Abstract 3453: Induction of differentiation in high-risk ependymoma stem-like cells by treatment with the HDAC inhibitor Vorinostat

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Despite intensive radio- and chemotherapy, incompletely resectable ependymomas are associated with a poor prognosis, and novel treatments have been difficult to develop due to the lack of appropriate pre-clinical models. We here report on the generation of a first pre-clinical ependymoma model (termed DKFZ-EP1NS) with long term self-renewal capacity, and the use of histonedeacetylase-inhibitors (HDACi) in the treatment of highly aggressive ependymoma cells. We were able to isolate ependymoma cells and grow them in spheres using serum-free neurosphere media conditions. We then characterized them for genetic aberrations, marker expression and tumorigeneity in an orthotopic xenotransplant model. The DKFZ-EP1NS cells were kept under neurosphere culture conditions for up to 9 months, displaying long term self-renewal. Freezing for storage and thawing was routinely possible. Genetic aberrations (loss at 1p36, chromosome 9 incl. homozygous deletion at CDKN2A and 14q) found in the DKFZ-EP1NS corresponded to the aberrations discovered in the primary ependymoma and subsequent recurrent tumors of the patient. DKFZ-EP1NS cells display several markers associated with normal stem cells as well as cancer stem cells. Orthotopically transplanted mice displayed first tumors after 9 months in the striatum of the brain, and tumors phenotypically recapitulated the original tumor. Serial transplantation yielded secondary tumors in half the time. Subcutaneous or intraperitoneal transplantation did not recapitulate the original intracranial histopathological phenotype, indicating that the orthotopic niche is required for the induction of the chracteristic phenotype. Although the cells were resistant to commonly used chemotherapeutic agents, they responded to HDACi-treatment in vitro at doses comparable to peak plasma levels in patients. In vitro-treatment of DKFZ-EP1NS cells with the HDACi Vorinostat led to morphological changes resembling neuronal differentiation. Indeed, neuronal markers showed a marked upregulation as measured by quantitative RT-PCR. Finally, stem cell-specific properties such as the neurosphere initiation capacity were lost upon treatment with Vorinostat in vitro. In summary, we were able to establish a first ependymoma cell line with stem cell-like properties recapitulating human disease in an orthotopic xenograft model, allowing for pre-clinical evaluation of drugs targeting the cancer stem cell compartment in ependymoma. Our data derived from applying well known drugs to this in vitro-model suggest that Vorinostat may have differentiation potential in the treatment of ependymoma cells resistant to conventional chemotherapeutic drugs in vivo as well. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3453. doi:10.1158/1538-7445.AM2011-3453