我们之前已经证明，编码 p53 诱导型 Mir34a microRNA 的基因的普遍缺失会增加小鼠中结肠炎相关结直肠癌 (CAC) 的数量和侵袭性。由于 p53 通路与肿瘤微环境 (TME) 中的细胞介导的肿瘤抑制有关，我们删除了骨髓细胞中的 Mir34a，并使用 scRNA-Seq（单细胞 RNA 测序）对这些细胞中的 CAC 进行了表征。这揭示了特定巨噬细胞亚型的增加，例如 Cdk8 巨噬细胞和 Mrc1、M2 样巨噬细胞。后者显示 21 种已知的 Mir34a 靶 mRNA 表达升高，包括 Csf1r、Axl、Foxp1、Ccr1、Nampt 和 Tgfbr2，以及 32 种预测的 Mir34a 靶 mRNA。此外，与 Mir34a 丰富的 BMDM 相比，Mir34a 缺陷的 BMDM 表现出迁移增强、Csf1r 表达升高以及向 M2 样极化的转变。同时删除 Csf1r 或使用 Csf1r 抑制剂治疗可减轻这些小鼠的 CAC 负担和侵袭。值得注意的是，骨髓 Mir34a 功能的丧失导致了一种显着的炎症性 CAC 细胞亚型，该亚型显示出上皮细胞和巨噬细胞标记。这些细胞表现出高水平的 EMT 转录因子 Zeb2，因此可能增强 CAC 的侵袭性。综上所述，我们的结果为 CAC 中骨髓 Mir34a 的肿瘤抑制作用提供了体内证据，这种作用至少部分是通过抑制 Mir34a 靶标（例如 Csf1r）维持巨噬细胞处于 M1 样状态来介导的。总的来说，这些发现可能有助于确定治疗 CAC 的新治疗靶点和方法。© 2024。作者。

We have previously shown that general deletion of the gene encoding the p53-inducible Mir34a microRNA enhances the number and invasion of colitis-associated colorectal cancers (CACs) in mice. Since the p53-pathway has been implicated in tumor-suppression mediated by cells in the tumor microenvironment (TME) we deleted Mir34a in myeloid cells and characterized CACs in these with scRNA-Seq (single cell RNA sequencing). This revealed an increase in specific macrophage subtypes, such as Cdk8+ macrophages and Mrc1+, M2-like macrophages. The latter displayed elevated expression of 21 known Mir34a target mRNAs, including Csf1r, Axl, Foxp1, Ccr1, Nampt, and Tgfbr2, and 32 predicted Mir34a target mRNAs. Furthermore, Mir34a-deficient BMDMs showed enhanced migration, elevated expression of Csf1r and a shift towards M2-like polarization when compared to Mir34a-proficient BMDMs. Concomitant deletion of Csf1r or treatment with a Csf1r inhibitor reduced the CAC burden and invasion in these mice. Notably, loss of myeloid Mir34a function resulted in a prominent, inflammatory CAC cell subtype, which displayed epithelial and macrophage markers. These cells displayed high levels of the EMT transcription factor Zeb2 and may therefore enhance the invasiveness of CACs. Taken together, our results provide in vivo evidence for a tumor suppressive role of myeloid Mir34a in CACs which is, at least in part, mediated by maintaining macrophages in an M1-like state via repression of Mir34a targets, such as Csf1r. Collectively, these findings may serve to identify new therapeutic targets and approaches for treatment of CAC.© 2024. The Author(s).