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L.F. Petersen



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    P1.02 - Biology/Pathology (ID 614)

    • Event: WCLC 2017
    • Type: Poster Session with Presenters Present
    • Track: Biology/Pathology
    • Presentations: 1
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      P1.02-013 - ATM Mutation as a Predictor for Mutation Burden in NSCLC (ID 10468)

      09:30 - 09:30  |  Author(s): L.F. Petersen

      • Abstract

      Background:
      Ataxia telangiectasia-mutated (ATM) is a critical first responder to DNA damage in the cell, but despite being one of the most mutated genes in lung cancer, no specific mutation hotspots have been linked with disease development. Our own quantitative analysis of ATM protein levels in patient samples suggests that ATM is lost in 20-25% of cases and that this loss correlates with poor overall survival and increased response to adjuvant chemotherapy treatments. We believe that this may be the result of increased genomic instability within the cancer cells caused by a lack of adequate DNA repair. Given that ATM-deficient cancers may have higher genetic instability, and that ATM is so highly mutated in lung cancer, we sought to quantify the relationship between ATM mutations and genomic instability, as measured by somatic mutation burden.

      Method:
      Using genomic and sequencing data available from publically available databases including the Broad Institute Cancer Cell Line Encyclopedia (CCLE) and the NIH Cancer Genome Atlas (TCGA), we correlated mutations in ATM and other genes involved with the DNA damage response with the total number of mutations annotated in ~900 cancer cell lines and ~200 lung adenocarcinomas.

      Result:
      We show that in cell lines across all cancer types, and particularly in lung, breast, and esophageal cancers, mutations in ATM correlate with a significantly higher number of total mutations. Only mutations in the direct damage response genes appeared to associate with total mutations, whereas p53 – while more commonly mutated – did not correlate with higher mutations in cell lines or patients. In lung cancer patients, however, neither ATM mutations nor ATM protein levels were similarly correlated with higher mutation burden.

      Conclusion:
      We have identified a potential relationship between ATM mutation and total somatic mutations in cancer cell lines which may be indicative of overall genetic instability. Analysis of the ATM mutations in both cell lines and patient samples clearly shows that there are no specific hotspots for mutation in ATM that correlate with increased total mutations. Thus screening for ATM mutations alone may not be sufficient to indicate loss of function or instability. However, this data may prove useful in developing panels of targets to screen as mutation hotspots of instability, and ultimately to help identify patients that may benefit from targeted or modified therapy options based on ATM-deficiency or higher genetic instability.

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    P3.02 - Biology/Pathology (ID 620)

    • Event: WCLC 2017
    • Type: Poster Session with Presenters Present
    • Track: Biology/Pathology
    • Presentations: 1
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      P3.02-077 - Platin Sensitivity and ATM-Deficiency in Non-Small Cell Lung Cancer (ID 10415)

      09:30 - 09:30  |  Author(s): L.F. Petersen

      • Abstract

      Background:
      Platinum based antineoplastic therapies (platins) are a first line treatment for non-small cell lung cancer (NSCLC) that generate DNA breaks and stimulate DNA damage response pathways. An inability to repair damage generated by these agents leads to cytotoxicity and cell death. A key mediator of the DNA damage response is ataxia telangiectasia mutated (ATM), an activator of downstream targets involved in DNA repair, cell cycle arrest, and apoptosis. Our lab has demonstrated that cell lines lacking ATM show increased sensitivity to platins. We hypothesize that platin exposure will activate ATM and that cells deficient in ATM will be innately sensitive to platins. Here we assess the molecular action of ATM in response to platins to determine if ATM-deficiency is predictive of platin sensitivity.

      Method:
      ATM status was determined in five NSCLC cell lines using western blotting and RT-qPCR. Cell lines were treated with varying concentrations cisplatin, carboplatin and oxaliplatin for 18-hours and assessed for ATM phosphorylation by western blot. Additionally, downstream targets of ATM (KAP-1, p53, and gamma-H2AX) were investigated to determine ATM pathway activation. Knockdown cell lines were generated using shRNA to ATM before testing for IR and cisplatin sensitivity using clonogenic assay. ATR and ATM inhibitors were tested on knockdown cell lines to investigate pathway response differences after cisplatin and IR.

      Result:
      NSCLC cell lines NCI-H226, NCI-H460, and NCI-H522 were found to be ATM-proficient whereas cell lines NCI-H23 and NCI-H1373 were found to be ATM-deficient. ATM-proficient cell lines demonstrated an increased level of phosphorylated-ATM in response to treatments with cisplatin, carboplatin, and oxaliplatin. ATM knockdown cell lines were found to have increased sensitivity to IR, however analysis of cisplatin sensitivity was inconclusive with only 1 out of 4 showing increased sensitivity. ATR inhibition in combination with cisplatin caused a large increase in DNA damage response from ATM and DNA-PKcs suggesting an avenue for synthetic lethality.

      Conclusion:
      It is clear that platin exposure induced an ATM mediated signalling response and that cells lacking ATM showed deficiencies in the phosphorylation of key downstream targets. Cells deficient in ATM may therefore be more susceptible to platin therapy due to an impaired DNA repair response. However, the predictive capabilities of ATM loss for platin sensitivity is still unclear. This data suggests that individuals with low or non-functioning ATM may be candidates for precision low dose therapies that exploit this deficiency.