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Scientists have found a way to create modified immune cells that can seek and destroy melanoma.

In a new study published in the Journal of Clinical Investigation researchers tested modified dendritic cells, a component of the immune system, in patients with melanoma. 

Researchers explain that cells express a complex known as the proteasome, which is basically a garbage disposal for cells.

There are two types of proteasomes: constitutive proteasomes (cPs), which are found in normal tissues, and immunoproteasomes (iPs), which are found in stressed or damaged cells. In damaged cells, the immunoproteasomes or iPs generate protein fragments that are displayed on the surface of distressed cells.  These protein fragments are later recognized by the dendritic cells and destroyed by the immune system.

However, most cancer cells, including melanoma, only express constitutive proteasomes or cPs, which make it impossible for these damaged cells to express the protein fragments that are recognized by the immune system.  

To make it easier for the immune system to spot cancer cells, lead researcher Scott Pruitt and researchers at Duke University and Merck Research Laboratories engineered a dendritic cell that recognizes protein fragments of cancer specific antigens made by cPs.  Researchers then injected these modified dendritic cells into patients who were in remission from melanoma.

The study consisted of 12 participants. Four patients were vaccinated with regular dendritic cells, three patients received cells that underwent a control treatment and five patients received dendritic cells that recognized cancer-made protein fragments.

The findings revealed that vaccination with all three types of dendritic cells triggered an immune response, which peaked after three to four vaccinations with dendritic cells.  However, patients who received the modified dendritic cells had longer lasting immune response and fewer circulating melanoma cells.  Researchers found that treatment with modified dendritic cells resulted in a partial clinical response in one patient who had active disease and a complete clinical response in another patient with active disease.

Researchers said the findings suggest that altering dendritic cells in a way so that they can recognize cP-produced tumor antigens enhances immune recognition of melanoma cells.