Identification of a novel synthetic lethality of combined inhibition of hedgehog and PI3K signaling in rhabdomyosarcoma
- We previously reported that aberrant HH pathway activation confers a poor prognosis in rhabdomyosarcoma (RMS). Searching for new treatment strategies we therefore targeted HH signaling. Here, we identify a novel synthetic lethality of concomitant inhibition of HH and PI3K/AKT/mTOR pathways in RMS by GLI1/2 inhibitor GANT61 and PI3K/mTOR inhibitor PI103. Synergistic drug interaction is confirmed by calculation of combination index (CI < 0.2). Similarly, genetic silencing of GLI1/2 significantly increases PI103-induced apoptosis. GANT61 and PI103 also synergize to induce apoptosis in cultured primary RMS cells emphasizing the clinical relevance of this combination. Importantly, GANT61/PI103 cotreatment suppresses clonogenic survival, three-dimensional sphere formation and tumor growth in an in vivo model of RMS. Mechanistic studies reveal that GANT61 and PI103 cooperate to trigger caspase-dependent apoptosis via the mitochondrial pathway, as demonstrated by several lines of evidence. First, GANT61/PI103 cotreatment increases mRNA and protein expression of NOXA and BMF, which is required for apoptosis, since knockdown of NOXA or BMF significantly reduces GANT61/PI103-induced apoptosis. Second, GANT61/PI103 cotreatment triggers BAK/BAX activation, which contributes to GANT61/PI103-mediated apoptosis, since knockdown of BAK provides protection. Third, ectopic expression of BCL-2 or non-degradable phospho-mutant MCL-1 significantly rescue GANT61/PI103-triggered apoptosis. Fourth, GANT61/PI103 cotreatment initiate activation of the caspase cascade via apoptosome-mediated cleavage of the initiator caspase-9, as indicated by changes in the cleavage pattern of caspases (e.g. accumulation of the caspase-9 p35 cleavage fragment) upon addition of the caspase inhibitor zVAD.fmk. Thus, combined GLI1/2 and PI3K/mTOR inhibition represents a promising novel approach for synergistic apoptosis induction and tumor growth reduction with implications for new treatment strategies in RMS.
Author: | Ulrike Graab, Heidi Hahn, Simone FuldaORCiDGND |
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URN: | urn:nbn:de:hebis:30:3-395277 |
DOI: | https://doi.org/10.18632/oncotarget.2726 |
ISSN: | 1949-2553 |
Pubmed Id: | https://pubmed.ncbi.nlm.nih.gov/25749378 |
Parent Title (English): | Oncotarget |
Publisher: | Impact Journals LLC |
Place of publication: | [S.l.] |
Document Type: | Article |
Language: | English |
Date of Publication (online): | 2015/03/06 |
Date of first Publication: | 2015/03/06 |
Publishing Institution: | Universitätsbibliothek Johann Christian Senckenberg |
Release Date: | 2016/02/17 |
Tag: | PI3K; apoptosis; hedgehog; rhabdomyosarcoma |
Volume: | 6 |
Issue: | 11 |
Page Number: | 14 |
First Page: | 8722 |
Last Page: | 8735 |
Note: | Licensed under a Creative Commons Attribution 3.0 License. |
HeBIS-PPN: | 378210033 |
Institutes: | Medizin / Medizin |
Dewey Decimal Classification: | 6 Technik, Medizin, angewandte Wissenschaften / 61 Medizin und Gesundheit / 610 Medizin und Gesundheit |
Sammlungen: | Universitätspublikationen |
Licence (German): | Creative Commons - Namensnennung 3.0 |