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 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.
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