Plasma Membrane Proteomics Identifies Biomarkers Associated with MMSET Overexpression in T(4;14) Multiple Myeloma

// Zhigang Xie 1 , Jayantha Gunaratne 2 , Lip Lee Cheong 3 , Shaw Cheng Liu 1 , Tze Loong Koh 4 , Gaofeng Huang 4 , Walter P. Blackstock 2 , Wee Joo Chng 1,3,4 1 Cancer Science Institute of Singapore, National University of Singapore, Singapore 2 Quantitative Proteomics Group, Institute of Molecular and Cell Biology, Agency for Science, Technology and Research, Singapore 3 Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 4 Department of Haematology-Oncology, National University Cancer Institute of Singapore, National University Healthy System, Singapore Correspondence: Wee Joo Chng, email: // Keywords : SILAC, quantitative proteomics, oncotargets, multiple myeloma Received : May 23, 2013 Accepted : June 24, 2013 Published : June 26, 2013 Abstract Multiple myeloma (MM) is characterized by recurrent chromosomal translocations. MMSET , identified by its fusion to the IgH locus in t(4;14) MM, is universally overexpressed in t(4;14) MM. In order to identify cell surface biomarkers associated with t(4;14) MM for small molecule or antibody based therapies, we knocked down MMSET expression with shRNA and generated a cell line pair from KMS11, a t(4;14) MM cell line. We used quantitative mass spectrometry to identify plasma membrane proteins associated with MMSET overexpression. Using this approach, 50 cell surface proteins were identified as differentially expressed between KMS11 and KMS11/shMMSET. Western blot and flow cytometry analysis indicated SLAMF7 was over-expressed in t(4;14) MM cell lines and down-regulated by MMSET shRNAs. SLAMF7 expression was also confirmed in primary t(4;14) MM samples by flow cytometry analysis. Quantitative RT-PCR and ChIP analysis indicated MMSET might regulate the transcription level of SLAMF7 and be an important functional element for SLAMF7 promoter activity. Furthermore, SLAMF7 shRNA could induce G1 arrest or apoptosis and reduce clonogenetic capacity in t(4;14) MM cells. Overall, these results illustrated SLAMF7 might be a novel cell surface protein associated with t(4;14) MM. It is potential to develop t(4;14) MM targeted therapy by SLAMF7 antibody mediated drug delivery.