A small subset of patients with nonsmall cell lung cancer (NSCLC) harbors mutations in the epidermal growth factor receptor (EGFR) that predict unique sensitivity to EGFR tyrosine kinase inhibitors ...(TKIs). The characteristics and behavior of brain metastases (BMs) in these patients have not been well described. The longitudinal records of all NSCLC patients who underwent EGFR mutation screening at our center from August 2004 to November 2008 were reviewed for eligibility, and 93 patients were identified who developed BM during the course of their disease. Survival was estimated using the Kaplan-Meier method and the log-rank test. Multivariable predictors were assessed via the Cox proportional hazards model. Among the 93 patients with BM, 41 (44%) had mutations in EGFR, including 13 exon 19 deletions and 12 L858R mutations. Eighty-three percent of patients with BM were treated initially with whole brain radiation, either alone (53%) or in combination with craniotomy for neurosurgical resection (22%) or stereotactic radiosurgery (8%). Median survival from the time of BM was 11.7 months and was longer for patients with an EGFR mutation (14.5 vs 7.6 months, P = .09). On multivariable analysis, EGFR mutation (HR: 0.50, 95% CI: 0.30-0.82), age (HR: 1.03, 95% CI: 1.00-1.05), and active extracranial disease (HR: 3.30, 95% CI: 1.70-6.41) were independently associated with survival. In NSCLC patients with BM, EGFR mutation status is associated with improved survival, independent of age, functional status, extracranial disease status, and number of BMs.
We hypothesised that gene expression in histologically normal (HN) epithelium (NlEpi) would differ between breast cancer patients and usual-risk controls undergoing reduction mammoplasty (RM), and ...that gene expression in NlEpi from cancer-free prophylactic mastectomy (PM) samples from high-risk women would resemble HN gene expression.
We analysed gene expression in 73 NlEpi samples microdissected from frozen tissue. In 42 samples, we used microarrays to compare gene expression between 18 RM patients and 18 age-matched HN (9 oestrogen receptor (ER)+, 9 ER-) and 6 PM patients. Data were analysed using a Bayesian approach (BADGE), and validated with quantitative real-time PCR (qPCR) in 31 independent NlEpi samples from 8 RM, 17 HN, and 6 PM patients.
A total of 98 probe sets (86 genes) were differentially expressed between RM and HN samples. Performing hierarchical analysis with these 98 probe sets, PM and HN samples clustered together, away from RM samples. qPCR validation of independent samples was high (84%) and uniform in RM compared with HN patients, and lower (58%), but more heterogeneous, in RM compared with PM patients. The 86 genes were implicated in many processes including transcription and the MAPK pathway.
Gene expression differs between the NlEpi of breast cancer cases and controls. The profile of cancer cases can be discerned in high-risk NlEpi from cancer-free breasts. This suggests that the profile is not an effect of the tumour, but may mark increased risk and reveal the earliest genomic changes of breast cancer.
In mammalian cells, DNA double-strand breaks (DSBs) are repaired by three pathways, nonhomologous end-joining (NHEJ), gene conversion (GC) and single-strand annealing (SSA). These pathways are ...distinct with regard to repair efficiency and mutagenic potential and must be tightly controlled to preserve viability and genomic stability. Here, we employed chromosomal reporter constructs to characterize the hierarchy of NHEJ, GC and SSA at a single I-SceI-induced DSB in Chinese hamster ovary cells. We discovered that the use of GC and SSA was increased by 6- to 8-fold upon loss of Ku80 function, suggesting that NHEJ is dominant over the other two pathways. However, NHEJ efficiency was not altered if GC was impaired by Rad51 knockdown. Interestingly, when SSA was made available as an alternative mode for DSB repair, loss of Rad51 function led to an increase in SSA activity at the expense of NHEJ, implying that Rad51 may indirectly promote NHEJ by limiting SSA. We conclude that a repair hierarchy exists to limit the access of the most mutagenic mechanism, SSA, to the break site. Furthermore, the cellular choice of repair pathways is reversible and can be influenced at the level of effector proteins such as Ku80 or Rad51.
Repair of radiation damage to DNA WILLERS, H; DAHM-DAPHI, J; POWELL, S. N
British journal of cancer,
04/2004, Volume:
90, Issue:
7
Journal Article
Peer reviewed
Open access
DNA double-strand breaks constitute the most dangerous type of DNA damage induced by ionising radiation (IR). Accordingly, the resistance of cells to IR is modulated by three intimately related ...cellular processes: DNA repair, recombination, and replication. Significant discoveries in this field of research have been made over the last few years. A picture seems to be emerging in which perturbations of recombination in cancer cells are a more widespread cause of genomic instability than previously appreciated. Conversely, such cells may also be more sensitive to certain chemotherapeutic drugs and to IR. Thus, the alterations in recombination that promote carcinogenesis by causing genomic instability may also be the weakness of the tumours that arise in this setting, a concept which could hold great promise for the advancement of cancer treatment in the not too distant future.
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