Abstract 619: CHK2 and DNAPKc deficiency reduces DNA repair capacity and increases transformation efficiency in human bronchial epithelial cells.
Authors: Teneng Ivo , Willink Randy , Do Kieu C. , Dagucon Christopher , Belinsky Steven A. 
Published: August 2014

Reduced DNA repair capacity (DRC) and polymorphisms in genes involved in the repair pathways are associated with increased risk for lung cancer. Studies from our lab have demonstrated an association between increased double strand breaks (DSB) and increased risk for gene promoter hypermethylation. The goal of this study was to identify genes in the DSB repair pathway that may be rate limiting for DNA repair and to determine the effect of gene knockdown on genomic stability, DRC, gene promoter methylation, and cellular transformation. CHK2 is an important DNA damage sensor and cell cycle regulator gene that is important in maintaining genomic stability. DNAPKc is a kinase within the non-homologous end joining (NHEJ) pathway that participates in DNA repair by inducing conformational changes that allows access to DSB sites, and reduced activity is associated with lung cancer. Expression of CHK2 was reduced in 4 of 10 tumor-derived lung cancer cell lines, while 3 cell lines had undetectable levels of DNAPKc. We developed an in vitro model using human telomerase/cyclin dependent kinase 4-immortalized human bronchial epithelial cell lines (HBECs) to identify key molecular changes that drive transformation and clonal outgrowth of preneoplastic lung epithelial cells during exposure to carcinogens. CHK2 and DNAPKc were stably knocked down in HBEC2 and HBEC3 to determine their role in DRC, genomic instability and transformation. Knockdown of neither CHK2 nor DNAPKc affected microsatellite instability, nor was deficiency of either gene sufficient to induce spontaneous transformation in HBEC2 and HBEC3. Knockdown of CHK2 or DNAPKc decreased DRC in HBEC2 and HBEC3 in response to bleomycin, (a DSB-inducing carcinogen) indicating an important role for both genes in DSB repair. Knockdown cell lines were treated with bleomycin once a week for 12 weeks to determine the effect of gene deficiency on transformation. DNAPKc deficiency increased transformation efficiency in HBEC2 and HBEC3 by 14- and 4.5- fold, respectively, while CHK2 deficiency increased transformation efficiency in HBEC3 by 6- fold compared to bleomycin treated controls. Studies are ongoing to determine changes induced in the transcriptome and methylome in DNA repair-deficient cells during transformation. These studies will highlight the roles of CHK2 and DNAPKc in DSB repair, malignant transformation, and will shed more light on the role of DNAPKc and CHK2 in reprograming the genome.

Supported by R01 ES15262 to SAB

Citation Format: Ivo Teneng, Randy Willink, Kieu C. Do, Christopher Dagucon, Steven A. Belinsky. CHK2 and DNAPKc deficiency reduces DNA repair capacity and increases transformation efficiency in human bronchial epithelial cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 619. doi:10.1158/1538-7445.AM2013-619