Serial proteomic analysis identifies small extracellular vesicle-MASP2 as an early biomarker of chemotherapy response in advanced pancreatic cancer.

[BACKGROUND] The average survival of advanced pancreatic cancer (APC) is 6-12 months with first-line chemotherapy. Only one-third receive second-line treatment. No early biomarker exists to guide chemotherapy efficacy before tumor progression occurs. Circulating small extracellular vesicles (sEVs) are a potential source of biomarker discovery.

[METHODS] Longitudinally collected sEVs from chemotherapy treated APC patients at pre-treatment, remission and relapse underwent proteomic profiling by mass spectrometry (MS). GO and KEGG analyses assessed differential protein characteristics, while protein-protein interactions and upstream analyses explored potential mechanisms. A candidate biomarker was validated by ELISA in larger patient cohorts of responders and non-responders. Gene knock-down and overexpression studies and tumor immunohistochemistry (IHC) evaluated potential function and localization.

[RESULTS] MS identified 34 proteins unique to remission, 132 unique to treatment resistance, and 9 differential across both phases. Complement cascade alterations best reflected response to treatment. Lectin pathway component MASP2 (Mannose-Binding Lectin-Associated Serine Protease 2) emerged as a predictive biomarker: >20 % decline in sEV-MASP2 levels at month 2 (M2) of chemotherapy predicted response in 72 % of responders, whereas >20 % increase predicted treatment resistance in 73 % of non-responders. sEV-MASP2 at M2 was prognostic for survival (11 vs. 8 months; p = 0.0037), unlike CA 19-9 (11 vs. 12 months) and retained significance when CA 19-9 was unevaluable. Functional data indicated that sEV-MASP2 alterations largely reflect systemic rather than tumor site-specific activity.

[CONCLUSIONS] Complement pathway activity tracks with chemotherapy response and resistance in PC. Changes in sEV-MASP2 may serve as an early predictive/prognostic biomarker, helping to improve decision making in this lethal malignancy.