Genomic Rearrangements in Lung Adenocarcinoma: Lineage Relationship between In Situ and Invasive Components
Stephen J Murphy, Faye R Harris, Marie-Christine Aubry, Joema Felipe Lima, Sarah H Johnson, Bruce W Eckloff, Charlie T Seto, Michael Asiedu, Tobias Peikert, Ping Yang, George Vasmatzis, Dennis A Wigle. Mayo Clinic, Rochester, MN
Background: The molecular events in the initiation and progression of invasive lung adenocarcinoma remain poorly characterized. Some are thought to develop through an adenocarcinoma in situ, minimally invasive adenocarcinoma, invasive adenocarcinoma sequence; however, the direct evidence for this remains sparse. The goal of our study was to assess lineage relationships between in situ and invasive components within adenocarcinomas with prominent lepidic growth pattern.
Design: Frozen tissue from 14 lung adenocarcinomas with mixtures of invasive (INV) together with an adjacent in situ component (IS), varying in ratio between 40 to 80%, were selected from our Lung Specimen Registry. Laser capture microdissection of each component was performed for each tumor. Genomic DNA was isolated using a direct in situ whole genome amplification methodology, and Next Generation Sequencing performed using an Illumina Mate Pair library protocol. Discordantly mapping Mate Pair sequence reads were determined using binary indexing mapping algorithms and potential genomic rearrangements verified by PCR.
Results: Multiple identical genomic break points unique to a patient tumor were identified within both the IS and INV components in 13 (of 14) cases. The total number of events per case ranged from 4 to 215 and the number of identical events shared between the IS and INV components ranged from 30 to 90%. Chromosomal catastrophe was observed in 2 cases; in one, it was common to both the IS and INV components but in another was only seen in the IS component with just one common event shared with the INV component. Recurrent genomic breakpoints between cases were also observed, with the 2 most common loci involving 8q24.3 and 12q14.1 in 5 and 4 of the 14 cases respectively. PCR validation on selected alterations confirmed that a subset of genomic break points identified with the Mate Pair protocol in both the IS and INV in all cases and not in germ line DNA. A small number of these genomic breakpoints also validated in associated non-neoplastic tissues. However, further evidence predicted these events to be restricted to zonal regions surrounding the tumor tissue.
Conclusions: Our study demonstrates unique chromosomal alterations present in both the IS and INV components of individual lung adenocarcinomas suggesting clonal relatedness and progression. The identification of identical genomic events in restricted regions of the adjacent non-neoplastic lung lends support to a potential mutant stem cell populating the local tumor environment from which the adenocarcinomas emerged.
Monday, March 4, 2013 1:00 PM
Poster Session II # 292, Monday Afternoon