Summary of the probe development efforts to identify inhibitors of the interaction of the Ras and Rab interactor 1 protein (Rin1) and the c-abl oncogene 1, non-receptor tyrosine kinase (Abl)
Name: Summary of the probe development efforts to identify inhibitors of the interaction of the Ras and Rab interactor 1 protein (Rin1) and the c-abl oncogene 1, non-receptor tyrosine kinase (Abl). ..more
Source (MLPCN Center Name): The Scripps Research Institute Molecular Screening Center (SRIMSC)
Affiliation: The Scripps Research Institute, TSRI
Assay Provider: John Colicelli, UCLA
Network: Molecular Library Probe Production Centers Network (MLPCN)
Grant Proposal Number: 1 R01 CA136699-01A1
Grant Proposal PI: John Colicelli, UCLA
External Assay ID: RIN1-ABL_INH_SUMMARY
Name: Summary of the probe development efforts to identify inhibitors of the interaction of the Ras and Rab interactor 1 protein (Rin1) and the c-abl oncogene 1, non-receptor tyrosine kinase (Abl).
Chromosome translocations that join the BCR and ABL1 (a.k.a. c-Abl) genes give rise to BCR-ABL1 fusion proteins causative in chronic myeloid leukemia (CML), some cases of acute lymphocytic leukemia (ALL) and occasionally other myeloproliferative disorders (1). In addition, ETV6 forms fusion oncogenes with ABL1 (2) and the closely related ABL2 (a.k.a. Arg) (3) in some leukemias. ABL proteins are non-receptor tyrosine kinases normally under tight regulation, but BCR-ABL1 fusions are constitutively active. The ABL kinase inhibitor imatinib mesylate (a.k.a. STI571 or Gleevec) is an effective treatment for CML (4), demonstrating that direct oncoprotein targeting can be used to manage cancer and perhaps eventually be part of a curative therapy. Some leukemias with activated ABL oncoproteins do not respond to imatinib, however, and for CML patients who do respond there is a significant risk of developing resistance due to strong selective pressure for BCR-ABL1 kinase domain mutations that block inhibitor action (5). Resistance and relapse are even more common in BCR-ABL1 positive ALL. Some attempts have been made to circumvent resistance by reducing BCR-ABL1 expression (6, 7) or stability (8, 9) or by targeting collaborative signaling pathways (10-12). A more direct approach for improving treatment would be to maintain focus on reducing tyrosine kinase activity by targeting oncogenic ABL outside the catalytic site.
RIN1 is a RAS effector protein that binds to and activates ABL tyrosine kinases (13, 14). Signaling is initiated by low affinity binding of a proline rich sequence on RIN1 to the SH3 domain of ABL. This interaction leads to phosphorylation of RIN1 on tyrosine 36, which subsequently associates with the ABL SH2 domain. The resulting stable divalent interaction (RIN1 proline-rich motif and phospho-Tyr36 bound to ABL SH3 and SH2 domains, respectively) relieves the ABL autoinhibitory fold and leads to activation of the ABL kinase through enhanced catalytic efficiency (13). Both ABL1 and ABL2 are activated by RIN1, and this requires only the ABL SH3, SH2 and kinase domains. Activation by RIN1 is independent of ABL trans-phosphorylation and is unaffected by an imatinib-resistance mutation (13). Silencing of RIN1 results in less tyrosine phosphorylation of the ABL substrate CRKL, and deletion of the mouse Rin1 gene causes reduction in basal levels of phospho-CRKL (14). These data demonstrate that RIN1 directly stimulates the tyrosine kinase activity of ABL proteins and is required for maintaining normal ABL kinase activity.
