CD44 Expression in Different Plasma Cell Diseases

CD44 expression in different plasma cell diseases Introduction Myeloma is a genetically complex disease which develops via a multistep process whereby plasma cells are driven towards malignancy through the accumulation of genetic “hits” over time. This multistep process permits myeloma to have four recognisable clinical stages including monoclonal gammopathy of undetermined significance (MGUS) , smouldering multiple myeloma (SMM) , multiple myeloma (MM) and plasma cell leukemia (PCL). CD44 as a complex adhesion molecule, is highly expressed in a variety of solid tumors and involved in metastasis and chemotherapy resistance . Previous studies had found that CD44 was also highly expressed in MM, and associated with advanced clinical stage, extramedullary myeloma (EM) and poor survival. However the relation of CD44 expression in different plasma cell disease remain unknown. Patients and Methods Newly diagnosed MGUS (n=12), SMM (n=11), MM (n=133) and PCL (n = 8) patients who were hospitalized in our hospital from December 2017 to December 2020 were enrolled. The diagnosis was based on the criteria of the International Myeloma Working Group. CD44 was detected by flow cytometry as follows: 2 ml of heparin anticoagulated bone marrow was collected from the patients at the time of diagnosis, 1×10 6 cells were detected, and a gate was set for identifying abnormal plasma cells characterized by CD138 and CD38. CD44 positive was defined as more than 20% of the plasma cells expressed CD44. Results From December 2017 to December 2020, a total of 164 patients diagnosed in our hospital were included in the study, including 12 MGUS patients, 11 SMM patients, 133 MM patients and 8 PCL patients. The expression proportion (7.9%±11.9%, 11.2%±15.5%, 40.2%±37.7%, 81.9%±25.6%, P < 0.001) and expression intensity (the mean fluorescence intensity was 1 742.8±1 023.1, 2 915.7±923.0, 6 692.6±11 275.5, 25 359.6±22 604.5, P=0.001) of CD44 on the monoclonal plasma cells of MGUS, SMM, MM and PCL patients gradually increased. In 133 MM patients, 73 cases were for CD44 positive. CD44 positive patients were more likely to show ＞3 focal bone lesion (75.3% VS 50.0%, P=0.002), and international staging system（ISS）III stage (68.5% VS 51.7%, P=0.048) compared those with CD44 negative. CD44 expression rate was significantly higher in MM patients with extramedullary disease (n=26) than those without (n=107) (56.7%VS 36.2%, P=0.031) Conclusion: Our study showed that from MGUS, SMM, MM to PCL, the CD