Preclinical impact of bevacizumab on brain and tumor distribution of irinotecan and temozolomide.

Glioblastoma (GBM) is the most common primary malignant brain tumour in adults. Prognosis of GBM patients is poor with median overall survival around 15 months. Temozolomide is the chemotherapeutic agent used in the standard of care of newly diagnosed GBM patients relying on radiotherapy with concurrent chemotherapy followed by chemotherapy alone. Irinotecan has shown some efficacy in recurrent malignant gliomas. Bevacizumab has been combined with irinotecan in the treatment of recurrent GBM and with temozolomide in newly diagnosed GBM. As the efficacy of GBM treatments relies on their brain distribution through the blood brain barrier, the aim of the present preclinical work was to study, in in vivo models, the impact of bevacizumab on brain and tumor distribution of temozolomide and irinotecan. Our results show that bevacizumab pre-treatment was associated with a reduced temozolomide brain distribution in tumor-free mice. In tumor bearing mice, bevacizumab increased temozolomide tumor distribution, although not statistically significant. In both tumor-free and tumor-bearing mice, bevacizumab does not modify brain distribution of irinotecan and its metabolite SN-38. Bevacizumab impacts brain distribution of some anti-tumor drugs and potentially their efficacy in GBM. Further studies are warranted to investigate other therapeutic combination.

Multi-omics analysis of primary glioblastoma cell lines shows recapitulation of pivotal molecular features of parental tumors.

Background: Glioblastoma (GBM) is the deadliest primary brain cancer in adults. Emerging innovative therapies hold promise for personalized cancer treatment. Improving therapeutic options depends on research relying on relevant preclinical models. In this line we have established in the setting of the GlioTex project (GBM and Experimental Therapeutics) a GBM patient-derived cell line (GBM-PDCL) library. A multi-omic approach was used to determine the molecular landscape of PDCL and the extent to which they represent GBM tumors. Methods: Single nucleotide polymorphism array, expression arrays, exome sequencing, and RNA sequencing were used to measure and compare the molecular landscapes of 20 samples representing 10 human GBM tumors and paired GBM-PDCLs. Results: Copy number variations were similar for a median of 85% of the genome and for 59% of the major focal events. Somatic point mutations were similar in a median of 41%. Mutations in GBM driver and "druggable" genes were maintained in 67% of events. Mutations that were not conserved in the PDCL were mainly low allelic fraction and/or non-driver mutations. Based on RNA expression profiling, PDCLs cluster closely to their parental tumor with overexpression of pathways associated with cancer progression in PDCL. Conclusions: Overall, PDCLs recapitulate pivotal molecular alterations of paired-parental tumors supporting their use as a preclinical model of GBM. However, some driver aberrations are lost or gained in the passage from tumor to PDCL. Our results support using PDCL as a relevant preclinical model of GBM. Further investigations of changes between PDCLs and their parental tumor may provide insights into GBM biology.

Preclinical Efficacy of the MDM2 Inhibitor RG7112 in MDM2-Amplified and TP53 Wild-type Glioblastomas.

PURPOSE: p53 pathway alterations are key molecular events in glioblastoma (GBM). MDM2 inhibitors increase expression and stability of p53 and are presumed to be most efficacious in patients with TP53 wild-type and MDM2-amplified cancers. However, this biomarker hypothesis has not been tested in patients or patient-derived models for GBM. EXPERIMENTAL DESIGN: We performed a preclinical evaluation of RG7112 MDM2 inhibitor, across a panel of 36 patient-derived GBM cell lines (PDCL), each genetically characterized according to their P53 pathway status. We then performed a pharmacokinetic (PK) profiling of RG7112 distribution in mice and evaluated the therapeutic activity of RG7112 in orthotopic and subcutaneous GBM models. RESULTS: MDM2-amplified PDCLs were 44 times more sensitive than TP53-mutated lines that showed complete resistance at therapeutically attainable concentrations (avg. IC50 of 0.52 µmol/L vs. 21.9 µmol/L). MDM4-amplified PDCLs were highly sensitive but showed intermediate response (avg. IC50 of 1.2 µmol/L), whereas response was heterogeneous in TP53 wild-type PDCLs with normal MDM2/4 levels (avg. IC50 of 7.7 µmol/L). In MDM2-amplified lines, RG7112 restored p53 activity inducing robust p21 expression and apoptosis. PK profiling of RG7112-treated PDCL intracranial xenografts demonstrated that the compound significantly crosses the blood-brain and the blood-tumor barriers. Most importantly, treatment of MDM2-amplified/TP53 wild-type PDCL-derived model (subcutaneous and orthotopic) reduced tumor growth, was cytotoxic, and significantly increased survival. CONCLUSIONS: These data strongly support development of MDM2 inhibitors for clinical testing in MDM2-amplified GBM patients. Moreover, significant efficacy in a subset of non-MDM2-amplified models suggests that additional markers of response to MDM2 inhibitors must be identified.