Immunohistochemical characterisation of the monoclonal antibody BLCA-38 for the detection of prostate cancer

Abstract

Background: Monoclonal antibodies (MAbs) can be used to detect, image and treat cancers. This study aimed to characterise the binding of BLCA-38 MAbs to human prostate cancer cell lines, human prostate cancer biopsy samples and normal tissues to enable future targeted studies.

Methods: BLCA-38 antigen expression on cancer lines was determined by flow cytometry; that on patient specimens from normal tissues and cancers was tested by immunohistochemistry using fresh frozen tissues or paraffin-embedded tissues that had undergone antigen retrieval.

Results: Cell surface BLCA-38 antigen expression was seen on DU-145, PC-3, PC-3 M and PC-3 M-MM2 prostate cancer lines, but LNCaP, MDA PCa 2a or MDA PCa 2b lines were negative. Other human lines, including 8/12 bladder cancer and A431 vulval epidermoid cells, but not breast cancer lines, expressed BLCA-38 antigen. Staining occurred in glandular epithelial cells in the majority of frozen, and paraffin-embedded prostate cancer tissues and was occasionally seen in prostatic intraepithelial neoplasia (PIN). No staining was observed in normal cadaver tissues or in benign areas from various other cancer tissues.

Conclusions: The BLCA-38 antibody binds to the majority of human prostate cancers but not to normal cells, and has potential for targeting novel therapies in patients with this disease.

Fig. 1

Flow cytometric profiles of human cancer cell lines stained for membrane expression of BLCA-38. X-axis log scale of green fluorescence units, Y-axis number of events. The clear histogram represents staining obtained with secondary antibody only; solid histogram represents staining using BLCA-38 against the named cell lines grown in culture

Fig. 2a-h

Indirect immunohistochemical staining of BLCA-38 expression in prostate cancer cell lines, xenografts in nude mice and human prostate tumour biopsies. Strong membrane and cytoplasmic staining were seen in a cytospins of the positive cell line DU-145, by green immunofluorescence; b paraffin sections of the DU-145 xenograft, by immunoperoxidase/DAB; c PC-3 xenografts grown s.c. detected by immunoalkaline phosphatase/fast red; d PC-3 lymph node metastases detected by immunoalkaline phosphatase/fast red. Inserts show negative controls, a stained with irrelevant isotype–matched MAbs or b,c,d procedure controls where no primary antibody was used. e Human prostate cancers of Gleason score 6 (frozen section), insert shows normal prostate (frozen section). f PIN in human prostate cancer specimen (formalin-fixed, paraffin-embedded). g Human prostate cancers of Gleason score 9 (formalin-fixed, paraffin-embedded). h Positive staining in intraductal carcinoma of the prostate, but with no staining of the basal cells, that stain positively for cytokeratin 34βE₁₂ (insert, formalin-fixed, paraffin-embedded). Original magnification of images: a,b,e–h (also inserts) at ×40; c,d (also inserts) at ×20