Background and objectives: CD45 is a critical regulator of signaling threshold in immune cells. There are clinical and animal studies suggesting that the CD45-negative phenotype is the phenotype of progressive multiple myeloma (MM). The aims of this study were to confirm this hypothesis and to test the prognostic value of CD45 expression in newly diagnosed MM patients.
Design and methods: In a retrospective study of 95 newly diagnosed MM patients treated with high dose therapy we used 4-color flow cytometry to determine CD45 expression and correlated the immunophenotipic data with clinical data.
Results: Thirty of 95 patients (31.5%) lacked CD45 expression at diagnosis. The CD45 phenotype significantly affected the overall survival (OS) of the patients, like the most common presenting prognostic parameters analyzed including b-2-microglobulin, age and 14q32 translocations. CD45 negative MM patients had a significantly worse OS than did CD45 positive cases of MM: 28.7% cumulative survival at 4 years, median 42 months vs not reached; p = 0.004. Furthermore, CD45 remained the only parameter adversely affecting OS in multivariate analysis.
Interpretation and conclusions: The CD45 negative phenotype could reflect the phenotype of progressive disease in relation to the intrinsic malignancy of the MM clone. Indeed, CD45 negative myeloma cells appear to have a greater capacity to circulate, disseminate and clone as well as being less sensitive to apoptosis.