Features of the Immunophenotype of Tumor Plasmocytes in the Bone Marrow and Peripheral Blood for Multiple Myeloma Complicated By Plasmacytomas

Introduction: tumor cells multiple myeloma (MM) are characterized by variability of the immunophenotypic profile. The existing differences in the expression of membrane proteins of bone marrow plasma cells and circulating plasma cells in peripheral blood can reflect the characteristics of the clinical manifestations of the disease and its course. We studied the surface phenotype of tumor plasma cells in the bone marrow and circulating plasma cells in peripheral blood in patients with multiple myeloma complicated by visible plasmacytomas. The aim was to study the immunophenotype characteristics of tumor plasma cells in the bone marrow (PC BM) and circulating tumor cells in the peripheral blood (CTC MM) with multiple myeloma complicated by visible plasmacytomas.

Materials and methods: 15 patients with MM, aged from 41 to 85 years (Me 58 years) were examined. In all patients, the 3rd stage of the ISS disease and the plasmacytoma of different localization. The average index on the Karnovsky scale is 40%. In 9 (60%) patients, the plasmacytomas were more than 7 cm in diameter (bulky disease). In the studied group, the average level of plasma cells in BM is 18.8%. Two patients received renal replacement therapy. In 12 (80%) patients, plasmacytomas were observed in the debute of the disease, and for 3(20%) appeared in the course of therapy. Thirteen patients had plasmocytomas with bone lesions of different locations, and 3 patients had extramedular plasmacytomas. Six patients were with newly diagnosed MM, 9 patients had previously received antitumor therapy (VCP, VMP, RVD), the average number of courses was 4.6 (1-7 courses). At the finish of the induction courses, only one patient received a partial response. All patients underwent immunophenotypic examination of PC BM and CTC MM by 4-color flow cytometry using a panel of monoclonal antibodies to CD38, CD138, CD45, CD56, CD19, CD20, CD117, CD27, CD11c, CD33 (Becton Dickinson, USA).

Results: all MM patients with plasmocytomas were high positive expression of CD56, CD81, CD27 and CD11c molecules on plasma cells of BM and PB. All patients were high level of CD38 + / CD138 + expression on bone marrow plasma cells, while plasma cells in the peripheral blood had predominantly the CD38 + / CD138- (p <0.05) phenotype. Significantly higher expression of the CD33 adhesive molecule was observed on bone marrow tumor cells with the newly diagnosed disease, compared to its values at the CTC of MM (p˂0.05). In the same group of patients, there were significantly high rates of expression of costimulatory CD28 protein by tumor plasma cells in the bone marrow compared to its values in peripheral blood (p<0.05). In the group of patients with plasmacytomas that appeared during treatment, the expression of CD28 was significantly higher on CTC MM (p˂0.05). In the same group, significantly higher expression of CD56 + on PC BM was observed compared with CTC MM (p˂0.05).

Conclusions: The revealed differences in the features of the expression of the studied adhesive proteins on the PC of BM and CTC MM determine the clinical course of MM and can be negative indicators for the prognosis of MM, complicated by plasmocytomas.