HPV-positive clinically advanced squamous cell carcinoma of the urinary bladder (aBSCC): A comprehensive genomic profiling (CGP) study

Background: Advanced bladder squamous cell carcinoma (aBSCC) is an uncommon form of urinary bladder malignancy when compared with the much higher urothelial carcinoma incidence. We studied the genomic alteration (GA) landscape in a series of aBSCC based on the association with human papilloma virus (HPV) to determine if differences in GA would be observed between the positive and negative groups. Methods: Using a hybrid capture-based FDA-approved CGP assay, a series of 171 aBSCC were sequenced to evaluate all classes of GA. Tumor mutational burden (TMB) was determined on up to 1.1 Mbp of sequenced DNA and microsatellite instability (MSI) was determined on up to 114 loci. Programmed cell death ligand -1 (PD-L1) expression was determined by IHC (Dako 22C3) with negative expression when PD-L1 was 0, lower expression of positivity set at 1 to 49%, and higher expression set at ≥50% expression. Results: Overall, 11 (6.4%) of the aBSCC were found to harbor HPV sequences (10 HPV16 and 1 HPV 11). HPV+ status was identified slightly more often in women (NS) and in younger patients (P = 0.04); 2 female patients with aBSCC had a prior history of SCC including 1 anal SCC and 1 vaginal SCC. HPV+ aBSCC had fewer GA/tumor (P < 0.0001), more inactivating mutations in RB1 (P = 0.032), and fewer inactivating GA in CDKN2A (P < 0.0001), CDKN2B (P = 0.05), TERT promoter (P = 0.0004) and TP53 (P < 0.0001). GA in genes associated with urothelial carcinoma including FGFR2 and FGFR3 were similar in both HPV+ and HPV- aBSCC groups. MTAP loss (homozygous deletion) which has emerged as a biomarker for PRMT5 inhibitor-based clinical trials was not identified in any of the 11 HPV+ aBSCC cases, which was significantly lower than the 28% positive frequency of MTAP loss in the HPV- aBSCC group (P < 0.0001). MTOR and PIK3CA pathway GA were not significantly different in the 2 groups. Putative biomarkers associated with immunotherapy (IO) response, including MSI and TMB status, were also similar in the 2 groups. PD-L1 expression data was available for a subset of both HPV+ and HPV- cases and showed high frequencies of positive staining which was not different in the 2 groups. Conclusions: HPV+ aBSCC tends to occur more often in younger patients. As reported in other HPV-associated squamous cell carcinomas, HPV+ aBSCC demonstrates significantly reduced frequencies of inactivating mutations in cell cycle regulatory genes with similar GA in MTOR and PIK3CA pathways. The implication of HPV in the pathogenesis of bladder cancer remains unknown but warrants further exploration and clinical validation.