Radiosensitizing effects of ectopic miR-101 on non-small-cell lung cancer cells depend on the endogenous miR-101 level.
OBJECTIVE
Previously, we showed that ectopic miR-101 could sensitize human tumor cells to radiation by targeting ATM and DNA-PK catalytic subunit (DNA-PKcs) to inhibit DNA repair, as the endogenous miR-101 levels are low in tumors in general. However, the heterogeneity of human cancers may result in an exception. The purpose of this study was to test the hypothesis that a few tumor cell lines with a high level of endogenous miR-101 would prove less response to ectopic miR-101.


METHODS
Fourteeen non-small-cell lung cancer (NSCLC) cell lines and one immortalized non-malignant lung epithelial cell line (NL20) were used for comparing endogenous miR-101 levels by real-time reverse transcription-polymerase chain reaction. Based on the different miR-101 levels, four cell lines with different miR-101 levels were chosen for transfection with a green fluorescent protein-lentiviral plasmid encoding miR-101. The target protein levels were measured by using Western blotting. The radiosensitizing effects of ectopic miR-101 on these NSCLC cell lines were determined by a clonogenic assay and xenograft mouse model.


RESULTS
The endogenous miR-101 level was similar or lower in 13 NSCLC cell lines but was 11-fold higher in one cell line (H157) than in NL20 cells. Although ectopic miR-101 efficiently decreased the ATM and DNA-PKcs levels and increased the radiosensitization level in H1299, H1975, and A549 cells, it did not change the levels of the miR-101 targets or radiosensitivity in H157 cells. Similar results were observed in xenograft mice.


CONCLUSIONS
A small number of NSCLC cell lines could have a high level of endogenous miR-101. The ectopic miR-101 was able to radiosensitize most NSCLC cells, except for the NSCLC cell lines that had a much higher endogenous miR-101 level. These results suggest that when we choose one miRNA as a therapeutic tool, the endogenous level of the miRNA in each tumor should be considered.
Department of Radiation Oncology, School of Medicine and the Winship Cancer Institute, Emory University, Atlanta, GA 30322, USA.
Susie
S
Chen
Hongyan
H
Wang
Wooi Loon
WL
Ng
Walter J
WJ
Curran
Ya
Y
Wang
D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D002289:Carcinoma, Non-Small-Cell Lung / Q000378:metabolism / Q000532:radiotherapy*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor / Q000378:metabolism / Q000528:radiation effects; D051747:DNA-Activated Protein Kinase / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008175:Lung Neoplasms / Q000378:metabolism / Q000532:radiotherapy*; D051379:Mice; D008819:Mice, Nude; D035683:MicroRNAs / Q000378:metabolism* / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011836:Radiation Tolerance / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection / Q000379:methods; D014410:Tumor Stem Cell Assay; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*; D023041:Xenograft Model Antitumor Assays / Q000379:methods
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C534072:MIRN101 microRNA, human; D035683:MicroRNAs; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; D051747:DNA-Activated Protein Kinase; D017346:Protein Serine-Threonine Kinases