Identification of MEK162 as a Radiosensitizer for the Treatment of Glioblastoma

Abstract

Glioblastoma (GBM) is a highly aggressive and lethal brain cancer type. PI3K and MAPK inhibitors have been studied preclinically in GBM as monotherapy, but not in combination with radiotherapy, which is a key component of the current standard treatment of GBM. In our study, GBM cell lines and patient representative primary cultures were grown as multicellular spheroids. Spheroids were treated with a panel of small-molecule drugs including MK2206, RAD001, BEZ235, MLN0128, and MEK162, alone and in combination with irradiation. Following treatment, spheroid growth parameters (growth rate, volume reduction, and time to regrow), cell-cycle distribution and expression of key target proteins were evaluated. , the effect of irradiation (3 × 2 Gy) without or with MEK162 (50 mg/kg) was studied in orthotopic GBM8 brain tumor xenografts with endpoints tumor growth and animal survival. The MAPK-targeting agent MEK162 was found to enhance the effect of irradiation as demonstrated by growth inhibition of spheroids. MEK162 downregulated and dephosphorylated the cell-cycle checkpoint proteins CDK1/CDK2/WEE1 and DNA damage response proteins p-ATM/p-CHK2. When combined with radiation, this led to a prolonged DNA damage signal. data on tumor-bearing animals demonstrated a significantly reduced growth rate, increased growth delay, and prolonged survival time. In addition, RNA expression of responsive cell cultures correlated to mesenchymal stratification of patient expression data. In conclusion, the MAPK inhibitor MEK162 was identified as a radiosensitizer in GBM spheroids and in orthotopic GBM xenografts The data are supportive for implementation of this targeted agent in an early-phase clinical study in GBM patients.

Preclinical evaluation of binimetinib (MEK162) delivered via polymeric nanocarriers in combination with radiation and temozolomide in glioma

“…Despite high drug loading efficacy of the nanocarriers (~ 40% at 50 µM loading concentration), the biological efficacy of encapsulated MEK162 in polymersomes was low compared with the free drug: 1 µM free MEK162 caused a large inhibition of spheroid growth, while MEK162 delivered via the nanocarriers was less effective. Previously, we showed that free MEK162 was synergistic to radiation [6], and this was not confirmed in the present study on the endpoint spheroid growth delay, with MEK162 delivered via polymersomes (cf. Fig.…”

“…direct DNA damage induction by the methylating drug TMZ and inhibition of the MAPK signaling pathway by MEK162. Mechanistically, MAPK inhibition leads to down-regulation and dephosphorylation of the cell cycle checkpoint proteins CDK1/CDK2/WEE1 and of the DNA damage response proteins p-ATM/p-CHK2, finally inhibiting cell proliferation, which was demonstrated in a previous report from our laboratory [6].…”

“…Previous data from our laboratory showed the MAPK inhibitor MEK162 (binimetinib) to act as radiosensitizer. The drug, when combined with fractionated irradiation, enhanced the radiation induced growth inhibition of multicellular GBM spheroids [6]. In vivo experiments, using a murine orthotopic GBM8 model, demonstrated that MEK162 additional to radiation delayed tumour growth and prolonged the survival time of the animals [6].…”

Inhalation anesthesia and shielding devices to allow accurate preclinical irradiation of mice with clinical linac-based systems: Design and dosimetric characteristics

“…Moreover, the target box setup allowed us to anesthetize with isoflurane, position, and radiate up to 12 mice within 5 minutes. The target box has already proven its value in the identification of radiosensitizers for the treatment of pediatric brain tumors and glioblastoma [17,18], whilst the TBI box has been used in several studies, such as those for head-and-neck cancer [19]. In conclusion, the target box allows easy immobilization and positioning of the mice, the mice remain well controlled under anesthesia during the radiations, and both devices support accurate administration of the radiation dose.…”

Refining Radiation for the Next Century

“…It is also unclear how selective an AKT inhibitor needs to be, as the allosteric AKT inhibitor MK2206 produced sensitization to IR in glioblastoma cells that was independent of the p53 status. IR sensitization of glioblastoma was also observed with an inhibitor of the MAPK pathway, MEK162 or binimetinib, which downregulated and dephosphorylated the cell-cycle checkpoint proteins CDK1/CDK2/WEE1 and DNA damage response proteins phosphorylated ATM or CHK2 (2). When combined with IR, the MEK1/2 inhibitor binimetinib prolonged DNA damage and increased apoptosis probably by abrogating the G 2 -M checkpoint.…”