TAMs-derived IL-1β inducing DDX21 enhances CRC proliferation and metastasis via JAK2/STAT3 pathway

Tumor-associated macrophages (TAMs) are major components of tumor microenvironment that frequently associated with proliferation and metastasis in colorectal cancer (CRC). Our recent study found that DDX21 promotes CRC metastasis via phase separation. However, whether the relationship between DDX21 and tumor microenvironment in CRC remains unclear.

RT-qPCR, migration and invasion assay, immunohistochemistry staining and evaluation, multiple bioinformatics analyses, Western blot analysis, enzyme-linked immunosorbent assay (ELISA),tumor sphere-formation assay and colony formation assay, Co-Immunoprecipitation (Co-IP) assay, and in vivo experiments were performed to study the biological role of TAMs in CRC progression.

In this study, we found that CRC-conditioned macrophages enhanced DDX21 expression and tumor proliferation, migration, invasion and stemness. Mechanistically, TAMs-derived IL-1β activated the JAK2/STAT3 pathway, and then p-STAT3⁷⁰⁵ enhanced DDX21 protein stability by binding to DDX21. Surprisingly, DDX21 also increased ZEB1 expression, which in turn led to the production of CCL8 that promoted macrophage recruitment. Moreover, inhibition of CCL8 or IL-1β reduced macrophage migration and CRC metastasis, respectively. In vivo, TAMs enhanced the growth and metastasis of CRC and IL-1β knockdown impaired TAMs-induced CRC tumorigenesis. Clinically, IL-1β and CD206 expression in TAMs was significantly associated with malignant characteristics and prognosis of CRC patients.

Our data indicates that TAMs-derived IL-1β enhances CRC stemness, migration and invasion by regulating the JAK2/STAT3/DDX21 and ZEB1, which in turn leads to the production of CCL8 that promotes macrophage recruitment. Targeting TAMs secreting factor-IL-1β might be an important candidate factor for immunotherapy in CRC.