Abstract 4809: Elucidating acquired drug resistance in multiple myeloma using expression proteomics and phosphorylation profiling

Introduction: Multiple myeloma (MM) is an incurable malignancy of the plasma cell. While patients may initially respond to treatment, the development of acquired drug resistance (ADR) is a consistent feature of the disease. In order to understand the processes involved in ADR, proteomics is used to examine multiple phenotypic outcomes associated with drug resistance in cell line models. Both protein expression and phosphorylation data will be mined for biological mechanisms and candidate biomarkers for detection of ADR in MM patients. Experimental Procedures: Using cell line models of melphalan and doxorubicin resistance, protein expression is compared using spectral counts and extracted ion chromatograms from GeLC-MS/MS data. In addition, phosphorylation profiles are created using SCX peptide fractionation with IMAC phosphopeptide enrichment prior to LC-MS/MS cataloging. Additional hypothesis-driven experiments are conducted using liquid chromatography-multiple reaction monitoring mass spectrometry (LC-MRM) for targeted quantification. In addition to steady state comparisons between naive and drug resistant cells, initial responses to therapy are also evaluated. Assays developed for interrogation of cell line models can be translated to patient specimens. Data Summary: GeLC-MS/MS expression measurements typically produce semi-quantitative data for > 2,000 proteins (2+ peptides per protein). Phosphorylation analysis has produced a catalog of > 1,000 sites across the entire group of cell lines. Data are manually evaluated for proteins relevant to MM and mapped to pathways using Metacore GeneGO. Because both melphalan and doxorubicin produce DNA damage, common processes include DNA damage repair, cell cycle regulation, and apoptosis. Each drug also produces unique phenotypes. For example, doxorubicin resistance is mediated in large part by multidrug resistance proteins; melphalan resistance is marked by increases in redox proteins. LC-MRM of heat shock proteins and Bcl-2 family apoptosis regulators supplements existing data. LC-MRM is also used to examine the response in the expression of proteins involved in ADR at the onset of treatment in naive MM cells. Conclusions: Proteomics can further elucidate the biological processes involved with ADR in MM to generate candidate biomarkers. LC-MRM is used in cell line models to develop a platform for assessing panels of proteins related to ADR, which can ultimately be translated to assist in clinical decisions for tailoring therapy to the individual patient. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4809. doi:1538-7445.AM2012-4809