Abstract
A tumour-associated antigen (TAA.62) with an apparent mol. wt. of 62 kd, identified by a human monoclonal antibody (IgG2, kappa-light chain), was found to be expressed at elevated levels in the cytoplasmic compartment of malignant as compared with normal mammary epithelial cells in both tissues and cultured cells. Increased levels of cytoplasmic expression of the antigen were also observed in malignant cells of cervix, colon, kidney, lung, and stomach. The patterns of expression of TAA.62 in cultured cells mirrored those of tissues and the antigen was expressed at elevated levels in the established breast cancer lines or oncogenically transformed mammary carcinoma cell line (tumourigenic) compared with the immortalised mammary epithelial cell line (non-tumourigenic). Aliquots of TAA.62 were purified to homogeneity from the conditioned-medium of malignant and immortalised breast cells by immunoaffinity chromatography using immobilised anti-TAA.62 antibody, and gel filtration. Both preparations of TAA.62 yielded a single band with an apparent molecular weight of 62 kd under reducing condition on sodium dodecyl sulphate-polyacrylamide gel electrophoresis, and both were identical in terms of size and immunoreactivity to anti-TAA.62 antibody. However, TAA.62(T) isolated from tumourigenic cell lines itself interacted with a cell surface molecule having an apparent molecular weight of 160 kd on both the malignant and immortalised cells: TAA.62(I) isolated from immortalized cell lines, showed no comparable interaction. Scatchard analysis of the concentration-dependent binding of TAA.62(T) to 160 kd-receptor molecule revealed a 2.6 x 10(4) binding sites per cell. The association constant of such binding was determined to be approximately 16.6 nM. Finally, addition of anti-TAA.62 antibody to culture medium resulted in the inhibition of proliferation of the malignant cells, but showed no effect on the normal cells. The results suggest that TAA.62 may interact as a ligand with its 160 kd cell surface receptor with a possible growth related function.
Highlights
Little information is available concerning molecules that regulate the growth of human mammary carcinoma cells
This paper reports the application of a human monoclonal antibody (IgG2, kappa-light chain) as a probe to purify and characterise an antigen, that is secreted at elevated levels by oncogenically transformed or established lines of mammary carcinoma cells, compared with immortalised counterparts
The immortalised cell line (184A1) is non-tumorigenic whereas the oncogenically transformed (184AIN4-T-D1O) mammary epithelial cell line is highly tumourigenic in nude mice (Clark et al, 1988)
Summary
Little information is available concerning molecules that regulate the growth of human mammary carcinoma cells. The lack of success in this field may be in part attributed to an approach that has relied heavily upon attempts to use xenogenic monoclonal antibodies as probes to identify such molecules (Ceriani et al, 1977; Herylyn et al, 1980; Minna et al, 1981). Xenogenic species are likely to evoke immune response preferentially to immunologically dominant antigens. The generation of monoclonal antibodies that detect functionally relevant molecules may be hindered by the production of multiple antibodies to such immunogenically dominant antigens in human cell preparations used for immunisation in the mouse
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
