Human FcγRIII (CD16) Polymorphism Screening Is Enhanced with Pyrosequencing Analysis

Abstract 4911

Surface specific antigens expressed on the cell membrane of hematopoietic cells are attractive target for antibody mediated cancer cells therapy. Monoclonal antibodies involve various mechanisms to eliminate cancer cells, including antibody dependent cellular cytotoxicity (ADCC) and phagocytosis (ADCP) mediated by immune effector cells such as NK cells and macrophages bearing FcγRIIIA (CD16) receptor. Previous studies reported that clinical efficacy of monoclonal antibodies can be linked to the single nucleotide polymorphism found at position 559 in cDNA of the gene encoding FcγRIIIA. This allelic polymorphism generateses the following allotypes V/V, F/V or F/F at amino acid position 158 and can affect binding of mAbs and immune cell effector function. CD16-mediated binding is most efficient with the V/V genotype, and least efficient with the F/F genotype, leading to a range of efficacy in mAb-mediated targeted therapies. Currently, many patients are not screened for CD16 heterozygosity. Nevertheless there is a clear need for a diagnostic assay that will allow estimating the allelic polymorphism of a patient undergoing treatment with monoclonal antibodies utilizing ADCC/ADCP. Here we hypothesized that the pyrosequencing might improve a screening for polymorphisms of human FcγRIIIA-158 receptor. We studied 42 normal human subjects for the incidence of V/V, F/V and F/F CD16 polymorphisms using pyrosequencing technologies and compared to nested PCR-based allele-specific restriction assay. Compared to pyrosequencing, the nested PCR-based allele-specific restriction assay was 0. 33 sensitive and 1. 0 specific in discriminating the V/V and F/F genotypes, and 0. 33 sensitive and 0. 7 specific for the V/V and F/V genotypes (Table 1). Compared to pyrosequencing, the nested PCR-based allele-specific restriction assay was relatively insensitive and not specific in distinguishing the V/V genotype from other genotypes. Since the efficacy of the mAb-based targeted immunotherapy may be highly dependent upon the CD16 polymorphism in any given individual, we propose that pyrosequencing of the CD16 receptor be routinely evaluated in all patients. Such practices might prevent patients from randomizing to receive targeted therapies to that hematological malignancies for that have little or no therapeutic potential.