Expression and pharmacological inhibition of TrkB and EGFR in glioblastoma

A member of the Trk family of neurotrophin receptors, tropomyosin receptor kinase B (TrkB, encoded by the NTRK2 gene) is an increasingly important target in various cancer types, including glioblastoma (GBM). EGFR is among the most frequently altered oncogenes in GBM, and EGFR inhibition has been tested as an experimental therapy. Functional interactions between EGFR and TrkB have been demonstrated. In the present study, we investigated the role of TrkB and EGFR, and their interactions, in GBM. Analyses of NTRK2 and EGFR gene expression from The Cancer Genome Atlas (TCGA) datasets showed an increase in NTRK2 expression in the proneural subtype of GBM, and a strong correlation between NTRK2 and EGFR expression in glioma CpG island methylator phenotype (G-CIMP+) samples. We showed that when TrkB and EGFR inhibitors were combined, the inhibitory effect on A172 human GBM cells was more pronounced than when either inhibitor was given alone. When U87MG GBM cells were xenografted into the flank of nude mice, tumor growth was delayed by treatment with TrkB and EGFR inhibitors, given alone or combined, only at specific time points. Intracranial GBM growth in mice was not significantly affected by drug treatments. Our findings indicate that correlations between NTRK2 and EGFR expression occur in specific GBM subgroups. Also, our results using cultured cells suggest for the first time the potential of combining TrkB and EGFR inhibition for the treatment of GBM.

Abstract A66: Anticancer activity of selective TrkB inhibition in medulloblastoma cells

Medulloblastomas (MB) occur in the central nervous system and are the most common pediatric intracranial tumors. Despite the knowledge regarding the molecular biology of these tumors, patients still suffer long-term side effects in consequence of the current treatments. Several advances have collaborated to the identification of new therapeutic targets for cancer treatment, including the characterization of BDNF/TrkB signalling in cell fate. This pathway has been associated with increased proliferative capabilities, invasiveness, and chemotherapy resistance in many types of cancer. We have previously shown that the selective TrkB inhibitor, ANA-12, markedly reduced the viability and survival of MB cell lines. These findings provided a rationale to further investigations relating TrkB inhibition as a potential novel strategy for MB treatment. We investigated the effects of ANA-12 in apoptosis and the effects of combined treatment with cisplatin in MB cell viability. Human MB cell lines D283 and UW-228 were treated with increasing concentrations of ANA-12 (5, 20, or 30 μM) or BDNF (50 ng/ml) for 24 or 48 hours. Cells were also treated with different combinations of ANA-12 and cisplatin for 48 hours. Cell viability was assessed by trypan blue cell counting. Cell apoptosis was analyzed by flow cytometry to annexin-V and propidium iodide staining. Data represent at least three independent experiments performed in triplicates. Statistical analyses: two-way ANOVA followed by followed by Tukey for multiple comparisons. We found that ANA-12 leads to a dose- and time-dependent reduction of D283 and UW-228 MB cell viability. ANA-12 at 30 μM increased the population of apoptotic cells in both MB cell lines. In D283 29.9% and 61.9% of the cells were apoptotic after 24 and 48 hours of treatment, respectively. In UW-228 apoptosis rates were 49.1% after 24 hours and 80.7% after 48 hours. When used in combination, ANA-12 enhanced cisplatin cytotoxic effects in UW-228 cells. Cell viability in the presence of 5 μM of cisplatin alone was 37.48% (UW-228) and 49.8% (D283), but decreased with the combination of 20 μM of ANA-12, 18.4% (UW-228) and 23.4% (D283). Here we present the evidence that in human MB, ANA-12 decreases viability, induces apoptosis, and acts synergistically with cisplatin in suppressing MB cell viability.

Citation Format: Amanda Thomaz, Kelly V. Pinheiro, Camila A. da Silva, Caroline B. de Farias, Rafael Roesler. Anticancer activity of selective TrkB inhibition in medulloblastoma cells [abstract]. In: Proceedings of the AACR International Conference held in cooperation with the Latin American Cooperative Oncology Group (LACOG) on Translational Cancer Medicine; May 4-6, 2017; São Paulo, Brazil. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(1_Suppl):Abstract nr A66.