| First Author | Wang X | Year | 2020 |
| Journal | Signal Transduct Target Ther | Volume | 5 |
| Issue | 1 | Pages | 35 |
| PubMed ID | 32296015 | Mgi Jnum | J:360103 |
| Mgi Id | MGI:7797563 | Doi | 10.1038/s41392-020-0124-z |
| Citation | Wang X, et al. (2020) The Ap-2alpha/Elk-1 axis regulates Sirpalpha-dependent tumor phagocytosis by tumor-associated macrophages in colorectal cancer. Signal Transduct Target Ther 5(1):35 |
| abstractText | The inhibitory receptor signal regulatory protein-alpha (Sirpalpha) is a myeloid-specific immune checkpoint that engages the "don't eat me" signal CD47, which is expressed on tumor and normal tissue cells. However, the profile and regulatory mechanism of Sirpalpha expression in tumor-associated macrophages (TAMs) are still not clear. Here, we found that the expression of Sirpalpha in TAMs increased dynamically with colorectal cancer (CRC) progression. Mechanistically, CRC cell-derived lactate induced the nuclear translocation of the transcription factor Ap-2alpha from the cytoplasm in TAMs. Ap-2alpha functioned as a transcription factor for Elk-1 by binding to the conserved element GCCTGC located at -1396/-1391 in the mouse Elk-1 promoter. Subsequently, the Elk-1 protein bound to two conserved sites, CTTCCTACA (located at -229/-221) and CTTCCTCTC (located at -190/-182), in the mouse Sirpalpha promoter and promoted Sirpalpha expression in TAMs. Functionally, the macrophage-specific knockout of Ap-2alpha notably promoted the phagocytic activity of TAMs and suppressed CRC progression, whereas these effects were prevented by the transgenic macrophage-specific expression of Elk-1, which regulated TAM phagocytosis and CRC development in a Sirpalpha-dependent manner. Furthermore, we showed that Elk-1 expression was positively correlated with Sirpalpha expression in TAMs and was associated with poor survival in CRC patients. Taken together, our findings revealed a novel mechanism through which CRC evades innate immune surveillance and provided potential targets for macrophage-based immunotherapy for CRC patients. |
