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M. Grinberg
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MINI 10 - ALK and EGFR (ID 105)
- Event: WCLC 2015
- Type: Mini Oral
- Track: Biology, Pathology, and Molecular Testing
- Presentations: 1
- Moderators:T. Yap, T. Li
- Coordinates: 9/07/2015, 16:45 - 18:15, Mile High Ballroom 1a-1f
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MINI10.05 - ALK Rearrangements in Non-Small Cell Lung Cancer: Comprehensive Integration of Genomic, Gene Expression and Protein Analysis (ID 2731)
17:10 - 17:15 | Author(s): M. Grinberg
- Abstract
- Presentation
Background:
Identification of EML4-ALK fusion proteins has revolutionized the treatment of a subgroup of non-small cell lung cancer (NSCLC) patients. Although the gene inversion is regarded as the relevant event for therapy response, the relation between gene rearrangement, mRNA and protein levels has not been evaluated in detail. Thus, the objective of this study was to comprehensively define the molecular relations induced by ALK rearrangements in a large representative Swedish NSCLC cohort incorporating genomic, gene expression and protein data, as well as corresponding clinical correlates.
Methods:
ALK protein analysis was performed on 860 NSCLC patients (551 adenocarcinoma, 224 squamous cell carcinomas, 85 large cell carcinomas/NOS) using immunohistochemistry (IHC) on tissue microarrays (TMAs), applying an established monoclonal ALK antibody (clone D5F3, Cell signaling). In parallel, ALK rearrangement was determined by fluorescent in situ hybridization (FISH, Abbott, Vysis ALK Break Apart FISH Probe Kit) on the same TMAs. A subgroup of patients was additionally analyzed utilizing gene expression microarrays (Affymetrix, n=194) or RNA-sequencing (n=202). The RNA sequencing data was also used to identify ALK gene fusions.
Results:
ALK protein expression was observed in 12/860 (1.4%). ALK rearrangement was detected in 11/860 samples (1.3%) by FISH analysis. Of 194 patients evaluated by microarray, six (3.1%) showed high ALK gene expression and of 202 patients analyzed by RNA-seq, nine (4.5%) demonstrated high ALK transcript levels. Of the 11 FISH rearranged patients, eight (73%) showed positive protein expression. High ALK gene expression was observed in all four ALK-FISH rearranged samples with matching microarray or RNA-seq data. Of five patients with positive protein expression, only three (83%) showed high gene expression levels according to gene expression microarray and RNA-seq data. RNA-seq revealed that 2/202 samples were ALK rearranged, both of which were detected by FISH and IHC. One sample that was not rearranged according to RNA-seq-data did, however, demonstrate rearrangement with FISH.
Conclusion:
The overall frequency of ALK rearrangements in this NSCLC cohort was lower than previously reported, with a significant but variable correlation on different molecular levels. It is possible that technical issues with regard to the use of TMAs, where only a fraction of the whole tumor is represented, may have hampered the results. Therefore, the FISH and IHC analysis will be complemented with assessments on whole tissue sections. The discordant results also stress the need for careful validation of these methods before they can be implemented in the clinical practice.
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