RSPO3 is a marker candidate for predicting tumor aggressiveness in ovarian cancer

BACKGROUND: Ovarian cancer, a highly aggressive and heterogeneous gynecological malignancy that has long been difficult for physicians to identify and treat, requires more effective and precise molecular targets. R-spondin 3 (RSPO3) is a secreted protein that plays a tumorigenic role in several human cancers. However, the functional contribution and prognostic role of RSPO3 in ovarian cancer remain unclear. METHODS: RSPO3 expression in ovarian cancer tissues was assessed using western blotting, quantitative real-time polymerase chain reaction (qRT-PCR), and immunohistochemistry, and its relationships to clinicopathological parameters were investigated using the data of 179 ovarian cancer patients. RSPO3’s biological function was evaluated using Cell Counting Kit-8, colony formation, wound healing, and Matrigel transwell assay in RSPO3-knockdown and RSPO3-overexpression ovarian cancer cell lines SKOV3 and OVCAR3. The possible biological processes associated with RSPO3 were identified using functional enrichment analysis based on the transcriptome sequencing data from The Cancer Genome Atlas (TCGA) ovarian cancer cohort and our experimental cells, and further verified using western blotting and immunofluorescence in the ovarian cancer cell model. RESULTS: The RSPO3 mRNA and protein levels were both upregulated in ovarian cancer tissues. High RSPO3 expression was correlated with lymphovascular space invasion (LVSI), lymph node metastasis, distant metastasis, and advanced tumor stage. Survival analysis showed that RSPO3 is an independent prognostic marker in ovarian cancer. Moreover, in vitro RSPO3 knockdown significantly inhibited the invasion ability of ovarian cancer cells, while overexpression significantly promoted it. Using transcriptome sequencing and pathway validation experiments, we demonstrated for the first time that RSPO3 promotes ovarian cancer invasiveness through activation of the PI3K/AKT pathway and modulation of epithelial-mesenchymal transition (EMT), while the common Wnt/β-catenin signaling pathway was not involved. CONCLUSIONS: RSPO3 plays a definite oncogenic role and promotes tumor aggressiveness in ovarian cancer, which may serve as a potential prognostic marker and therapeutic target for this disease.