New therapy uses cellular recycling to combat multiple myeloma

A groundbreaking study from VCU Massey Comprehensive Cancer Center introduces an innovative therapeutic approach targeting multiple myeloma by harnessing the cancer cells’ own waste disposal system. The research, recently published in Cell Death & Disease, reveals how a novel autophagy-targeting chimera (AUTAC) exploits lysosome-mediated degradation pathways to dismantle MCL1, a critical survival protein in multiple myeloma cells, showing enhanced efficacy when combined with proteasome inhibitors.

Multiple myeloma cells depend heavily on the survival protein MCL1 to evade apoptosis, traditionally degraded via the proteasome pathway. Proteasome inhibitors, a standard treatment for multiple myeloma, cause an accumulation of unwanted proteins, inducing toxic stress to the cancer cells. However, the cells often evade death by activating autophagy—a cellular recycling mechanism—enabling resistance and resumption of tumor growth.

Challenging the prevailing strategy of blocking autophagy to combat drug resistance, researchers at VCU devised an AUTAC molecule that reroutes autophagy to selectively degrade MCL1. By forcing MCL1 degradation through the lysosome instead of the proteasome, this approach circumvents typical resistance mechanisms. The combined use of AUTAC with proteasome inhibitors in preclinical models resulted in a notable 50% reduction in multiple myeloma cell viability within 48 hours, providing compelling proof of principle for this dual-targeted strategy.

Targeted protein degradation, the foundation of this method, represents a paradigm shift from conventional inhibitors that merely block protein function; instead, it eliminates the proteins completely. Such precision diminishes the likelihood of cancer cells adapting through compensatory pathways, offering a promising avenue to overcome tumor resilience.

A pivotal concern with targeting MCL1 has been potential cardiac toxicity, given the protein’s role in heart function. Encouragingly, evaluations of cardiac models demonstrated that this AUTAC approach induced minimal toxicity while maintaining potent anti-cancer activity. Moreover, preliminary evidence suggests that this strategy may extend beyond multiple myeloma, effectively degrading MCL1 in non-small cell lung cancer, hinting at broader oncological applications.

The VCU team plans to refine the AUTAC molecule through medicinal chemistry to enhance its potency and selectivity before advancing to further preclinical testing. Their work not only opens new therapeutic possibilities for multiple myeloma but also encourages exploration of autophagy-mediated degradation pathways in other MCL1-dependent malignancies, such as breast cancer and melanoma.

This study exemplifies how clever manipulation of intracellular degradation systems can transform treatment landscapes, turning a cancer cell’s defense mechanism against itself. By integrating autophagy-targeted degradation with established proteasome inhibition, researchers may have unveiled a potent weapon in the fight against resistant cancers.