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Principal Investigator
Alice Sigurdson
Position Title
About this CDAS Project
PLCO (Learn more about this study)
Project ID
Functional DNA Repair Assays for Lung Cancer Risk: Prospective Analysis
Several investigators worldwide have used functional tests (e.g. G2 or mutagen sensitivity, host-cell reactivation, and Comet assays) in case-control studies to evaluate human cancer risk associated with various measures of DNA damage or in vitro DNA damage repair capacity (DRC). Many of these studies provide data suggesting that elevated DNA damage induced by in vitro mutagen exposure, or reduced DRC, was associated with increased cancer risk at several sites such as head and neck, lung, brain, breast, bladder, melanoma, and non-melanoma skin cancer. The predictiveness of these assays has, however, been hotly debated because the tests were performed on biologic specimens collected after cancer diagnosis and may be measuring the consequence rather than the underlying causes of cancer. Our objective is to assess lung cancer risk in relation to selected DNA repair functional assays using prospectively collected (pre-diagnostic) cryopreserved samples that have been EBV-transformed into lymphoblastoid cell lines, thus addressing the potential reverse-causation bias of previous studies. We are studying lung cancer because of the high public health impact of this disease and because these assays have been applied most often in lung cancer case-control studies. We will be the first to apply these assays in pre-diagnostic samples to assess cancer risk. We plan to evaluate 100 lung cancer cases and 100 age-, gender-, and smoking-matched controls within the Prostate, Lung, Colon, and Ovary (PLCO) Trial with cryopreserved whole blood collected 0.5-5 years prior to cancer diagnosis. We hypothesize that higher baseline DNA damage, increased mutagen sensitivity, and lower DRC will be associated with an elevated risk of lung cancer. Other analyses will explore differences in risk according to lung cancer histology, time from blood collection to diagnosis, and family history of lung or other cancers.

1. Create immortalized lymphoblastoid cell lines (LCLs) from cryopreserved B lymphocytes derived from PLCO vials that were step-frozen in DMSO.
2. Perform functional or related assays on 200 LCLs, comparing cases and controls for:
a. Single strand DNA break damage as an indicator of capacity to handle oxidative DNA damage (Comet Assay). Lung cancer cases will have higher levels of DNA damage than controls.
b. Capacity to repair bulky DNA adducts (Host cell reactivation (HCR) assay using benzo(a)pyrene diol epoxide (BPDE) as the test mutagen). Lung cancer cases will have a lower capacity to repair bulky adducts compared to controls.
c. Sensitivity to inducers of double strand DNA breaks (mutagen sensitivity assay for unrepaired chromatid breaks after bleomycin exposure). Lung cancer cases will have increased frequencies of chromatid breaks compared to controls.
3. Follow-on study: Re-sequence for DNA repair pathway gene variants among the 40 persons occupying the extremes in the distribution tails for each of the 3 assays. This aim is designed to discover the gene variants contributing to the extremes in the phenotypes measured. Because cryopreserved lymphocytes were collected before cancer onset from more than 50,000 participants in the PLCO Trial, PLCO investigators are in a unique position to carry out these studies. In addition, these cell lines will be a continuing resource, growing increasingly valuable with further characterization and will provide an unlimited source of DNA.


Neil Caporaso (NCI, DCEG)
Michael Hauptmann (NCI, DCEG)
Richard Hayes (NCI, DCEG)
Wen-Yi Huang (NCI, DCEG)
Irene Jones (Lawrence Livermore Nat'l Laboratory)
Margaret Spitz (UT M.D. Anderson Cancer Center (UTMDACC))
Qingyi Wei (UTMDACC)
Douglas Reding (Marshfield Clinic)
Alice Sigurdson (NCI, DCEG)
Jeffery Struewing (LPG, CCR, NCI, NIH)
Xifeng Wu (UTMDACC)

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