Intracellular bacteria rely on eukaryotic metabolites for their fitness and pathogenesis. Yet, the mechanisms of how host metabolites promote bacterial physiology and immune evasion are often unclear. Here, we employed obligate cytosolic Rickettsia parkeri, which parasitizes over fifty host metabolites, to investigate bacterial utilization of host glutathione (GSH). We observed that GSH depletion impaired R. parkeri intracellular survival. Super-resolution microscopy revealed that GSH depletion caused bacterial chaining in the host cytosol, prohibiting proper actin-based motility and cell-to-cell spread. GSH was especially critical for bacterial survival in primary macrophages, where it enabled R. parkeri to evade ubiquitylation and antibacterial autophagy. Cell division and survival defects were restored by supplementing N-acetylcysteine, suggesting that GSH serves as a cysteine source for R. parkeri. Together, these data suggest that Rickettsia requires GSH as a nutrient source to promote cell division, actin-based motility, evasion of antibacterial autophagy, and intracellular survival. This knowledge contributes to the expanding paradigm that GSH plays diverse roles in the pathogenesis of intracellular bacteria and represents a potential target for host-acting therapeutics.
© 2025. The Author(s).

Signal transducer and activator of transcription 3 (STAT3) is a well-described transcription factor that mediates oxidative phosphorylation and glutamine uptake in bulk acute myeloid leukemia (AML) cells and leukemic stem cells (LSCs). STAT3 has also been shown to translocate to the mitochondria in AML cells, and phosphorylation at the serine 727 (pSTAT3 S727) residue has been shown to be especially important for STAT3's mitochondrial functions. We demonstrate that inhibition of STAT3 results in impaired mitochondrial function and decreased leukemia cell viability. We discovered a novel interaction of STAT3 with voltage-dependent anion channel 1 (VDAC1) in the mitochondria which provides a mechanism through which STAT3 modulates mitochondrial function and cell survival. Through VDAC1, STAT3 regulates calcium and oxidative phosphorylation in the mitochondria. STAT3 and VDAC1 inhibition also result in significantly reduced engraftment potential of LSCs, including primary samples resistant to venetoclax. These results implicate STAT3 as a therapeutic target in AML.

B-cell acute lymphoblastic leukemia (B-ALL) is a leading cause of death in childhood and outcomes in adults remain dismal. There is therefore an urgent clinical need for therapies that target the highest risk cases. Mutations in the histone acetyltransferase CREBBP confer high-risk and increased chemoresistance in ALL. Performing a targeted drug-screen in isogenic human cell lines, we identify a number of small molecules that specifically target CREBBP-mutated B-ALL, the most potent being the BCL2-inhibitor Venetoclax. Of note, this acts through a non-canonical mechanism resulting in ferroptotic rather than apoptotic cell death. CREBBP-mutated cell lines show differences in cell-cycle, metabolism, lipid composition and response to oxidative stress, predisposing them to ferroptosis, which are further dysregulated upon acquisition of Venetoclax resistance. Lastly, small-molecule inhibition of CREBBP pharmacocopies CREBBP-mutation, sensitizing B-ALL cells, regardless of genotype, to Venetoclax-induced ferroptosis in-vitro and in-vivo, providing a promising drug combination for broader clinical translation in B-ALL.
© 2025. The Author(s).

Lung adenocarcinoma (LUAD) remains the leading cause of cancer deaths worldwide. Apurinic/apyrimidinic endonuclease 1 (APE1), an enzyme integral to DNA repair and redox signaling, is notably upregulated in LUAD. Here we reveal that APE1 amplification, primarily via allele duplication, strongly correlates with poor prognosis in LUAD patients. Using human LUAD cell lines and a KRAS-driven mouse model, we showed that APE1 deletion hampered cell proliferation and tumor growth, highlighting its role in tumorigenesis. Mechanistically, APE1 promoted the transcription of urea cycle genes CPS1 and ARG2 by modulating the presence of G-quadruplex (G4) structures in their promoter regions. APE1 loss disrupted the urea cycle and pyrimidine metabolism, inducing metabolic reprogramming and growth arrest, which could be rescued by CPS1 or pyrimidine restoration. These findings uncover APE1's role in transcriptional regulation of urea cycle metabolic reprogramming via G4 structure, providing a potential therapeutic target LUAD patients with elevated APE1 expression.
© 2025 The Author(s).

Immune evasion is a characteristic hallmark of cancer. Immunotherapies aim to activate and support the body's immune system to recognize and fight tumor cells. Induction of immunogenic cell death (ICD) and the associated activation of danger signaling pathways can increase the immunogenicity of tumor cells. Therapeutic ICD stimuli activate endoplasmic reticulum stress pathways and apoptosis leading to the cellular expression of damage-associated molecular patterns (DAMPs). The aim of our in vitro study was to investigate whether mistletoe extracts induce characteristics of immunogenic tumor cell death in cancer cell lines.
Three human breast cancer cell lines and one murine melanoma cell line (SKBR3, MDA-MB-231, MCF-7, and B16F10) were treated with aqueous, fermented Viscum album extract (VAE: Iscador Qu spec.) and taxol or tunicamycin as positive controls, respectively. To investigate whether VAE induces ribotoxic stress, we measured the ER stress regulators p-eIF2a, ATF4, and CHOP by Western blot. Cell surface exposure of DAMPs (calreticulin, heat shock proteins hsp70 and hsp90), apoptosis and induction of mitochondrial reactive oxygen species (ROS) were assessed by flow cytometry. HMGB1 and ATP were quantified by ELISA and chemiluminescence assay, respectively.
Treatment with VAE resulted in phosphorylation of eIF2α in all cancer cell lines tested and increased calreticulin (CRT) exposure on the surface of pre-apoptotic SKBR3 breast cancer and B16F10 mouse melanoma cells. VAE exerted a concentration-dependent effect in all cell lines, resulting in a significantly increased exposure of three DAMPs (CRT, hsp70 and hsp90) on the surface of early apoptotic cells. Furthermore, VAE elevated mitochondrial ROS production and the release of ATP. HMGB1 release was not induced by VAE.
In this in vitro study, we demonstrated for the first time the potential of a mistletoe extract to induce surrogate markers of immunogenic cancer cell death. This is a primary step in investigating the potential of VAEs to contribute to ICD-induced tumor-specific immune activation.
© 2025. The Author(s).