Expression of O6-alkylguanine-DNA alkyltransferase in Mer+ and Mer- human cell extracts probed with specific monoclonal antibodies.
The response of human cells to the mutagenic, carcinogenic, and lethal effects of alkylating agents that produce O6-alkylguanine adducts in DNA is largely determined by the cellular content of O6-alkylguanine-DNA alkyltransferase. Because a subgroup of human tumor cell lines (termed Mer-) that are hypersensitive to such agents appears to lack the transferase activity, we questioned whether this DNA-repair protein is produced in a non-functional mutant form or is simply not expressed in such cells. Ten human cell lines were examined by immunoblot analysis of crude extracts with monoclonal antibodies specific for the human alkyltransferase. Four Mer+ cell lines, high in transferase activity, clearly expressed the protein. This repair protein, however, was immunologically undetectable in six Mer- cell lines. It should be feasible therefore to predict sensitivity to O6-guanine-alkylating drugs or carcinogens by immunohistochemical staining of tumor or tissue specimens.
von Wronski, MA; Bigner, DD; Brent, TP
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