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Cancer Res. 2019 Dec 5. pii: canres.2808.2018. doi: 10.1158/0008-5472.CAN-18-2808. [Epub ahead of print]

Cooperative blockade of PKCα and JAK2 drives apoptosis in glioblastoma.

Author information

1
Neurology, University of California, San Francisco.
2
University of California, San Francisco.
3
Radiation Oncology, Dana Farber Cancer Institute.
4
Department of Neurological Surgery, Helen Diller Research Center, University of California, San Francisco.
5
Department of Cellular Molecular Pharmacology, University of California, San Francisco.
6
Department of Neurology, University of California, San Francisco waweiss@gmail.com.

Abstract

The mechanistic target of rapamycin (mTOR) signaling is dysregulated prominently in human cancers including glioblastoma, suggesting mTOR as a robust target for therapy. Inhibitors of mTOR have had limited success clinically however, in part because their mechanism of action is cytostatic rather than cytotoxic. Here, we tested three distinct mTOR kinase inhibitors (TORKis) PP242, KU-0063794, and sapanisertib against glioblastoma cells. All agents similarly decreased proliferation of glioblastoma cells, whereas PP242 uniquely induced apoptosis. Apoptosis induced by PP242 resulted from off-target cooperative inhibition of Janus kinase 2 (JAK2) and protein kinase C alpha (PKCα). Induction of apoptosis was also decreased by additional on-target inhibition of mTOR, due to induction of autophagy. As EGFR inhibitors can block PKCα, EGFR inhibitors erlotinib and osimertinib were tested separately in combination with the JAK2 inhibitor AZD1480. Combination therapy induced apoptosis of glioblastoma tumors in both flank and in patient-derived orthotopic xenograft models, providing a preclinical rationale to test analogous combinations in patients.

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