Identification of Differential Tumor Subtypes of T1 Bladder Cancer
Stage T1 bladder cancers have the highest progression and recurrence rates of all non-muscle invasive bladder tumors. T1 tumors are heterogeneous; while most T1 patients are treated with BCG, many will progress and die from bladder cancer, and particularly aggressive tumors could be treated by early cystectomy. To better understand the molecular heterogeneity of T1 cancers, we performed transcriptome profiling and unsupervised clustering, identifying five consensus subtypes of T1 tumors treated with reTUR, induction and maintenance BCG. The T1-LumGU subtype was associated with CIS (6/13, 46% of all CIS), had high E2F1 and EZH2 expression, and enriched E2F target and G2M checkpoint Hallmarks. T1-Inflam was inflamed and infiltrated with immune cells. While most T1 tumors were classified as luminal papillary, the T1-TLum subtype had the highest median Luminal Papillary score and FGFR3 expression, no recurrence events, and the fewest copy number gains. T1-Myc and T1-Early subtypes had the most recurrences (14/30 within 24 months), highest median MYC expression, and, when combined, had significantly worse recurrence-free survival than the other three subtypes. T1-Early had 5 (38%) recurrences within the first 6 months of BCG, and repressed IFN-alpha and IFN-gamma Hallmarks and inflammation. We developed a single-patient T1 classifier and validated our subtype biology in a second cohort of T1 tumors. Future research will be necessary to validate the proposed T1 subtypes and to determine if therapies can be individualized for each subtype. Overall design: Identify and characterize unsupervised expression subtypes in RNA-seq data, validate a single-sample subtype classifier in a second cohort.