Triple-negative breast cancer (TNBC) is a subtype of breast cancer characterized by limited treatment options and unfavorable clinical outcomes. Therefore, the research described in this thesis... Show moreTriple-negative breast cancer (TNBC) is a subtype of breast cancer characterized by limited treatment options and unfavorable clinical outcomes. Therefore, the research described in this thesis focused on the exploration of novel targeted therapies for TNBC. Through high-throughput screening, we assessed the responsiveness of TNBC cells to kinase inhibitors, which indicated a notable sensitivity to cyclin-dependent kinase (CDK) inhibitors. Building upon these findings, this thesis systematically compares the efficacy of targeting various transcription-associated CDKs, with CDK9 and CDK12 emerging as highly potent targets for disrupting TNBC cell proliferation. Transcription-associated CDKs play multiple roles in regulating mRNA transcription. Yet, inhibitors of these CDK’s induced selective, rather than global, changes in gene expression. This provides insights into their mechanisms of action and suggesting potential opportunities for combination therapy. Furthermore, our research elucidated the mechanism underlying the synergistic effects of combining kinase inhibitors with transcriptional CDK inhibitors, by demonstrating that this is mediated through the inhibition of cellular drug efflux by ABCG2. In conclusion, this thesis highlights the potential of transcription-associated CDK inhibitors as a promising avenue for treating TNBC. The insights from this thesis will help to further steer the (pre)clinical development and strategy of using transcription-associated CDK inhibitors for the treatment of TNBC. Show less
The research described in this thesis focused on identifying novel drug targets and synergistic combinations for triple-negative breast cancer (TNBC), a virulent subtype of breast cancer with a... Show moreThe research described in this thesis focused on identifying novel drug targets and synergistic combinations for triple-negative breast cancer (TNBC), a virulent subtype of breast cancer with a dismal prognosis and limited therapeutic options. In particular, the work centred on reversing resistance of TNBC cells to EGFR inhibitors. High-throughput kinase inhibitor library-based screens were utilised to evaluate the potential of novel targeted agents in a panel of TNBC cell lines and subsequently identify TNBC-specific genetic dependencies using siRNA-based screening. The signal transduction pathways perturbed by drug treatment were delineated and subsequently scrutinised using transcriptomic profiling and western blotting. The impact of drug treatment or gene silencing on cell death, proliferation, cell cycle progression and migration was assessed simultaneously. This work demonstrated that TNBC cell lines resistant to both MEK and Akt inhibitors are sensitive to disruption of CDK function. Additionally, it revealed that novel CDK inhibitors with strong activity against P-TEFb/CDK9 are highly effective against TNBC cells as single agents and in combination with multiple targeted therapies. These agents provoked profound down-regulation of multiple oncogenic pro-proliferative pathways, the silencing of which was detrimental to TNBC cell proliferation, thus defining several genes as potential future drug targets. Show less
