Simultaneous fluorescence immunophenotyping and interphase cytogenetics (fiction) in multiple myeloma

Multiple myeloma (MM) is a disease characterized by a proliferation of malignant plasma cells (PC) in the bone marrow; survival rate varies greatly but it is generally poor and related to abnormalities of specific chromosomes, as translocations involving the Ig heavy chain gene at 14q32 or partial/ total deletion of chromosome 13. Conventional cytogenetics of MM is difficult owing to the low proliferation rate of malignant PC; it has to be considered poorly informative if not associated to separation or immunophenotyping techniques. We present the results of FICTION analysis of patients at the beginning of the disease.This technique combines immunofluorescence and FISH analysis on interphase cells. Immunophenotyping was performed by a primary antibody against CD138 (also called syndecan 1), a heparan sulfate rich membrane glycoprotein expressed on normal and malignant plasma cells only, followed by a secondary antibody AMCA-labeled. Interphase FISH experiments were performed on the same slide using a probe (Texas red-labeled) specific for the RB (13q14.2) locus, associated with Tel (13q) DNA probe (fluoresceine-labeled).Results: PC were detected by the intense signal of AMCA, while chromosome 13 probes were analyzed with Texas Red- and FITC-filters. The results obtained with FICTION procedure were compared with those obtained with the FISH analysis on interphase cells and chromosome samples using the same probes.