The novel cytotoxicity of neutrophils in the peripheral blood of breast cancer patients versus women without breast cancer.

44 Background: Using murine mammary tumor models, recent research conducted by our laboratory at the Sloan-Kettering Institute indicates that select neutrophils are mobilized and entrained by a primary breast tumor and uniquely have the capacity to inhibit metastatic seeding in the lung (Granot Z et al. unpublished). We sought to determine whether entrainment of cytotoxic neutrophils also occurs in blood samples from women with newly diagnosed breast cancer as contrasted to those garnered from healthy women. Methods: Subjects were 21 newly diagnosed pre-operative breast cancer patients without evidence of metastatic disease, 9 healthy female volunteers with no history of any cancer, and 3 patients with newly diagnosed DCIS. Neutrophils were purified from the blood samples. Cytotoxicity was evaluated by incubating isolated neutrophils with luciferase labeled MDA-MB-231 cells. Luciferase activity, as a reflection of % cell kill, was measured using a Bio-Tek microplate luminescence reader. Results: Significant cytotoxicity was notably observed when MDA-MB-231 cells were co-cultured with neutrophils purified from patients with invasive tumors. Pre-operative breast cancer patients (n=21) had a cell kill range of 0-30% (mean = 12.1%), whereas healthy subjects (n=9) had a cell kill range of 0.2-8% (mean = 2.6%), p<0.004. DCIS patients (N=3) had a cell kill range of 3-4% (mean = 2.7). Conclusions: To date, this preliminary work is the first to demonstrate the cytotoxic role of select neutrophils in the peripheral blood of breast cancer patients as contrasted with those from women without breast cancer. Further studies are needed to evaluate the prognostic and therapeutic role of cytotoxic neutrophils.