Plasma Exosome-Derived Sentrin SUMO-Specific Protease 1: A Prognostic Biomarker in Patients With Osteosarcoma

Abstract

Background: The exosomes contain many important proteins that can be used for early tumor diagnosis or patient prognosis analysis. In this study, we investigated plasma exosome-derived sentrin SUMO-specific protease 1 (SENP1) levels as a prognostic biomarker in patients with osteosarcoma.

Methods: The expression of SENP1 protein in osteosarcoma tissues and adjacent tissues was detected by immunohistochemistry (IHC). The exosomes were identified by transmission electron microscopy, nanoparticle tracking analysis, and western blotting. ELISA was used to detect plasma exosome-derived SENP1 levels to assess prognosis in patients with osteosarcoma.

Results: IHC showed that the positive expression rate of SENP1 in osteosarcoma tissues was 88.33%, whereas that in adjacent tissues was 46.67% (P < 0.05). Plasma exosome-derived SENP1 levels were related to tumor size, tumor location, necrosis rate, pulmonary metastasis, and surgical stage. Both disease-free survival (DFS) and overall survival (OS) were worse in patients who had higher plasma exosome-derived SENP1 levels compared with those in patients with lower plasma exosome-derived SENP1 levels (P < 0.001). The area under the receiver operating characteristic curve (AUROC) of plasma exosome-derived SENP1, as 1-year DFS and 3-year DFS prognostic biomarkers, was 0.90 (95% CI: 0.83-0.98) and 0.96 (95% CI: 0.94-0.99), respectively. As to OS, the AUROC of plasma exosome-derived SENP1 for 1-year and 3-year prediction was 0.90 (95% CI: 0.82-0.99) and 0.96 (0.93-0.98), respectively. The plasma exosome-derived SENP1 was better than plasma SENP1 as a prognostic biomarker both in DFS and OS.

Conclusions: Our findings show that the plasma exosome-derived SENP1 may serve as a novel and independent prognostic predictor in clinical applications.

Keywords: exosomes; osteosarcoma; prognostic biomarker; sentrin sumo-specific protease 1 (SENP1); small ubiquitin-related modifier (SUMO).

Figure 1

Immunohistochemical analysis of SENP1 expression in osteosarcoma tissues and adjacent tissues. (A) High SENP1 expression in osteosarcoma tissues at 100×, 200× and 400× magnification. Low SENP1 expression in adjacent tissues at 100×, 200× and 400× magnification; (B) the positive rate of SENP1 protein expression in osteosarcoma tissues and adjacent tissues. (*P < 0.05).

Figure 2

Patient exosome characterization. (A) TEM images showed typical exosomes with oval or bowl-shaped microvesicles. (B) NTA data revealed that patient plasma exosome peak sizes were 50–120 nm. (C) Western blotting showed that patient plasma exosomes were positive for the four exosomal markers, annexin V, Tsg101, CD9, and CD63.

Figure 3

Relationship between plasma exosome-derived SENP1 levels and tumor characteristics. (A) No significant differences were observed between male and female patients (P = 0.104). (B) No significant differences were found between patients aged <20 and >20 years (P = 0.133). (C) Plasma exosome-derived SENP1 levels of patients with osteosarcoma with tumor size >10 cm were significantly higher than those in patients with tumor size <10 cm (P < 0.001). (D) Plasma exosome-derived SENP1 levels of patients with osteosarcoma located in distal extremity were significantly higher than those in patients with osteosarcoma located in proximal extremity (P = 0.008). (E) Plasma exosome-derived SENP1 levels of patients with osteosarcoma with necrosis rate >90% were significantly higher than those in patients with necrosis rate <90% (P < 0.001). (F) Plasma exosome-derived SENP1 levels of patients with osteosarcoma with pulmonary metastasis were significantly higher than those in patients without pulmonary metastasis (P < 0.001). (G) Plasma exosome-derived SENP1 levels of patients with osteosarcoma in surgical stag III;+IV were significantly higher than those in patients with osteosarcoma in surgical stage I+II (P < 0.001).

Figure 4

Association of plasma exosome-derived SENP1 levels with disease-free survival (DFS) and overall survival (OS) in patients with osteosarcoma. (A) Among all patients with osteosarcoma, DFS was worse in patients who had higher compared with lower plasma exosome-derived SENP1 levels (P < 0.001). (B) Among all patients with osteosarcoma, OS was worse in patients who had higher compared with lower plasma exosome-derived SENP1 levels (P < 0.001).

Figure 5

Prognostic value of plasma exosome-derived SENP1 levels in patients with osteosarcoma. (A) AUC for plasma exosome-derived SENP1 levels and plasma SENP1 levels for the prognostic value in patients with osteosarcoma 1-year DFS were 0.90 (95% CI: 0.83–0.98) and 0.52 (95% CI: 0.31–0.73), respectively. (B) AUC for plasma exosome-derived SENP1 levels and plasma SENP1 levels for the prognostic value in patients with osteosarcoma 3-year DFS were 0.96 (95% CI: 0.94–0.99) and 0.51 (95% CI: 0.41–0.60), respectively. (C) AUC for plasma exosome-derived SENP1 levels for the prognostic value in patients with osteosarcoma 1-year OS were 0.90 (95% CI: 0.82–0.99) and 0.59 (95% CI: 0.39–0.78), respectively. (D) AUC for plasma exosome-derived SENP1 levels for the prognostic value in patients with osteosarcoma 3-year OS were 0.96 (95% CI: 0.93–0.98) and 0.53 (95% CI: 0.43–0.62), respectively.