Expression Profiling of Extracellular Microvesicles Reveals Intercellular Transmission of Oncogenic Pathways

Circulating microvesicles (MVs) have been described as important players in cell-to-cell communication carrying biological information both in normal and pathologic condition. MVs released by cancer cells may incorporate biomolecules such as active lipids, proteins and RNA, which can be delivered and internalized by recipient cells potentially altering gene expression of receiving cells eventually impacting disease progression. In this study, we took advantage of a leukemia in vitro model to investigate MVs as vehicles of protein coding messages. Leukemic cell lines (K562, REH and SHI-1) carrying recurrent translocations were analyzed. In the leukemic cells these translocations are transcribed into oncogenic fusion transcripts. Here, using gene expression microarrays we monitored leukemic fusion transcripts as hallmarks of leukemic cells transcriptome to track mRNA transfer from parental cells to MVs. Transcriptome analysis of K562 cells and released MVs disclosed MVs as not just “small scale cells”. In fact, a number of transcripts related to membrane activity, cell surface receptors and extracellular communication were enriched in the MVs pool. On the other hand, sets of transcripts related to the basal cellular functions and transcripts of the BCR-ABL oncogenic pathway downstream of the fusion protein were detected in MVs as well as in parental K562 cells. Moreover, through co-culture analyses uptake of leukemic MVs in receiving cells was confirmed and an MV-dosage dependent increase of target cell proliferation was demonstrated. Our study provides novel understanding of tumor-derived MVs as carrier of protein coding messages. For the first time a whole transcriptome gene expression analysis has been performed comparing K562 parental cells and released MVs, showing an enrichment of transcripts coding for oncogenic proteins and for proteins involved in key cellular pathways. Gene expression was measured on Affymetrix in 5 independent experiments of K562 cell lines and microvesicles derived from theK563 cell line