Understanding the regulation and impact of variant splicing in non-small cell lung cancer
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Embargo End Date
2028-09-25
ICR Authors
Authors
Cooley, R
Document Type
Thesis or Dissertation
Date
2025-09-25
Date Accepted
Abstract
Alternative splicing is a molecular mechanism that allows a single gene to encode multiple proteins. It is a complex and tightly controlled process used to regulate normal gene expression but is often dysregulated in cancer. Compounds that can modulate alternative splicing are currently being explored as a
potential new class of therapeutic agent in cancer, highlighting the need to understand the process of splicing, its regulation, and its impact.
While a growing selection of tool compounds exists to investigate splicing, the knowledge gap in this field is delaying progress. Multiple splicing
modulators with different mechanisms of action have advanced to clinical trials, but toxicity or lack of response have prevented most compounds from
progressing to the clinic. The discovery of new splicing modulator tool compounds with novel targets and mechanisms of action would be beneficial in
helping understand the regulation and dysregulation of splicing in cancer and how this may be exploited therapeutically.
Phenotypic screens using splicing-based reporter assays have produced many splicing modulators, amongst them risdiplam, the first small-molecule
splicing modulator to gain FDA approval. This study describes a similar strategy built around MCL1 splicing in a non-small cell lung cancer background.
MCL1 (myeloid cell leukemia-1 protein) is a regulator of apoptosis in several cancers and was chosen for exploration because of its sensitivity to splicing
modulation through a multitude of signalling pathways and splicing modulators. Constitutive splicing of MCL1 produces the anti-apoptotic variant MCL1L,
which is present in high levels in NSCLC, while alternative splicing produces MCL1S, a pro-apoptotic variant.
In an effort to identify novel splicing tool compounds, the human NSCLC cell line NCI-H1299 was engineered to express a tagged MCL1 that reports on
the generation of the pro-apoptotic MCL1S splice variant using a split luciferase HiBiT reporter assay. Using this model, high-throughput small molecule
phenotypic screening of compound libraries was undertaken. A single screen hit, CCT803, was discovered to increase mRNA and protein levels of
MCL1S and induce splicing changes across the transcriptome. The extensive characterisation and deconvolution of CCT803 suggest a novel mechanism
of action involving splicing factor relocalisation and a molecular target that does not show pan-essentiality. Further investigation of this compound and its effects on splicing may help to narrow the knowledge gap for splicing in NSCLC, providing evidence for splicing as a therapeutic target.
Citation
2025
DOI
Source Title
Publisher
Institute of Cancer Research (University Of London)
ISSN
eISSN
Collections
Research Team
RNA Bio and Mol Therap