Because human ABL fusion oncoproteins consistently retain the autoinhibitory SH3 and SH2 domains, we reasoned that these constitutively active tyrosine kinases might still be subject to positive regulation by RIN1. Indeed, RIN1 binds to and enhances the catalytic, transforming and leukemogenic properties of BCR-ABL1. Deletion of RIN1 blocked transformation of bone marrow cells by BCR-ABL1 and ETV6-ABL1. Transformation was rescued by ectopic RIN1, indicating a cell autonomous mechanism. BCR-ABL1T315I, a drug resistant mutant found in CML patients, was also dependent on RIN1 for transformation. Silencing of RIN1 in human leukemia cells reduced phospho-tyrosine levels and sensitized cells to imatinib. The dependence of BCR-ABL1 on a directly binding regulator (RIN1) provides a unique point of vulnerability that could be exploited to treat kinase inhibitor-resistant leukemias. In addition, combining drugs that inhibit BCR-ABL1 activation by RIN1 with standard ABL kinase inhibitors could provide therapy that is more efficacious and less prone to resistance and disease relapse. Finally, the concept of interference with positive regulators may be applicable to the targeted therapy of other oncogenic kinases.
Summary of Probe Development Effort:
This probe development effort is focused on the identification of identify inhibitors of the RIN1-ABL interaction. All AIDs that contain results associated with this project can be found in the "Related Bioassays" section of this Summary AID.
1. Wong, S. and O.N. Witte, The BCR-ABL story: bench to bedside and back. Annu Rev Immunol, 2004. 22: p. 247-306.
2. Papadopoulos, P., et al., The novel activation of ABL by fusion to an ets-related gene, TEL. Cancer Res, 1995. 55(1): p. 34-38.
3. Iijima, Y., et al., A new ETV6/TEL partner gene, ARG (ABL-related gene or ABL2), identified in an AML-M3 cell line with a t(1;12)(q25;p13) translocation. Blood, 2000. 95(6): p. 2126-2131.
4. Deininger, M., E. Buchdunger, and B.J. Druker, The development of imatinib as a therapeutic agent for chronic myeloid leukemia. Blood, 2005. 105(7): p. 2640-2653.
5. Gorre, M.E., et al., Clinical resistance to STI-571 cancer therapy caused by BCR-ABL gene mutation or amplification. Science, 2001. 293(5531): p. 876-880.
6. Bueno, M.J., et al., Genetic and epigenetic silencing of microRNA-203 enhances ABL1 and BCR-ABL1 oncogene expression. Cancer Cell, 2008. 13(6): p. 496-506.
7. Chen, R., V. Gandhi, and W. Plunkett, A sequential blockade strategy for the design of combination therapies to overcome oncogene addiction in chronic myelogenous leukemia. Cancer Res, 2006. 66(22): p. 10959-10966.
8. Kawano, T., et al., MUC1 oncoprotein regulates Bcr-Abl stability and pathogenesis in chronic myelogenous leukemia cells. Cancer Res, 2007. 67(24): p. 11576-11584.
9. Wu, L.X., et al., Disruption of the Bcr-Abl/Hsp90 protein complex: a possible mechanism to inhibit Bcr-Abl-positive human leukemic blasts by novobiocin. Leukemia, 2008. 22(7): p. 1402-1409.
10. Dierks, C., et al., Expansion of Bcr-Abl-positive leukemic stem cells is dependent on Hedgehog pathway activation. Cancer Cell, 2008. 14(3): p. 238-249.
11. Hess, P., et al., Survival signaling mediated by c-Jun NH(2)-terminal kinase in transformed B lymphoblasts. Nat Genet, 2002. 32(1): p. 201-205.
12. Zhao, C., et al., Hedgehog signalling is essential for maintenance of cancer stem cells in myeloid leukaemia. Nature, 2009. 458(7239): p. 776-779.
13. Cao, X., et al., Enhancement of ABL kinase catalytic efficiency by a direct binding regulator is independent of other regulatory mechanisms. J Biol Chem, 2008. 283(46): p. 31401-31407.
14. Hu, H., et al., RIN1 is an ABL tyrosine kinase activator and a regulator of epithelial-cell adhesion and migration. Curr Biol, 2005. 15(9): p. 815-823.
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