Identification of targets for rational pharmacological therapy in childhood craniopharyngioma

Abstract

Introduction: Pediatric adamantinomatous craniopharyngioma (ACP) is a histologically benign but clinically aggressive brain tumor that arises from the sellar/suprasellar region. Despite a high survival rate with current surgical and radiation therapy (75-95 % at 10 years), ACP is associated with debilitating visual, endocrine, neurocognitive and psychological morbidity, resulting in excheptionally poor quality of life for survivors. Identification of an effective pharmacological therapy could drastically decrease morbidity and improve long term outcomes for children with ACP.

Results: Using mRNA microarray gene expression analysis of 15 ACP patient samples, we have found several pharmaceutical targets that are significantly and consistently overexpressed in our panel of ACP relative to other pediatric brain tumors, pituitary tumors, normal pituitary and normal brain tissue. Among the most highly expressed are several targets of the kinase inhibitor dasatinib - LCK, EPHA2 and SRC; EGFR pathway targets - AREG, EGFR and ERBB3; and other potentially actionable cancer targets - SHH, MMP9 and MMP12. We confirm by western blot that a subset of these targets is highly expressed in ACP primary tumor samples.

Conclusions: We report here the first published transcriptome for ACP and the identification of targets for rational therapy. Experimental drugs targeting each of these gene products are currently being tested clinically and pre-clinically for the treatment of other tumor types. This study provides a rationale for further pre-clinical and clinical studies of novel pharmacological treatments for ACP. Development of mouse and cell culture models for ACP will further enable the translation of these targets from the lab to the clinic, potentially ushering in a new era in the treatment of ACP.

Figures

Fig. 1

Gene expression of potential targets for therapeutic intervention in ACP. Expression of the indicated genes in ACP relative to a broad range of pediatric and adult brain tumor types: atypical teratoid/rhabdoid tumor (AT/RT), choroid plexus papilloma (CPP), ependymoma (EPN), glioblastoma multiforme (GBM), medulloblastoma (MED), meningioma (MEN), pilocytic astrocytoma (PA), primitive neuroectodermal tumor (PNET); peripheral pediatric solid tumors: malignant peripheral nerve sheath tumors (MPNST), rhabdomyosarcoma (RMS); in addition to malignant (pituitary adenoma) and normal pituitary (PT and N_P respectively); and normal brain and choroid plexus (N_B and N_CP respectively). Dasatinib targets, LCK (lymphocyte-specific protein tyrosine kinase), EPHA2 (ephrin type-A receptor 2) and SRC (SRC proto-oncogene, non-receptor tyrosine kinase) (a). Sonic hedgehog homolog (b). Matrix metalloproteases 9 & 12 (c). EGF pathway genes (d). Values are expressed as log2 gene expression. Horizontal red bars represent the mean, and error bars represent standard error of the mean (SEM)

Fig. 2

Overexpression of active protein isoforms for SHH, MMP9 and MMP12 in ACP relative to other common pediatric brain tumors and normal brain. Western blot analysis was used to determine latent preforms and cleaved active isoforms of the indicated proteins. (Abbr: AT/RT, atypical teratoid/rhabdoid tumor; EPN, ependymoma; GBM, glioblastoma; MED, medulloblastoma; PA, pilocytic astrocytoma; Norm, normal brain)

Fig. 3

Transcriptome cluster analysis reveals similarities between ACP, meningioma and rhabdomyosarcoma, with no relationship to adult pituitary or pituitary adenoma. Unbiased hierarchical clustering analysis of a panel of craniopharyngioma tumor samples compared to other pediatric tumors, normal brain tissue, pituitary tissue and adult pituitary adenomas. The top 30 % most variant genes, were used to generate the clustering dendrogram above. (AT/RT, atypical teratoid/rhabdoid tumor; CPP, choroid plexus papilloma; MPNST, malignant peripheral nerve sheath tumor; GBM, glioblastoma multiforme)

Fig. 4

Expression of the indicated genes in pediatric ACP. p63 gene expression in the indicated tumor and normal tissue types (a). Wnt pathway (b) and β-catenin (TCF/LEF) target gene expression (c). Genes at chromosome 4p5 locus (d). Values are expressed as log2 (a) or as fold-difference of individual ACP samples relative to the average of all other tumor and normal samples (b-d)

Fig. 5

Expression of the indicated developmental and cancer-related genes in individual pediatric ACP samples. Epidermal growth factor (EGF) family genes (a). Genes involved in pituitary development (b). Developmental genes from the Notch (c), Six transcription factor (d), Sonic hedgehog (Shh) (e), Bone morphogenetic protein (BMP) and Fibroblast growth factor (FGF) (f) families. Values expressed are fold-difference of individual ACP samples relative to the average of all other tumor and normal samples