Background
Prostate cancer (PCa) constitutes a major oncological burden for men in Italy, ranking among the most frequently diagnosed malignancies. Among men with suspected PCa due to high PSA and/or positive digital rectal examination, only a subset is diagnosed with clinically significant disease (ISUP grade > 1), requiring timely intervention.
Objectives
Non invasive accurate identification of clinically significant PCa prior magnetic resonance imaging and/or bioptic sampling remains challenging and would allow for both a reduction of unnecassary second-level investigations (SLI) and a timely identification of potentially aggressive PCa.
Methods
The circulating proteome of 150 men referred for SLI at the Biella and Torino (Molinette) hospitals was investigated by the Olink Explore HT platform. Individuals with ISUP grade >1 PCa (n=95) were compared to those with non-PCa (n=38) or ISUP grade 1 tumors (n=17).
Results
Proetomic profiling enabled the simultaneous quantification of 5400 circulating proteins, revealing 14 upregulated and 92 downregulated proteins in individuals with ISUP >1 PCa. Geneset enrichment analysis suggests the following 3 main biological processes are overrepresented in higher-grade PCa: hyperactive inflammatory and cytotoxic signaling, which is the most clinically relevant theme, largely driven by IL6 and the Granzymes; enhanced neuro-secretory and intracellular trafficking, with a highly active internal cellular transport system, likely for promoting growth and communication (the upregulation of RAB3GAP1 and DNM1, alongside the synaptic vescicle localization geneset, suggests the tumor cells or cells in the microenvironment are rapidly packaging and secreting factors like IL6 that promote cancer progression; activation of G-protein signaling further links to altered cell polarity, migration, and the tumor's ability to respond to external signals from the microenvironment); upregulation of global regulatory and survival pathways with proteins such as NPM1 and ATXN7 signalling, a widespread metabolic and transcriptional reprogramming necessary for aggressive growth. On the other hand, the genesets overrepresented among the downregulated circulating proteins, suggest: widespread metabolic shutdown, with the downregulation of pathways responsible for normal cellular maintenance and energy production, suggesting a switch to an altered, tumor-specific metabolism; loss of differentiation, with downregulated signatures associated with normal development and mature cell states as well as overrepresentation of genesets reflecting a decrease in the machinery required for protein synthesis and maintenance, which often indicates poor differentiation; repressive chromatin reprogramming, with multiple downregulated genesets pointing to the active suppression of gene expression programs, often through chromatin modification; downregulation of immune and growth-regulating factors which represents a loss of immune signaling (loss of receptors such as IL9R, LILRB5, TLR1, CD86, LTB, CCL19) and normal growth control. This provides a vital counterpoint to the upregulated pathways indicating what the aggressive tumor has lost or actively suppressed to fuel its growth.
A specific proteomic diagnostic signature, capable of correctly classifying ISUP>1 tumors (ROC AUC=0.85), was derived and its orthogonal validation is ongoing.
Conclusions
Analysis of specific circulating proteins may represent a novel non-invasive tool to predict the presence of clinically significant PCa.

Volcano plot and differentially expressed proteins