Transcriptional profiling of patients with metastatic hormone-sensitive prostate cancer to uncover specific signatures linked to the transition from androgen-dependent to androgen-independent phenotype.

227 Background: Metastatic hormone-sensitive prostate cancers (mHSPC) are generally sensitive to androgen deprivation therapy (ADT). However, resistance often occurs, leading to disease progression. Understanding the transcriptomic changes underpinning the shift to antiandrogen resistance is crucial for identification of novel therapeutic vulnerabilities. Methods: Sixty patients with mHSPC undergoing ADT plus androgen receptor pathway inhibitors (ARPI) were enrolled. We defined non-responder (NR) patients (13/60) with biochemical/ radiological progression within 6 months of treatment and responder (R) (47/60) as those with stable disease or partial/complete response and eventually disease progression after 6 months. Total RNA was extracted from archived Formalin-Fixed Paraffin-Embedded (FFPE) basal prostate biopsies tissue samples using Maxwell RSC RNA FFPE Kit, and RNA was profiled using NanoString Tumor Signaling 360 Panel. Results: To identify gene signatures associated with response to ADT + ARPI, we analyzed differentially expressed genes between NR and R patients, through Rosalind platform Gene Set Analysis. Notably, NR patients exhibited significant upregulation of genes linked to cell cycle progression and DNA replication. The mitotic kinases AURKB and PLK1 were the most markedly upregulated genes in NR versus R samples (p=0.02 and p=0.01, respectively), suggesting enhanced cell cycle progression despite antiandrogen therapy. Coherent with these results, hyper-expression of KIF23 and CDC20 in NR vs R samples further confirmed aberrant cell cycle progression. Importantly, NR biopsies also exhibited increased expression of metastasis-promoting genes, such as HGF (p= 6.53 e-3 ), which may influence therapy response. Kaplan-Meier survival analysis reinforced the clinical significance of these findings, revealing that patients with hyper-expression of AURKB, KIF23, or CDC20, had shorter progression-free survival (PFS) compared to those with lower expression levels (p=0.0037, p=0.0007 and p=0.0289, respectively). These results underscore the potential of these molecular markers as predictive tools for resistance to ADT + ARPI and as potential targets for future therapeutic interventions. Conclusions: This study provides new insights into the transcriptomic landscape of mHSPC and identifies key gene signatures responsible for resistance to standard-of-care. Validation in larger cohorts is essential to confirm the predictive value of these genes and to identify patients eligible for novel combinatory treatments aimed at delaying this critical phenomenon.