Graduation Year


Document Type




Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Biology (Cell Biology, Microbiology, Molecular Biology)

Major Professor

Uwe Rix, Ph.D.

Committee Member

Nicholas J. Lawrence, Ph.D.

Committee Member

Keiran S. Smalley, Ph.D.

Committee Member

W. Douglas Cress, Ph.D.

Committee Member

Forest White, Ph.D.


bioinformatics, drug combination, lung cancer, network, Proteomics, RNA-seq


Lung cancer is the second most common cancer type and is associated with high mortality rates. The survival rate for lung cancer patients has increased slowly in the last decade mainly as the result of the development of novel targeted and immune therapies. However, non-small cell lung cancer patients lacking known or actionable driver mutations and small cell lung cancer patients with recurrent disease are still in urgent need of new therapies. Drug repurposing is an efficient way to identify new therapies since it uses clinically relevant small molecule drugs. Determination of off-targets of small molecules is a novel approach towards drug repurposing as unintended targets can play important roles for a new clinical application. Here we apply functional proteomics and systems pharmacology approaches to determine target profiles and differential mechanisms of action, independent of the intended targets, of small molecules with similar chemical structures. Using chemical proteomics, we elucidated the differential target profiles of two clinical CDK4/6 inhibitors: palbociclib and ribociclib. We observed that palbociclib, but not ribociclib, is a dual protein and lipid kinase inhibitor that in addition to the intended cell cycle pathway modulates the PI3K/AKT and autophagy pathways. Furthermore, we investigated the off-targets of two MET/VEGFR inhibitors, foretinib and cabozantinib. Foretinib, but not cabozantinib, was found to reduce cell viability and induce cell cycle arrest and apoptosis in lung cancer cell lines. Using a systems pharmacology approach, which included chemical proteomics, phosphoproteomics and RNA-Seq, integrated data analysis and subsequent functional validation revealed a complex polypharmacology mechanism of action of foretinib, which involves the simultaneous inhibition of MEK, AURKB and FER protein kinases. Because AURKB is an important protein kinase for the proliferation of MYC-amplified small cell lung cancer cells, we were able to design a drug combination of foretinib with barasertib, a much more potent AURKB inhibitor, that enhanced specifically the cell death of MYC-amplified small cell lung cancer cells. In summary, we show that small structural changes of closely related clinical drugs can result in pronounced differences in their target profiles and anticancer activities through differential polypharmacology mechanisms and that an integrated systems pharmacology approach can identify new repurposing opportunities for these drugs in cancers with high unmet medical need.