Pharmacogenomic Analyses Implicate B Cell Developmental Status and <i>MKL1</i> as Determinants of Sensitivity toward Anti-CD20 Monoclonal Antibody Therapy
George W. Small,
Farida S. Akhtari,
Adrian J. Green,
Tammy M. Havener,
Michael Sikes,
Julia Quintanhila,
Ricardo D. Gonzalez,
David M. Reif,
Alison A. Motsinger-Reif,
Howard L. McLeod,
Tim Wiltshire
Affiliations
George W. Small
Pharmacotherapy and Experimental Therapeutics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
Farida S. Akhtari
Biostatistics and Computational Biology Branch, Division of Intramural Research, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
Adrian J. Green
Department of Biological Sciences, Bioinformatics Research Center, North Carolina State University, Raleigh, NC 27695, USA
Tammy M. Havener
Structural Genomics Consortium and Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
Michael Sikes
Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, USA
Julia Quintanhila
Clinical Development, Foundation Medicine, Boston, MA 02141, USA
Ricardo D. Gonzalez
Pharmacotherapy and Experimental Therapeutics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
David M. Reif
Predictive Toxicology Branch, Division of Translational Toxicology, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
Alison A. Motsinger-Reif
Biostatistics and Computational Biology Branch, Division of Intramural Research, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
Howard L. McLeod
Center for Precision Medicine and Functional Genomics, Utah Tech University, 225 South University Ave, St. George, UT 84770, USA
Tim Wiltshire
Pharmacotherapy and Experimental Therapeutics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
Monoclonal antibody (mAb) therapy directed against CD20 is an important tool in the treatment of B cell disorders. However, variable patient response and acquired resistance remain important clinical challenges. To identify genetic factors that may influence sensitivity to treatment, the cytotoxic activity of three CD20 mAbs: rituximab; ofatumumab; and obinutuzumab, were screened in high-throughput assays using 680 ethnically diverse lymphoblastoid cell lines (LCLs) followed by a pharmacogenomic assessment. GWAS analysis identified several novel gene candidates. The most significant SNP, rs58600101, in the gene MKL1 displayed ethnic stratification, with the variant being significantly more prevalent in the African cohort and resulting in reduced transcript levels as measured by qPCR. Functional validation of MKL1 by shRNA-mediated knockdown of MKL1 resulted in a more resistant phenotype. Gene expression analysis identified the developmentally associated TGFB1I1 as the most significant gene associated with sensitivity. qPCR among a panel of sensitive and resistant LCLs revealed immunoglobulin class-switching as well as differences in the expression of B cell activation markers. Flow cytometry showed heterogeneity within some cell lines relative to surface Ig isotype with a shift to more IgG+ cells among the resistant lines. Pretreatment with prednisolone could partly reverse the resistant phenotype. Results suggest that the efficacy of anti-CD20 mAb therapy may be influenced by B cell developmental status as well as polymorphism in the MKL1 gene. A clinical benefit may be achieved by pretreatment with corticosteroids such as prednisolone followed by mAb therapy.
