Immunohistochemical investigation of thymidylate synthase in cervical cancer

We prepared a polyclonal antibody against recombinant human thymidylate synthase (TS) to evaluate its use in immunohistochemical analysis. Formalin-fixed, paraffin-embedded sections of specimens of cervical tissue were prepared from 35 patients with cervical cancer. The TS immunoreactivity was studied by employing the peroxidase-labeled antibody method with our prepared antibody. At the same time, the TS activity was determined with the 5-fluoro-2'-deoxyuridylate (FdUMP)-TS-binding assay in fresh-frozen specimens of these cervical cancers. We observed a positive correlation (r = 0.658) between the degree of TS immunoreactivity and the TS activity in the binding assay of 9 patients with grade 4 (strongly positive) TS immunoreactivity, while 7 patients (78%) exhibited a TS activity of 5 pmol/g tissue or greater. Nine patients with a TS immunoreactivity of grade 1 (negative to weakly positive) showed a TS activity <5 pmol/g tissue. The difference between the two groups was statistically significant (p < 0.01). TS expression was easily detected by the immunohistochemical technique which will allow the assessment of the relationship between TS activity and patient outcome.