Laura Vízkeleti1 2, Orsolya Papp1, Marcin Krzystanek3, Krisztina Pálóczy4, Edit Buzás4, Judit Moldvay5, Györgyné Vidra6, Lilla Reiniger2 7, István Csabai8, Dávid Szüts9, Orsolya Pipek8, Eszter Németh8, Csilla Bacsányi10, Attila Bagó10, Orsolya Rusz12, Violetta Piurkó1, Hui Kang11, Jinmei Wang11, Kai Wang11, József Tímár1 2, Zoltán Szállási2 3 12
1 2nd Department of Pathology, Semmelweis University, Budapest
2 MTA-SE-NAP B Brain Metastasis Research Group, Semmelweis University, Budapest
3 Department of Bio and Health Informatics, Technical University of Denmark, Lyngby, Denmark
4 Department of Genetics, Cell- and Immunobiology, Semmelweis University, Budapest
5 Department of Tumor Biology, National Korányi Institute of Pulmonology, Budapest
6 Department of Anatomy, Histology and Embryology, Semmelweis University, Budapest
7 1st Department of Pathology and Experimental Cancer Research, Semmelweis University, Budapest
8 Institute of Physics, Eötvös Loránd University, Budapest
9 Genome Stability Research Group, Institute of Enzimology, Hungarian Academy of Sciences, Budapest
10 National Institute of Clinical Neurosciences, Budapest
11 Gene Company Ltd., Hong Kong
12 Children's Hospital, Harvard Medical School, Boston, MA, USA
Introduction: Brain metastasis is one of the most severe consequence of cancer dissemination. Approximately 40% of patients with advanced lung cancer develop it during progression.
Aims: To compare primary lung tumor with corresponding brain metastasis to reveal genetic patterns and potential biomarkers of brain dissemination. To collect blood exosomes to evaluate their potential utility for the early detection of brain metastasization.
Method: Seven primary lung cancer and brain metastasis pairs (5 LUAD, 1 SCLC and 1 LUSC) were analyzed with whole genome sequencing. In 5 cases, exosomes were also isolated using filtration and ultracentrifugation. ExoDNA was then purified and whole genome amplified.
Results: SNV/InDel pattern was similar in the examined pairs. The vast majority of mutations in primary and metastatic samples was SNV, whereas the present of InDel was characteristic for exoDNAs. Shared mutations in primary tumors and brain metastases were >99% SNVs and mainly C>A substitutions, characterizing Signature 4 (smoking associated). Regarding private mutations, the proportion of InDel was 15-20%. LUSC brain metastasis was mainly characterized by Signatures 1 and 3, whereas Signatures 2, 5, 8 and 13 were present in LUAD, where a huge area of chr11 covered densely with C>A mutations. ExoDNA shows Signature 16 in LUAD, and Signatures 9 and 23 in LUSC. Several actionable mutations in driver genes were also revealed (e.g. BRAF or TP53). More than 99% of exoDNA reads was aligned to dinucleotide repeats (e.g. (GA)n) or retrotransposonal elements (e.g. L1 or LTR). The majority of non-coding regions was associated with the TSS site of genes.
Conclusion: Distinct mutation signatures can be observed in brain metastases and exosomes. In contrast to pancreatic tumors, exoDNA does not represent the whole genome, but consisted of repeated sequences. This suggests the possible importance of alterations in gene regulatory mechanisms in the brain dissemination of lung cancer.
Supported by the ÚNKP-17-4-II-SE-65 New National Excellence Program of the Ministry of Human Capacities
E-mail address: email@example.com