IQ Motif Containing GTPase-Activating Protein 3 Is Associated with Cancer Stemness and Survival in Pancreatic Ductal Adenocarcinoma.

Introduction: Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal types of malignancy, with poor prognosis and rising incidence. IQ motif containing GTPase-activating protein 3 (IQGAP3) is a member of the IQGAPs family of scaffolding proteins that govern multiple cellular activities like cytoskeletal remodeling and cellular signal transduction. This study aimed to analyze the expression and biological function of IQGAP3 in PDAC.

Methods: We analyzed IQGAP3 expression in 81 PDAC samples by immunohistochemistry. RNA interference was used to inhibit IQGAP3 expression in PDAC cell lines.

Results: Immunohistochemical analysis of IQGAP3 showed that 54.3% of PDACs were positive for cytoplasmic expression of IQGAP3, with no expression found in non-neoplastic tissue. Furthermore, IQGAP3 expression was an independent poor prognostic factor in our immunostaining-based studies and analyses of public databases. Our cohort and the Cancer Genome Atlas database indicated that IQGAP3 is co-localized with kinesin family member C1 (KIFC1), which we previously reported as a cancer stem cell-associated protein. IQGAP3 small interfering RNA treatment decreased PDAC cell proliferation and spheroid colony formation via ERK and AKT pathways.

Discussion/conclusion: These results suggest that IQGAP3, a transmembrane protein, is involved in survival and stemness and may be a promising new therapeutic target for PDAC.