Jennifer Wu and colleagues, at the University of Washington, now investigate how prostate cancers evade this anti-tumor defense strategy. The researchers found that MIC-expressing prostate cancer cell lines were able to activate natural killer cells, thus, initially, this defense mechanism appeared intact. Analysis of prostate tumor biopsies showed that the cell surface localization of MIC was highest in early-stage tumors. The researchers noted that tumors from later-stage patients, however, could no longer activate natural killer cells, and that there were high levels soluble MIC in the blood serum of these patients.
These data showed that the later stage tumors were shedding the MIC from their cell surfaces, and that this was the means by which prostate cancer cells could overcome this particular form of immune surveillance. The deficiency in the ability to activate natural killer cells could be overcome in tissue culture by stimulating the cells with the cytokine IL-2 or IL-15. The authors further investigated how soluble MIC level in serum related to prostate-specific antigen (PSA); PSA measurements are used as a biomarker for the presence of prostate cancer. Soluble MIC serum levels did not correspond with PSA serum levels, but they were highly correlative with high-grade and invasive tumor status in pros
Contact: Laurie Goodman
Journal of Clinical Investigation