Expression of Adhesion Molecule CD56 in Tumor Plasma Cells in Bone Marrow as a Prognostic Factor in Multiple Myeloma

Aim. To study immunohistochemical parameters of tumor plasma cells in bone marrow and to assess how the expression of adhesion molecule CD56 impacts overall survival (OS) of multiple myeloma (MM) patients. Materials & Methods. The trial included 35 patients (19 men and 16 women) aged 23 to 73 years (with median age of 58 years) with newly diagnosed MM. At disease onset plasmacytoma was diagnosed in 21 patients. In all patients bone marrow core biopsy was performed followed by histologic and immunohistochemical (IHC) examinations. IHC examination was based on the panel of CD56, CD166, CXCR4, Ki-67, and c-MYC/CD138 antibodies. Kaplan-Meier survival curves and significance assessment by means of Cox's F-Test were used. Results. Expression mean values of most of studied markers (CD56, CXCR4, c-MYC, and Ki-67) in bone marrow of patients without plasmacytoma (n = 14) appeared to be higher than in patients with plasmacytoma at MM onset. Expression mean value is understood as percentage ratio of plasma cells expressing a studied marker to total cell count of tumor substrate. High expression of chemo-kine receptors (CXCR4), and adhesion molecules (CD56) probably inhibits plasma cell migration and impedes ex-tramedullary tumor progression. Comparison of protein expression by tumor plasma cells in bone marrow in the groups with bone extramedullary plasmacytoma shows a distinct regularity referring to CD56 adhesion molecule. For example, CD56 expression is significantly (р < 0.05) lower in terms of the count of tumor plasma cells with marker expression in bone marrow of MM patients with extramedullary plasmacytoma compared with patients with bone plasmacytoma (1 ± 1 % vs. 65.71 ± 12.12 %). Comparison of MM patients' OS depending on CD56 expression by tumor plasma cells in bone marrow showed that 4-year OS of patients with CD56 expression in bone marrow was significantly higher being 80 % vs. 38 % in the group with CD56 expression less than in 10 % of tumor cells. Conclusion. Expression of adhesion molecule CD56 in tumor plasma cells in bone marrow can be regarded as a prognostic factor in MM. Probably, when at disease onset CD56 expression is identified in less than 10 % of tumor cells in bone marrow, more detailed additional examination of patients should be carried out to rule out extramedullary lesions in different organs and tissues.