Fig. 4
Basal and trastuzumab-mediated cytotoxicity of BC cell lines induced by PBMCs derived from the MTS patients according to the FcγRIIIA 158V>F and FcγRIIA 131R>H genotypes. PBMCs from MTS patients were analyzed for their cytolytic activity in an ADCC assay using trastuzumab (2 µg/ml) and SKBR3 (a, d), BT474 (b, e) and MCF-7 (c, f) cell lines at different effector to target cell ratios (E:T = 2:1, 5:1, 10:1, 20:1). PBMCs were incubated with target cells in medium alone (BASAL) or in the presence of trastuzumab (ADCC). Results are expressed as % of 51Cr specific release and are the mean of experiments with MTS patients at each E:T ratio. CV % was calculated as the standard deviation of cell lysis values among all the PBMC samples tested divided by the mean and multiplied by 100. CV at 20:1 E:T ratio for SKBR3: ADCC = 72 %, BASAL = 114 %; for BT474: ADCC = 81 %, BASAL = 108 %; for MCF-7: ADCC = 78 %, BASAL = 140 %. a–c V/V carriers (n = 3) and F carriers (n = 6) refer to PBMCs from patients carrying the FcγRIIIA (158 V/V) wild type genotype and the heterozygous (V/F) together with the mutated (F/F) genotype, respectively, when incubated with target cells in the absence of trastuzumab. Likewise, V/V carriers + Trast and F carriers + Trast, respectively, are referred to PBMCs, showing the genotypes described above, incubated in the presence of trastuzumab. d–f H/H carriers (n = 4) and R carriers (n = 5) refer to PBMCs from patients carrying the FcγRIIIA (131H/H) wild type genotype and the heterozygous (H/R) together with the mutated (R/R) genotype, respectively, when incubated with target cells in the absence of trastuzumab. Likewise, H/H carriers + Trast and R carriers + Trast, respectively, are referred to PBMCs, showing the genotypes described above, incubated in the presence of trastuzumab. Asterisks on the curves indicate significant ADCC at the specified E:T ratio evaluated using a paired Student’s t test (see “Results” for P values). MTS metastatic, ADCC antibody-dependent cellular cytotoxicity, Trast trastuzumab