Rab coupling protein (RCP) plays physiological roles in the regulation of intracellular transport events through endosomal trafficking, receptor sorting, and recycling. Moreover, RCP has been known to augment tumorigenesis, cancer cell invasion, epithelial to mesenchymal transition, and metastasis by coordinating the
activation of the β1 integrin/integrin ligand kinase/EGFR signaling axis with Slug expression. Various cancers have exhibited high levels of RCP expression, which has been correlated with poor prognosis. The purpose of the present study is to determine the role of and underlying mechanism of RCP in the progression and
metastasis of ovarian cancer. Immunoblotting of SKOV-3 ovarian cancer cells transfected with or without RCP and immunohistochemical (IHC) staining of paraffin-embedded tumor tissue samples from 82 patients with ovarian cancer who underwent surgical resection with or without chemotherapy were utilized to evaluate
the correlation between the expression of RCP and that of p-FAK, p-EGFR, and p-STAT3. Furthermore, the association between the expression of RCP, p-FAK, p-EGFR, and p-STAT3 and clinicopathologic characteristics as well as outcomes of patients with ovarian cancer was investigated. Immunoblotting data showed that
cells transfected with RCP had a significantly greater RCP expression compared to those transfected with a control vector. Moreover, IHC staining showed that RCP expression was increased in tumor tissues compared to normal ovarian tissues, with positive staining in 59 (72%) samples. According to the extent and intensity of
IHC staining, low and high RCP expression was in 39 (48%) and 43 (52%) samples, respectively. The expression of RCP was associated with that of p-FAK, p-EGFR, and p-STAT3. Moreover, RCP overexpression was significantly associated with a serous tumor subtype, poor histologic grade, advanced FIGO stage, bilateral
ovarian cancer site, lymph node metastasis, and peritoneal carcinomatosis. While high RCP expression was correlated with poor progression-free survival (PFS) (p = 0.027) and overall survival (OS) (p = 0.045), the co-expression of RCP with p-FAK, p-EGFR, and p-STAT3 showed significantly poor PFS and OS. Advanced FIGO stage, high neutrophil to lymphocyte ratio, and high expression of p-STAT3 were recognized as independent prognostic factors for poor OS in patients with ovarian cancer, whereas lymph node metastasis and advanced FIGO stage were independently associated with poor PFS. In conclusion, RCP expression was closely associated with the expression of p-FAK, p-EGFR, and p-STAT3, suggesting that RCP induces cancer progression and metastasis by activating STAT3 phosphorylation through the FAK/EGFR axis. Despite having no independent
prognostic significance, RCP expression was associated with poor PFS and OS in patients with ovarian cancer. Further clearly understanding of the mechanisms and roles by which signaling factors, such as RCP, p-FAK, p-EGFR, and p-STAT3, affect the metastatic process and outcomes of ovarian cancer would be helpful in
establishing effective cancer treatment by predicting patients outcomes and developing new targeted agents.