Targeted Mass Spectrometry Assays for Specific Quantification of Urinary proPSA Isoforms

Area of Science:

• Biochemistry
• Analytical Chemistry
• Oncology

Background:

• Prostate cancer (PCa) is a significant cause of male cancer deaths.
• Prostate-specific antigen (PSA) precursor forms (proPSA) are linked to PCa.
• Existing antibody-based assays face challenges in specific proPSA isoform recognition.

Purpose of the Study:

• To develop antibody-free, targeted mass spectrometry assays for quantifying specific proPSA isoforms in urine.
• To evaluate the diagnostic utility of these proPSA isoforms in distinguishing PCa patients from healthy controls.

Main Methods:

• Utilized Lys-C digestion to generate specific surrogate peptides from proPSA isoforms.
• Employed long-gradient liquid chromatography for enhanced separation.
• Developed targeted mass spectrometry assays for simultaneous quantification of [-2], [-4], [-5], and [-7] proPSA isoforms.

Main Results:

• The assays successfully quantified multiple proPSA isoforms in voided urine samples.
• A combination of [-2] and [-4] proPSA isoforms achieved an AUC of 0.86 for PCa detection.
• All four quantified proPSA isoforms combined yielded an AUC of 0.85.

Conclusions:

• Antibody-free mass spectrometry assays offer a viable method for proPSA isoform quantification.
• ProPSA isoforms, particularly [-2] and [-4], demonstrate potential as biomarkers for PCa detection in urine.
• Further validation in larger cohorts is necessary to confirm clinical utility.