Colorectal cancer (CRC) remains the second leading cause of cancer mortality in the UK, with tumour recurrence being a major factor affecting long-term CRC patient survival. Colorectal cancer stem cells (CSCs) represent a therapeutic target to overcome tumour relapse in CRC but their targetability is limited by CSC plasticity: the ability of tumour cells to dedifferentiate and reacquire stem cell properties. BCL-3 is overexpressed in a subset of CRCs, correlating with lower CRC patient survival. Recently, BCL-3 has been proposed as a driver for stem cell plasticity in CRC by pushing cells towards a more stem-like phenotype to enhance tumour cell survival. However, the molecular mechanism is yet to be elucidated. To investigate this, BCL-3 null colorectal cancer cell lines were generated using CRISPR-Cas9ᴰ¹⁰ᴬ genome editing. This enabled the stem cell function of BCL-3 to be examined in 3D cell culture whilst facilitating long term analysis of BCL-3 loss. Proteomic and phosphoproteomic analyses of SW620 BCL-3-/- cells were performed to identify potential mechanisms by which BCL-3 drives stem cell plasticity in CRC cells. In line with previous studies, results showed the stem cell capacity of CRC cells was reduced following BCL-3 deletion. Wnt signalling, OXPHOS and transcriptional regulation of ESCs were identified as three pathways significantly altered in BCL-3-deficient cells, with OXPHOS found to be the most significantly downregulated pathway. Seahorse XF metabolic analyses confirmed loss of BCL-3 reduced OXPHOS and not glycolysis in multiple BCL-3-/- CRC lines. Results suggest BCL-3 promotes OXPHOS in CRC cells, identifying a novel metabolic role of BCL-3 in CRC. Given metabolic reprogramming towards OXPHOS has been shown to promote dedifferentiation and enhance stem cell properties in colorectal CSCs, this work provides insight into the mechanism by which BCL-3 promotes stem cell plasticity in CRC and exposes a potential metabolic vulnerability that could be exploited to improve the treatment of CRC.
Investigating the mechanistic role of BCL-3 in promoting stem cell plasticity in colorectal cancer
Timms, P. (Author). 25 Jan 2022
Student thesis: Doctoral Thesis › Doctor of Philosophy (PhD)