High expression of SPINT2 promotes immune infiltration and tumor progression in ovarian cancer

This study aimed to identify the function and mechanism of Serine Peptidase Inhibitor, Kunitz Type 2 (SPINT2) in ovarian cancer (OC). The expression of SPINT2 was analyzed using the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) database. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed to identify enriched functional categories of SPINT2 and its correlated genes. Correlation of SPINT2 with OC immune infiltration level was analyzed using the Tumor IMmune Estimation Resource (TIMER) web server. The effect of SPINT2 on cell proliferation was detected using cell counting kit-8 (CCK-8) and colony formation assay. Its effects on cell migration and invasion were examined using the transwell assay. Function of SPINT2 in M2 macrophage recruitment was detected using the migration assay. The role of SPINT2 on M2 macrophage differentiation was evaluated using M2 macrophage markers and by detection of interleukin 10 (IL-10) release. An OC cohort study (GSE12470) showed that SPINT2 was highly expressed in OC. The high SPINT2 expression was related to shorter overall survival (OS) and poor recurrence-free survival (RFS). GO and KEGG analysis indicated that SPINT2 associated genes played roles in glycoprotein catabolism, cell adhesion and T cell differentiation. SPINT2 also played a key role in infiltration of macrophages in OC. shSPINT2 reduced viability and colony formation ability of ovarian cancer cell line SK-OV-3 cells. Moreover, shSPINT2 also inhibited the cell migration and invasion. Co-culture of shSPINT2 transfected SK-OV-3 cells with macrophages inhibited the migration of M2 macrophages, and inhibited macrophages polarization from M0 to M2. These results suggested that SPINT2 is involved in infiltration of tumor-associated macrophages (TAMs). SPINT2 also plays an important role in the polarization and migration of macrophages. These findings suggested that SPINT2 has the potential to be explored as a biomarker for OC and a potential target.