Mechanism of LMNB1 activating GPR84 through JAK-STAT pathway to mediate M2 macrophage polarization in lung cancer

Background: It is reported that G protein-coupled receptor 84 (GPR84) can participate in inflammation and immune regulation to repress anti-tumor responses. However, the function of GPR84 in lung Cancer (LC) and its potential molecular mechanisms are still largely unknown.

Methods: Bioinformatics and molecular experiments were employed to assess the expression of GPR84 in LC. The pathways enriched by GPR84 were analyzed by the Kyoto Encyclopedia of Genes and Genomes. Bioinformatics prediction identified the potential upstream regulatory factors of GPR84, which were verified through dual luciferase and chromatin immunoprecipitation experiments. Cell viability was measured by methyl thiazolyl tetrazolium assay. The expression levels of key proteins related to the janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway such as JAK2, p-JAK2, p-STAT3, and STAT3 were detected by western blot. Macrophages were co-cultured with LC cells. Flow cytometry was employed to examine the proportion of mannose receptor-positive cells. The expression levels of M2 polarization marker genes chitinase-like protein 3, arginase-1, and found in inflammatory zone 1 were measured by quantitative reverse transcription polymerase chain reaction. We applied an enzyme-linked immunosorbent assay to determine levels of cytokines (interleukin-10 and transforming growth factor beta) to evaluate the M2 macrophage polarization.

Results: GPR84 was highly expressed in LC and substantially enriched in the JAK-STAT pathway. GPR84 facilitated the M2 polarization of macrophages in LC. Adding the JAK-STAT pathway inhibitor weakened the promoting effect of GPR84 overexpression on M2 macrophage polarization. Furthermore, GPR84 also had an upstream regulatory factor lamin B1 (LMNB1). Knocking down LMNB1 blocked the JAK-STAT signaling pathway to repress M2 macrophage polarization in LC, while overexpression of GPR84 reversed the impact of LMNB1 knockdown on macrophage polarization.

Conclusion: The project suggested that the LMNB1/GPR84 axis can facilitate M2 polarization of macrophages in LC by triggering the JAK-STAT pathway. Targeting LMNB1/GPR84 or blocking the JAK-STAT pathway may be a novel approach for LC diagnosis and treatment.

GPR84; JAK-STAT; LMNB1; Lung cancer; M2 macrophage; Macrophage activation.