Profile of Checkpoint Molecules Expression on Bone Marrow Cell Populations in Patients with High-Risk Myelodysplastic Syndrome

• Published in: Blood 2020-11, Vol.136 (Supplement 1), p.43-44
• Main Authors: Tcvetkov, Nikolai Yu, Morozova, Elena V., Epifanovskaya, Olga S., Babenko, Elena V., Barabanshikova, Maria V., Lepik, Kirill V., Bakin, Eugene A., Vlasova, Julia J., Smirnova, Anna G., Zander, Axel R., Moiseev, Ivan S.
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2020-141997

Background Immune checkpoint (IC) inhibitors (ICI) is a promising group of agents with potential effect in myelodysplastic syndrome (MDS). However, there is not enough data on the pattern of IC expression in MDS bone marrow, though this can guide future therapies with ICI. Methods We prospectively included 57 patients with high risk MDS during 2019-2020 years after signing informed consent for participation in research. We used 7 eight-colored panels in each patient to define IC expression on T- and NK-cells (CD3, CD8, CD4, CD56, CD16), myeloid precursors (CD117, CD34), T-regulators (CD25, CD4), myeloid-derived suppressor cells (CD15, CD11b, CD14, HLA-DR, CD33). In each population we assessed expression of CD279, CD152, CD223, TIM3, CD273, CD274, CD275, CD80. Results In lymphoid populations we observed an extremely high percentage of PD-1 positive lymphocytes (10.5 ± 8.0% of all nucleated cells), including PD-1 positive CD4 lymphocytes (6.3 ± 3.7%) and CD8 lymphocytes (4.7 ± 3.5%). Interestingly, on average 63 ± 34% of all lymphocytes were PD-1 positive (Figure 1A), which indicates an extreme degree of T-cell exhaustion and significant exploitation of the PD-1 system by a malignant tumor. Among the PD-1 ligands PD-1L predominated, however it was present only on a small percentage of myeloid precursors (2.2 ± 0.39% of nucleated cells), but most of the PD-1L ligand expression was observed on granulocytes in the process of their differentiation from myeloid precursors (5.8 ± 4.1% of nucleated cells), and in some patients the proportion of such granulocytes reached more than 20%. Moreover, on the cells of the monocytic series, PD-1L is practically not expressed, but CD80 is expressed, a ligand for CTLA4 (1.6 ± 0.7% of nucleated cells). Interestingly, despite the presence of expression of CD80 on monocytic and dendritic cells, the receptor for this ligand on T-lymphocytes was practically absent. The proportion of such cells was only 0.02 ± 0.01%, i.e. the expression of CD80 facilitates the activation of lymphocytes through interaction with CD28 rather than the suppression of the immune response through CD152. Thus, it can be suggested that CTLA4 does not have a clinically significant role in MDS. At the same time, a certain number of TIM3 positive lymphocytes were observed, the proportion of which was 0.42 ± 0.16%, and the percentage of lymphocytes carrying this receptor was 3.6 ± 1.2% (Figure 1A). However, significantly greater TIM3 expression was detected on