The unpredictable progression of melanoma makes it one of the most deadly forms of skin cancers. Now researchers say they’ve identified a second instance of melanoma cells fusing with blood cells in order to enable its metastasis into secondary organs in the body.
In the new report, researchers from Yale Cancer Centered studied the tumor biopsies of a melanoma patient who had received a bone marrow transplant. The resulting DNA analysis revealed the tumor had a mixture of two genetic profiles: one from the patient, and one from the donor. Researchers noted that the fusion happened in the primary tumor, as well as in the lymph nodes where the cancer had spread.
“The cancer cell and white blood cell DNA were mixed into the same nucleus,” said John Pawelek, the study’s senior author. “The hybrid has both the white blood cell propensity to move into lymph nodes as well as the dividing characteristics of the primary tumor.”
The Yale team’s results confirm a 2013 study, which reported the same genetic fusion event between melanoma cells and white blood cells. Together, the evidence supports the long-standing hypothesis that melanoma cells travel from the primary tumor site to distant organs via help from the blood cells.
"Our results provide the first proof in humans of a theory, proposed in 1911 by a German pathologist, that metastasis can occur when a leukocyte and cancer cell fuse and form a genetic hybrid,” said Pawelek.
"This could open the way to new therapy targets, but much work needs to be done to determine how fusion occurs, the frequency of such hybrids in human cancers, and the potential role of hybrids in metastasis,” said Pawelek. “There are a lot of steps involved in that process and those steps are all vulnerable to targeting."
Of note, the World Health Organization estimates that between 2 and 3 million people worldwide has skin cancer. And of that, about 132,000 people have melanoma. The incidence of skin cancer is only rising, as experts believe the depletion of the ozone layer will result in an additional 300,000 new cases every year.
Additional sources: Yale Cancer Center