Study shines light on cancer metastasis theory

New York - New research could clarify the long-held “soil and seed” organ-specific metastasis theory that different cancerous tumor types spread only to specific, preferred organs.

A study led by researchers at Weill Cornell Medical College and Memorial Sloan-Kettering Cancer Center proposes a new mechanism controlling cancer metastasis that offers novel diagnostic and treatment potential.

The findings, published online by Nature Medicine, show how melanoma cancer cells release small “exosome” vesicles (microscopic particles filled with different molecules such as proteins and nucleic acids) that travel to the bone, liver, lung and brain and establish an environment ripe for spreading tumor cells.

The researchers say these cancer exosomes have various effects, such as triggering inflammation, promoting leaky blood vessels and “educating” bone-marrow progenitor cells to participate in the coming metastatic activity. The fact that the exosomes circulate in the blood - making them readily measurable and accessible - could be advantageous to cancer diagnoses, prognoses and treatment.

The researchers discovered two ways to reduce exosomal-induced metastasis. One was to target the protein Rab27a, responsible for production of exosomes. Another was to proactively educate bone-marrow-derived cells using exosomes from melanoma cells, which rarely metastasize.

In a Weill Cornell Medical College news release, study co-senior author David C. Lyden, M.D., said, “The exosome profile could be useful in a number of ways - to help detect cancer early, to predict the aggressiveness of a patient’s tumor and response to chemotherapy or other treatments, and to understand the risk of cancer recurrence or spread before traditional methods would be able to.”

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