Absolute quantification of tumor antigens using embedded MHC-I isotopologue calibrants
Lauren Stopfer, Aaron S. Gajadhar, Bhavin Patel, Sébastien Gallien, Dennie T. Frederick, Genevieve M. Boland, Ryan J. Sullivan, Forest M. White
Abstract
Absolute quantification measurements (copies per cell) of peptide major histocompatibility complex (pMHC) antigens are necessary to inform targeted immunotherapy drug design; however, existing methods for absolute quantification have critical limitations. Here, we present a platform termed SureQuant-IsoMHC, utilizing a series of pMHC isotopologues and internal standard-triggered targeted mass spectrometry to generate an embedded multipoint calibration curve to determine endogenous pMHC concentrations for a panel of 18 tumor antigens. We apply SureQuant-IsoMHC to measure changes in expression of our target panel in a melanoma cell line treated with a MEK inhibitor and translate this approach to estimate antigen concentrations in melanoma tumor biopsies.