Faculty Bibliography

The aim of this study was to develop a flow cytometric test to quantitate low levels of circulating myeloma plasma cells, and to determine the relationship of these cells with disease stage. Cells were characterized using five-parameter flow cytometric analysis with a panel of antibodies, and results were evaluated by comparison with fluorescent consensus-primer IgH-PCR. Bone marrow myeloma plasma cells, defined by high CD38 and Syndecan-1 expression, did not express CD10, 23, 30, 34 or 45RO, and demonstrated weak expression of CD37 and CD45. 65% of patients had CD19- 56+ plasma cells, 30% CD19- 56(low), and 5% CD19+ 56+, and these two antigens discriminated myeloma from normal plasma cells, which were all CD19+ 56(low). Peripheral blood myeloma plasma cells had the same composite phenotype, but expressed significantly lower levels of CD56 and Syndecan-1, and were detected in 75% (38/51) of patients at presentation, 92% (11/12) of patients in relapse, and 40% (4/10) of stem cell harvests. Circulating plasma cells were not detectable in patients in CR (n = 9) or normals (n = 10), at a sensitivity of up to 1 in 10,000 cells. There was good correlation between the flow cytometric test and IgH-PCR results: myeloma plasma cells were detectable by flow cytometry in all PCR positive samples, and samples with no detectable myeloma plasma cells were PCR negative. Absolute numbers decreased in patients responding to treatment, remained elevated in patients with refractory disease, and increased in patients undergoing relapse. We conclude that flow cytometry can provide an effective aternative to IgH-PCR that will allow quantitative assessment of low levels of residual disease.

AIM/OBJECTIVE:To assess whether p53 gene mutation is important in the pathogenesis and progression of multiple myeloma. METHODS:Thirty eight DNA samples (derived predominantly from bone marrow) obtained from 31 patients with multiple myeloma were examined for mutations in p53 exons 5-9 by polymerase chain reaction single strand conformation polymorphism. Twenty three samples were analysed at the time of diagnosis (one patient had plasma cell leukaemia), three in plateau phase, and 12 at relapse (one plasma cell leukaemia and one extramedullary relapse). RESULTS:One p53 mutation was detected in this group of patients (3.2%). This was seen in the diagnostic bone marrow sample of a 35 year old man with stage IIA disease and occurred in exon 6 as a result of a silent A to G transition at codon 213 (CGA-->CGG), a polymorphism that has been reported in about 3% of breast and lung tumours. CONCLUSIONS:p53 gene mutations are rare events in multiple myeloma and would seem to be of limited value as a prognostic factor.