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Monotherapy efficacy of blood-brain barrier permeable small molecule reactivators of protein phosphatase 2A in glioblastoma.

ABSTRACT: Glioblastoma is a fatal disease in which most targeted therapies have clinically failed. However, pharmacological reactivation of tumour suppressors has not been thoroughly studied as yet as a glioblastoma therapeutic strategy. Tumour suppressor protein phosphatase 2A is inhibited by non-genetic mechanisms in glioblastoma, and thus, it would be potentially amendable for therapeutic reactivation. Here, we demonstrate that small molecule activators of protein phosphatase 2A, NZ-8-061 and DBK-1154, effectively cross the in vitro model of blood-brain barrier, and in vivo partition to mouse brain tissue after oral dosing. In vitro, small molecule activators of protein phosphatase 2A exhibit robust cell-killing activity against five established glioblastoma cell lines, and nine patient-derived primary glioma cell lines. Collectively, these cell lines have heterogeneous genetic background, kinase inhibitor resistance profile and stemness properties; and they represent different clinical glioblastoma subtypes. Moreover, small molecule activators of protein phosphatase 2A were found to be superior to a range of kinase inhibitors in their capacity to kill patient-derived primary glioma cells. Oral dosing of either of the small molecule activators of protein phosphatase 2A significantly reduced growth of infiltrative intracranial glioblastoma tumours. DBK-1154, with both higher degree of brain/blood distribution, and more potent in vitro activity against all tested glioblastoma cell lines, also significantly increased survival of mice bearing orthotopic glioblastoma xenografts. In summary, this report presents a proof-of-principle data for blood-brain barrier-permeable tumour suppressor reactivation therapy for glioblastoma cells of heterogenous molecular background. These results also provide the first indications that protein phosphatase 2A reactivation might be able to challenge the current paradigm in glioblastoma therapies which has been strongly focused on targeting specific genetically altered cancer drivers with highly specific inhibitors. Based on demonstrated role for protein phosphatase 2A inhibition in glioblastoma cell drug resistance, small molecule activators of protein phosphatase 2A may prove to be beneficial in future glioblastoma combination therapies.

SUBMITTER: Merisaari J

PROVIDER: S-EPMC7425423 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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Monotherapy efficacy of blood-brain barrier permeable small molecule reactivators of protein phosphatase 2A in glioblastoma.

Merisaari Joni J Denisova Oxana V OV Doroszko Milena M Le Joncour Vadim V Johansson Patrik P Leenders William P J WPJ Kastrinsky David B DB Zaware Nilesh N Narla Goutham G Laakkonen Pirjo P Nelander Sven S Ohlmeyer Michael M Westermarck Jukka J

Brain communications 20200111 1

Glioblastoma is a fatal disease in which most targeted therapies have clinically failed. However, pharmacological reactivation of tumour suppressors has not been thoroughly studied as yet as a glioblastoma therapeutic strategy. Tumour suppressor protein phosphatase 2A is inhibited by non-genetic mechanisms in glioblastoma, and thus, it would be potentially amendable for therapeutic reactivation. Here, we demonstrate that small molecule activators of protein phosphatas ...[more]

PMID: 32954276

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Project description:Introduction The standard treatment for glioblastoma (GBM) patients is surgical tumor resection, followed by radiation and chemotherapy with temozolomide (TMZ). Unfortunately, 60% of newly diagnosed GBM patients express high levels of the DNA repair enzyme O6-methylguanine-DNA methyltransferase (MGMT) and are TMZ-resistant, and all patients eventually become refractory to treatment. The blood-brain barrier (BBB) is an obstacle to the delivery of chemotherapeutic agents to GBM, and BBB-permeable agents that are efficacious in TMZ-resistant and refractory patients are needed. The large amino acid transporter 1 (LAT1) is expressed on the BBB and in GBM and is detected at much lower levels in normal brain tissue. A LAT1-selective therapeutic would potentially target brain tumors while avoiding uptake by healthy tissue. Methods We report a novel chemical entity (QBS10072S) that combines a potent cytotoxic chemotherapeutic domain (tertiary N-bis(2-chloroethyl)amine) with the structural features of a selective LAT1 substrate and tested it against GBM models in vitro and in vivo. For in vitro studies, DNA damage was assessed with a gamma H2A.X antibody and cell viability was assessed by WST-1 assay and/or CellTiter-Glo assay. For in vivo studies, QBS10072S (with or without radiation) was tested in orthotopic glioblastoma xenograft models, using overall survival and tumor size (as measured by bioluminescence), as endpoints. Results QBS10072S is 50-fold more selective for LAT1 vs. LAT2 in transport assays and demonstrates significant growth suppression in vitro of LAT1-expressing GBM cell lines. Unlike TMZ, QBS10072S is cytotoxic to cells with both high and low levels of MGMT expression. In orthotopic GBM xenografts, QBS10072S treatment significantly delayed tumorigenesis and prolonged animal survival compared to the vehicle without adverse effects. Conclusion QBS10072S is a novel BBB-permeable chemotherapeutic agent with the potential to treat TMZ-resistant and recurrent GBM as monotherapy or in combination with radiation treatment.

Dataset Information

Monotherapy efficacy of blood-brain barrier permeable small molecule reactivators of protein phosphatase 2A in glioblastoma.

Publications

Monotherapy efficacy of blood-brain barrier permeable small molecule reactivators of protein phosphatase 2A in glioblastoma.

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