Analysis of differentially expressed proteins in lymph fluids related to lymphatic metastasis in a breast cancer rabbit model guided by contrast‑enhanced ultrasound

Abstract

The aim of the present study was to identify differentially expressed proteins in the lymph fluid of rabbits with breast cancer lymphatic metastasis compared with healthy rabbits and to analyze and verify these proteins using proteomics technologies. In the process of breast cancer metastasis, the composition of the lymph fluid will also change. Rabbits with breast cancer lymph node metastasis and normal rabbits were selected for analysis. Lymph fluid was extracted under the guidance of percutaneous contrast-enhanced ultrasound. Label-free quantitative proteomics was used to detect and compare differences between the rabbit cancer model and healthy rabbits and differential protein expression results were obtained. Bioinformatics analysis was performed using Kyoto Encyclopedia of Genes and Genomes and Gene Ontology analysis software, selecting the most significantly differentially expressed proteins. Finally, parallel reaction monitoring technology was applied for validation. A total of 547 significantly differentially expressed proteins were found in the present study, which included 371 upregulated proteins and 176 downregulated proteins. The aforementioned genes were mainly involved in various cellular and metabolic pathways, including upregulated proteins, such as biliverdin reductase A and isocitrate dehydrogenase 2 and downregulated proteins, such as pyridoxal kinase. The upregulated proteins protein disulfide-isomerase 3, protein kinase cAMP-dependent type I regulatory subunit α and ATP-binding cassette sub-family C member 4 participated in immune regulation, endocrine regulation and anti-tumor drug resistance regulation, respectively. Compared with healthy rabbits, rabbits with breast cancer metastasis differentially expressed of a number of different proteins in their lymph, which participate in the pathophysiological process of tumor occurrence and metastasis. Through further research, these differential proteins can be used as predictive indicators of breast cancer metastasis and new therapeutic targets.

Keywords: breast cancer; contrast-enhanced ultrasonography; differentially expressed protein; lymph node metastasis; proteomics.

Figure 1.

Ultrasound imaging patterns of sentinel lymph nodes. (A) Homogeneous enhancement, (B) heterogeneous enhancement, (C) peripheral ring enhancement with no internal enhancement and (D) no enhancement with lymphatic vessel bypass around the lymph node. Respective features are indicated with arrows.

Figure 2.

Tumor volume in rabbits over the course of the experiment.

Figure 3.

Differentially expressed proteins in LNPG and CG groups of rabbits. (A) Volcano plot of differentially expressed proteins and a (B) Venn diagram of differentially expressed proteins in the LNPG and CG groups. CG, normal group; LNPG, metastasis group; FC, fold-change.

Figure 4.

GO enrichment analysis of the differentially expressed proteins in LNPG and CG groups of rabbits. (A) GO term annotation, (B) top 20 BP term enrichment bubble chart, (C) top 20 CC term enrichment bubble chart and (D) top 20 MF term enrichment bubble chart. GO, gene ontology; LNPG, metastasis group; CG, normal group; BP, biological processes; CC, cellular components; MF, molecular functions.

Figure 5.

KEGG enrichment analysis of differentially expressed proteins in LNPG and CG groups of rabbits. (A) Top 20 KEGG pathway bubble chart and (B) top 12 KEGG pathway enrichment butterfly chart. KEGG, Kyoto Encyclopedia of Genes and Genomes; LNPG, metastasis group; CG, normal group.

Figure 6.

Parallel reaction monitoring validation results for differentially expressed proteins. LNPG, metastasis group; CG, normal group. *P<0.05, **P<0.01 vs. CG group.