Exosomes, small membrane vesicles once thought to do little more than clean up a cell’s trash, have recently been recognized for their ability to carry diverse and complex messages around the body. (See “Exosome Explosion,” July 2011.) A new study published this week (May 27) in Nature Medicine demonstrates the importance of exosomes in promoting melanoma metastasis. Specifically, the vesicles appear to carry messages from the melanoma cells to the bone marrow, where they instruct bone marrow progenitor cells to become pro-vasculogenic and pro-metastatic, the researchers argue, through the transfer of the receptor tyrosine kinase MET.
“Our study is the first, to our knowledge, to show that transfer of the MET oncoprotein from tumor-derived exosomes to bone marrow progenitor cells promotes the metastatic process in vivo,” the authors wrote.
In addition to promoting metastasis, these cancer-derived exosomes may also serve as important biomarkers, with the levels of specific proteins within the vesicles yielding clues about the stage of the disease, likelihood of metastasis, and patient survival. Indeed, in comparing exosomes from patients with varying stages of melanoma, the researchers found that those with higher exosome-protein content tended to have a later stage of the disease, and even among patients with stage 4 cancer, higher protein content correlated with shorter survival times. (Hat tip to Genetic Engineering & Biotechnology News.)