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BackgroundMetabolic stress resulting from nutrient deficiency is one of the hallmarks of a growing tumour. Here, we tested the hypothesis that metabolic stress induces breast cancer stem-like cell (BCSC) phenotype in triple-negative breast cancer (TNBC).MethodsFlow cytometry for GD2 expression, mass spectrometry and Ingenuity Pathway Analysis for metabolomics, bioinformatics, in vitro tumorigenesis and in vivo models were used.ResultsSerum/glucose deprivation not only increased stress markers but also enhanced GD2+ BCSC phenotype and function in TNBC cells. Global metabolomics profiling identified upregulation of glutathione biosynthesis in GD2high cells, suggesting a role of glutamine in the BCSC phenotype. Cueing from the upregulation of the glutamine transporters in primary breast tumours, inhibition of glutamine uptake using small-molecule inhibitor V9302 reduced GD2+ cells by 70–80% and BCSC characteristics in TNBC cells. Mechanistic studies revealed inhibition of the mTOR pathway and induction of ferroptosis by V9302 in TNBC cells. Finally, inhibition of glutamine uptake significantly reduced in vivo tumour growth in a TNBC patient-derived xenograft model using NSG (non-obese diabetic/severe combined immunodeficiency with a complete null allele of the IL-2 receptor common gamma chain) mice.ConclusionHere, we show metabolic stress results in GD2+ BCSC phenotype in TNBC and glutamine contributes to GD2+ phenotype, and targeting the glutamine transporters could complement conventional chemotherapy in TNBC.

Gangliosides are acidic glycosphingolipids involved in cell-adhesion, signal-transduction and tumor progression. GD3 synthase (GD3S/ ST8SIA1 ), a key enzyme in ganglioside biosynthesis, is upregulated in many cancers, including GD2 + breast cancer stem-like cells (BCSCs) in triple-negative breast cancer (TNBC). Here, we demonstrated the immunomodulatory role of GD3S and identified a fully humanized anti-GD2 antibody, naxitamab, as a therapeutic tool to target GD3S/GD2 + breast tumors. GD3S expression correlates with immune-checkpoint activation and reduced immune infiltration. Ectopic overexpression of GD3S suppressed macrophage-mediated phagocytosis and NK or T cell-induced cell death in BC cells. Lipidomic analysis identified GD2 as the major effector ganglioside altered upon GD3S overexpression in TNBC cells. Moreover, naxitamab treatment enhanced macrophage-mediated phagocytosis and NK cell-mediated cytotoxicity and inhibited tumor growth in a TNBC patient-derived xenograft model. Our findings highlight GD3S-driven immunosuppression and provide proof-of-concept that naxitamab, with activated immune cells, reverses this effect, revealing its therapeutic potential in treating GD2 + BC.

Induced pluripotent stem cell (iPSC)–derived natural killer (NK) cells offer an opportunity for a standardized, off‐the‐shelf treatment with the potential to treat a wider population of acute myeloid leukaemia (AML) patients than the current standard of care. FT538 iPSC‐NKs express a high‐affinity, noncleavable CD16 to maximize antibody dependent cellular cytotoxicity, a CD38 knockout to improve metabolic fitness, and an IL‐15/IL‐15 receptor fusion preventing the need for cytokine administration, the main source of adverse effects in NK cell–based therapies. Here, we sought to evaluate the potential of FT538 iPSC‐NKs as a therapy for AML through their effect on AML cell lines and primary AML cells. We observed that FT538 iPSC‐NKs induce effector‐to‐target cell ratio dependent apoptosis in cell lines and primary AML cells, including cells from high‐risk patients. Flow cytometric analysis revealed that FT538 iPSC‐NKs induce AML cell death when combined with the AML therapies: cytarabine, venetoclax and gilteritinib. Moreover, cytarabine did not affect FT538 iPSC‐NK viability, suggesting that iPSC‐derived NK therapies and chemotherapy may be a promising treatment combination. This study provides the basis for further study of iPSC‐derived NK cell therapies as a treatment option for high‐risk AML patients, particularly those with disease resistant to standard therapies.

We identified activin A receptor type I ( ACVR1 ), a member of the TGF-β superfamily, as a factor favoring acute myeloid leukemia (AML) growth and a new potential therapeutic target. ACVR1 is overexpressed in FLT3- mutated AML and inhibition of ACVR1 expression sensitized AML cells to FLT3 inhibitors. We developed a novel ACVR1 inhibitor, TP-0184, which selectively caused growth arrest in FLT3- mutated AML cell lines. Molecular docking and in vitro kinase assays revealed that TP-0184 binds to both ACVR1 and FLT3 with high affinity and inhibits FLT3/ ACVR1 downstream signaling. Treatment with TP-0184 or in combination with BCL2 inhibitor, venetoclax dramatically inhibited leukemia growth in FLT3 -mutated AML cell lines and patient-derived xenograft models in a dose-dependent manner. These findings suggest that ACVR1 is a novel biomarker and plays a role in AML resistance to FLT3 inhibitors and that FLT3/ ACVR1 dual inhibitor TP-0184 is a novel potential therapeutic tool for AML with FLT3 mutations.

Mesenchymal stromal cells (MSCs) in the bone marrow (BM) microenvironment have been shown to induce chemotherapy resistance in acute myeloid leukemia (AML) cells, but the mechanism is not clear. We hypothesized that stromal cells induce a stem-like phenotype in AML cells, thereby promoting tumorigenicity and chemotherapy resistance. We found that aldehyde dehydrogenase (ALDH), an enzyme that is highly expressed in hematopoietic as well as leukemic stem cells was dramatically activated in AML cells co-cultured with BM-MSCs mainly through upregulation of a specific isoform, ALDH2. Mechanistic studies revealed that stroma-derived TGF-β1 induced an ALDH+ phenotype in AML cells via the non-canonical TGF-β pathway through p38 activation. Inhibition of ALDH2 using specific inhibitors significantly inhibited BM-MSC-induced ALDH activity and sensitized AML cells to chemotherapy. Collectively, our data indicate that BM stroma induces a stem-like phenotype in AML cells through the non-canonical TGF-β pathway. Inhibition of ALDH2 sensitizes AML cells to chemotherapy.