation by ICMT, and palmitoylation14. Recently, additional post-translational modifications such as mono-ubiquitination and acetylation have been shown to play a key role in regulating Ras activation. Mono-ubiquitination occurs at K-Ras Lys147 which enhances GTP loading15. Acetylation at K-Ras Lys104 decreases GEF-induced nucleotide exchange, suggesting SIRT2 and HDAC6 deacetylases as potential targets to inhibit16.
5. Nanomedicine and siRNA KnockdownA recent study suggests that targeting mutant K-Ras via combined delivery of siRNA and arsenic-encapsulated vesicles to induce apoptosis and down-regulation of the mutant K-Ras's ability to proliferate and migrate in pancreatic cancer treatment is worthwhile17. Moreover, siRNA treatments targeting the inhibition of K-Ras in combination with RAF and PI3K can impair mutant colorectal cancer in xenograft models18.
SummaryAs researchers discover additional Ras regulatory mechanisms, sensitive and quantitative methods to measure activated levels of this GTPase take on increasing importance. To aid researchers with identifying and characterizing cancer therapeutics, Cytoskeleton, Inc. offers many small G-protein tools such as pull-down and G-LISA activation assays which are widely used to measure the activated levels of small G-proteins. Small G-protein antibodies, activators, and inhibitors are also available to help elucidate Ras activation pathways.
Small G-Protein Activation Assay KitsProduct Cat. # Amount
Ras Activation Assay Biochem Kit (bead pull down format) BK008 50 assays
RhoA Activation Assay Biochem Kit (bead pull down format) BK036 80 assays
Rac1 Activation Assay Biochem Kit (bead pull down format) BK035 50 assays
Cdc42 Activation Assay Biochem Kit (bead pull down format) BK034 50 assays
G-LISA Ras Activation Assay Biochem Kit (colorimetric format) BK131 96 assays
G-LISA RhoA Activation Assay Biochem Kit (colorimetric format) BK124 96 assays
G-LISA Rac 1 Activation Assay Biochem Kit (colorimetric format) BK128 96 assays
G-LISA Cdc42 Activation Assay Biochem Kit (colorimetric format) BK127 96 assays More resources and products available online!
1. Wang W. et al. 2012. Ras inhibition via direct Ras binding—is there a path forward. Bioorg. Med. Chem. Lett. 22, 5766-5776.
2. Castellano E. and Santos E. 2011. Functional specificity of Ras isoform: so similar but so different. Genes Cancer. 2, 216-231.
3. Burns M.C. et al. 2014. Approach for targeting Ras with small molecules that activate SOS-mediated nucleotide exchange. Proc. Natl. Acad. Sci. U.S.A. 111, 3401-3406.
4. Baines A. et al. 2011. Inhibition of Ras for cancer treatment: the search continues. Future Med. Chem. 3, 1787-1808.
5. Ostrem J. et al. 2013. K-Ras (G12C) inhibitors allosterically control GTP affinity and effector interactions. Nature. 503, 548-551.
6. Hennig A. et al. 2015. Ras activation revisited: role of GEF and GAP systems. Biol. Chem. doi: 10.1515/hsz-2014-0257.
7. Nissan M.H. et al. 2014. Loss of NF1 in Cutaneous Melenama Is Associated with RAS Activation and MEK Dependence. Cancer Res. 74, 2340
8. Stephen A.G. et al. 2014. Dragging Ras Back in the Ring. Cancer Cell. 25, 272-281.
9. Online: http://www.cancer.gov/cancertopics/research-updates/2013/MEK.
10. Online: http://www.cancer.gov/researchandfunding/priorities/ras/advance-research/events/ras-fagin-video.
11. Hong X. et al. 2014. Opposing activities of the Ras and Hippo pathways converge on regulation of YAP protein turnover. EMBO J. 33, 2447-2457.
12. Kapoor A. et al. 2014. Yap1 activation enables bypass of oncogenic Kras addiction in pancreatic cancer. Cell. 158, 185-197.
13. Li W. et al. 2014. Merlin/NF2 loss-driven tumorigenesis linked to CRL4(DCAF1)-me-diated inhibition of the hippo pathway kinases Lats1 and 2 in the nucleus. Cancer Cell. 26, 48-60.
14. Gysin S. et al. 2011. Therapeutic strategies for targeting ras proteins. Genes Cancer. 2, 359-372.
15. Sasaki A.T. et al. 2011. Ubiquitination of K-Ras enhances activation and facilitates binding to select downstream effectors. Sci. Signal. 4, ra13.
16. Yang M.H. 2013. HDAC6 and SIRT2 Regulate the acetylation state and oncogenic activity of mutant K-RAS. Mol. Cancer Res. 11, 1072-1077.
17. Zeng L. et al. 2014. Combination of siRNA-directed Kras oncogene silencing and arsenic-induced apoptosis using a nanomedicine strategy for the effective treat-ment of pancreatic cancer. Nanomedicine. 10, 463-472.
18. Yuan T.L. et a. 2014. Development of siRNA Payloads to Target KRAS-Mutant Can-cer. Cancer Discovery. 4, 1182.
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Acetyl Lysine Antibody Mouse Monoclonal Validated in WB, IP, IF, ChIP
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Phosphotyrosine Antibody Mouse Monoclonal Validated in WB, IP, IF
APY03-SAPY03
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SUMO-2/3 Mouse Monoclonal Antibody Validated in WB, IP, IF
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Ubiquitin Antibody Mouse Monoclonal Validated in WB, IF
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