Telomere maintenance and DNA damage responses during lung carcinogenesis.
OBJECTIVE
Telomere shortening is an early event in bronchial carcinogenesis, preceding P53/Rb pathway inactivation and telomerase reactivation, and leading to DNA damage responses (DDR). As their inactivation in cancer increases genetic instability, our objective was to identify the chronology of telomere machinery critical events for malignant progression.


METHODS
We have evaluated telomere length by fluorescence in situ hybridization and analyzed DDR proteins p-CHK2, p-ATM, and p-H2AX, and telomeric maintenance proteins TRF1 and TRF2 expression by immunohistochemistry in normal bronchial/bronchiolar epithelium, and in 109 bronchial preneoplastic lesions, in comparison with 32 squamous invasive carcinoma (SCC), and in 27 atypical alveolar hyperplasia (AAH) in comparison with 6 adenocarcinoma in situ (AIS; formerly bronchiolo-alveolar carcinoma) and 24 invasive adenocarcinoma (ADC).


RESULTS
Telomere length critically shortened at bronchial metaplasia stage to increase gradually from dysplasia to invasive SCC; in bronchiolo-alveolar lesions, telomere length decreased from normal to AIS and increased from stage I to II to stage III to IV ADC. Expression of TRF1 and TRF2 increased progressively from dysplasia to SCC and from AAH to invasive ADC. The expression of concomitant DDR proteins increased significantly from low- to high-grade dysplasia and from AAH to AIS and stage I to II ADC. P-CHK2 and p-H2AX expressions were highly correlated and both decreased, along with p-ATM, in SCC and advanced ADC.


CONCLUSIONS
Telomere attrition occurs at the earliest stage of lung carcinogenesis as an initiating event, preceding TRF1 and TRF2 overexpression for telomere stabilization. In contrast, dismiss of DDR, through p-H2AX and p-CHK2 downregulation, represents a late progressing event associated with SCC and ADC progression.
Lantuejoul
Sylvie
S
Department of Pathology, CHU A Michallon, Grenoble, France. SLantuejoul@chu-grenoble.fr
Raynaud
Christophe
C
Salameire
Dimitri
D
Gazzeri
Sylvie
S
Moro-Sibilot
Denis
D
Soria
Jean-Charles
JC
Brambilla
Christian
C
Brambilla
Elizabeth
E
D000230:Adenocarcinoma / Q000235:genetics* / Q000378:metabolism; D002282:Adenocarcinoma, Bronchiolo-Alveolar / Q000235:genetics* / Q000378:metabolism; D064007:Ataxia Telangiectasia Mutated Proteins; D002294:Carcinoma, Squamous Cell / Q000235:genetics; D018797:Cell Cycle Proteins / Q000378:metabolism; D064447:Checkpoint Kinase 2; D004249:DNA Damage; D004268:DNA-Binding Proteins / Q000378:metabolism; D018450:Disease Progression; D006657:Histones / Q000378:metabolism; D006965:Hyperplasia / Q000473:pathology; D007150:Immunohistochemistry; D008168:Lung / Q000378:metabolism / Q000473:pathology; D008175:Lung Neoplasms / Q000235:genetics* / Q000378:metabolism; D011230:Precancerous Conditions / Q000235:genetics* / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D016615:Telomere / Q000648:ultrastructure*; D035321:Telomeric Repeat Binding Protein 1 / Q000378:metabolism; D035341:Telomeric Repeat Binding Protein 2 / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000378:metabolism
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C468783:H2AX protein, human; D006657:Histones; C504753:TERF2 protein, human; D035321:Telomeric Repeat Binding Protein 1; D035341:Telomeric Repeat Binding Protein 2; D025521:Tumor Suppressor Proteins; D064447:Checkpoint Kinase 2; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C578634:CHEK2 protein, human; D017346:Protein Serine-Threonine Kinases