Loss of DAB2IP expression in human urothelial carcinoma is associated with poorer recurrence-free survival

Prognostic value of AIB1 and EIF5A2 in intravesical recurrence after surgery for upper tract urothelial carcinoma

Objectives

The aim of this study was to investigate the prognostic effect of amplified in AIB1 and EIF5A2 expression on postoperative intravesical recurrence for upper urinary tract urothelial carcinoma (UTUC) and improve postoperative risk stratification and prediction of intravesical chemotherapy benefit.

Materials and methods

We evaluated immunohistochemical expression of AIB1 and EIF5A2 in 109 UTUC patients to determine the predictive significance in intravesical recurrence. A prognostic model was developed based on univariate and multivariate analyses.

Results

Intravesical recurrence occurred in 18 out of the 109 (16.5%) patients during the follow-up period. Significant associations of high expression of AIB1 and EIF5A2 with shortened bladder recurrence interval (median: 24 months vs 46 months, P=0.021; 28 months vs 39 months, P=0.002) were demonstrated. In different subsets of UTUC patients, high expression of AIB1 was a prognostic indicator in high grade (P=0.006) and pT2–4 (P=0.007), and high expression of EIF5A2 for high grade (P=0.014), pT2–4 (P=0.002) and pN0 (P=0.009). Moreover, in multivariate analysis, AIB1 and EIF5A2 expression (P=0.034 and 0.022, respectively) together with pN stage (P=0.009) provided significant independent predictors for intravesical recurrence after surgery for UTUC. Surgical approach with radical nephroureterectomy (RNU) was an informative factor toward good oncologic outcomes for intravesical recurrence (P=0.056). Based on a prognostic model with these factors, patients with UTUC were classified into the low-risk group and the high-risk group. In a subset analysis, the patients in the high-risk group were found to have a favorable response to intravesical chemotherapy (P=0.047). A nomogram based on the multivariate analysis was developed to predict intravesical recurrence accurately and guide postoperative intravesical instillations. The concordance index (c-index) of this model was 0.806.

Conclusion

High expression of AIB1 and EIF5A2 were independent predictors for intravesical recurrence after RNU and might be able to predict which patients benefit from postoperative intravesical chemotherapy.

DAB2IP with tumor-inhibiting activities exhibits frameshift mutations in gastrointestinal cancers

A scaffold protein DAB2 and its interaction partner DAB2IP have putative tumor suppressor gene (TSG) functions. Previous studies identified that both DAB2 and DAB2IP genes were inactivated by promoter hypermethylation in human cancers, but their mutational alterations in cancers remain largely unknown. The aim of our study was to find whether DAB2 and DAB2IP were mutated in gastric (GCs) and colorectal cancers (CRCs) by DNA sequencing. Both DAB2 and DAB2IP have mononucleotide repeats in their coding sequence that could be mutation targets in high microsatellite instability (MSI-H) cancers. We analyzed GC and CRC tissues and found that 8 of 34 GCs (23.5%) and 15 of 79 CRCs (20.0%) with MSI-H harbored DAB2IP frameshift mutations. DAB2 frameshift mutations were found in 2 of 79 CRCs (2.5%) with MSI-H. These mutations were not detected in microsatellite stable (MSS) cancers. We also found intratumoral heterogeneity (ITH) of DAB2IP frameshift mutations in 7 of 16 CRCs (43.8%). Loss of DAB2IP protein expression was found in approximately 20% of GCs and CRCs irrespective of MSI and DAB2IP frameshift mutation status. Our study shows that the TSG DAB2IP harbored frameshift mutations and ITH as well as expression loss. Together these tumor alterations might play a role in tumorigenesis of GC and CRC with MSI-H by down-regulating the tumor-inhibiting activities of DAB2IP.