Significance of dysregulated M2 macrophage and in the ovarian metastasis of gastric cancer.

BACKGROUND

Prognosis of gastric cancer (GC) patients with ovarian metastasis (OM) remains poor. We hereby characterized the role of tumor immune microenvironment (TIME) and identified potential key regulators in the OM with the aim of understanding its molecular basis to develop novel therapeutic targets.

METHODS

Transcriptomic analyses of paired primary and ovarian metastatic lesions of seven GC patients from Fudan University Shanghai Cancer Center uncovered and functionally annotated their differentially expressed genes (DEGs). CIBERSORT analysis revealed differential TIME between primary GCs and OMs, which was further validated by multiplex immunofluorescence (mIF). Unique overexpression of candidate regulator in OMs was validated by an immunohistochemical (IHC) staining-based cohort study and cell growth, migration and invasion assays were conducted to characterize its function in GC progression.

RESULTS

Functional enrichment analyses of DEGs between GCs and matched OMs revealed multiple significantly dysregulated immune-related and cancer-related pathways. Distinctive subsets of immune cells, especially M2 macrophage, were selectively enriched in metastatic lesions. mIF-based quantification further validated the overexpression of CD68CD206 M2 macrophage in the OMs. Estrogen receptor 2 (), which encodes estrogen receptor β (ERβ), was not only potentially correlated with M2 macrophage but also overexpressed in the OM of GC. was up-regulated in cancerous tissue and its high expression correlated with younger age, more advanced lymph node metastasis and pathological stage, as well as a worse patient survival. IHC staining of ERβ in the cohort of paired primary and metastatic GCs validated its selective overexpression in OMs. Small-interfering RNAs (siRNAs)-induced knockdown of significantly inhibited the invasion and migration of both AGS and HGC-27 GC cell lines.

CONCLUSIONS

Comparative RNA-sequencing analysis revealed the dysregulated TIME, M2 macrophage in particular, between primary GC and OM. potentially correlated with M2 macrophage and played pro-oncogenic roles in GC progression and metastasis.