Conflict of interest: Nothing to declare.
Overcoming resistance to sonic hedgehog inhibition by targeting p90 ribosomal S6 kinase in pediatric medulloblastoma
Article first published online: 12 AUG 2013
© 2013 Wiley Periodicals, Inc.
Pediatric Blood & Cancer
Volume 61, Issue 1, pages 107–115, January 2014
How to Cite
Pambid, M. R., Berns, R., Adomat, H. H., Hu, K., Triscott, J., Maurer, N., Zisman, N., Ramaswamy, V., Hawkins, C. E., Taylor, M. D., Dunham, C., Guns, E. and Dunn, S. E. (2014), Overcoming resistance to sonic hedgehog inhibition by targeting p90 ribosomal S6 kinase in pediatric medulloblastoma. Pediatr. Blood Cancer, 61: 107–115. doi: 10.1002/pbc.24675
Additional Supporting Information may be found in the online version of this article at the publisher's web-site.
- Issue published online: 12 NOV 2013
- Article first published online: 12 AUG 2013
- Manuscript Accepted: 3 JUN 2013
- Manuscript Received: 22 APR 2013
- Hannah's Heroes Foundation
- Mitacs Internship Program
- p90 ribosomal S6 kinase;
- Sonic Hedgehog medulloblastoma
Molecular subtyping has allowed for the beginning of personalized treatment in children suffering from medulloblastoma (MB). However, resistance inevitably emerges against these therapies, particularly in the Sonic Hedgehog (SHH) subtype. We found that children with SHH subtype have the worst outcome underscoring the need to identify new therapeutic targets.
High content screening of a 129 compound library identified agents that inhibited SHH MB growth. Lead molecular target levels, p90 ribosomal S6 kinase (RSK) were characterized by immunoblotting and qRT-PCR. Comparisons were made to human neural stem cells (hNSC). Impact of inhibiting RSK with the small molecule BI-D1870 or siRNA was assessed in growth assays (monolayer, neurosphere, and soft agar). NanoString was used to detect RSK in a cohort of 66 patients with MB. To determine BI-D1870 pharmacokinetics/pharmacodynamics, 100 mg/kg was I.P. injected into mice and tissues were collected at various time points.
Daoy, ONS76, UW228, and UW426 MB cells were exquisitely sensitive to BI-D1870 but unresponsive to SHH inhibitors. Anti-tumor growth corresponded with inactivation of RSK in MB cells. BI-D1870 had no effect on hNSCs. Inhibiting RSK with siRNA or BI-D1870 suppressed growth, induced apoptosis, and sensitized cells to SHH agents. Notably, RSK expression is correlated with SHH patients. In mice, BI-D1870 was well-tolerated and crossed the blood–brain barrier (BBB).
RSK inhibitors are promising because they target RSK which is correlated with SHH patients as well as cause high levels of apoptosis to only MB cells. Importantly, BI-D1870 crosses the BBB, acting as a scaffold for development of more long-lived RSK inhibitors. Pediatr Blood Cancer 2014;61:107–115. © 2013 Wiley Periodicals, Inc.