Disruption of NOTCH signaling by a small molecule inhibitor of the transcription factor RBPJ

San Diego, Calif., July 25, 2019 Researchers at the Stanford Cardiovascular Institute and the Department of Medicine, Stanford University, Sanford-Burnham-Prebys Medical Discovery Institute, Icagen, Human BioMolecular Research Institute, University Medical Center Ulm, Germany, Regencor, Sanofi, France and ChemRegen, Inc., have reported on a small molecule that potently inhibited hematologic cancer and promoted skeletal muscle differentiation. Writing July 25, 2019 in the journal Scientific Reports, the team described how they found and tested a RBPJ Inhibitor-1 (RIN1), a small molecule, drug-like compound that can be used to decrease cancer.


“In the United States, hematologic cancer is a leading cause of cancer-related fatalities.  Currently, 10% of new cancer diagnosis and 10% of cancer deaths are due to hematologic cancer“ said Jiongjia Cheng, Ph.D., a leading cancer researcher not involved with the study. “Using a non-toxic small molecule to decrease hematologic cancer is very attractive.”


Study leads to safe anti-cancer drug


NOTCH proteins are trans-membrane receptors that transduce signals from cell-bound families of ligands to mediate cell-cell interactions in processes as diverse as fetal development, heart disease and cancer. NOTCH plays a pivotal role during normal development and in congenital disorders and cancer. Inhibition of RBPJ was deemed a desirable point to modulate NOTCH signaling, potentially affording a useful probe and potential clinical candidate. RBPJ is the main transcriptional effector of NOTCH signaling. To identify selective inhibitors of RBPJ, a primary screen was developed to detect inhibitors of a functional interaction between RBPJ and the scaffold protein SHARP that was followed by secondary assays to establish efficacy against NOTCH. 


In early studies, a primary assay was screened against 1,780,000 compounds from Sanofi, Tucson. Primary positive “hits” were retested through a dose-range to confirm potency. Ultimately, 130 compounds showed dose-responsive inhibition comprising 14 distinct chemical families plus 17 singletons. Counter screens were run to show selectivity. The small molecule inhibitor RIN1 disrupted the interaction between NOTCH and RBPJ. RIN1 also blocked the functional interaction of RBPJ with SHARP, a scaffold protein that forms a transcriptional repressor complex with RBPJ in the absence of NOTCH signaling.


When added to hematologic cancer cells, RIN1 potently suppressed the proliferation of three hematologic tumor cell lines (i.e., Jurkat and KOPT-K1 T-ALL, and REC-1 MCL). It is notable that the potencies and efficacies of RIN1 relative to other agents was robust across cancer cell lines. RIN1 effectively blocked proliferation of all cancer cells tested but it appeared RBPJ played a relatively more important role in controlling Jurkat cell proliferation than did NOTCH cleavage.


How RIN1 works


Developing new medications for cancer is important. Despite its prevalence, therapeutic options for hematologic cancer are limited. Drug resistance and drug-induced side effects also limit treatment.


For hematologic cancer, like other cancers, the challenging part is figuring out the cellular pathways that direct cancer growth and how these pathways can be interrupted and halted. A non-toxic chemical that inhibits key cancer-promoting pathways is a very promising strategy.


RIN1 is the first small molecule inhibitor of RBPJ signaling. RBPJ can either activate genes by forming a complex with the NOTCH ICD when NOTCH is active, or silence an overlapping but non-identical set of genes by recruiting co-repressors in the absence of NOTCH signaling.  RIN1 chokes hematologic cancer cell proliferation, ultimately altering cellular behavior and in this case decreasing cancer cell growth.


Media contacts: To arrange on-site, phone, or Skype interviews with the researchers involved in this study, please contact John Cashman at (858) 458-9305 / JCashman@hbri.org.



This research was funded by California Institute for Regenerative Medicine, the National Institute of Health, Stanford School of Medicine, the DFG (German Research Foundation) and the Human BioMolecular Research Institute.


The study was co-authored by Cecilia Hurtado, Stanford Cardiovascular Institute and the Department of Medicine, Alena Safarova, Icagen, Michael Smith, Icagen, Raeeun Chung, Stanford Cardiovascular Institute and the Department of Medicine, Arne A. N. Bruyneel, Stanford Cardiovascular Institute and the Department of Medicine, Jorge Gomez-Galeno, Human BioMolecular Research Institute and ChemRegen, Franz Oswald, University Medical Center, Germany, Christopher J. Larson, Sanford-Burnham-Prebys Medical Discovery Institute, John R. Cashman, Human BioMolecular Research Institute, Pilar Ruiz-Lozano, Regencor, Philip Janiak, Sanofi, France, Teri Suzuki, Icagen, and Mark Mercola Stanford Cardiovascular Institute and the Department of Medicine.




About Human BioMolecular Research Institute

The Human BioMolecular Research Institute is a non-profit research institute conducting basic research focused on unlocking biological and chemical principles related to diseases of the human brain, cardiovascular disease and cancer. The Institute conducts fundamental studies of central nervous system disorders, heart disease and cancer including stem cell approaches and translates findings into new drug development to address human illness. In addition, the Institute promotes scientific learning through community service and public access by disseminating information and sharing research with collaborators, colleagues and the public. For more information, visit us at www.HBRI.org.


About Stanford University

Stanford University is a leading teaching and research institution. The University is organized around three traditional schools consisting of 40 academic departments at the undergraduate and graduate level and four professional schools that focus on graduate programs in Law, Medicine, Education and Business. It is one of only 45 National Cancer Institute-designated comprehensive cancer centers in the country, a rare honor distinguishing exceptionally high achievement in research, clinical care, education and community outreach and partnerships. For more information, visit med.stanford.edu.


About ChemRegen Inc.

ChemRegen is a for-profit company doing research directed at identifying small molecules of use for addressing human diseases. The approach is to develop regenerative medicines to work in conjunction with stem cells to cure major human diseases including heart disease, cancer and other diseases. For more information, visit www.ChemRegen.com.