Lysosomal Disruption Boosts Cancer Drug Effectiveness Against RNA Polymerase

This groundbreaking study reveals how cancer cells exploit lysosomes—cellular recycling centers—to resist powerful RNA polymerase inhibitors, and demonstrates a promising strategy to overcome this resistance.

Researchers investigated two RNA polymerase I inhibitors: CX-3543 (quarfloxin) and CX-5461 (pidnarulex), which target the cellular machinery responsible for ribosome production. They discovered that CX-3543 unexpectedly accumulates within lysosomes, where it becomes sequestered and less effective. This accumulation triggers lysosomal membrane permeabilization and activates protective cellular stress responses, including autophagy and TFEB-mediated pathways that help cancer cells survive.

The team tested whether disrupting lysosomes could release the trapped drug and enhance its effectiveness. Using chloroquine derivatives or blue light exposure to damage lysosomal membranes, they successfully liberated CX-3543 from its cellular prison. This combination dramatically increased both RNA transcription inhibition and cancer cell death compared to either treatment alone.

In mouse studies using fibrosarcoma tumors, combining CX-3543 with the chloroquine derivative DC661 significantly reduced tumor growth compared to single-agent therapy. Similar synergistic effects were observed when combining chloroquine derivatives with CX-5461.

These findings reveal an unexpected mechanism of drug resistance and suggest that targeting lysosomes could enhance the effectiveness of RNA polymerase inhibitors. The research opens new avenues for combination cancer therapies that could overcome cellular resistance mechanisms.