Downregulation of IQGAP2 Correlates with Prostate Cancer Recurrence and Metastasis.

IQGAP2 was recently reported as a tumor suppressor of prostate cancer (PC). Nonetheless, its clinical implications remain unknown. To address this issue, we extracted data related to IQGAP2 mRNA expression and genomic alterations from multiple large datasets within the Oncomine and cBioPortal databases and performed in silico analyses to determine a potential association of IQGAP2 mRNA expression and its genomic alterations with PC progression. In 4 cohorts consisting of 118 normal prostate tissues and 277 PCs, IQGAP2 mRNA expression was significantly elevated particularly in low-grade (primary Gleason score ≤3) PCs; these changes separate PC from normal tissues with area under curve values of 0.7-0.8. Significant reductions in IQGAP2 mRNA levels and gene copy number occurred in more than 70 metastases compared to at least 230 local PCs. This duo-alteration in IQGAP2 expression supports IQGAP2 elevation suppressing and its downregulation facilitating PC progression. Deletion and missense mutations were detected in 23 of 492 primary PCs; these alterations significantly associate with PC recurrence (HR=2.71; 95% CI: 1.35-5.44; P=.005) after adjusting for known risk factors and correlate with reductions in disease-free survival (DFS, P=.002). IQGAP2 (5q13.3) genomic alterations were observed in SPOP-marked PCs and co-occurred with deletion in the RN7SK (16p12.2), SNORA50A (16q21), and SNORA50C (17q23.3) genes; the co-occurrence associated with reductions in DFS (P=4.14e-4). In two independent PC populations, MSKCC (n=130) and TCGA provisional (n=490), reductions in IQGAP2 mRNA expression were significantly associated with DFS. Collectively, this investigation reveals an association of IQGAP2 with PC progression.