Walking back osteosarcoma steps: proteomic profiling of bone marrow mesenchymal stem cells and primary and lung colonizing osteosarcoma human cell lines.

Abstract

Osteosarcoma (OS), the most common malignant bone tumor, has a 20% five-year survival rate for metastatic disease and treatment-resistant patients. Rapid lung dissemination and acquired chemotherapy resistance remain as major clinical challenges. Mesenchymal stem cells (MSC) may contribute directly or indirectly to OS origin and progression. To identify potential metastasis biomarkers, we made a proteomic screening of non-metastatic SAOS2, metastatic LM7 OS cells and BM-MSC using a shotgun approach by a tandem nanocapillary liquid chromatography-mass spectrometry system. We identified 1049 proteins for BM-MSC, 1567 for SAOS2, and 1424 for LM7. To obtain gene ontology terms of the identified proteins, an enrichment analysis of the gene groups was carried out. The three cell populations shared 661 proteins corresponding to protein metabolism, metabolism, and energy-related pathways (25.72%, 22.37%, and 22.37% respectively). Individually, SAOS2 and LM7 cells showed the same number of shared proteins with BM-MSC, but the 64-shared proteins were not the same. Most relevant differences were that VEGF and PDGF signaling pathways were 2.25 fold-increased in LM7-MSC vs. SAOS2-MSC shared proteins. Further, citric acid and electron transport pathways were upregulated in SAOS2-MSC shared proteins. A comparison between SAOS2 and LM7 also shows upregulation of VEGF/PDGF signaling and other metastatic-related pathways in LM7 cells. Our results on the comparison of both OS cells to MSC, suggest that MSC may have a relevant role in OS progression, dictating not only tumor initiation but also metastatic dissemination. Further, LM7 cells had higher expression levels of proteins related to a mesenchymal phenotype and stem-related genes, suggesting a closer relation with MSC. Lung disease remains a major mortality factor in OS. Identification of mechanisms and differentially expressed genes associated with metastasis would help in discovering promising markers and therapeutic targets.