Establishment of Anti-Human ATRX Monoclonal Antibody AMab-6

Epitope mapping of an anti-alpha thalassemia/mental retardation syndrome X-linked monoclonal antibody AMab-6

The alpha-thalassemia/mental-retardation-syndrome-X-linked (ATRX) gene is located on the q arm of the X chromosome. ATRX gene mutations were first discovered in pancreatic neuroendocrine tumors, and subsequently in other cancer subtypes, including gliomas. Molecular subgrouping of gliomas has been more important than conventional histological classifications. Mutations in the isocitrate dehydrogenase (IDH), telomerase reverse transcriptase (TERT) promoter, and ATRX and the codeletion of chromosomes 1p/19q are used as biomarkers for diagnosing the subtypes of diffuse gliomas. We recently developed a sensitive monoclonal antibody (mAb) AMab-6 against ATRX by immunizing mice with recombinant human ATRX. AMab-6 can help to detect ATRX mutations via Western blotting and immunohistochemical analyses. In this study, we characterized the binding epitope of AMab-6 using enzyme-linked immunosorbent assay (ELISA), Western blotting, and immunohistochemical analysis, and found that Gln2368 of ATRX is critical for AMab-6 binding to ATRX. Our findings could be applied to the production of more functional anti-ATRX mAbs.

Elevated TERT Expression in TERT-Wildtype Adult Diffuse Gliomas: Histological Evaluation with a Novel TERT-Specific Antibody

Telomerase reverse transcriptase (TERT) is important for the biology of diffuse gliomas. TERT promoter mutations are selectively observed among 1p/19q-codeleted oligodendrogliomas and isocitrate dehydrogenase gene- (IDH-) wildtype glioblastoma (GBM). However, TERT transcripts range widely in various cancers including gliomas, and TERT protein expression has been rarely investigated thus far. It would be thus critical to examine the expression level of TERT in tumors in addition to its mutational status, and sensitive and specific methods are urgently needed to examine TERT protein expression for the assessment of TERT biology in gliomas. Using our newly developed TERT-specific monoclonal antibody (TMab-6) applicable to human tissue, we found an unexpected increase in TERT expression in TERT-wildtype as well as TERT-mutated gliomas and in tumor vasculature. This is the first extensive analysis on the expression of TERT immunoreactivity in human glioma tissue, suggesting that TERT protein expression may be regulated by several mechanisms in addition to its promoter mutation.

Development of RAP Tag, a Novel Tagging System for Protein Detection and Purification

Affinity tag systems, possessing high affinity and specificity, are useful for protein detection and purification. The most suitable tag for a particular purpose should be selected from many available affinity tag systems. In this study, we developed a novel affinity tag called the “RAP tag” system, which comprises a mouse antirat podoplanin monoclonal antibody (clone PMab-2) and the RAP tag (DMVNPGLEDRIE). This system is useful not only for protein detection in Western blotting, flow cytometry, and sandwich enzyme-linked immunosorbent assay, but also for protein purification.