Proteomic Profiles Associated With Postsurgical Progression in Nonfunctioning Pituitary Adenomas

Abstract

Context: There is a lack of reliable biomarkers capable of predicting postoperative tumor progression of nonfunctioning pituitary adenomas (NFPAs).

Objective: To discover proteomic profiles associated with postoperative tumor progression in patients with NFPAs. This was a case-controlled exploratory study at a tertiary university hospital. Tissue samples were obtained from 46 patients with residual tumor following surgery for NFPAs of gonadotroph lineage. Two patient groups were compared: patients requiring reintervention due to residual tumor progression (cases; reintervention group, n = 29) and patients with a residual tumor showing no progression for a minimum of 5 years (controls; radiologically stable group, n = 17). Differentially expressed proteins (DEPs) between patient groups were measured.

Results: Global quantitative proteomic analysis identified 4074 proteins, of which 550 were differentially expressed between the 2 groups (fold change >80%, false discovery rate-adjusted P ≤ .05). Principal component analysis showed good separation between the 2 groups. Functional enrichment analysis of the DEPs indicated processes involving translation, ROBO-receptor signaling, energy metabolism, mRNA metabolism, and RNA splicing. Several upregulated proteins in the reintervention group, including SNRPD1, SRSF10, SWAP-70, and PSMB1, are associated with tumor progression in other cancer types.

Conclusion: This is the first exploratory study analyzing proteomic profiles as markers of postoperative tumor progression in NFPAs. The findings clearly showed different profiles between tumors with indolent postoperative behavior and those with postoperative tumor progression. Both enriched pathways involving DEPs and specific upregulated proteins have previously been associated with tumor aggressiveness. These results suggest the value of proteomic profiling for predicting tumor progression in patients with NFPAs.

Keywords: nonfunctioning pituitary adenoma; quantitative proteomics; reintervention; tumor progression.

Figure 1.

Flowchart describing the study inclusion and exclusion criteria for patients. IHC, immunohistochemistry; NFPA, nonfunctioning pituitary adenoma; RT, radiotherapy.

Figure 2.

(A) PCA of radiologically stable tumors (AA) and tumors requiring reintervention (AB) based on their proteomic expression profiles showed a clear separation of the 2 patient groups, except for 1 patient (23AB; asterisk). The variation was explained by component 1 (32.8%) and component 2 (10.8%). (B) Unsupervised hierarchical clustering of significantly upregulated proteins (FC > 80%; FDR-adjusted P ≤ .05) showed 2 main clusters corresponding well to the control group (15 tumors, stable) and the cases group (25 tumors, reintervention), except for 5 patients comprising patients from both groups. FC, fold change; FDR, false discovery rate; PCA, principal component analysis.

Figure 3.

(A) Volcano plot of P vs log₂ FC in radiologically stable tumors (left) compared with tumors requiring reintervention (right). Significantly upregulated and downregulated proteins are highlighted (in blue) (FC > 80%; P ≤ .05). Proteins within ellipses are described in the text. (B) Violin plot presenting proteins with the highest degree of differential expression between study groups. FC, fold change.

Figure 4.

(A) Reactome pathway analysis displayed as a dot plot of the top 20 enriched pathways derived from the 550 proteins displaying significantly altered expression patterns (FC > 80%; FDR-adjusted P ≤ .05). The color of the dot designates the significance of the change in expression (adjusted P). The size of the dot signifies the number of enriched proteins. The X-axis represents the protein ratio (ie, the percentage of enriched target proteins among total proteins), and the Y-axis shows the name of the pathway. (B) Dot plot of the top 20 enriched Gene Ontology biological processes based on the 550 proteins showing significantly altered expression patterns (FC > 80%; FDR-adjusted P ≤ .05). The X-axis shows Rich factor and the color of the dot designating the significance of the change in expression (adjusted P). The size of the dot represents the number of proteins assigned to each biological process. (C) PPI and functional enrichment analysis for the 550 proteins showing significant differential expression revealed tight clusters of proteins associated with translation (left), RNA splicing (middle) and energy metabolism (right). FC, fold change; FDR, false discovery rate; PPI, protein–protein interaction.