Radiotherapy Increases 12-LOX and CCL5 Levels in Esophageal Cancer Cells and Promotes Cancer Metastasis via THP-1-Derived Macrophages

BACKGROUND: Dioxygenase 12-lipoxygenase (12-LOX) plays an important role in tumorigenesis and promotes angiogenesis and proliferation in several tumors, including prostate and breast tumors. Radiotherapy enhances the expression of 12-LOX in esophageal squamous cell carcinoma (ESCC). Two types of macrophages can be found in the tumor microenvironment. The M2 subtype accelerates tumor progression; however, the relationship between 12-LOX and macrophages is not well established. Here, we explore this interaction and its effect on ESCC to induce tumor progression. METHODS AND RESULTS: RT-qPCR and Western blot analyses were used to evaluate the mRNA and protein expression levels of 12-LOX and chemokine (C-C motif) ligand 5 (CCL5) in ESCC after radiotherapy. CCL5 expression was increased by 12-LOX upregulation but was suppressed by the well-established 12-LOX inhibitor, baicalein. Furthermore, CCL5 attracted and repolarized human myeloid leukemia mononuclear cells (THP-1)-derived macrophages. Finally, ESCC co-culture with THP-1-derived macrophages led to a strong cancer migratory capacity. CONCLUSION: Radiation-induced 12-LOX overexpression in ESCC upregulates CCL5 expression, thereby attracting THP-1-derived macrophages and promoting their polarization to the M2 subtype, which enhances cellular metastasis.