Dissecting Chemoresistance in Small Cell Lung Cancer

  • Maximilian Schenk

Student thesis: Phd

Abstract

Small cell lung cancer (SCLC) patients initially respond well to first-line chemotherapy but very quickly develop acquired chemoresistance. Until recently, the mechanisms underlying acquired chemoresistance have been largely unknown, which can be attributed to a lack of pre-clinical model systems. The aim of my PhD was to identify novel mechanisms of acquired chemoresistance by utilising circulating tumour cell derived explant models (CDX) following three different strategies: First, I investigated genomic and transcriptional changes in longitudinal models of resistance derived from patients at baseline and at disease progression. Second, I generated novel models of acquired resistance by re-challenging CDX models with chemotherapy in vivo. Finally, I performed CRISPR/Cas9 genetic screens on CDX models and SCLC cell lines. Transcriptional analysis of longitudinal resistance models revealed the recurrent upregulation of soluble guanylate cyclases (sGCs) in our resistant models. I established that sGC activation and transcription is regulated through nitric oxide (NO) and Notch signalling, respectively. Both genetic and pharmacological targeting of the NO/sGC signalling pathway chemosensitized a CDX progression model, revealing this pathway as a potential vulnerability of relapsed SCLC. By re-challenging CDX models with chemotherapy, I established four novel paired acquired chemoresistance CDX models. My results indicated that acquired chemoresistance developed gradually and that CDX models showed a heterogeneous response when passaged over multiple generations. Finally, I demonstrated that CDX models can be genetically modified ex vivo to express the Cas9 nuclease, that the genetic modification was maintained after implant of the cells in mice, and that CDX cells are amenable to CRISPR/Cas9 mediated editing. A genome wide screen on a SCLC cell line established the knockout of BCL-2 associated X (BAX) as a mechanism of acquired cisplatin resistance. In summary, by following these three different strategies I identified novel mechanisms of acquired resistance in SCLC that could potentially be translated for novel treatment strategies.
Date of Award31 Dec 2021
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorCaroline Dive (Supervisor) & Fiona Blackhall (Supervisor)

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