TIC10/ONC201 synergizes with Bcl-2/Bcl-xL inhibition in glioblastoma by suppression of Mcl-1 and its binding partners in vitro and in vivo
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Georg Karpel-Massler1, Maïmouna Bâ1, Chang Shu1, Marc-Eric Halatsch3, Mike-Andrew Westhoff4, Jeffrey N. Bruce2, Peter Canoll1, Markus D. Siegelin1
1Department of Pathology & Cell Biology, Columbia University Medical Center, New York, New York, U.S.A
2Department of Neurosurgery, Columbia University Medical Center, New York, New York, U.S.A
3Department of Neurosurgery, Ulm University Medical Center, Ulm, Germany
4Department of Pediatrics and Adolescent Medicine, Ulm University Medical Center, Ulm, Germany
Keywords: glioblastoma, apoptotic resistance, TIC10/ONC201, ABT263, multi-targeting
Received: August 04, 2015 Accepted: September 29, 2015 Published: October 12, 2015
Glioblastoma is the most frequent primary brain tumor in adults. Current therapeutic options are sparse and the prognosis of patients suffering from this disease is grim. Abundance in intratumoral heterogeneity among different deregulated signaling pathways is a hallmark of glioblastoma and likely accounts for its recurrence and resistance to treatment. Glioblastomas harbor a plethora of deregulated pathways driving tumor formation and growth. In this study, we show that TIC10/ONC201, a promising compound that is currently in planned clinical development, along with Bcl-2/Bcl-xL inhibition by ABT263 yields a strong synergistic antiproliferative effect on pediatric, adult, proneural glioblastoma and glioma stem-like cells. On the molecular level, treatment with TIC10/ONC201 results in a posttranslational decrease of the anti-apoptotic Bcl-2 family member, myeloid cell leukemia 1 (Mcl-1), through modulation of the chaperone Bag3 and the deubiquitinase Usp9X. Consistently, the combination treatment of TIC10/ONC201 and ABT263 required the presence of functional BAX and BAK to drive intrinsic apoptosis, but is surprisingly independent of the extrinsic apoptotic pathway. Moreover, the expression of Noxa protein was required for efficient apoptosis induction by TIC10/ONC201 and ABT263. Importantly, the drug combination of TIC10/ONC201 and the BH3-mimetic, ABT263, led to a regression of tumors in vivo, without any notable toxicity and side effects. Overall, TIC10/ONC201 along with Bcl-2/Bcl-xL inhibition holds significant promise as a novel potential approach for the treatment of recalcitrant tumors such as glioblastoma.
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