A transcriptomic signature of tertiary Gleason 5 predicts worse clinicopathological outcome

Objective: To investigate the genomic features of tertiary pattern 5 (TP5) on radical prostatectomy specimens in an effort to explain the poor clinical outcomes associated with this disease subtype.

Patients and methods: Data from 159 men with Gleason Grade Group (GGG) 3 or 4 were considered. All patients had Decipher diagnostic testing with transcript profiles and single-channel array normalisation (SCAN)-normalised expression of coding genes. The relationship between Decipher and TP5 was investigated by linear and binary logistic regressions. A differential transcriptomic analysis between patients with and without TP5 was performed. The prognostic role of these genes on progression-free survival (PFS) and overall survival (OS) was evaluated using The Cancer Genome Atlas.

Results: In all, 52/159 (33%) patients had GGG 3-4 with TP5 disease. TP5 was associated with a higher Decipher score (β 0.07, 95% confidence interval [CI] 0.02-0.13; P = 0.04) and higher likelihood of falling within the intermediate- or high-risk categories (odds ratio 3.34, 95% CI 1.34-8.35; P = 0.01). Analysis of microarray data revealed an 18-gene signature that was differentially expressed in patients with TP5; 13 genes were over- and five under-expressed in the TP5 cohort. The overexpression of cyclin dependent kinase inhibitor 2B (CDKN2B), polo-like kinase 1 (PLK1), or cell division cycle 20 (CDC20) was associated with worse PFS. The group harbouring overexpression of at least one gene had a 5-year PFS rate of 50% vs 74% in the group without overexpression (P < 0.001).

Conclusions: Our studies have elucidated unique genomic features of TP5, whilst confirming previous clinical findings that patients harbouring TP5 tend to have worse prognosis. This is the first RNA-based study to investigate the molecular diversity of TP5 and the first correlating CDKN2B to poorer prognosis in patients with prostate cancer.