Abstract 1751: Prognostic value of CD20/CD73 ratio in sensitive and relapsed/refractory diffuse large B-cell lymphoma cell lines
Authors: Gu Juan J. , Mavis Cory , Wang Jessica , Mandeville Taylor , Hernandez-Ilizaliturri Francisco 
Published: April 2023

Abstract
Purpose: Developing novel therapy strategies to treat relapsed/refractory diffuse large B-cell lymphoma (r/r DLBCL) is critically needed. Previous studies in our group found despite dysregulation of apoptotic pathway in resistant DLBCL, upregulation in glycose metabolism and energetic ATP production were also found in r/r DLBCL. Therefore, decreasing or blockage ATP production may provide a novel method to overcome resistance in lymphoma. ATP/ADP is hydrolyzed into AMP by NTPDases, and AMP into adenosine and phosphate by ecto-5’-nucleotidase, known as CD73. CD73 is the rate limiting enzyme anchored the surface of tumor and immune cell. The expression level of CD73 on the tumor was reported significantly associated with inferior prognosis in variety of cancers. Moreover, expression level of CD73 on immune cell has been shown immunosuppression in multiple cancers. Targeting CD73 by monoclonal antibody or small inhibitor currently underwent multiple clinical trials. However, the role of CD73 in r/r DLBCL and the relationship between CD73 and CD20 have not been explored.
Methods: Germinal center B-cell like, activated B-cell like lymphoma, Burkitt’s lymphoma and rituximab resistant cell lines generated in our lab were used. Surface expression of CD73 and CD20 were determined by staining anti-CD73 FITC and anti-CD20 Per-cy5.5 antibodies and running flow cytometry. The expression levels of CD73 and CD20 were detected by media fluorescence index (MFI). The CD20/CD73 ratio was calculated by CD73 MFI/CD20 MFI.
Result: Previously our group found surface CD20 levels exhibited a linear correlation with rituximab induced cellular mediated cytotoxicity. The CD20 MFI of germinal center B-cell like, activated B-cell like lymphoma, Burkitt’s lymphoma and rituximab resistant cell lines were: DHL4 8652, DOHH2 6472, TMD8 3981, RL 2849, Raji 2011, U2932 604, RL 4RH 599 and Raji 4RH 576. The higher MFI of CD20, the more sensitive to rituximab treatment. Here we discovered that the surface level of CD73 had an inverse correlation with CD20 level in these cell lines. In detail, CD73 MFI were: DHL4 464, DOHH2 387, TMD8 363, RL 299, Raji 611, U2932 486, RL 4RH 631 and Raji 4RH 702. The CD20/CD73 ratio of cell lines from high to low were DOHH2, DHL4, TMD8, RL, Raji, U2932, Raji 4RH and RL 4RH, respectively. This CD20/CD73 ratio in each of cell lines was found more straight forward to represent the sensitivity of rituximab or chemo drug treatment in vitro condition.
Conclusion: Our study was first time to reveal the association between CD20/CD73 ratio and immune-chemo response in lymphoma cell lines, especially in resistant lymphoma in vitro condition. This may give us prognostic value of CD20/CD73 ratio in predicting lymphoma response to immune/chemotherapy in clinical setting. Further study to find CD20 and CD73 association in the clinical setting and mechanism of action need to be warranted.
Citation Format: Juan J. Gu, Cory Mavis, Jessica Wang, Taylor Mandeville, Francisco Hernandez-Ilizaliturri. Prognostic value of CD20/CD73 ratio in sensitive and relapsed/refractory diffuse large B-cell lymphoma cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1751.