Ratio of Immune Response to Tumor Burden Predicts Survival Via Regulating Functions of Lymphocytes and Monocytes in Diffuse Large B-Cell Lymphoma

Abstract

Background/Aims: Diffuse large B-cell lymphoma (DLBCL) is an aggressive disease, and is the most common type of lymphoma in adults. Although significant progress in treatment has been made using chemotherapy combinations, there exist a large amount of relapse or refractory cases. Thus, effective clinical biomarkers for DLBCL are urgently needed. Our study aims to explore the predictive significance of using the immune response to tumor burden ratio [defined as the lymphocyte to monocyte ratio (LMR)/lactate dehydrogenase (LDH) levels] in 184 DLBCL patients and the potential mechanism underlying the use of the LMR to tumor burden ratio in predicting patient survival. Methods: The correlation between serum LDH levels and tumor levels assessed by PET-CT was determined using Spearman’s correlation analysis. Clinical data from 184 DLBCL patients was assessed using receiver operating characteristic curve analysis and survival analysis. The potential correlation between tumor burden and lymphocytes or monocytes was analyzed by immunohistochemical staining, flow cytometry, and ELISA analysis of patient samples. In addition, we performed in vitro studies to further determine the effects of tumor burden on the anti-tumor activity of T lymphocytes. Results: We observed that serum LDH was an excellent surrogate marker of tumor burden in DLBCL patients, and that the ratio of LMR to LDH was an independent prognostic biomarker capable of predicting survival in DLBCL patients. Further analysis showed that a high tumor burden was correlated with decreased Ki67 expression in T cells, either in the solid tumor tissue or in the circulating blood. In addition, based on an in vitro co-culture study, a higher tumor burden led to the suppression of the anti-tumor response of T cells. Furthermore, we found that a higher tumor burden was correlated with the differentiation of monocytes to tumor associated macrophages in the tumor micro-environment. Both results demonstrate the importance of considering both the immune system and tumor burden for prognostic analysis. Conclusion: Our study has identified a novel clinical biomarker, namely, the immune response to tumor burden ratio, that can be used to distinguish survival outcomes in DLBCL patients, and demonstrated the potential mechanism underlying the use of this biomarker, that incorporates both the immune system and tumor burden, for use in future clinical applications.