Occurrence of dysregulated oncogenes in primary plasma cells representing consecutive stages of myeloma pathogenesis: indications for different disease entities.

This study investigated the expression pattern in primary plasma cells (PCs) of putative oncogenes suggested to be involved in multiple myeloma (MM) development. cDNA archives were generated by global reverse transcription polymerase chain reaction from CD38++/CD19-/CD56-/++ aberrant PCs of a prospective cohort of 96 subjects, including healthy individuals, patients with monoclonal gammopathies of undetermined significance (MGUS), MM and MM with extramedullary manifestations (ExMM). The cDNA archives were analysed quantitatively for expression of the cyclin D1, fibroblast growth factor receptor 3 (FGFR3), C-MYC, C-MAF and cyclin D3 oncogenes. In addition, all patients were screened for IGH-MMSET hybrid transcripts. None of the analysed oncogenes was randomly distributed. C-MYC and cyclin D3 expression increased at the extramedullary transformation stage. Furthermore, C-MYC and cyclin D3 expression in CD56+ MM was similar to MGUS, whereas CD56- MM was similar to ExMM. FGFR3/IGH-MMSET was only observed among CD56+ MM patients, whereas an increased frequency of C-MAF dysregulation was seen among CD56- MM. High cyclin D1 expression levels were identified at similar frequencies at all stages, whereas the frequency of patients with low cyclin D1 levels increased during MM development. These data support the stepwise transformation model accumulating genetic alterations and proliferative capacity during MM initiation and development resulting in different clinical entities.