What question did this study set out to answer?

To evaluate the efficacy of AUTAC in degrading Mcl1 in cancer cells while ensuring cardiac cell viability.

April 5, 2026

Abstract 4676: Therapeutic exploitation of AUTAC in hematologic malignancies with cardiac protection

Resultado clave

AUTAC-targeted Mcl1 degradation reduced multiple myeloma cell viability by over 50% while causing minimal cytotoxicity and preserving mitochondrial function in cardiac cells.

Puntos clave

To evaluate the efficacy of AUTAC in degrading Mcl1 in cancer cells while ensuring cardiac cell viability.
Utilized myeloma cell lines (U266B1, RPMI-8226) and cardiac cell lines (AC16, H9c2) for testing.
Assessed cell viability with CellTiter-Glo assay and IncuCyte imaging.
Measured mitochondrial membrane potential using TMRE fluorescence.
Analyzed Mcl1 degradation and autophagy dynamics via Western blotting and confocal microscopy.
Knocked down ATG5 using shRNA to confirm autophagy dependency.
AUTAC selectively degraded Mcl1 without affecting other Bcl2 family members.
Inhibition of autophagy with 3-MA or CQ blocked Mcl1 degradation, confirming autophagy dependence.
More than 50% reduction in viability of U266B1 and RPMI-8226 myeloma cells was observed.
Minimal cytotoxicity and preserved mitochondrial function in AC16 and H9c2 cardiac cells were recorded.
AUTAC showed significantly lower cardiotoxicity compared to conventional Mcl1 inhibitors.

PICO estructurado

Does AUTAC targeting Mcl1 reduce multiple myeloma cell viability while preserving cardiac cell viability compared to conventional Mcl1 inhibitors in cell models?

Población

Multiple myeloma cell lines (U266B1, RPMI-8226) and cardiac cell lines (AC16, H9c2)

Intervención

Autophagy-targeting chimera (AUTAC) designed to selectively degrade Mcl1

Comparador

Conventional Mcl1 inhibitors

Resultado

Cell viability and mitochondrial functionsurrogate

AUTAC-mediated degradation of Mcl1 offers a potentially cardio-safe therapeutic strategy for multiple myeloma by selectively inducing apoptosis in malignant cells while sparing cardiac cells.

Resultado numérico

Tasa de eventos absoluta: 0% vs 0%

Resumen

Abstract Background: Myeloid cell leukemia-1 (Mcl1) is a critical member of the Bcl2 family that plays an essential role in regulating apoptosis and maintaining mitochondrial integrity, particularly within cardiac tissue. While Mcl1 overexpression is a major driver of resistance to multiple anticancer therapies, its pharmacologic inhibition has been hampered by dose-limiting cardiotoxicity, representing a significant and unresolved challenge in cardio-oncology. The development of safer therapeutic strategies that selectively target Mcl1 in cancer cells while sparing cardiac cells remains a high-priority goal. In this study, our group investigated a novel autophagy-targeting chimera (AUTAC) designed to selectively degrade Mcl1 via the autophagy-lysosomal pathway. We aimed to determine whether AUTAC could induce selective cytotoxicity in multiple myeloma cells while preserving cardiac cell viability and mitochondrial function. Methods: Multiple myeloma cell lines (U266B1, RPMI-8226) and cardiac cell lines (AC16, H9c2) were used as tumor and cardiac models, respectively. Cell viability was assessed using the CellTiter-Glo assay and IncuCyte live-cell imaging. Mitochondrial membrane potential was measured by TMRE fluorescence. Effects of AUTAC on Mcl1 and autophagy dynamics were evaluated by Western blotting, confocal microscopy, and inhibition studies with 3-methyladenine (3-MA) and chloroquine (CQ). To confirm autophagy dependence, ATG5 was knocked down using shRNA. Results: Treatment with AUTAC selectively induced lysosomal degradation of Mcl1, without detectable effects on other anti-apoptotic Bcl2 family members, including Bcl2 and BclxL. Pharmacological inhibition of autophagy with 3-MA (early-stage inhibitor) or CQ (late-stage inhibitor) effectively blocked AUTAC-mediated Mcl1 degradation, confirming that the process required an intact autophagy-lysosomal pathway. Furthermore, knockdown of ATG5 abolished Mcl1 reduction, reinforcing the autophagy dependence of this degradation mechanism. Functionally, AUTAC treatment led to a greater than 50% reduction in cell viability in U266B1 and RPMI-8226 multiple myeloma cells, accompanied by increased apoptotic signaling. In contrast, AUTAC caused minimal cytotoxicity in AC16 and H9c2 cells, maintaining mitochondrial function and morphology. Compared with conventional Mcl1 inhibitors, AUTAC exhibited substantially reduced cardiotoxicity, underscoring its favorable safety profile. Conclusions: Targeted lysosomal degradation of Mcl1 via AUTAC represents a promising therapeutic strategy that repurposes autophagy for selective oncogenic protein removal. AUTAC effectively degraded Mcl1 in malignant cells while sparing cardiac cells from apoptosis and mitochondrial injury, highlighting its potential as a next-generation, cardio-safe alternative to conventional Mcl1 inhibitors. Citation Format: Ahmed M. Elshazly, Nayyerehalsadat Hosseini, Senthil K. Radhakrishnan. Therapeutic exploitation of AUTAC in hematologic malignancies with cardiac protection abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 4676.

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