is frequently expressed in ependymal tumours and associated with prognostic relevant subgroups.

AIMS

An ependymoma shows divergent morphological and molecular features depending on their location. The paired box 6 () transcription factor is a putative tumour suppressor and drives cancer cells towards a stem cell-like state. A transcriptome study reported high expression in ependymal tumours, but data on protein expression are lacking.

METHODS

We, therefore, analysed expression by immunohistochemistry in 172 ependymoma samples and correlated its expression to histology, WHO grade, anatomical location and molecular subgroups.

RESULTS

Mean nuclear expression in ependymoma was 27.5% (95% CI 23.3 to 31.7). expression in subependymoma (mean: 5%) was significantly lower compared with myxopapillary (30%), WHO grade II (26%) and anaplastic ependymoma (35%). Supratentorial ependymomas also displayed significant lower levels (15%) compared with spinal cord tumours (30%). Expression levels in YAP1-fused ependymoma (41%) were higher compared with REL-associated protein (RELA)-fusion positive tumours (17%), while expression was similar in posterior fossa group A (33%) and B (29%) ependymomas. Kaplan-Meier analysis in RELA-fusion positive ependymomas and posterior fossa group B showed a significant better outcome for at or above the cut-off of 19.45% compared with tumours with below the cut-off.

CONCLUSIONS

We demonstrate that is frequently expressed in human ependymal tumours and immunohistochemistry may be helpful in determining prognostic relevant subgroups.