Multicolor interphase cytogenetics for the study of plasma cell dyscrasias

Abstract

Specific chromosomal abnormalities such as chromosome 13 deletions and some translocations affecting the immunoglobulin heavy chain (IGH) gene, namely t(4;14)(p16;q32) and t(14;16)(q32;q23) have been associated with an adverse prognosis in multiple myeloma. Conventional cytogenetic techniques fail to detect these aberrations in the majority of cases. Thus, we have developed a novel set of interphase fluorescence in situ hybridization (I-FISH) assays targeting those regions frequently lost on chromosome 13 as well as those oncogenes most recurrently involved in translocations with the IGH locus in multiple myeloma, i.e. IRTA1/2 (1q21), FGFR3/MMSET (4p16), CCND3 (6p21), IRF4 (6p25), CCND1 (11q13), MAF (16q23), and MAFB (20q12). The probes were combined in a multicolor fashion to develop novel multicolor I-FISH (MI-FISH) assays, whose validity and applicability was evaluated in negative controls and in a series of 13 plasma cell neoplasias. Additionally, a combination of the novel MI-FISH assays with staining for the plasma cell-specific antigen VS38c by means of multicolor FICTION (M-FICTION, fluorescence immunophenotyping and interphase cytogenetics as a tool for the investigation of neoplasms) allowed us to selectively analyze the plasma cell compartment, and thereby to increase the assay sensitivity.