DARS mediated M2 polarization of tumor associated macrophages drives MPN progression

Abstract Chronic myeloproliferative neoplasms (MPNs) without the Philadelphia chromosome are clonal diseases of the bone marrow originating from hematopoietic stem cells. Their development is closely associated with driver gene mutations, immune microenvironment dysregulation, and metabolic reprogramming. Aspartyl-tRNA synthetase (DARS) encodes aspartyl-tRNA synthetase, a member of the aminoacyl-tRNA synthetase family. Our previous studies have shown that DARS is highly expressed in MPNs patients, and its expression is associated with tumor-associated macrophages. High expression of DARS promotes tumor cell proliferation both in vivo and in vitro. Here, we demonstrate that DARS plays a pro-tumor proliferative role in MPNs disease progression through tumor-macrophage interactions. In order to further explore the relationship between DARS and the polarization of macrophages in myeloproliferative neoplasms, we used flow cytometry and qRT-PCR to detect the polarization markers. The results showed that in MPNs patients, DARS was expressed on M1 - and M2 - type macrophages, and its abnormal expression was associated with M2 polarization. Therefore, we conducted further studies on the relationship between abnormally expressed DARS and tumor-associated macrophage polarization in MPNs. We first explored the relationship between DARS expression on macrophages and M2 macrophage polarization. We constructed DARS-knockdown tumor-associated macrophages using lentivirus and conditioned medium co-culture. Flow cytometry and qRT-PCR were used to detect polarization-related markers. The results showed that after knocking down DARS in tumor - associated macrophages, the secretion of cytokines such as IL - 6, IL - 8, IL - 10, and IFN - α decreased. Also, the proportion of M2 - polarized cells decreased. When we co-cultured these DARS-knockdown macrophages with MPNs tumor cells and assessed tumor cell proliferation, we found that these macrophages significantly inhibited MPNs cell proliferation and promoted their apoptosis. We also investigated the effect of DARS, which is highly expressed on tumor cells, on the polarization of tumor-associated macrophages. After knocking down DARS expression on tumor cells using lentivirus and co-culturing them with macrophages, we found that this knockdown in MPNs tumor cells significantly reduced the number of M2-polarized macrophages in the co-culture system, and this effect was associated with a reduction in IL-8 secretion by tumor cells. When these polarized macrophages were co-cultured with wild-type tumor cells, they were found to inhibit the proliferation of MPNs tumor cells and promote their apoptosis. Our findings provide new insights into the role of DARS in MPNs from the perspective of metabolic-immune interactions and provide new theoretical basis for DARS as a novel biomarker for MPNs prognosis assessment.