Macrophages promote cell proliferation in colorectal cancer via IL-1β-mediated downregulation of miR-28-3p.

Infiltration of macrophages is associated with tumor progression and poor prognosis in multiple malignancies, but the underlying mechanisms by which macrophages contribute to colorectal cancer (CRC) have not yet been elucidated. The purpose of this study was to discuss the potential mechanisms of macrophages in CRC. The MTT assay was used to assess cell viability. The expression of the proliferation-related marker PCNA was detected by Western blot analysis. The 10 most important factors (PDGF, VEGF, TNFα, bFGF, IL-8, TGF-β, IFN-γ, SPARC, IL-1β and IL-6) secreted by macrophages were knocked down by RNA interference (RNAi), and the mRNA expression levels of these 10 factors were analyzed by qRT-PCR. The effect of these factors on cell proliferation was assessed by the MTT assay. The miRNAs regulated by IL-1β in CRC cells were identified by miRNA microarray and qRT-PCR analyses. The proliferation ability of miR-28-3p inhibitor on CRC cells was detected by colony formation assay. The association of IL-1β and miR-28-3p expression with the clinicopathological characteristics in patients with CRC was analyzed by TCGA RNA-seq data. As a result, macrophages promoted the proliferation of CRC cells in a time- and number-dependent manner, and these effects were associated with the upregulation of PCNA and the macrophage-secreted cytokine IL-1β, which had the most significant effect on CRC cell proliferation. Furthermore, downregulation of miR-28-3p was induced by IL-1β in CRC cells. The miR-28-3p inhibitor promoted the proliferation in CRC cells. Moreover, upregulation of IL-1β expression or downregulation of miR-28-3p expression was associated with poor survival in patients with CRC. Therefore, these data demonstrated that macrophages promoted CRC cell proliferation via IL-1β-mediated downregulation of miR-28-3p.