EXTH-48. SMALL MOLECULAR TARGETING OF HOX-PBX BINDING IN GLIOBLASTOMA AS A NOVEL THERAPEUTIC TREATMENT

Abstract

The HOX genes encode a family of transcription factors that play an essential role in embryonic patterning, but are dysregulated in numerous cancers, including glioblastoma. Previous research indicates that HOX genes are overexpressed expressed in glioblastoma tumours compared to healthy astrocytes. HXR9, a small hexapeptide, was shown to have strong cytotoxic effects on glioblastoma ‘parental’ and cancer stem cells. In this study we assessed whether a new small molecular mimic (SMM) of HXR9 had similar or increased therapeutic potential. Glioblastoma cell lines were treated with varying doses of HXR9 and SMM, with cell viability determined by MTS assay. Mode of death was determined via annexin-V/7-AAD counterstain assay. RT-PCR and western blot analysis was used to determining the molecular pathway utilised by HXR9 and SMM. SMM was shown to be cytotoxic in, a dose dependent manner, in all cell lines used. Some cell lines exhibited increased sensitivity to SMM when compared to HXR9 treatment. Mode of death was determined to be apoptosis. C-Fos, a sub unit of the pro-apoptotic complex AP-1, was shown to be elevated following treatment with both HOX-PBX inhibitors. C-Fos up regulation was accompanied in all cell lines with a sharp down regulation of Bcl-2. C-Jun, an important subunit in AP-1, was shown to be unaffected by treatment, but was shown to be expressed in all cell lines prior to treatment. Results show that aberrantly expressed HOX and PBX proteins in glioblastoma can be targeted with cytotoxic effect. HXR9 and SMM treatment causes apoptosis through up regulation of C-Fos, and subsequent down regulation of Bcl-2. This mechanism may be caused by an increase of AP-1 activity, which in turn causes suppression in Bcl-2 expression.