Differential transactivation of human metallothionein-IIa in cisplatin-resistant and -sensitive cells.
Cells with acquired anticancer drug resistance frequently exhibited broad cross-resistance to other anticancer agents. Increased human metallothionein (hMT) IIa transcription has been found in some cells with acquired resistance to cisplatin (CP). A panel of 5'hMT-IIa promoter deletions linked to the chloramphenicol acetyl transferase ((5'-hMT-IIaCAT) were used to demonstrate that certain cis-elements are important for the increased hMT-IIa transcription in CP-resistant cells (SCC25/CP) compared to CP-sensitive cells (SCC25). We further identified trans-acting factor differences between SCC25 and SCC25/CP cells using gel mobility shift assays. Significant increases in binding of specific factors to the -286 to -160 and -96 to -51 region were seen in CP-resistant SCC25/CP cells compared to sensitive SCC25 cells. Using cross-competition and super gel shift analyses, we identified enhanced Spl and AP-2 binding activity in SCC25/CP cells. By Western blot analysis and immunoprecipitation, we demonstrated that the level of Spl was unchanged between the two cells types whereas AP-2 was elevated twofold in SCC25/CP cells. Our results indicated that the selection of CP-resistant phenotype in SCC25/CP was accompanied by increased Spl and AP-2 DNA binding activities, which are likely not only to enhance hMT-IIa transcription but could also alter expression of other genes responsible for a broader anticancer drug cross-resistance. Thus, altered trans-acting factors could account for the complex cross-resistant phenotype found in some anticancer drug-resistant cells.
Yang
Y Y
YY
Department of Pharmacology, University of Pittsburgh School of Medicine, PA 15261, USA.
Robbins
P D
PD
Lazo
J S
JS
D000970:Antineoplastic Agents / Q000378:metabolism / Q000494:pharmacology; D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics / Q000378:metabolism; D002945:Cisplatin / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D004587:Electrophoresis, Agar Gel; D017930:Genes, Reporter; D005822:Genetic Vectors; D006258:Head and Neck Neoplasms / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008668:Metallothionein / Q000235:genetics / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D009363:Neoplasm Proteins; D008668:Metallothionein; D015500:Chloramphenicol O-Acetyltransferase; D002945:Cisplatin