The Oncoprotein Phenotype of Plasma Cells from Patients with Multiple Myeloma

Abstract

The expression of 6 different oncoproteins and 2 tumour suppressor gene products in the plasma cells of 63 bone marrow samples was used to determine a profile of the oncogenic phenotype of patients with multiple myeloma. Dual label flow cytometry after periodatelysine paraformaldehyde fixation was used to detect cell surface phenotype and intracellular protein expression simultaneously. The normal range for both the incidence and intensity of expression was determined for each protein by analysing plasma cells (high CD38 intensity) in 22 normal bone marrow samples. The percentage of myeloma patients with a greater than normal incidence of plasma cells expressing these proteins was 53% for c-myc, 28% for Rb, 28% for bcl-2, 27% for c-fos, 24% for p53 wild, 22% for p53 mutant, 13% for c-neu and 13% for pan-ras. When a panel of 8 antibodies was used, 82% of the samples (n = 28) had an increased incidence of expression by at least one oncoprotein or tumour suppressor gene product. The 5 patients with a normal incidence of expression of all 8 proteins were in plateau stage and 4 had not received chemotherapy for more than 12 months. The number of patients with an increased incidence of expression by 2 or more oncoproteins was significantly greater (X2 = 9.0; p < 0.005) in progressive disease (55%) than in stable disease (14%) but there was no specific phenotype pattern associated with progressive disease. All 6 oncoproteins and both tumour suppressor gene products had a greater incidence and intensity of expression in progressive than in stable disease. The expression of c-myc oncoprotein correlated with c-myc mRNA expression in the same samples (n = 10) but c-myc did not correlate with either the plasma cell labelling index (r = -0.15) nor serum thymidine kinase (r = 0.10). Our results suggest that there is a heterogeneous, non-systematic but almost universal presence of activated oncogenes and tumour suppressor genes in the plasma cells of patients with multiple myeloma and that disease progression is associated with the accumulation of a variety of secondary genetic changes which confer increased malignant behaviour.

Immunophenotypic Aberrations, DNA Content, and Cell Cycle Analysis of Plasma Cells in Patients with Myeloma and Monoclonal Gammopathies

“…The fact that MG patients acquire chromosomal changes gradually within several related plasma cell subclones (120) and that some chromosomal abnormalities, such as monosomy 13, are associated with transition of MG to myeloma also supports this hypothesis (46,47). Oncogenes also play a role in the conversion of MG into myeloma as well in the proliferation and survival of malignant plasma cells (53)(54)(55)(56)(57). For instance, loss or inactivation of Rb1 and p53 tumor suppressor (54) and mutational activation of N-and K-ras oncogenes (55,57) are frequent findings in myeloma but not in MG, suggesting that these molecular events occur late during the process of oncogenesis.…”

“…Phenotypic and DNA abnormalities proved to be useful in predicting the clinical aggressiveness and response to therapy (42,43) as well as in distinguishing between MG and myeloma (44,45). Other variables that may improve accuracy in predicting both progression of MG and prognosis of myeloma patients are cytogenetic abnormalities (46 -52), activation of oncogenes or inactivation of tumor suppressor genes (53)(54)(55)(56)(57), imbalance between apoptosis-suppressor and -inducer proteins (58,59) and multidrug resistance gene expression (41,60,61).…”

Paraproteinemia, plasmacytoma, myeloma and HIV infection

“…[19][20][21][22][23][24] Comparison of myelomatous and normal plasma cells has revealed activation of various oncogenes, 19,24 disruption of tumor suppressor genes, 19,24 mutations in the IL-6 transducer protein gp130, 22 and altered expression of cell differentiation (CD) antigens. 25,26 Further progression of multiple myeloma, characterized clinically by escape from the plateau phase, may be mediated by these factors as well as additional mechanisms such as enhanced nucleoside transport and multidrug resistance.…”

Expression of Bcl-2 family of proteins in fresh myeloma cells

“…4 Expression of Bcl-2 in myeloma cells has been investigated by some groups. 5,6 Sangfelt et al 7 reported that high level expression of Bcl-2 was correlated with resistance to IFN. Ong et al 8 showed that patients who survived for an extremely short time following diagnosis exhibited low levels of expression of Bcl-2 in myeloma cells.…”