Jorge A Benitez1,2, Darren Finlay3, Anthony Castanza4, Alison D Parisian1,5, Jianhui Ma1, Ciro Longobardi6, Alex Campos4,3, Raghavendra Vadla1, Alejandro Izurieta1, Gianluca Scerra6, Tomoyuki Koga1,7, Tao Long4,3, Lukas Chavez4, Jill P Mesirov4, Kristiina Vuori3, Frank Furnari1,8. 1. Ludwig Cancer Research, University of California at San Diego, La Jolla, California. 2. Bristol-Myers Squibb, San Diego, California. 3. Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California. 4. Department of Medicine and Moores Cancer Center, University of California at San Diego, La Jolla, California. 5. Biomedical Sciences Graduate Program, University of California at San Diego, La Jolla, California. 6. Department of Medicine and Medical Biotechnology, University of Naples "Federico II", Naples, Italy. 7. Department of Neurosurgery, University of Minnesota, Minneapolis, Minnesota. 8. Department of Pathology, University of California at San Diego, La Jolla, California.
Abstract
BACKGROUND: Glioblastoma (GBM) is the most common primary brain tumor in adults with a median survival of approximately 15 months; therefore, more effective treatment options for GBM are required. To identify new drugs targeting GBMs, we performed a high-throughput drug screen using patient-derived neurospheres cultured to preferentially retain their glioblastoma stem cell (GSC) phenotype. METHODS: High-throughput drug screening was performed on GSCs followed by a dose-response assay of the 5 identified original "hits." A PI3K/mTOR dependency to a proteasome inhibitor (carfilzomib), was confirmed by genetic and pharmacologic experiments. Proteasome Inhibition Response Signatures were derived from proteomic and bioinformatic analysis. Molecular mechanism of action was determined using three-dimensional (3D) GBM-organoids and preclinical orthotopic models. RESULTS: We found that GSCs were highly sensitive to proteasome inhibition due to an underlying dependency on an increased protein synthesis rate, and loss of autophagy, associated with PTEN loss and activation of the PI3K/mTOR pathway. In contrast, combinatory inhibition of autophagy and the proteasome resulted in enhanced cytotoxicity specifically in GSCs that did express PTEN. Finally, proteasome inhibition specifically increased cell death markers in 3D GBM-organoids, suppressed tumor growth, and increased survival of mice orthotopically engrafted with GSCs. As perturbations of the PI3K/mTOR pathway occur in nearly 50% of GBMs, these findings suggest that a significant fraction of these tumors could be vulnerable to proteasome inhibition. CONCLUSIONS: Proteasome inhibition is a potential synthetic lethal therapeutic strategy for GBM with proteasome addiction due to a high protein synthesis rate and autophagy deficiency.
BACKGROUND: Glioblastoma (GBM) is the most common primary brain tumor in adults with a median survival of approximately 15 months; therefore, more effective treatment options for GBM are required. To identify new drugs targeting GBMs, we performed a high-throughput drug screen using patient-derived neurospheres cultured to preferentially retain their glioblastoma stem cell (GSC) phenotype. METHODS: High-throughput drug screening was performed on GSCs followed by a dose-response assay of the 5 identified original "hits." A PI3K/mTOR dependency to a proteasome inhibitor (carfilzomib), was confirmed by genetic and pharmacologic experiments. Proteasome Inhibition Response Signatures were derived from proteomic and bioinformatic analysis. Molecular mechanism of action was determined using three-dimensional (3D) GBM-organoids and preclinical orthotopic models. RESULTS: We found that GSCs were highly sensitive to proteasome inhibition due to an underlying dependency on an increased protein synthesis rate, and loss of autophagy, associated with PTEN loss and activation of the PI3K/mTOR pathway. In contrast, combinatory inhibition of autophagy and the proteasome resulted in enhanced cytotoxicity specifically in GSCs that did express PTEN. Finally, proteasome inhibition specifically increased cell death markers in 3D GBM-organoids, suppressed tumor growth, and increased survival of mice orthotopically engrafted with GSCs. As perturbations of the PI3K/mTOR pathway occur in nearly 50% of GBMs, these findings suggest that a significant fraction of these tumors could be vulnerable to proteasome inhibition. CONCLUSIONS: Proteasome inhibition is a potential synthetic lethal therapeutic strategy for GBM with proteasome addiction due to a high protein synthesis rate and autophagy deficiency.
Authors: Grant L Lin; Kelli M Wilson; Michele Ceribelli; Benjamin Z Stanton; Pamelyn J Woo; Sara Kreimer; Elizabeth Y Qin; Xiaohu Zhang; James Lennon; Surya Nagaraja; Patrick J Morris; Michael Quezada; Shawn M Gillespie; Damien Y Duveau; Aleksandra M Michalowski; Paul Shinn; Rajarshi Guha; Marc Ferrer; Carleen Klumpp-Thomas; Sam Michael; Crystal McKnight; Paras Minhas; Zina Itkin; Eric H Raabe; Lu Chen; Reem Ghanem; Anna C Geraghty; Lijun Ni; Katrin I Andreasson; Nicholas A Vitanza; Katherine E Warren; Craig J Thomas; Michelle Monje Journal: Sci Transl Med Date: 2019-11-20 Impact factor: 17.956
Authors: M P Myers; I Pass; I H Batty; J Van der Kaay; J P Stolarov; B A Hemmings; M H Wigler; C P Downes; N K Tonks Journal: Proc Natl Acad Sci U S A Date: 1998-11-10 Impact factor: 11.205
Authors: Andrew C Hsieh; Yi Liu; Merritt P Edlind; Nicholas T Ingolia; Matthew R Janes; Annie Sher; Evan Y Shi; Craig R Stumpf; Carly Christensen; Michael J Bonham; Shunyou Wang; Pingda Ren; Michael Martin; Katti Jessen; Morris E Feldman; Jonathan S Weissman; Kevan M Shokat; Christian Rommel; Davide Ruggero Journal: Nature Date: 2012-02-22 Impact factor: 69.504