Semi‐quantitative Analysis of DNA Topoisomerase‐I mRNA Level Using Reverse Transcription‐Polymerase Chain Reaction in Cancer Cell Lines: Its Relation to Cytotoxicity against Camptothecin Derivative

Expression of DNA topoisomerase (Topo)‐I mRNA in various cancer cell lines was detected using the reverse transcription‐polymerase chain reaction (RT‐PCR) method. The cytoplasmic polyadenylated RNA isolated from cancer cell lines was reverse‐transcribed and the complementary DNA was amplified by PCR primed with Topo‐I specific primers. Fidelity of the amplified sequence was confirmed by restriction endonuclease digestion and Southern blot hybridization. The level of Topo‐I mRNA was correlated positively with the cytotoxicity of a Topo‐I inhibitor, a camptothecin derivative. This RT‐PCR method may be applicable to the assessment of sensitivity of cells to Topo‐I targeted drugs, especially when only small quantities of cell samples are available.