The tyrosine kinase activity of the C-erbB-2 gene product (p185) is required for growth inhibition by anti-p185 antibodies but not for the cytotoxicity of an anti-p185-ricin-a chain immunotoxin
✍ Scribed by Feng Ji Xu; Cinda M. Boyer; Duk Soo Bae; Shu Wu; Marilee Greenwald; Kathy O'Briant1; Yin Hua Yu; Gordon B. Mills; Robert C. Bast Jr.
- Publisher
- John Wiley and Sons
- Year
- 1994
- Tongue
- French
- Weight
- 657 KB
- Volume
- 59
- Category
- Article
- ISSN
- 0020-7136
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✦ Synopsis
Our previous studies have demonstrated that 7 of 10 IgG antibodies against distinct epitopes on the extracellular domain of the c-erb6-2 gene product (p185) inhibit the anchorageindependent growth of SKBr3 human breast-cancer cells that overexpress this transmembrane tyrosine kinase growth-factor receptor. Two of 7 growth-inhibitory antibodies also block the binding and function of the gp30 and p75 c-erbB-2 ligands. In this report we have studied phosphorylation of p185 and different intracellular substrates after binding of antibodies that do or do not inhibit tumor-cell growth. A correlation has been found between antibodies that inhibit growth and the intensity of tyrosine phosphorylation of p185. A t late intervals, serine phosphorylation of at least 3 intracellular substrates is increased preferentially by growth-inhibitory antibodies. To test the importance of pi85 kinase activity more critically, NIH3T3 cells were transfected with an expression vector containing the full-length human c-erb6-2 gene (cell line I73 I3), c-erb6-2 with deletion of the kinase region from codons 751-979 (cell line 9309) or c-erbB-2 with deletion of most of the intracellular domain from codons 684-I255 (cell line 93 10). Unconjugated antibodies inhibited anchorage-independent growth of 173 I 3 cells as well as SKBr3 cells, but did not inhibit growth of either 9309 or 93 I0 cells. In contrast, the cytotoxic effect of anti-p 185r i c h A chain (RTA) conjugates was comparable for I73 13,9309 and 9310. The tyrosine-kinase activity of p185 is required for growth inhibition mediated by unconjugated anti-p I85 antibodies, but not for the cytotoxic activity of anti-p185-RTA immunotoxins.