Comparison of immunohistochemistry with immunoassay (ELISA) for the detection of components of the plasminogen activation system in human tumour tissue

Enzyme-linked immunosorbent assay (ELISA) methods and immunohistochemistry (IHC) are techniques that provide information on protein expression in tiss ue samples. Both methods have been used to investigate the impact of the pl asminogen activation (PA) system in cancer. In the present paper we first c ompared the expression levels of uPA, tPA, PAI-1 and uPAR in a compound gro up consisting of 33 cancer lesions of Various origin (breast, lung, colon, cervix and melanoma) as quantitated by ELISA and semi-quantitated by IHC. S econdly, the same kind of comparison was performed on a group of 23 melanom a lesions and a group of 28 breast carcinoma lesions. The two techniques we re applied to adjacent parts of the same frozen tissue sample, enabling the comparison of results obtained on material of almost identical composition . Spearman correlation coefficients between IHC results and ELISA results f or uPA, tPA, PAI-1 and uPAR varied between 0.41 and 0.78, and were higher f or the compound group and the breast cancer group than for the melanoma gro up. Although a higher IHC score category was always associated with an incr eased median ELISA value, there was an overlap of ELISA values from differe nt scoring classes. Hence, for the individual tumour cases the relation bet ween ELISA and IHC is ambiguous. This indicates that the two techniques are not directly interchangeable and that their value for clinical purposes ma y be different.