Acute myeloid leukemia (AML) remains one of the most formidable challenges in oncology, notorious for its aggressive nature and dismal survival rates. Despite advances in cancer therapeutics, AML retains a high mortality rate, with approximately 70% of patients succumbing to the disease within five years of diagnosis. This is largely due to its biological complexity and the heterogeneity of genetic mutations driving its progression. Unlike some other hematological malignancies, AML has proven remarkably resistant to certain targeted therapies, particularly proteasome inhibitors— a class of drugs that have transformed the treatment landscape in related cancers like multiple myeloma. A groundbreaking study led by researchers at the University of California San Diego now unravels the biological underpinnings that shield AML cells from the effects of proteasome inhibition and charts a promising path forward for more effective therapies.
Proteasomes function as the cellular “garbage disposals” responsible for degrading and recycling damaged or unneeded proteins. These molecular complexes are vital for maintaining cellular homeostasis, especially in rapidly dividing cells such as cancer cells that generate large volumes of defective or misfolded proteins. Inhibition of the proteasome pathway leads to an accumulation of protein waste, triggering cellular stress and, ultimately, apoptosis in susceptible cancer types like multiple myeloma. However, AML’s intrinsic resistance to proteasome inhibitors has long puzzled researchers and clinicians alike. The UC San Diego team’s latest research elucidates this resistance by revealing AML’s ability to activate compensatory stress-response mechanisms that bypass the blockade of proteasome activity.
Central to this resilience are two alternative degradation pathways AML cells employ: one governed by the heat shock factor 1 (HSF1) gene and the other autophagy, a self-digestive process that cells use to recycle damaged organelles and proteins. Unlike multiple myeloma cells which succumb to proteasome inhibition, AML cells deftly reroute their intracellular traffic to these secondary systems, effectively circumventing the therapeutic “roadblock.” Through this molecular detour, AML cells continue to clear toxic protein aggregates and sustain their pathogenic proliferation. Consequently, monotherapy with proteasome inhibitors fails to produce clinically meaningful responses in most AML patients.
Lead investigator Robert Signer, Ph.D., explains this biological contingency with a vivid analogy: AML cells encountering proteasome inhibition are akin to drivers rerouting around a highway construction zone via alternative exits, whereas multiple myeloma cells become trapped in gridlock. This “off-ramp” detour mechanism allows AML to maintain proteostasis under proteasome stress, a discovery that shaped the team’s approach to overcoming therapeutic resistance. By designing combinatorial interventions that simultaneously target the proteasome and these backup pathways, researchers aimed to cut off AML’s escape routes.
To this end, the study evaluated the effect of co-administering proteasome inhibitors with Lys05, a potent autophagy inhibitor. Lys05 functions by disrupting the lysosomal degradation pathway, thus impeding cellular autophagy. Experimental data derived from cultured AML patient cells demonstrated a significant reduction in cancer cell viability and colony formation, affirming that dual inhibition effectively overwhelms AML’s protein clearance systems. Moreover, in preclinical mouse models, this therapeutic strategy not only diminished disease burden but also substantially extended survival without inducing significant toxicity, underscoring its potential clinical relevance.
Kentson Lam, M.D., Ph.D., the study’s first author, emphasizes the critical advantage of this approach: it is largely mutation-agnostic. Given the broad spectrum of genetic alterations driving AML, personalized therapies targeting specific mutations benefit only subsets of patients. The dual pathway targeting demonstrated efficacy in a wide array of AML cell lines and patient-derived samples regardless of their mutational landscape, offering a more universally applicable treatment paradigm. This breakthrough moves the field closer to therapies capable of overcoming one of AML’s most vexing challenges—the extreme heterogeneity and adaptability of tumor cells.
The researchers underscore the translational potential of these findings as they pursue further identification of compounds capable of disabling AML’s multifaceted survival pathways. This includes exploring drugs that suppress HSF1-regulated stress responses, which, when combined with proteasome inhibitors and autophagy blockers, could comprehensively cripple AML’s proteostatic defenses. Such combinations have the potential to enter early-phase clinical testing, laying the groundwork for novel, more effective AML treatment regimens.
Interestingly, the team leveraged their extensive expertise in stem cell biology to inform their therapeutic strategy. Unlike multiple myeloma cells, AML cells originate from hematopoietic stem cells, imparting unique physiological traits and resilience mechanisms. Understanding the molecular circuitry that governs stem cell proteostasis illuminated the rationale for targeting multiple recycling pathways simultaneously. This cross-disciplinary insight exemplifies how fundamental biology can guide innovative cancer therapy development.
This work also challenges the conventional focus on genetic mutations as the primary targets for AML treatment, by suggesting that cancer cell metabolism and protein homeostasis represent vulnerable aspects that can be therapeutically exploited. Targeting the cell’s stress response and degradation systems disrupts the cancer cells’ ability to manage proteotoxic stress, tipping the balance towards cell death. This paradigm shift could inspire similar approaches across other malignancies marked by therapeutic resistance.
Ultimately, the significance of this research lies in its promise to expand treatment options for AML patients, many of whom currently face limited and toxic therapies. By illuminating the mechanisms of AML cell survival under proteasome inhibition and pioneering combination strategies to overcome those defenses, this study offers new hope for improving patient outcomes in a disease notorious for its lethality. The research community and medical practitioners alike eagerly anticipate further validation of these findings in clinical trials, which could herald a new era of mutation-agnostic, pathway-targeted therapies for AML.
The fight against AML continues to underscore the complexity of cancer biology but also highlights how unraveling a tumor’s survival tactics at a molecular level can yield transformative therapeutic insights. As Signer remarks, the ultimate objective is to translate scientific discovery into treatments that enhance patients’ lives—a goal that this breakthrough brings tantalizingly within reach.
Subject of Research: Acute myeloid leukemia (AML), proteasome inhibitors, autophagy mechanisms, cancer therapy resistance.
Article Title: Not specified.
News Publication Date: October 20, 2025.
References: Published in Blood, October 20, 2025.
Keywords: Myeloid leukemia, multiple myeloma, stem cells, autophagy, protease inhibitors.
