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Effects of immune inhibitory receptor LILRB2 on proliferation and apoptosis of leukemia cell lines

YU Xiao-ting1, XIE Li1, ZHAN Meng-na2, ZHENG Jun-ke1, YU Zhuo1   

  1. 1.Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Basic Medicine Faculty of Shanghai Jiao Tong University, Shanghai 200025, China; 2.Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
  • Online:2014-07-28 Published:2014-08-11
  • Supported by:

    Program for Professor of Special Appointment “Eastern Scholar” at Shanghai Institutions of Higher Learning；Shanghai Pujiang Program, 13PJ1405600

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Abstract:

Objective To explore the expression, function, and relevant mechanism of the immune inhibitory receptor of leukocyte immunoglobulin-like receptors subfamily B member 2 (LILRB2) in human leukemia cell lines and to provide new clues for the targeting treatment of leukemia. Methods The expressions of LILRB2 in leukemia cell lines, such as THP1, U937, and K562 were detected by the flow cytometry and Western blotting. The shRNA plasmids specific for the knockdown of LILRB2 (with GFP tag) was constructed and by which the virus was packaged. THP1 cells with high expression of LILRB2 were then infected by the virus. Cell lines with steady expression of GFP+ were obtained by the flow cell sorting. The knockdown efficiency of shRNA at both mRNA level and protein level was detected. The changes of cell proliferation and apoptosis at different time points were observed and the relevant molecular mechanisms, such as changes of downstream regulatory signals, were analyzed after the knockdown of LILRB2. Results All three cell lines expressed LILRB2 and the expression level of LILRB2 of THP1 cells was the highest. The Real-Time PCR and Western blotting findings showed that among four constructed shRNAs plasmids, shLILRB2-717 and shLILRB2-1312 significantly down-regulated the expression of LILRB2. The inhibition of LILRB2 expression in THP1 cells dramatically decreased the proliferation and significantly increased the apoptosis. The results of the flow cytometry indicated that the apoptotic rates of cells of the shLILRB2-717 group and shLILRB2-1312 group at the early stage were (7.90±1.61)% and (24.80±1.32)%, much higher than (3.96±0.48)% of the control group (Scramble group) (P<0.05). The apoptotic rates of cells of the two groups at the late stage were (13.80±0.98)% and (23.60±1.03)%, much higher than (10.80±0.48)% of the Scramble group (P<0.05). The knockdown of LILRB2 led to significant down-regulation of expressions of SHP1 and p-SHP1, which indicated that LILRB2 might regulate the proliferation and apoptosis of leukemia cell lines through SHP1. Conclusion Immune inhibitory receptor LILRB2 can be expressed in a variety of leukemia cell lines. The inhibition of LILRB2 expression can lead to significant down-regulation of SHP1 and p-SHP1 in THP1 cells and mass apoptosis, which suggests that SHP1 may positively regulate the development of leukemia.

Key words: immune inhibitory receptor, leukocyte immunoglobulin-like receptor subfamily B member 2, leukemia, apoptosis, SHP1