Statins, common cholesterol control drugs, are appreciated to have promising anticancer activity through inhibition of the mevalonate pathway. Several lines of evidence suggest that certain tumours are susceptible to statins, but the underlying molecular features arbitrating this sensitivity remain unknown. We hypothesize that (i) not all statins will behave equivalently in the context of anticancer therapy, and (ii) a molecularly-defined subset of tumours are intrinsically sensitive to statins. My objectives have therefore been to further our understanding of functional differences between statins influencing their anticancer effects, and to investigate molecular features associated with statin sensitivity in breast cancer. Specifically, this thesis addresses two aims: (i) to characterize differential interactions between four statins and the xenobiotic transporter P-glycoprotein (P-gp; also known as ABCB1), and (ii) to identify molecular features associated with fluvastatin and lovastatin sensitivity in breast tumour cell lines. We first characterized the interactions of statins with P-gp in vitro and in multidrug-resistant (MDR) tumour cells. While lovastatin could directly bind to P-gp and modulate MDR, no significant interactions were observed with fluvastatin. Fluvastatin may therefore be appropriate for use in unselected patients, to avoid adverse drug interactions with coadministered P-gp substrate chemotherapeutics. Fluvastatin has also shown promise in breast cancer treatment, where molecular features predictive of statin sensitivity would be particularly valuable. A panel of 19 immortalized breast cell lines was therefore characterized for sensitivity to fluvastatin and lovastatin. Relatively statin-sensitive cells underwent apoptosis upon statin treatment, and were more likely to have an estrogen receptor alpha (ERα)-negative, basal-like phenotype. By mining available baseline gene expression data, a candidate 10-gene signature predictive of fluvastatin sensitivity was also generated. Taken together, this research provides insight into molecular markers of statin sensitivity that may facilitate fast-tracking of these drugs to clinical trials in subsets of cancer patients most likely to respond.

Statins, common cholesterol control drugs, are appreciated to have promising anticancer activity through inhibition of the mevalonate pathway. Several lines of evidence suggest that certain tumours are susceptible to statins, but the underlying molecular features arbitrating this sensitivity remain unknown. We hypothesize that (i) not all statins will behave equivalently in the context of anticancer therapy, and (ii) a molecularly-defined subset of tumours are intrinsically sensitive to statins. My objectives have therefore been to further our understanding of functional differences between statins influencing their anticancer effects, and to investigate molecular features associated with statin sensitivity in breast cancer. Specifically, this thesis addresses two aims: (i) to characterize differential interactions between four statins and the xenobiotic transporter P-glycoprotein (P-gp; also known as ABCB1), and (ii) to identify molecular features associated with fluvastatin and lovastatin sensitivity in breast tumour cell lines. We first characterized the interactions of statins with P-gp in vitro and in multidrug-resistant (MDR) tumour cells. While lovastatin could directly bind to P-gp and modulate MDR, no significant interactions were observed with fluvastatin. Fluvastatin may therefore be appropriate for use in unselected patients, to avoid adverse drug interactions with coadministered P-gp substrate chemotherapeutics. Fluvastatin has also shown promise in breast cancer treatment, where molecular features predictive of statin sensitivity would be particularly valuable. A panel of 19 immortalized breast cell lines was therefore characterized for sensitivity to fluvastatin and lovastatin. Relatively statin-sensitive cells underwent apoptosis upon statin treatment, and were more likely to have an estrogen receptor alpha (ERα)-negative, basal-like phenotype. By mining available baseline gene expression data, a candidate 10-gene signature predictive of fluvastatin sensitivity was also generated. Taken together, this research provides insight into molecular markers of statin sensitivity that may facilitate fast-tracking of these drugs to clinical trials in subsets of cancer patients most likely to respond.