Decidual-Like Natural Killer Cells Are Enriched in Melanomas and Acquire CD9 Through Melanoma Cell Contact

Researchers identified a specialized population of natural killer (NK) cells in melanoma tumors that share similar characteristics with NK cells found at the maternal-fetal interface. These decidual-like NK cells were present in melanoma tumors but were rare or absent in peripheral blood from healthy donors and melanoma patients. The cells were detected in primary tumors, lymph nodes, and distant metastases in both male and female patients. A patient with progressive disease treated with tumor-infiltrating lymphocyte therapy showed higher frequency of these cells. Direct contact between healthy NK cells and melanoma cells expressing CD9 caused the NK cells to acquire CD9, an effect that did not occur when cells were separated by a membrane. These findings suggest that direct interaction with melanoma cells may contribute to the development of this specialized NK cell population.