Proteomic and bioinformatic approach relates bone marrow-originated tumor cells with lungcolonizing ability, rather than bone marrowresiding tumor cells, to a bone marrow mesenchymal stem cell phenotype

Abstract

A challenge in osteosarcoma (OS) is lung metastasis occurrence. OS, a bone marrow (BM)–associated tumor, is the most frequent pediatric bone tumor. A large percentage of patients diagnosed without metastasis would already present micrometastasis non-detectable by conventional methods. To identify metastasis associated-molecular signatures, we approached proteomics analysis demonstrating differential gene expression distinguishing OS cells with divergent lung-homing ability. Interestingly, subtle molecular differences distinguished the cellular content of both OS cell types. Major differences occurred in the secretome, and were associated to a functional behavior relevant to lungcolonization. To gain insight into spatial arrangements, we analyzed non-scaffold, anchorage-independent three-dimentional (3D) OS cell organizations. This would allow a more accurate comprehension of advantages to metastasize. We demonstrated that OS cells homing into the lungs had an increased ability to establish 3D structures, anattribute shared with mesenchymal stem cells (MSC). This would point that cellto-cell contact is a prominent feature in lung-colonizing cells. Since our previous results demonstrated that the secretome of divergent OS cells mostly distinguished lung-homing ability, we analyzed gene ontology (GO) terms in the secretome from OS cells and BM-derived MSC. MSC share the original OS niche. Surprisingly and related to cell hierarchy, we demonstrated that OS cells leaving the primary tumor rather than those remaining at the primary niche, share molecular and GO terms with MSC. Further, lung-colonizing OS cells had higher levels of expression of stem-related genes and lower expression of differentiation markers. These points the necessity to target stem-like tumor residing cells.