Zalcitabine induces ferroptosis in multiple myeloma through the TFAM-cGAS-STING-SLC7A11 axis.

BACKGROUND

Multiple myeloma (MM) is a refractory malignant plasma cell disease, with drug resistance and relapse posing major therapeutic challenges. This study investigates the potential of zalcitabine, a nucleoside analog, as an anti-MM agent and explores its mechanism of action.

METHODS

The anti-MM effects of zalcitabine were evaluated using in vitro cell proliferation assays and in vivo mouse models. Mechanistic investigations were conducted to validate the causal chain. We performed rescue experiments via mitochondrial transcription factor A (TFAM) overexpression and using ferroptosis inhibitors. Concurrently, downstream molecular events, namely mitochondrial DNA release, activation of the cGAS-STING pathway, levels of lipid peroxidation, and SLC7A11 protein expression, were systematically measured. Additionally, we monitored mitophagy and evaluated its functional impact by testing the combined effect of zalcitabine and mitophagy blockade. Clinical relevance was analyzed via bioinformatics and patient samples, and TFAM knockdown was performed to assess its sensitivity to proteasome inhibitors.

RESULTS

Zalcitabine effectively inhibited MM cell proliferation and tumor growth. It suppressed TFAM expression, triggering mitochondrial DNA release and activation of the cGAS-STING pathway, which ultimately induced ferroptosis. TFAM overexpression or ferroptosis inhibition attenuated zalcitabine’s cytotoxicity. Zalcitabine-induced mitophagy was identified as a compensatory survival response, and its blockade enhanced therapeutic efficacy. Clinically, TFAM was significantly overexpressed in MM patient samples and correlated with advanced disease and poor prognosis. Importantly, TFAM knockdown enhanced the sensitivity of MM cells to proteasome inhibitors.

CONCLUSIONS

Our findings reveal a novel TFAM–cGAS–STING–ferroptosis axis as the mechanism underlying the anti-MM activity of zalcitabine. These findings not only verify TFAM as a novel and promising therapeutic target in MM but also support its potential as a prognostic biomarker for the disease.