ABSTRACT
The aim of the present study was to investigate if basal telomerase activity levels may predict sensitivity to cytotoxic drugs in a panel of human esophageal carcinoma cell lines. The TRAPeze telomerase detection assay was used to investigate telomerase activity in the cell lines. Cytotoxic drug sensitivity for 20 standard cytotoxic agents was assessed using the fluorometric microculture cytotoxicity assay (FMCA). Telomerase activity was detected in all cell lines with a broad range of activity levels. Drug sensitivity also varied considerably between the cell lines. Except for a P value towards a correlation between mitoxantrone and telomerase activity (P=0.054), no statistically significant correlation was found between telomerase activity levels and sensitivity to investigated drugs, including key drugs such as cisplatin (P=0.9), 5-fluorouracil (P=0.8) and doxorubicin (P=0.54). We therefore conclude that basal telomerase activity level is not a key determinant of sensitivity to standard cytotoxic drugs in esophageal carcinoma cell lines.
Subject(s)
Antineoplastic Agents/pharmacology , Cytotoxins/pharmacology , Esophageal Neoplasms , Telomerase/analysis , Biomarkers, Tumor , Cell Line, Tumor , Drug Screening Assays, Antitumor , Enzyme Activation/drug effects , Esophageal Neoplasms/drug therapy , Esophageal Neoplasms/enzymology , Humans , Predictive Value of TestsABSTRACT
The aim of the present study was to explore hTERT as a target for IFN-induced sensitization to apoptosis in multiple myeloma (MM). IFN-alpha and IFN-gamma downregulated telomerase activity in the IL-6-dependent MM cell line U-266-1970. In MM cells undergoing IFN-induced sensitization to Fas-mediated apoptosis, the repression of telomerase was increased as compared to IFN-alpha treatment alone. Similar to the sensitization effect of IFN, the use of a dominant negative IkappaBalpha vector inhibiting hTERT activity via transcriptional targeting resulted in augmentation of Fas-mediated apoptosis. The mechanism underlying the reduction of telomerase activity by IFN was shown to be transcriptional repression of the hTERT gene. The present study does not support a direct effect of IFN on NF-kappaB binding to the hTERT promoter as underlying the transcriptional repression. We conclude that one potential mechanism whereby IFNs induce apoptosis sensitization is by repressing hTERT transcription and telomerase activity, thereby constituting attractive targets for MM therapy.
Subject(s)
Apoptosis/drug effects , DNA-Binding Proteins/genetics , Interferons/pharmacology , Multiple Myeloma/physiopathology , Promoter Regions, Genetic/drug effects , Telomerase/genetics , Cell Line, Tumor , Down-Regulation , G1 Phase/drug effects , Humans , I-kappa B Proteins/pharmacology , Interferon-alpha/pharmacology , Interferon-gamma/pharmacology , Multiple Myeloma/genetics , NF-KappaB Inhibitor alpha , NF-kappa B/antagonists & inhibitors , Promoter Regions, Genetic/physiology , Transcription, Genetic/drug effects , fas Receptor/pharmacologyABSTRACT
The aim of the present study was to investigate the effect of transforming growth factor-beta1 (TGF-beta1) on telomerase activity in a panel of human anaplastic thyroid carcinoma (ATC) cell lines. Addition of TGF-beta1 decreased the telomerase activity in HTh 74 and KTC-1 cells, while in C 643 and HTh 7 an increased activity was observed. The decreased telomerase activity appeared to be due to transcriptional repression of the hTERT promoter. Addition of a PI-3 kinase inhibitor (LY294002) abrogated the stimulatory effect of TGF-beta1 on the telomerase activity, indicating the possible involvement of hTERT activation via phosphorylation. Furthermore, the MEK-inhibitor U0126 had similar effects suggesting dual regulatory mechanisms. Interestingly, the cell lines differed genetically in that ATC cell lines responding with increased telomerase activity harbored a p53 mutation. In conclusion, TGF-beta1 exerts opposing effects on telomerase activity in ATC cell lines, possibly reflecting deregulation of TGF-beta1 signaling in a more malignant genotype.
