Significantly Increased Detection Rate of High Risk Cytogenomic Markers by Interphase FISH on Enriched Plasma Cells.
Ramya Muddasani, Ming Zhao, Lynne V Abruzzo, James M You, L Jeffrey Medeiros, Denise Lovshe, Gary Lu. UT MD Anderson Cancer Center, Houston, TX
Background: Accurate detection of high risk cytogenomic markers is clinically important for the design of appropriately therapy in patients with plasma cell myeloma (PCM). However, plasma cells in routine bone marrow (BM) aspirate samples are often diluted by blood negatively impacting our ability to detect cytogenomic markers by fluorescence in situ hybridization (FISH). The aim of this study was to improve the sensitivity of detection of cytogenomic markers in PCM patients by FISH using enriched plasma cells derived from BM aspirate samples.
Design: Plasma cells from BM aspirates, collected from 20 patients, were enriched using a magnetic cell sorting procedure (Miltenyi Biotec Inc. California) manually allowing for selection of CD138+ cells. iFISH was performed on enriched plasma cells using a standard laboratory protocol. FISH probes in this study were selected to detect high risk cytogenomic markers in PCM: del(17p13)/TP53, del(13q14)/Rb1, amp(1q21)/CKS1B, and IGH rearrangement. Cases positive for IGH rearrangement were followed up using probes for IGH/FGFR3 and/or IGH/MAF. A total of 200 interphase nuclei were analyzed for each sample. FISH studies was also performed on paired samples from the same cases prior to plasma cell enrichment.
Results: Plasma cell counts in the enriched samples ranged from 31% to 93%, compared with 1% to 18% in the pre-enriched samples. Therefore, the enrichment procedure substantially increased the purity of the plasma cell population. High-risk cytogenomic markers were detected in 12/20 (60%) enriched samples compared with 3/20 (15%) pre-enriched samples, yielding a 4 times higher detection rate in the enriched specimens. Of the 12 iFISH-positive cases detected, 5 were positive for TP53 deletion (25%), 4 for Rb1 deletion (20%), 4 for CKS1B amplification (20%), and 5 for IGH rearrangement (25%). Of the 5 cases positive for IGH rearrangement, 2 were positive for IGH/CCND1, 1 for IGH/MAF, 1 with del(IGHV), and 1 with no specific IGH rearrangement. Of the 3 FISH-positive cases from pre-enriched samples, 2 (10%) were positive for deletion TP53, 2 (10%) for deletion Rb1, 1 (5%) for CKS1B amplification, and 1 (5%) for IGH rearrangement (5%).
Conclusions: FISH on CD138-enriched plasma cells significantly increases the detection rate for high-risk cytogenomic markers in PCM. Our data suggest that application of this plasma cell enrichment method in the clinical cytogenetic laboratory is useful for the workup of PCM bone marrow aspirate samples.
Monday, February 28, 2011 8:15 AM
Platform Session: Section G 1, Monday Morning