Bromodomain containing 4 inhibition combats gastric precancerous lesions via modulating macrophage polarization

Objective: Gastric precancerous lesions (GPL), characterized by intestinal metaplasia and dysplasia, marks a pivotal juncture in the transformation from gastritis to gastric Cancer. Research on GPL could offer fresh perspectives on preventing Cancer occurrence.

Methods: This study employed 1-methyl-3-nitro-1-nitrosoguanidine (MNNG) to establish GPL rat models and knocked BRD4 down in vivo to assess its impact on the lesions and macrophage morphology. Following that, the impacts of BRD4 knockdown on the malignant phenotypes of human gastric epithelial GES-1 cells were determined. Moreover, conditioned medium from macrophage was gathered and used for GES-1 Cell Culture. The involvement of macrophage polarization in the BRD4 regulatory mechanism in GES-1 cells was assessed.

Results: This study elucidated that MNNG induced an increase level of BRD4 in the rat models. BRD4 knockdown reduced lesions based on pathological sections and immunohistochemistry to detect proliferative antigens. Western blotting and immunofluorescence showed that BRD4 knockdown suppressed epithelial-mesenchymal transition and macrophage M2 polarization. In in vitro experiments, BRD4 knockdown inhibited the malignant phenotype of GES-1 cells and the differentiation of THP-1 cells into M2 macrophages, respectively. The conditioned medium from M2 macrophages with BRD4 knockdown was co-incubated with GES-1 cells, which attenuated the malignant phenotypes compared with the medium from M2 macrophages.

Conclusion: Through in vivo and in vitro experiments, BRD4 upregulation was found to already occur during GPL, affecting macrophage polarization and epithelial cell cancerization. This finding provides an experimental basis for strategies targeting BRD4 inhibition at this critical stage.

Gastric cancer; Gastric precancerous lesion; Gene regulation; MNNG; Macrophage polarization.