Dysregulation of epigenetic mechanisms is known to play an important role in the development and progression of cancer. One such mechanism is manifested as altered levels of histone modifications involved in regulating gene transcription. N-terminal histone tails can have a variety of modifications, such as phosphorylation, methylation and acetylation at specific amino acid residues which are conserved throughout eukaryotes and function by altering chromatin structure and creating binding sites for chromatin readers, writers or erasers.
Numerous studies have reported aberrant global levels of several histone H3 and H4 post-translational modifications (PTMs) in a wide range of solid tumor types. These changes have been shown to be predictive of clinical outcome, raising the possibility that histone modifications have potential as epigenetic biomarkers. Clinical samples have immense potential for biomarker identification since they are often accompanied with valuable information pertaining to patient history, treatment courses and disease outcome. The preferred method for clinical sample preservation is formalin-fixation followed by paraffin embedding (FFPE). While extraction and downstream analysis of DNA and RNA from FFPE samples is now routine, proteomic studies of FFPE samples is hampered by extensive protein cross-linking generated by formalin fixation. Analysis of histone PTMs in patient archival samples is limited to low-throughput immunohistochemical staining, and is not an ideal approach for mining large sample cohorts for biomarker identification. Western blot or ELISA methods, which have large sample requirements, are simply not an option for FFPE samples.
We have developed a multiplex bead-based ELISA assay which enables simultaneous interrogation of thirteen histone H3 PTMs. The assay is performed in 96-well plates and is ideally suited for profiling histone modification levels in limiting or small samples. We will present the application of this technology in a variety of sample types including frozen tissue, formaldehyde-cross linked cells and tissues, and in small molecule inhibitor screens with as few as 2,000 cells per well. The ability to simultaneous detect up to thirteen histone H3 PTMs provides a unique feature that enables determination of for on-target and off-target effects within the same sample.
Citation Format: Mary Anne Jelinek, Melissa Ritland, AJ Westergren. A multiplex histone H3 PTM assay for epigenetic biomarker discovery in tissue biopsy and archived clinical samples [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2392. doi:10.1158/1538-7445.AM2017-2392