ABSTRACT
Capicua (CIC) is a transcriptional repressor that counteracts activation of genes downstream of receptor tyrosine kinase (RTK)/Ras/ERK signaling. It is well-established that tumorigenesis, especially in glioblastoma (GBM), is attributed to hyperactive RTK/Ras/ERK signaling. While CIC is mutated in other tumors, here we show that CIC has a tumor suppressive function in GBM through an alternative mechanism. We find that CIC protein levels are negligible in GBM due to continuous proteasome-mediated degradation, which is mediated by the E3 ligase PJA1 and show that this occurs through binding of CIC to its DNA target and phosphorylation on residue S173. PJA1 knockdown increased CIC stability and extended survival using in-vivo models of GBM. Deletion of the ERK binding site resulted in stabilization of CIC and increased therapeutic efficacy of ERK inhibition in GBM models. Our results provide a rationale to target CIC degradation in Ras/ERK-driven tumors, including GBM, to increase efficacy of ERK inhibitors.
Subject(s)
Glioblastoma/metabolism , Glioblastoma/pathology , Repressor Proteins/metabolism , Animals , Carcinogenesis/metabolism , Carcinogenesis/pathology , Cell Line, Tumor , Cell Proliferation/genetics , Cell Proliferation/physiology , Cell Transformation, Neoplastic/metabolism , Cell Transformation, Neoplastic/pathology , Drosophila , Drosophila Proteins/genetics , Drosophila Proteins/metabolism , Gene Expression Regulation, Developmental/genetics , Gene Expression Regulation, Developmental/physiology , HEK293 Cells , Humans , Male , Mice, Inbred C57BL , Mice, Transgenic , Mutation , Repressor Proteins/genetics , Signal Transduction/genetics , Signal Transduction/physiologyABSTRACT
An electrical impedance tomography (EIT) system images internal conductivity from surface electrical stimulation and measurement. Such systems necessarily comprise multiple design choices from cables and hardware design to calibration and image reconstruction. In order to compare EIT systems and study the consequences of changes in system performance, this paper describes a systematic approach to evaluate the performance of the EIT systems. The system to be tested is connected to a saline phantom in which calibrated contrasting test objects are systematically positioned using a position controller. A set of evaluation parameters are proposed which characterize (i) data and image noise, (ii) data accuracy, (iii) detectability of single contrasts and distinguishability of multiple contrasts, and (iv) accuracy of reconstructed image (amplitude, resolution, position and ringing). Using this approach, we evaluate three different EIT systems and illustrate the use of these tools to evaluate and compare performance. In order to facilitate the use of this approach, all details of the phantom, test objects and position controller design are made publicly available including the source code of the evaluation and reporting software.
