Alterations of plasma exosomal proteins and motabolies are associated with the progression of castration-resistant prostate cancer

Abstract

Background Current diagnosis tools for prostate cancer (PCa) such as serum PSA detection and prostate biopsy cannot distinguish dormant tumors from invasive malignancies, either be used as prognosis marker for castration resistant prostate cancer (CRPC), the lethal stage of PCa patients. Exosomes have been widely investigated as promising biomarkers for various diseases. We aim to characterize the proteomic and metabolomic profile of exosomes and to evaluate their potential value for the diagnosis of PCa, especially CRPC. We also investigate the functions of some specific exosome biomarkers in the progression of CRPC. Methods Integrated proteomics and metabolomics analysis were performed for plasma-derived exosomes collected from tumor-free controls (TFC), PCa and CRPC patients. Expression of specific exosomal proteins were further validated by targeted 4D-parallel reaction monitoring (PRM) mass spectrometry among the three cohorts. Tissue distribution and functional role of exosomal protein LRG1 was studied in clinical PCa tissue samples and cell line models. Results Three potential exosomal protein markers were identified. The apolipoprotein E level in PCa samples was 1.7-fold higher than that in TFC (receiver operating characteristic value, 0.74). Similarly, the levels of exosome-derived leucine-rich alpha2-glycoprotein 1 (LRG1) and inter-alpha-trypsin inhibitor heavy chain H3 (ITIH3) in the CRPC group were 1.7 and 2.04 times, respectively, higher than those in the PCa group (ROC values, 0.84 and 0.85, respectively), indicating that LRG1 and ITIH3 could serve as predictive markers for CRPC. For metabolomic evaluation of exosomes, a series of differentially expressed metabolites were identified, and a combined metabolite panel showed ROC value of 0.94 for distinguishing PCa from TFC and 0.97 for distinguishing CRPC from PCa. Immunohistochemistry of tissue microarray showed that LRG1 protein was significantly upregulated in advanced prostate cancer and functional assay revealed that ectopic expression of LRG1 can significantly enhance the malignant phenotype of prostate cancer cells. More importantly, PCa cell derived LRG1-overexpressed exosomes remarkably promoted angiogenesis. Conclusion Integration of proteomics and metabolomics data generated proteomic and metabolic signatures of plasma exosomes that may facilitate discrimination of CRPC from PCa and TFC patients, suggesting the potential of exosomal proteins and metabolites as CRPC markers. The study also confirmed the important role of exosomal protein LRG1 in PCa malignant progression.

Mass spectrometry‐based extracellular vesicle micromolecule detection in cancer biomarker discovery: An overview of metabolomics and lipidomics

“…This study is the first to reveal the potential relationship between 3′‐UMP and ESCC 59 . As for metabolites in pyrimidine metabolism, Liu et al observed low levels of dihydrothymine in EVs from PCa patients compared to noncancerous controls and proposed that PCa may prefer to maintain high levels of dihydrothymine in internal tumor cells instead of releasing them via EVs 71 …”

“…Differently, Eylem et al reported that proline was significantly decreased in both CRC patients’ serum and CRC cell supernatant compared to noncancerous controls 51 . Moreover, acetylglycine, an immunoregulation‐associated AA, is significantly higher in EVs from PCa patients relative to the healthy controls 71 …”

“…59 As for metabolites in pyrimidine metabolism, Liu et al observed low levels of dihydrothymine in EVs from PCa patients compared to noncancerous controls and proposed that PCa may prefer to maintain high levels of dihydrothymine in internal tumor cells instead of releasing them via EVs. 71 Additionally, two other EV metabolomic studies based on the lung cancer population also demonstrated changes in metabolites related to nucleotide metabolism in EVs from urine or PE. 23,62 To be noted, the group sets in a study by Hinzman et al were preradiation therapy (RT) and post-RT.…”

“…51 Moreover, acetylglycine, an immunoregulation-associated AA, is significantly higher in EVs from PCa patients relative to the healthy controls. 71 Besides those proteinogenic AAs, the nonproteinogenic AA ornithine also plays an essential role in cancer cell activity as well as tumor development. 72 For instance, accumulation of ornithine was observed in cancer-related EVs (upregulated in colon cancer urine and plasma 57 ; downregulated in malignant PE 23 ) in contrast to those of healthy controls.…”

Metabolomic biomarkers in liquid biopsy: accurate cancer diagnosis and prognosis monitoring

“…Phospholipids are important components of extracellular vesicles, and there is growing evidence that PCs, PEs, and SMs in EVs derived from biological fluids show significant differences between cancer patients and non-cancer controls ( 130 – 132 , 134 – 136 , 139 ). It has been proposed that changes in the fatty acids content of blood-derived extracellular vesicles may indicate the presence of cancer ( 133 , 136 – 138 , 140 ). Although there is currently no consensus on the diagnostic value of extracellular vesicle-derived lipid metabolites in different tumors, these findings suggest a great potential for metabolomics-based extracellular vesicle assays to advance into clinical practice.…”