Author of

• 25940

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  P2.03 - Biology (Not CME Accredited Session) (ID 952)

  • Event: WCLC 2018
  • Type: Poster Viewing in the Exhibit Hall
  • Track:
  • Presentations: 1
  • Moderators:
  • Coordinates: 9/25/2018, 16:45 - 18:00, Exhibit Hall

  • 26974

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    P2.03-36 - DNA Methylation: A More Sensitive Marker for Treatment Monitoring?  (ID 12916)

    16:45 - 18:00  |  Author(s): Shu Xia
    • Abstract

    Background
    

    Detection of genomic aberrations in cell-free DNA (cfDNA), requiring ultra-deep sequencing due to the low allelic frequencies (AF) of mutation, has been utilized to monitor treatment response. However, 20%-30% of patients yield no mutation from plasma genotyping despite deep sequencing depth, thus necessitating alternative monitoring method. The role of aberrant DNA methylation in the process of tumorigenesis both at individual genes and a genome-wide scale has been well elucidated. We investigated the potential of DNA methylation as a biomarker for treatment monitoring.

    a9ded1e5ce5d75814730bb4caaf49419 Method
    

    We investigated the performance of mutation and DNA methylation as biomarkers to evaluate response to osimertinib using a DNA methylation panel consisting of 100,000 CpG sites and a targeted panel for mutation detection consisting of 168 lung cancer related genes with an average sequencing depth of 1,000x and 10,000x, respectively. Longitudinal plasma samples from 6 patients undergoing osimertinib were collected prior to treatment and at regular interval until disease progression, ranged from 6 to 9 times. Methylation level of a given sample was reflected by the percentage of significantly methylated blocks, which were significantly hypermethylated blocks comparing to healthy individuals.

    4c3880bb027f159e801041b1021e88e8 Result
    

    All patients had EGFR sensitizing mutation and T790M at baseline. Four patients had additional concurrent mutations, including TP53, RB1, OR6F1 and BRCA2. At PD, all patients had detectable mutations except for one and 3 developed EFGR C797S. Four patients had at least two times of no detectable mutation during treatment. Among them, P05 and P06 had 5 and 6 times of no detectable mutation, respectively. In contrast, all patients had significantly methylated blocks detected at every point. In general, the trend of changes in mutation AF corresponds to the changes in the percentage of significantly methylated blocks in all patients except for one, who only had mutations detected at baseline and had consistently detectable DNA methylation at every point. Collectively, DNA methylation reached nadir at best response and gradually increased thereafter. An elevation of mutation AF or the emergence of new mutation(s) (molecular PD) was observed in 4 patients prior to PD assessed by imaging. In all patients, an elevation of DNA methylation was observed prior to PD assessed by imaging; among them, 3 had changes in DNA methylation prior to molecular PD, suggesting DNA methylation may be a more sensitive biomarker.

    8eea62084ca7e541d918e823422bd82e Conclusion
    

    Collectively, our study demonstrates DNA methylation, continuously increasing from the nadir (best response), can be utilized as a biomarker for treatment monitoring.

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• 25955

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  P3.01 - Advanced NSCLC (Not CME Accredited Session) (ID 967)

  • Event: WCLC 2018
  • Type: Poster Viewing in the Exhibit Hall
  • Track:
  • Presentations: 1
  • Moderators:
  • Coordinates: 9/26/2018, 12:00 - 13:30, Exhibit Hall

  • 27365

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    P3.01-14 - mTORC1 Regulates the Radiosensitivity of NSCLC Cells with Wildtype PI3KCA and KRAS Genes by Affecting EMT (ID 13125)

    12:00 - 13:30  |  Author(s): Shu Xia
    • Abstract

    Background
    

    Resistance to radiotherapy has been shown to be a key cause of treatment failure in NSCLC and associates with local recurrence and metastasis. Understanding how NSCLC cells sensitize to radiation is therefore important for developing new treatments and prognostics. It has been shown that mTORC1 can regulate tumor cell radiosensitivity, although the mechanisms that underlie this phenomenon are unclear. It have found that mTORC1 also regulates EMT, important to metastasis and recurrence. We therefore hypothesized that mTORC1 might affect NSCLC cell radiosensitivity by suppressing EMT.

    a9ded1e5ce5d75814730bb4caaf49419 Method
    

    We analyzed the expression of mTOR protein in NSCLC tissues from patients, in addition to adjacent and normal tissue.These data showed that mTOR protein was elevated in NSCLC tissue. We then evaluated the effect of the mTORC1 inhibitor RAD001 (everolimus) on in vitro radiosensitivity, protein levels, and dose-survival curves using NCI-H460 and NCI-H661 NSCLC cell lines. RAD001 inhibited the mTORC1 pathway in both lines and enhanced the radiosensitivity of NCI-H661 cells with wildtype PIK3CA and KRASgenes. However, there was no evidence of a similar effect in NCI-H460 cells with mutant PIK3CA and KRAS genes. We also analyzed the expression of various EMT-associated proteins after irradiation in RAD001-treated and control cells. This showed that mTORC1 inhibition led to changes in the expression of several EMT-associated proteins in NCI-H661 cells after irradiation. Finally, we used publicly available expression data to confirm that mTOR and EMT-associated genes were affected by irradiation at the transcript level in NSCLC cells.

    4c3880bb027f159e801041b1021e88e8 Result
    

    In conclusion, our study has revealed that the mTORC1 signaling pathway is involved in regulating the radiosensitivity of some non-small cell lung cancer (NSCLC) cells. Our data showed that there was increased expression of mTOR in primary tumors and matched adjacent tissues in patients with NSCLC. We also confirmed that the mTORC1 inhibitor RAD001 had a cytostatic effect on NCI-H661 and NCI-H460 NSCLC cells lines. However, mTORC1 inhibition only increased radiosensitivity and affected mTOR signaling downstream targets in NCI-H661 cells with wildtype PIK3CA and KRAS genes. RAD001 had only a marginal effect on NCI-H460 cells with mutant PIK3CA and KRASgenes. Finally, the effect of radiation on EMT-associated markers was also assessed, revealing that mTORC1 inhibition couldalleviate irradiation-specific EMT changesin NCI-H661 cells.

    8eea62084ca7e541d918e823422bd82e Conclusion
    

    these data suggest that mTORC1 inhibition in NSCLC may enhance radiosensitivity by affecting the expression of EMT-associated proteins.This suggests targeting mTORC1 may provide a potential new strategy for the treatment of NSCLC with wildtype PIK3CA and KRAS genes.

    6f8b794f3246b0c1e1780bb4d4d5dc53