Characterization of a Topoisomerase II Gene Rearrangement in a Human Small-Cell Lung Cancer Cell Line

摘要: BACKGROUND Small-cell lung cancer (SCLC) is a highly chemosensitive tumor, but the recurrent disease that common after initial response often unresponsive to further chemotherapy. Although mechanisms of drug resistance in SCLC have not been established, studies suggest alterations nuclear enzyme DNA topoisomerase II may reduce sensitivity cell action. This recognized as primary target for cytotoxic activity important antitumor agents. PURPOSE In this study, we attempted determine if altered forms are responsible reduced sensitivity. METHODS We characterized rearrangement p170 gene (also known TOP2) relatively chemoresistant line, NCI-H69, and compared expression line with those NCI-H187 line. Fragments complementary from were generated by polymerase chain reaction. Immunodetection was accomplished using monoclonal antibody 7E6 against human isoform. Using probes corresponding different regions, showed localized at 3' terminus one allele gene. RESULTS addition normal 6.2-kilobase (kb) messenger RNA (mRNA), NCI-H69 expressed 7.4-kb transcript, presumably encoded rearranged allele. Moreover, although longer than mRNA, lacked substantial portion 3'-terminal coding sequence. Topoisomerase extracts, determined P4 phage DNA-unknotting assay, more easily detected measured lower NaCl concentrations cells. CONCLUSION These results consistent hypothesis express, enzyme, an possibly which turn be transcribed IMPLICATION observations emphasize role determining such rearrangements contribute cells inhibitors.