Uptake of lipids from ascites drives NK cell metabolic dysfunction in ovarian cancer
Free fluid in the abdominal cavity is called ascites. When ascites occurs in patients with ovarian cancer it has always been recognised as an ominous sign of near death. Some understanding of why is now becoming clear. Previously it was thought that the loss of protein and general debility that occurs with ascites was responsible. This research suggests that the immune response to cancer is suppressed by fat content in the fluid.
The immune response to ovarian cancer is generated by a cellular mechanism via lymphocytes. There are two main types; T cells which are specific to the cancer cell antigen and Natural Killer (NK) cells which are non-specific and have a protective function by reducing metastasis of cancer and causing cell death.
In the presence of ascites, the immune response is suppressed. Using an experimental model with NK cells in ascitic fluid, the protection was impaired. This damage to lymphocyte function was not seen when the NK cells were placed in peritoneal fluid obtained from subjects who did not have cancer.
Further analysis of the components of ascites showed the active component causing impairment is the presence of phospho-lipids. These fats surround the NK cells, attaching to the cell membrane and preventing the normal cytotoxic action.