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Title: Identifying functionally important aberrations of Neurofibromin-1 in non-small cell lung cancer
Author: Wells, Greg
ISNI:       0000 0004 8506 2920
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2018
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Lung cancer is the most commonly diagnosed cancer worldwide. 87% of cases are classified as non-small cell lung cancer (NSCLC). Neurofibromin-1 (NF1) is a tumour suppressor gene which limits RAS mediated signal transduction within the MAPK pathway. Up-regulation of this pathway leads to uncontrolled cellular proliferation. Somatic mutations in NF1 are reported in 8-12% of NSCLC patients. It was hypothesised that NF1 variants have a functional consequence on the activation of the MAPK pathway. 86 NSCLC patients were recruited and consent obtained to access their archived formalin fixed paraffin embedded tumour tissue. Next generation sequencing (NGS) was used to screen the patients for NF1 variants. Copy number changes of NF1 were investigated using digital droplet PCR. Finally, the NanoString nCounter was utilised to measure mRNA gene expression signatures which relate directly to MAPK and PI3K/AKT/mTOR activation in order to determine whether the NF1 variants observed were functionally relevant. This study confirmed the prevalence of NF1 variants in NSCLC previously reported. Of the 25 NF1 variants identified 15 were novel with no previous reports in the literature or in databases. Analysis via the NanoString nCounter determined NF1 mRNA transcript 2 to be the predominantly expressed transcript in NSCLC. In accordance with previous reports it was shown that the MEK gene expression signatures was able to predict KRAS variants and therefore MAPK activation. Expanding on this using data from Pan-Lung TGCA the MEK signatures were shown to also predict EGFR and BRAF driver variants. Finally, we demonstrated that NF1 variants with loss of function of the GAP domain causes upregulation of the PI3K/AKT/mTOR pathway, while cases with co–occurring NF1 and RASA1 variants result in up regulation of the MAPK pathway. We also identified a third of NF1 loss of function cases which had an increased MEK signature score, which suggests unknown co-drivers are required in addition to NF1 for significant MAPK activation.
Supervisor: Danson, Sarah ; Dalton, Ann ; Wilson, Gill Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available