Abstract 5665: LILRB2 mediates the immune escape of breast tumor cells by degrading HLA-A

Abstract

Abstract Breast cancer has now risen to the number one cancer in the world, posing a great threat to human health. LILRB2 (leukocyte immunoglobulinlike receptor B2) is an important immunosuppressive receptor protein, which is mainly expressed in myeloid cells, such as macrophages and dendritic cells. At present, we have found clinically that patients with breast cancer bone and bone marrow metastasis have higher expression of LILRB2. In our research, we used Western blotting, real-time fluorescent quantitative Polymerase Chain Reaction (RT-PCR), flow cytometry, and other experimental methods to explore the expression and function of LILRB2 in breast cancer cells. In our research, we found that LILRB2does increase expression in breast cancer cells, therefore, we want to explore the role of LILRB2 in breast cancer cells. we find that LILRB2 will accelerate the proliferation of tumor cells and increase their migration ability. We tested the related signal pathways and found that LILRB2 can promote the enhancement of the NF-Kb signal pathway. Further, we have done related LILRB2 correlation analysis and found that LILRB2 can reduce human leukocyte antigen-A (HLA-A) Expression. Next, we tested the changes in the level of major histocompatibility complex (MHC-1) related mRNA and found that its mRNA expression increased, which was inconsistent with the decrease in its protein level we observed. Therefore, we used the proteasome inhibitor MG132 for treatment, and the results showed after adding MG132, the decrease in HLA-A expression caused by overexpression of LILRB2 was restored. Next, we knocked down the breast cancer cell line of membrane-associated ring finger (MARCH9). After we knocked down MARCH9, transfection of LILRB2 did not increase the ubiquitination of HLA-A. Therefore we show that LILRB2 can mediate the post-translational modification of HLA-A via MARCH9, which in turn mediates the degradation ofHLA-A. In conclusion, our research shows that LILRB2 maybe a candidate of clinical target for the treatment of breast cancer, preventing possible bone and bone marrow metastasis from breast cancer. Citation Format: Hui Zhao, zhiyuan jiang, zhiyu wang, yujie chang, shunyi ruan. LILRB2 mediates the immune escape of breast tumor cells by degrading HLA-A [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5665.