Abstract B8: Multiplex quantification of immunomodulatory proteins in tissue and plasma using next-gen targeted MRM mass spectrometry

Abstract

Abstract Quantifying the many immunomodulatory proteins in the “cancer-immunity cycle” is critical for both patient selection and development of novel immunotherapies. Conventional technologies to measure proteins (IHC, ELISA, Western blot, flow cytometry) are often semiquantitative, not multiplexable, feature poor specificity, and are difficult to develop. Due to these limitations, investigators have turned to mRNA-based measurements to infer protein expression of immunomodulatory factors. However, as has been unequivocally demonstrated for human breast, colorectal, and ovarian cancers (Pubmed IDs: 27251275, 25043054, 27372738), RNA levels can be poor predictors of protein levels or activity. Thus, direct quantification of proteins is desirable. As part of the National Cancer Institute’s Cancer Moonshot, we are developing >300 multiplex assays for quantifying immunomodulatory proteins in tissue and plasma using a next-gen technology for protein quantification, based on targeted multiple reaction monitoring mass spectrometry (MRM-MS). MRM-MS complements traditional immunoassays by enabling highly specific, precise, harmonizable quantification of proteins in biospecimens, even at high multiplex levels. As proof of concept, we will present a novel multiplex assay based on next-gen MRM-MS for quantification of 47 immunomodulatory proteins in plasma and/or tumor tissue. The technology uses immunoaffinity enrichment coupled with MRM-MS (immuno-MRM assay). Assay bioanalytical validation was conducted in accordance with industry standards for use in FFPE tissue and plasma matrices and included determination of limits of detection, linear range of response, intraday and interday repeatability, stability of analytes in sample processing, and characterization of reproducibility of endogenous analyte measurement. The mean linear range was over three orders of magnitude with median intra- and interday CVs less than 10%. The characterized assays are being applied to a panel of tumor specimens from a variety of cancer types to document detection and determine minimum sample requirements. Additional assay panels are under development to provide measurements of up to 350 immunomodulatory proteins. Citation Format: Jeffrey R. Whiteaker, Lei Zhao, Richard G. Ivey, Julia Voytovich, Regine M. Schoenherr, Dongqing Huang, Jacob J. Kennedy, Amanda G. Paulovich. Multiplex quantification of immunomodulatory proteins in tissue and plasma using next-gen targeted MRM mass spectrometry [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr B8.