This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Tang, X. Articles by Mao, L. Search for Related Content PubMed PubMed Citation Articles by Tang, X. Articles by Mao, L.

---

Cell Cycle, Cell Death, and Senescence

Hypermethylation of the Death-Associated Protein Kinase Promoter Attenuates the Sensitivity to Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand-Induced Apoptosis in Human Non–Small Cell Lung Cancer Cells ¹

Department of Thoracic/Head and Neck Medical Oncology, University of Texas M.D. Anderson Cancer Center, Houston, Texas

Requests for reprints: Li Mao, Molecular Biology Laboratory, Department of Thoracic/Head and Neck Medical Oncology, University of Texas M.D. Anderson Cancer Center, Unit 432, 1515 Holcombe Boulevard, Houston, TX 77030. Phone: 713-792-6363; Fax: 713-796-8655. E-mail: lmao{at}mdanderson.org

Death-associated protein (DAP) kinase plays an important role in IFN-, tumor necrosis factor (TNF)-, or Fas–ligand induced apoptosis. TNF-related apoptosis-inducing ligand (TRAIL) is a member of the TNF ligand family and can induce caspase-dependent apoptosis in cancer cells while sparing most of the normal cells. However, some of the cancer cell lines are insensitive to TRAIL, and such resistance cannot be explained by the dysfunction of TRAIL receptors or their known downstream targets. We reported previously that DAP kinase promoter is frequently methylated in non-small cell lung cancer (NSCLC), and such methylation is associated with a poor clinical outcome. To determine whether DAP kinase promoter methylation contributes to TRAIL resistance in NSCLC cells, we measured DAP kinase promoter methylation and its gene expression status in 11 NSCLC cell lines and correlated the methylation/expression status with the sensitivity of cells to TRAIL. Of the 11 cell lines, 1 had a completely methylated DAP kinase promoter and no detectable DAP kinase expression, 4 exhibited partial promoter methylation and substantially decreased gene expression, and the other 6 cell lines showed no methylation in the promoter and normal DAP kinase expression. Therefore, the amount of DAP kinase expression amount was negatively correlated to its promoter methylation (r = –0.77; P = 0.003). Interestingly, the cell lines without the DAP kinase promoter methylation underwent substantial apoptosis even in the low doses of TRAIL, whereas those with DAP kinase promoter methylation were resistant to the treatment. The resistance to TRAIL was reciprocally correlated to DAP kinase expression in 10 of the 11 cell lines at 10 ng/mL concentration (r = 0.91; P = 0.001). We treated cells resistant to TRAIL with 5-aza-2'-deoxycytidine, a demethylating reagent, and found that these cells expressed DAP kinase and became sensitive to TRAIL. These results suggest that DAP kinase is involved in TRAIL-mediated cell apoptosis and that a demethylating agent may have a role in enhancing TRAIL-mediated apoptosis in some NSCLC cells by reactivation of DAP kinase.

Key Words: DAP kinase • methylation • TRAIL • apoptosis • NSCLC

This article has been cited by other articles:

				S. Luxen, S. A. Belinsky, and U. G. Knaus Silencing of DUOX NADPH Oxidases by Promoter Hypermethylation in Lung Cancer Cancer Res., February 15, 2008; 68(4): 1037 - 1045. [Abstract] [Full Text] [PDF]