H. Robert Bergen, III (Presenter)
Mayo Clinic
Bio: Dr. Bergen has been developing MS-based clinical tests since 1974 starting with an isotope dilution assay for Vitamin A. He is currently developing proteomics-based clinical tests at the Mayo Clinic. Some of the tests translated to the clinical lab include transthyretin variants, alpha-1-antitrypsin, amyloid plaque isotyping, carbohydrate deficient glycoprotein syndrome, myostatin and related binders. He is currently interested in tests for measuring minimal residual disease in multiple myeloma and utilizing nanobodies as affinity reagents.
Authorship: H. Robert Bergen, III, Angela Dispenzieri, David R. Barnidge, Marina Ramirez-Alvarado, Surendra Dasari, David L. Murray
Mayo Clinic, Rochester MN 55905
| Short Abstract Therapeutic effectiveness in multiple myeloma (MM) currently requires monitoring the relevant myeloma cells in a bone marrow sample. Because these plasma cell clones are producing a clonal antibody we sought to identify the antibody the clone was producing directly. Utilizing blood plasma where the M-protein is >0.8g/dL we have been able to identify unique tryptic peptides corresponding to immunoglobulin light chain variable regions belonging to each patients clone. Subsequent blood samples are utilized to measure MRD and the target peptide corresponding to each patients clone is monitored. |
Long Abstract
Introduction
Current methods of measuring minimal residual disease (MRD) in multiple myeloma require a bone marrow aspiration to detect the level of relevant myeloma cells. However, these myeloma plasma cells are producing a monoclonal antibody that circulates in the peripheral circulation that can easily be detected in the early stages of disease by protein electrophoresis (M-spike; SPEP). Another approach would be to detect the level of circulating clonal immunoglobulin secreted by the myeloma plasma cells.
Methods
High M-spike serum is separated by SDS-PAGE and the light chain band excised, reduced, alkylated and analyzed by LC-MS/MS. Complementarity determining region (CDR) peptides are identified with de novo and database searches and peptides mapping to CDRs selected. MRD is determined by monitoring the target CDR peptides in subsequent serum samples after immunoprecipitation of the appropriate class (kappa or lambda).
Results
Analysis of 62 patients with no detectable disease by IHC (n=20) or 6-color flow cytometry (MFC) indicated a target peptide could be detected in 57 for an applicability of 91%. Of these 57 patients, all MRD-negative by IHC or MFC, disease was detected in 52 (91%).
Conclusions
Our initial results indicate MRD by LC-MS/MS more sensitive than IHC or MFC and does not require a bone marrow aspirate.
References & Acknowledgements:
This work has recently been accepted for publication; Bergen et al., Clinical Chemistry.
Research reported in this manuscript was supported by The National Cancer Center of the National Institutes of Health (NIH) under award R21CA187462 and CTSA Grant Number UL1 TR000135 from the National Center for Advancing Translational Science (NCATS) (H.R.B). The work is solely the responsibility of the authors and does not necessarily represent the official views of the NIH. Support was also provided by Gordon C. and Elizabeth W. Gilroy (H.R.B), the JABBS Foundation, the Robert A. Kyle Hematologic Malignancies Program, and the Mayo Clinic Center for Individualized Medicine (H.R.B).
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