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David Reisman



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    OA11 - Thymic and Other Thoracic Tumours: Targeted Therapies, Biomarkers and Neo/Adjuvant Radiotherapy (ID 919)

    • Event: WCLC 2018
    • Type: Oral Abstract Session
    • Track: Thymoma/Other Thoracic Malignancies
    • Presentations: 1
    • Moderators:
    • Coordinates: 9/25/2018, 13:30 - 15:00, Room 205 BD
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      OA11.06 - Two BRM Promoter Polymorphisms Do Not Predict Susceptibility or Prognosis of Thymoma (ID 12745)

      14:25 - 14:35  |  Author(s): David Reisman

      • Abstract
      • Presentation
      • Slides

      Background

      Brahma (BRM) is a critical protein subunit in chromatin remodeling, and insertions/deletions at its two polymorphic promotor sites (BRM-741 and BRM-1321) have been reported as susceptibility and/or prognostic markers in lung, head and neck, esophageal, pancreatic, and liver cancers. There is also early evidence of potential association with immune-related diseases such as ulcerative colitis and rheumatoid arthritis. As epigenetic silencing of BRM can be pharmacologically reversed, BRM polymorphisms in cancer might have therapeutic implications. Thymoma is a unique cancer in that it has immunological disease associations. We evaluated whether BRM-741 and BRM-1321 polymorphisms influence overall risk, survival, and time-to-progression of thymoma.

      a9ded1e5ce5d75814730bb4caaf49419 Method

      Thymoma cases and matched healthy controls were recruited in a comprehensive cancer centre. Study participants’ peripheral blood samples were collected and genotyped for BRM promoter polymorphisms. Multivariable logistic regression assessed risk of thymoma in case-control analyses. Association of BRM variants with overall survival (OS) and time-to-progression or recurrence (TTP) was assessed by multivariable Cox regression.

      4c3880bb027f159e801041b1021e88e8 Result

      Of 237 cases of histologically diagnosed thymoma and 948 age- and gender-matched healthy controls, thymoma patients had median age of 53 (range: 17-84) years; 121 (51%) were male; 76 (32%) had a history of myasthenia gravis. Median follow-up time was 7 years. 79% of patients were recurrence- and progression-free at 10-year follow-up (95% CI: 74-86%), and 81% of patients were alive at 10 years post-diagnosis (95% CI: 75-87%). Frequency of homozygous variants for either gene was not significantly different between thymoma cases and controls: homozygous BRM-741genotype (OR=1.0; 95%CI:0.6-1.8; P=0.95), homozygous BRM-1321 (OR=0.59; 95%CI:0.3-1.0; P=0.07) or double homozygous variants in both loci (OR=0.69; 95%CI:0.3-1.4; P=0.29). No association between BRM-741/BRM-1321 and OS and TTP was detected (For homozygous BRM-741, OS P=0.74, TTP P=0.93; for homozygous BRM-1321 OS P=0.39, TTP P=0.93). Consistently, there was also no association between double homozygous variants and OS and TTP (Double homozygous, OS P=0.64, TTP P=0.48). Heterozygous variants were also not associated with either risk or outcome.

      8eea62084ca7e541d918e823422bd82e Conclusion

      Results of this study do not support use of BRM promoter polymorphisms as susceptibility or prognostic markers for thymoma. Molecular biologic mechanisms of risk and prognosis remain elusive in malignant thymoma.

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    P2.06 - Mesothelioma (Not CME Accredited Session) (ID 955)

    • Event: WCLC 2018
    • Type: Poster Viewing in the Exhibit Hall
    • Track:
    • Presentations: 1
    • Moderators:
    • Coordinates: 9/25/2018, 16:45 - 18:00, Exhibit Hall
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      P2.06-23 - Association of Two BRM Promoter Polymorphisms and Tobacco Exposure with Malignant Pleural Mesothelioma (MPM) Risk and Survival (ID 12738)

      16:45 - 18:00  |  Author(s): David Reisman

      • Abstract

      Background

      Brahma (BRM) is a critical ATPase subunit of the SWI/SNF chromatin remodeling complex. Homozygous 6-7bp insertion variants at two polymorphic promotor sites (BRM-741/BRM-1321) cause epigenetic suppression of BRM expression and they have been reported as susceptibility and/or prognostic markers in many malignancies, including non-small cell lung cancer. As epigenetic silencing of BRM can be reversed pharmacologically, targeting BRM polymorphisms has significant therapeutic potential. We evaluated BRM-741/BRM-1321 polymorphisms’ association with risk and prognosis of malignant pleural mesothelioma (MPM). While the effect of tobacco in MPM remains controversial, its interaction with genetic polymorphisms in MPM is largely unknown. We evaluated associations between BRM polymorphisms-tobacco exposure and MPM.

      a9ded1e5ce5d75814730bb4caaf49419 Method

      MPM and age-distribution matched asbestos-exposed controls were recruited as part of an asbestos-exposure surveillance program. Participants were genotyped for BRM polymorphisms. Multivariable logistic regression assessed risk of MPM in case-control analyses. Association of BRM variants with overall survival (OS) was assessed by multivariable Cox regression. Secondary subset analyses were performed, stratified by smoking status.

      4c3880bb027f159e801041b1021e88e8 Result

      Of 265 MPM cases, 146 (55%) were ever-smokers; 51 (19%) were female; median age was 66 (range:21-84) years. Median OS was 18 months; median follow-up time was 15 months. Compared to 795 controls, there were no significant associations of BRM with risk (P>0.10, all comparisons). In contrast, compared to the wild-type genotype, the homozygous variant of BRM-741 and BRM-1321 were associated with lower OS, with adjusted hazard ratio (aHR)=2.56 [95%CI:1.7-3.8] and 2.07 [95%CI:1.4-3.1], respectively. Compared to patients carrying the double wild-type, patients homozygous at both loci had lower OS (aHR=2.70 [95%CI:1.7-4.4]).

      There was a significant differential effect of BRM polymorphisms on risk of MPM, by smoking status (interaction P<0.001): among ever-smokers, BRM homozygous variants in BRM-741, BRM-1321, or both conferred lower risks (adjusted odds ratios, aORs were between 0.18-0.28; each P<0.001), while for never-smokers, there was significantly greater risk conferred by carrying the homozygous variants (aORs between 2.7-4.4). Likewise, a similar differential effect by smoking status was seen in prognosis (interaction P<0.001): there was no association between BRM polymorphisms and OS in ever smokers (P>0.1, all comparisons), but in never-smokers, the aHR of carrying homozygous variants of BRM-741, BRM-1321 or both were 7.7 [95%CI:3.8-16], 4.0 [95%CI:2.1-7.7], and 8.6 [95%CI:3.7-20], respectively.

      8eea62084ca7e541d918e823422bd82e Conclusion

      Never-smokers who develop malignant pleural mesothelioma have an increased chance of carrying BRM homozygous variants in their germline DNA, which results in substantially worse prognosis. In contrast, in smokers, there may be a protective effect, with no difference in overall survival.

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