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Cancer drug resistance poses a significant challenge in oncology, often driven by intricate cross-talk among membrane-bound receptors that compromise mono-targeted therapies. We develop a dual membrane receptor degradation strategy leveraging Folate Receptor α (FRα) to address this issue. Folate Receptor α Targeting Chimeras-dual (FolTAC-dual) are engineered degraders designed to selectively and simultaneously degrade distinct receptor pairs: (1) EGFR/HER2 and (2) PD-L1/VISTA. Through modular optimization of modality configurations and geometries, we identify the “string” format as the most effective construct. Mechanistic studies demonstrate an ~85% increase in EGFR-binding affinity compared to the conventional knob-into-hole design, likely contributing to the improved efficiency of dual-target degradation. Proof-of-concept studies reveal that EGFR and HER2 FolTAC-dual effectively counteracts resistance in Trastuzumab/Lapatinib-resistant HER2-positive breast cancer models, while PD-L1 and VISTA FolTAC-dual rejuvenates immune responses in PD-L1 antibody-resistant syngeneic mouse models. These findings establish FolTAC-dual as a promising dual-degradation platform for clinical translation. Subject terms: Cancer immunotherapy, Targeted therapies, Protein design, Drug discovery and development

Atovaquone, an FDA-approved oxidative phosphorylation (OXPHOS) inhibitor, has shown promise in the treatment of epithelial ovarian cancer (EOC), the deadliest gynecologic malignancy. However, the precise mechanisms underlying its antitumorigenic effects remain unclear. We employed a longitudinal transcriptomic approach to characterize the molecular effects of atovaquone on EOC cells. Our findings demonstrate that atovaquone disrupts cellular homeostasis and metabolism, activates stress responses, and primes immune recognition. We observed temporal downregulation of genes and pathways involved in key cellular processes, such as the cell cycle and DNA replication, which correlated with reduced proliferative capacity. Atovaquone also downregulated both OXPHOS and glycolysis while upregulating the pentose phosphate pathway, suggesting a metabolic shift toward redox homeostasis restoration in response to severe oxidative stress. Consistent with oxidative stress, we found that atovaquone activated endoplasmic reticulum (ER) stress, which is linked to immunogenic cell death. During ER stress, calreticulin, a damage-associated molecular pattern (DAMP), translocates to the plasma membrane, where it promotes immune recognition. We observed that calreticulin was upregulated on the plasma membrane of atovaquone-treated EOC cells. Additionally, we detected increased levels of other DAMPs, such as high mobility group box 1 (HMGB1) and mitochondrial transcription factor A (TFAM), in the supernatants of atovaquone-treated cells, indicating the release of immunogenic molecules. Moreover, increased expression of ligands for activating receptors of NK cells was observed, and coculture experiments revealed enhanced NK cell activity toward atovaquone-treated cells. These results highlight atovaquone’s potential to activate immune responses, offering a new avenue for combination therapies in EOC treatment.

Due to the complexity of modeling tumor-host interactions within the tumor microenvironment in vitro, we developed a 3D heterotypic cellular breast cancer (BC) model. We generated spheroid models using MCF7, MDA-MB-231, and SK-BR-3 cell lines alongside cancer-associated (BrC4f) and normal (BN120f) fibroblasts in ultra-low attachment plates. Stromal spheroids (3Df) were formed using a liquid overlay technique (graphical abstract). The YT cell line and peripheral blood NK (PB-NK) cells were used as immune components in our 3D model. In this study, we showed that stromal cells promoted tumor cell aggregation into spheroids, regardless of the initial proliferation rates, with NK cells accumulating in fibroblast-rich regions. The presence of CAFs within the model induced alterations in the expression levels of MICA/B and PD-L1 by tumor cells within the 3D-2 model. The feasibility of utilizing a 3D cell BC model in combination with cytokines and PB-NKs was evaluated. We observed that IL-15 and IL-2 enhanced NK cell activity within spheroids, whereas TGFβ had varying effects on proliferation depending on the cell type. Stimulation with IL-2 and IL-15 or TGFβ1 altered PB-NK markers and stimulated their differentiation into ILC1-like cells in 3D models. These findings underscore the regulatory function of CAFs in shaping the response of the tumor microenvironment to immunotherapeutic interventions.