KDM6A expression loss is frequent in low grade non-invasive urothelial carcinomas of the urinary bladder.

OBJECTIVE

The gene lysine demethylase 6A (KDM6A) located on chromosome Xp11 often shows truncating mutations in urothelial carcinoma. Mutations resulting in protein expression loss can be detected by immunohistochemistry (IHC).

METHODS

A tissue microarray with >2,500 bladder tumors was analyzed by IHC. 78 cancers were sequenced for KDM6A.

RESULTS

KDM6A expression loss decreased from 36% of 345 pTaG2 low-grade to 23% of 152 pTaG2 high-grade and 18.5% of 92 pTaG3 tumors (p=0.0004) but not further in pT2-4 cancers (17.2-21.9%). KDM6A staining was unrelated to pT, pN, grade, and overall survival (p>0.1894) in 636 patients with pT2-4 cancers. KDM6A loss was more common in male (22.2%) than in female patients (15.4%; p=0.0067), and in tumors from males with Y-chromosome loss (36.1%) than without Y-loss (16.3%; p<0.0001). A KDM6A loss occurred in all 15 male and in 17 (74%) of 23 female patients with a truncating KDM6A mutation, but only 15 (75%) of 20 male and 17 (81%) of 21 female patients with KDM6A expression loss had a truncating mutation.

CONCLUSIONS

KDM6A expression loss is frequent in urothelial carcinoma and mostly due to truncating mutations. KDM6A IHC may be a useful tool for the distinction of neoplastic from non-neoplastic urothelial cells in follow-up examinations of patients with KDM6A deficient cancers.