Abstract 3123: Aberrant expression of CD33 is associated with poor prognosis in patients with multiple myeloma and tumor progression

Background: Aberrant antigen expressions of plasma cells in patients with multiple myeloma (MM) have used for diagnosis and monitoring residual disease during treatment. Here, we evaluated prognostic impact of aberrant antigens expression and identify functional roles of CD33 in MM. Methods: Patient characteristics and immunophenotype from bone marrow aspiration samples of 99 newly diagnosed MM patients in National Cancer Center of Korea were analyzed. Samples were stained with 12 antibodies using 4-color panel for flow cytometry with CD138 gated cells measuring CD38, CD19, CD117, CD45, CD20, CD33, CD13, CD56, CD28, cytoplasmic κ and cytoplasmic λ. Prognostic impact of antigen expressions was evaluated using Kaplan-Meier and log-rank test. To investigate the functional role of CD33 in MM, we evaluated immunophenotype of MM cell lines and performed in vitro experiment on CD33 expression. Transient CD33 knockdown was performed by using small interfering RNA (siRNA) through Amaxa nucleofector device. CD33 knockdown was evaluated using flow cytometry and quantitative real-time PCR. Proliferation was evaluated using IncuCyte Zoom live cell imaging and cell counting kit 8 (CCK-8). The role of CD33 in migration was studied using transwell assay following with IncuCyte Zoom and CCK-8 for quantification of the migrated cells. Results: The frequencies of antigen expression in newly diagnosed patients with MM were observed as following; expression of CD20, CD19, CD33, CD117, CD13, CD56 and CD38 were 3%, 6%, 15%, 19%, 33%, 66%, and 92%, respectively. CD33 and CD13 expression were associated with lower overall survival (OS; P = 0.014 and P = 0.036) in Kaplan-Meier analysis. When comparing clinical characteristics according to antigens expression, the level of anemia showed correlation with CD33 expression. Moreover, multivariate analysis showed that CD33 was independently prognostic of shorter progression free survival (PFS; P = 0.009) and OS (P = 0.024) with correction of clinical prognostic factors. Then we checked CD33 expression level in myeloma cell lines (H929, RPMI-8226, IM-9, and KMS-12-PE) and RPMI-8226 showed high expression of CD33. After knockdown of CD33 in RPMI-8226 by transient transfection, it showed significantly attenuated proliferation and decreased migration. Conclusion: Clinical and experimental data from our results showed that CD33 might be a prognostic marker, which was associated with tumor progression via increased proliferation and migration in MM. [This work was supported by a grant from the National Research Foundation (NRF) of Korea funded by the Korean government (MSIP; No. 2014R1A2A2A01002553).] Citation Format: Ki Hong Lee, Hee Seoung Seo, Ji Yeon Sohn, Eunyoung Lee, Hyewon Lee, Hyeon-Seok Eom, Sun-Young Kong. Aberrant expression of CD33 is associated with poor prognosis in patients with multiple myeloma and tumor progression. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3123.