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V. Perrina



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    MA17 - Genetic Drivers (ID 409)

    • Event: WCLC 2016
    • Type: Mini Oral Session
    • Track: Biology/Pathology
    • Presentations: 1
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      MA17.02 - Genome-Wide Copy Number and Mutational Analysis in Longitudinal Biopsies of Matched Primary and Metastatic Pulmonary Adenocarcinomas (ID 4702)

      14:26 - 14:32  |  Author(s): V. Perrina

      • Abstract
      • Slides

      Background:
      There are still limited data on the extent of intratumoral heterogeneity of cancer gene mutations and genome-wide copy number aberrations between primary tumors and metastases in non-small cell lung cancers (NSCLC). Deconvolution of the intermixture of tumor and stromal components remains a major challenge for such analysis. To overcome these limitations, we applied a refined nuclei flow sorting approach on matched longitudinal biopsies (primary/metastasis) from pulmonary adenocarcinomas.

      Methods:
      Multiparameter Ploidy Profiling (MPP) comprises the isolation of nuclei from frozen or formalin-fixed and paraffin embedded (FFPE) tissues, followed by multiparameter flow sorting by DAPI for DNA content (ploidy) and TTF1 as a lineage marker to enrich for tumor cell nuclei. Homogenous TTF1 expression was ascertained by immunohistochemistry. Sorted populations were subjected to genomic profiling by high resolution aCGH and NGS with the Ion Torrent™ Comprehensive Cancer Panel. This approach allows for the detection of genome-wide copy number aberrations and provides all exon-coverage of 409 well-known cancer genes. Sequencing was performed with a mean depth of 965x.

      Results:
      MPP was successfully applied on 44 frozen or FFPE tissue specimens from 19 patients. Clonally unrelated secondary primaries were found in three patients, defined by the absence of both shared copy number (CN) transition and somatic mutations. The concordance rate between primary tumor and corresponding metastases was 65.2% and reached 85.5% for mutations and copy number amplifications/deletions in the top 12 affected genes (including CDKN2A, KRAS, ATM, KEAP1, EGFR and STK11). The correlation of the allele frequencies between primary tumors and metastases was linear (r=0.87, p<0.001), irrespective of the time interval between the tissue resections. Overall, ploidy was not different between primary tumors and metastases. Additionally, the metastases did not bear a higher burden of private events (CN transitions and somatic mutations) than the primary tumors.

      Conclusion:
      MPP is a powerful method to increase the precision of downstream analysis due to unprecedented purity of tumor DNA. Our data argue for a high concordance rate of mutations and CN transitions between primary tumors and their corresponding metastases. Intriguingly, the ploidy remains remarkably stable during progression even after long time-periods, which suggests chromosomal stability with a limited degree of macroevolutionary shifts over time and space. Taken together, our data suggest the presence of at least two evolutionary patterns: 1) early/branched and 2) late/linear progression, with a continuum from high to low genetic divergence of the primary tumor and metastases to their most recent common ancestor.

      Information from this presentation has been removed upon request of the author.

      Information from this presentation has been removed upon request of the author.