SPP1 represents a therapeutic target that promotes the progression of esophageal squamous cell carcinoma by driving M2 macrophage infiltration
Background: Tumor-associated macrophages (TAMs) are an important component of the tumor microenvironment (TME). However, the crosstalk between esophageal squamous cell carcinoma (ESCC) cells and TAMs remains largely unexplored. Methods: Clinical samples and the TCGA database were used to evaluate the relevance of SPP1 and TAM infiltration in ESCC. Mouse models were constructed to investigate the roles of macrophages educated by SPP1 in ESCC. Macrophage phenotypes were determined using qRT?PCR and immunohistochemical staining. RNA sequencing was performed to elucidate the mechanism. Results: Increasing expression of SPP1 correlated with M2-like TAM accumulation in ESCC, and they both predicted poor prognosis in the ESCC cohort. Knockdown of SPP1 significantly inhibited the infiltration of M2 TAMs in xenograft tumors. In vivo mouse model experiments showed that SPP1-mediated education of macrophages plays essential roles in the progression of ESCC. Mechanistically, SPP1 recruited macrophages and promoted M2 polarization via CD44/PI3K/AKT signaling activation and then induced VEGFA and IL6 secretion to sustain ESCC progression. Finally, blockade of SPP1 with RNA aptamer significantly inhibited tumor growth and M2 TAM infiltration in xenograft mouse models.  Conclusions: This study highlights a SPP1-mediated crosstalk between ESCC cells and TAMs in ESCC. SPP1 could serve as a potential target in ESCC therapy. Overall design: Total RNA from THP1-derived macrophages educated with conditioned medium from KYSE150shSPP1#2 or KYSE150shNC cells for 48 h was harvested using TRIzol reagent for RNA extraction. Deep RNA sequencing (RNA-seq) was performed and analyzed on the BGI seq500 platform (BGI-Shenzhen, China).