Expression and shedding of ligands of the activating NK cell receptor NKG2D in tumor spheroids of cervical carcinoma. Tumor spheroids grown from CaSki and SiHa cells were analyzed for the expression and release of soluble NKG2DLs. Tumor spheroid formation was induced by seeding 104 cells into 1.5 % agarose-coated 96-wells. (A) Expression of NKG2DLs in tumor spheroids collected on day 0 (d0), day 1 (d1) and day 2 (d2) analyzed by flow cytometry. Data are presented as mean ± SEM of three independent experiments (n = 3), measured in duplicates. (B) Kinetics of soluble NKG2DL release. Supernatants of tumor spheroids were collected on three consecutive days (d0 – d2) and concentrated 10-fold. Shedding of sMICA, sMICB, sULBP1, sULBP2 and sULBP3 was quantified by ELISA. Data are shown as mean ± SEM in pg/ml per 10.000 cells of three independent experiments (n = 3), measured in duplicates.