Regulation and role of TBX2 and TBX3 in tumour progression

Thesis

TBX2 and TBX3 belong to the T-box family of transcription factors and are im- portant in embryonic development and tumourigenesis. Overexpression of TBX2/3 has been observed in several types of cancer, promoting tumour proliferation, senescence bypass and invasiveness.

Given their important contribution to tumour progression, it might be of therapeutic benefit to pharmacologically inhibit their expression for cancer treatment. To identify novel regulators of TBX2/3, we carried out a high throughput screen for FDA-approved drugs that could affect TBX2/3 expression and/or subcellular localisation using melanoma cells ectopically expressing TBX2/3. We identified hit drugs from the initial imaging-base screen and confirmed the results of selected compounds targeting calcineurin.

In addition to the regulation of TBX2/3 protein, to further understand their role in tumour progression, we undertook genome-wide ChIP-seq and RNA-seq experiments to identify potential target genes and explore functional implications. As there is a lack of ChIP-grade TBX2/3 antibodies, we tagged the endogenous proteins with 3xHA using the CRISPR/Cas9 system. The generated cell lines produced high-quality ChIP-seq datasets of TBX2 and TBX3 and revealed the repertoire of binding sites genome-wide. Surprisingly, TBX2 binds to not only T-elements as expected, but also to a subset of E-box sequences bound by USF2. Integrative analysis of ChIP-seq and RNA-seq datasets identified E2F1 as a novel target gene of TBX2 that promotes cell growth.

Last, but not least, we also identified novel cofactors of TBX2, with preliminary data suggesting that TBX2 represses gene expression by interacting with polycomb repressive complex 1, and may be converted to a transactivator when interacting with basis helix-loop-helix transcription factor USF2.

Authors: Lu, S

• DOI: 10.5287/ora-dqqaa8rd8
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: Tbx3; Cancer; Tbx2; Melanoma
• Subjects: Cancer; Molecular biology