Single nucleotide polymorphisms of the EpCAM-coding gene TACSTD1 in patients with ovarian cancer and their potential translational aspects.

Purpose: EpCAM is overexpressed in many neoplasms including ovarian cancer. We screened the EpCAM-coding gene TACSTD1 for single nucleotide polymorphisms (SNPs), which could alter ovarian cancer risk, impact upon disease progression, or alter binding of the therapeutic EpCAM-binding antibody, catumaxomab.

Methods: DNA fragments of 10 healthy volunteers were analyzed to identify SNPs. Subsequently, DNA of ovarian cancer patients (n = 117) and age-matched healthy controls (n = 115) was genotyped by restriction fragment length polymorphism and pyrosequencing. TACSTD1 genotypes 4461T>C were cloned into a gene expression vector; Hek293 cells were subsequently used for stable transfection. FACS analysis of the transfected Hek293 cells was conducted with HO-3-the EpCAM binding site of catumaxomab-to determine antibody binding.

Results: One SNP was detected in exon 3 (4461T>C; rs1126497), resulting in an amino acid exchange at position 115 (Met115Thr). Another polymorphism was found in the 3'UTR (17225A>G; rs1421). Genotyping of patients and controls for these SNPs did not reveal significant differences in genotype distribution. Regarding 17225A>G, the homozygous AA-genotype was associated with diminished progression-free survival (PFS; p = 0.032). Overall survival, FIGO-stage, grading, and age did not differ significantly between genotypes. FACS analysis of transfected Hek293 cells overexpressing EpCAM 115Met/Thr showed binding of HO-3 to both proteins.

Conclusions: The AA-genotype of 17225A>G seems to be associated with diminished PFS in ovarian cancer patients. The amino acid exchange resulting from 4461T>C does not appear to alter binding of HO-3, suggesting that treatment with catumaxomab can be offered to patients regardless of their TACSTD1-genotype.