2212

FCGR2A

Fc fragment of IgG, low affinity IIa, receptor (CD32);FCGR2A;Fc fragment of IgG, low affinity IIa, receptor (CD32)

Immunoglobulin G Fc receptor II|fc-gamma RII-a|fc-gamma-RIIa|fcRII-a|igG Fc receptor II-a|low affinity immunoglobulin gamma Fc region receptor II-a

1q23

protein-coding

OBJECTIVE: The aim of this study was to elucidate clinical implications of ABCB1, FCGR2A, and FCGR3A polymorphisms in patients with HER2-positive metastatic breast cancer (MBC) after taxane plus trastuzumab (TH) chemotherapy. METHODS: Using genomic DNA samples extracted from mononuclear cells of consecutive patients with HER2-positive MBC who received first-line TH, we analyzed five polymorphisms (ABCB1 1236C>T, ABCB1 2677G>T/A, ABCB1 3435C>T, FCGR2A 131H/R, and FCGR3A 158V/F) and then correlated them with the response rate, progression-free survival (PFS), overall survival (OS), and adverse events of patients. RESULTS: A total of 57 women were analyzed. The median age was 46 years (range 27-72). ABCB1 2677T carriers had a longer PFS (p = 0.037) along with a tendency toward a longer OS (p = 0.057). ABCB1 3435CC genotype carriers had a shorter PFS (p = 0.039) along with a tendency toward a shorter OS (p = 0.093). In combined analysis, PFS was significantly longer in ABCB1 1236CC and/or 2677TT carriers compared to the others (p = 0.006). FCGR2A 131H/R and FCGR3A 158V/F polymorphisms were not significantly associated with response rate, PFS, and OS. CONCLUSIONS: Our data support that ABCB1 polymorphisms may predict PFS after first-line TH chemotherapy in patients with HER2-positive MBC. In contrast, FCGR2A 131H/R and FCGR3A 158V/F polymorphisms could not predict treatment outcomes.

PURPOSE: Cetuximab, a chimeric immunoglobulin G 1 (IgG1) anti-epidermal growth factor receptor (EGFR) monoclonal antibody (mAb), has shown efficacy in 10% of patients with metastatic colorectal cancer (CRC). Recent studies demonstrate antibody-dependent cell-mediated cytotoxicity (ADCC) is one of the modes of action for rituximab and trastuzumab. Fragment c (Fc) portion of IgG1 mAb has shown to induce ADCC. Fragment c gamma receptors (FcgammaR) play an important role in initiating ADCC. Studies have shown that two IgG FcgammaR polymorphisms (FCGR2A-H131R and FCGR3A-V158F) independently predict response to rituximab in patients with follicular lymphoma. We tested the hypothesis of whether these two polymorphisms are associated with clinical outcome in metastatic CRC patients treated with single-agent cetuximab. PATIENTS AND METHODS: Thirty-nine metastatic CRC patients were enrolled onto the ImClone0144 trial. Using an allele-specific polymerase chain reaction (PCR) -based method, gene polymorphisms of FCGA2A-H131R and FCGA3A-V158F were assessed from genomic DNA extracted from peripheral blood samples. RESULTS: FCGR2A-H131R and FCGR3A-V158F polymorphisms were independently associated with progression-free survival (PFS; P = .037 and .055, respectively; log-rank test). Combined analysis of these two polymorphisms showed that patients with the favorable genotypes (FCGR2A, any histidine allele, and FCGR3A, any phenylalanine allele) showed a median PFS of 3.7 months (95% CI, 2.4 to 4.4 months), whereas patients with any two unfavorable genotypes (FCGR2A arginine/arginine or valine/valine) had a PFS of 1.1 months (95% CI, 1.0 to 1.4 months; P = .004; log-rank test). CONCLUSION: Our preliminary data suggest that these two polymorphisms may be useful molecular markers to predict clinical outcome in metastatic CRC patients treated with cetuximab and that they may indicate a role of ADCC of cetuximab.