Investigating resistance to chemotherapy in pancreatic cancer using a genome-wide CRISPR/Cas9 knockdown screen

Abstract

Pancreatic cancer has a particularly poor prognosis and no effective treatment is currently available. Gemcitabine, the standard chemotherapy has a very limited effect which is mainly due to the development of resistance to the drug. Therefore, studying cancer cell resistance to chemotherapy and developing new therapeutic compounds is crucial to improve pancreatic cancer treatment.

Acelarin, a new drug developed by NuCana plc, is an analogue of Gemcitabine, which has been shown to bypass cancer cell resistance mechanisms to Gemcitabine. Acelarin showed promising results in phase I and II clinical trial. Treatment with Acelarin demonstrated tumour reduction and long-term disease control in patients who were refractory to Gemcitabine or had relapsed after Gemcitabine treatment. Identifying potential cell resistance mechanisms and genes associated with Acelarin is of high interest.

In this thesis, a genome-wide knockdown screen using CRISPR/Cas9 methodology was used, in the pancreatic cancer cell line MiaPaCa2, to uncover genes and pathways involved in Gemcitabine and Acelarin resistance. This screen identified DCK and DCTPP1, both involved in the pyrimidine metabolism pathway, as potential modulators of cells response to Acelarin. These candidates were validated using several independent targeting sgRNAs to inactivate gene expression. DCK knockdown induced a marked increase of pancreatic cancer cells resistance to Acelarin with a 7-fold higher EC₅₀ than control cells, while DCTPP1 knockdown resulted in a consistent but more modest effect (1.5-fold increase of EC₅₀ compared to control).

This study has highlighted the potential implication of the pyrimidine metabolism pathway, through the regulation of nucleotide pools, in pancreatic cancer resistance to Acelarin and might provide interesting biomarkers for patients’ response to treatment.

Date of Award	28 Jun 2019
Original language	English
Awarding Institution	University of St Andrews
Supervisor	Paul Andrew Reynolds (Supervisor)