UC Davis

In this work, we delved into the concept of how C(5) amiloride derivatives, and broadly cationic amphiphilic drugs (CADs), utilize the lysosome, and conceivably the mitochondrion, to induce a novel cell death mechanism on cancer cells, regardless of subtype or drug resistance.In Chapter 1, we discuss how various CADs found in multiple drug classes can be repurposed as new cancer therapeutics against therapy-resistant tumor cell populations through the initiation of lysosomal membrane permeabilization (LMP), leading to lysosomal cell death (LCD) as a novel cell death mechanism. In Chapter 2, we explore the chemistry behind what makes C(5) amiloride derivatives potent anticancer drugs, in addition to synthesizing a new lipophilic compound, LLC1. We also confirm LLC1’s effects on resistant population of breast cancer and the utilization of the lysosome are similar to previous lead compound, hexamethylene amiloride (HMA). In Chapter 3, we elucidate the prospective mechanism of action for C(5) lipophilic amiloride derivatives utilizing HMA and LLC1 as our model. We determined that HMA and LLC1 can sequester in lysosomes and induce metabolic changes in lipid levels, particularly bis(monacylglycero)-phosphate (BMP) and lactosylceramide (LacCer). At the mitochondrial level, we see alterations in function through increased ROS production, decreased membrane permeabilization, and decreases ATP levels as well as possible drug targets in the mitochondria. In addition, these compounds suppress HSP70, further triggering LMP and a signaling cascade to induce LCD. It suggests these compounds could be working in synergy between both organelles to induce cell death after drug treatment. In Chapter 4, we conclude our exploration of LLC1 by performing in vivo studies to confirm its efficacy and toxicity in a 4T1-Balb/cJ breast cancer mouse model. Though the data is not sensational, it can serve as a guide for future studies with C(5) lipophilic amiloride derivatives.