Over-expression of IQGAP1 indicates poor prognosis in head and neck squamous cell carcinoma.

IQ-domain GTPase-activating protein 1 (IQGAP1) is associated with the development and progression of many human cancers. We aimed to investigate the expression and clinicopathological significances of IQGAP1 in head and neck squamous cell carcinoma (HNSCC). In this study, immunohistochemical staining of IQGAP1, co-inhibitory immune checkpoint molecules and macrophage markers were performed in human HNSCC samples to analyze the expression and correlation with clinicopathological characteristics. Immunoreactivity of IQGAP1 was also detected in immunocompetent mouse HNSCC tissue. We found that IQGAP1 expression level was significantly increased in human HNSCC compared with dysplasia and normal mucosa, and the expression of IQGAP1 in HNSCC was positively associated with advanced lymph node status. Besides, our data indicated that patients with higher IQGAP1 expression exhibited poor overall survival compared with patients with lower IQGAP1 expression. Furthermore, this study demonstrated that IQGAP1 expression was positively associated with TIM3, Galectin-9 (TIM3 ligand), B7H4, macrophage markers CD68 and CD163. In conclusion, these findings suggest that over-expression of IQGAP1 in human HNSCC may indicate poor prognosis.