Characterization of human NSCLC cell line with innate etoposide-resistance mediated by cytoplasmic localization of topoisomerase II alpha.
Topoisomerase (topo) II alpha is a target for many chemotherapeutic agents in clinical use. In tumor cells resistant to topo II poisons, there have been descriptions of quantitative and qualitative alterations involved in this enzyme. More recently, the cytoplasmic localization of topo II alpha has been described as a mechanism to confer drug resistance. Here, we report the characterization of a human non-small-cell lung cancer cell line, INER-37, which shows an innate resistance to etoposide. In this cell line, etoposide resistance was directly associated with the expression of topo II alpha resident mainly in the cytoplasmic region. At the molecular level, INER-37 cells carry on a heterozygous gene deletion, transcribing two different topo II alpha mRNAs: 4.8 kb and 2.0 kb. The bigger 4.8 kb mRNA (missing 1.3 kb of 3' mRNA and including the untranslated region) is translated into a truncated cytoplasmic protein of approximately 160 kDa. The protein truncation affects at least 96 amino acids in the COOH-terminal region where the more proximal bipartite nuclear localization signal is located. The INER-37 cell line is the first cancer cell line reported with an innate mutation affecting the 3'-end region of the topo II alpha gene that confers a cytoplasmic localization of the enzyme and therefore an increased resistance to etoposide.
de Lucio
Bautista
B
Depto. de Bioquímica, Instituto Nacional de Enfermedades Respiratorias-SSA, México, Clza. Tlalpan.
Manuel
Victor
V
Barrera-Rodríguez
Raul
R
D000951:Antigens, Neoplasm / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics; D000972:Antineoplastic Agents, Phytogenic / Q000493:pharmacokinetics* / Q000494:pharmacology*; D002289:Carcinoma, Non-Small-Cell Lung / Q000473:pathology*; D003593:Cytoplasm / Q000737:chemistry / Q000201:enzymology; D004252:DNA Mutational Analysis; D004250:DNA Topoisomerases, Type II / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics; D004268:DNA-Binding Proteins / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics; D019008:Drug Resistance, Neoplasm; D005047:Etoposide / Q000493:pharmacokinetics* / Q000494:pharmacology*; D020869:Gene Expression Profiling; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology*; D014407:Tumor Cells, Cultured
D000951:Antigens, Neoplasm; D000972:Antineoplastic Agents, Phytogenic; D004268:DNA-Binding Proteins; D005047:Etoposide; D004250:DNA Topoisomerases, Type II