Immunohistochemical detection of P-glycoprotein on frozen and paraffin-embedded tissue sections of normal and malignant tissues.

In this study the reactivity of the monoclonal antibodies (mabs) C 219, C 494 and 4E3 was compared on frozen and paraffin-embedded normal tissues and tumors. On frozen tissues we used an indirect immunoperoxidase method, while on paraffin sections a streptavidin-biotin method without antigen retrieval methods was used. In normal tissues all mabs were reactive with colon epithelium in frozen and paraffin-embedded sections. The bile canaliculi in the liver showed the most extensive reaction with C 219 in frozen sections, and to a lesser extent with C 494 and 4E3. C 219 reacted with the pancreatic acinar and ductal epithelium, whereas C 494 and 4E3 reacted predominantly in the stroma. The kidney showed positivity for all mabs in the collecting ducts and isolated solitary cells were reactive in the spleen. In the skin the eccrine part of the sweat glands was reactive for all mabs in paraffin sections. The lung, prostate and breast were negative for all mabs. Only in paraffin sections of various tissues did the C 494 appear to be reactive with nerve fibers and ganglion cells. Colon cancers were positive for P-170 with all mabs tested. In breast carcinoma C 494 showed positive reactions in 8/26 frozen and 4/22 paraffin sections, while 4E3 was reactive with 20/25 frozen but only with 1/21 paraffin sections. C 219 gave similar results in frozen (22/26) and paraffin (17/26) sections of breast cancer. Ovarian carcinomas were positive with C 494 in 11/20 of the frozen and in 11/15 of the paraffin sections, while 4E3 again reacted more weakly in paraffin (5/15) than in frozen (15/20) sections. C 219 gave positive reactions in all ovarian carcinomas in frozen (20/20) and paraffin sections (14/14). In the tumors, the most intense reaction for all mabs was obtained in the colon, followed by the ovary and breast. Enhanced staining was seen in paraffin sections for mab C 494 in ovarian carcinoma. By demonstrating the presence of both an external and internal epitope on frozen sections, the combined use of 4E3 and C 219 gave complementary information about the expression of P-170.