Tumor Immunology

Scientists at the Princeton University Branch of the Ludwig Institute for Cancer Research have uncovered how a #VitaminA by-product - not vitamin A itself - undermines #anticancer #immunity and #cancervaccine efficacy. ▪️ Specifically, they show that all-trans retinoic acid (a metabolic derivative of vitamin A) suppresses #immuneresponses within the #tumor microenvironment. In two complementary studies published in Nature Immunology and iScience, teams led by Cao Fang, Mark Esposito, Ph.D, and senior author Josh Rabinowitz, under the direction of Dr. Yibin Kang at Ludwig Princeton, demonstrate that retinoic acid produced by dendritic cells and cancer cells induces immune tolerance, weakens dendritic cell (DC) vaccines, disrupts T-cell activation, and promotes tumor growth. ▪️ Crucially, the researchers developed and preclinically validated KyA33, a first-in-class inhibitor of retinoic acid production via ALDH1A2/ALDH1A3 enzymes. Blocking this pathway restored dendritic cell function, enhanced cancer vaccine efficacy, and acted as a standalone immunotherapy in mouse cancer models. The work also resolves a long-standing paradox: while vitamin A has been popularly viewed as anti-cancer, excess vitamin A intake correlates with worse cancer outcomes - a contradiction explained by immune suppression driven by its by-product, retinoic acid. 💡 Key point: this research does not implicate vitamin A itself, but rather its metabolic by-product (retinoic acid) as a driver of immune sabotage in cancer. 🗃️ See comments for reference.

Cancer immunotherapy has helped many people, but a large portion of patients do not benefit. New research now suggests that some tumors evade immunotherapy because they lack specific immune cells that are critical for activating an effective anti-tumor response. Without these specialised cells present in the tumor environment, the immune system cannot be properly triggered to recognise and attack cancer, even when powerful immunotherapy drugs are used. The key players appear to be a subset of immune cells known as “dendritic cells,” which act like sentinels. In healthy immune responses, dendritic cells capture fragments of cancer cells and present them to T cells, which then multiply and mount a targeted attack. When these dendritic cells are absent or present in very low numbers inside a tumor, T cells remain inactive, leaving cancer free to grow. Researchers found that tumors from patients who did not respond to immunotherapy often lacked these essential cells. This discovery helps explain why some people’s cancers are “cold,” meaning they do not provoke a strong immune reaction. It also opens the door to new strategies that could turn cold tumors hot by increasing the number or activity of dendritic cells. Experimental approaches under study include therapies that attract dendritic cells into tumors or prime them outside the body and then reinfuse them. The findings do not mean all immunotherapy will fail without these cells, but they highlight a major factor influencing treatment success. By understanding the missing pieces of the immune response, scientists hope to develop combination therapies that give more patients lasting benefit from immunotherapy. Research Paper 📄 DOI: 10.1126/science.abg2752

Solid tumors remain challenging targets for CAR-T cell therapy, largely due to insufficient dendritic cell (DC) activity and tumor antigen heterogeneity. While CAR-T cells have shown remarkable success in blood cancers, their efficacy against solid tumors is limited by poor DC function, which restricts T cell expansion and the development of broad immune responses against multiple tumor antigens. Methods: Researchers engineered T cells to co-express two key factors: Flt3L (which promotes DC development) and XCL1 (which recruits cross-presenting dendritic cells). These "FX-engineered" T cells were tested in multiple mouse tumor models, including melanoma and colorectal cancer. The team used single-cell RNA sequencing to analyze immune cell interactions and validated their approach in humanized mouse models with functional human immune systems. Results: FX-engineered T cells demonstrated several key advantages: - Enhanced recruitment and activation of dendritic cells in tumors - Promotion of "antigen spreading" - where immune responses broaden to target additional tumor antigens beyond the original CAR target - Superior control of tumors with mixed antigens (addressing heterogeneity) - Increased expansion of both transferred and endogenous T cells - Maintained stem-like T cell populations that support long-term immunity - The approach proved effective in both mouse models and humanized systems, suggesting clinical potential. Conclusions: This study presents a promising strategy to enhance CAR-T cell therapy against solid tumors by engineering cells to recruit and activate dendritic cells. By promoting antigen spreading, FX-armed T cells can potentially overcome one of the major limitations of current CAR-T therapy: tumor escape through antigen loss or heterogeneity. The ability to engage endogenous immune responses while maintaining engineered T cell function represents an important advancement toward more effective solid tumor immunotherapy. Paper and research by @Zhen Xiao and larger team

Cancer immunotherapy has transformed treatment for many patients, yet a significant number still see little or no benefit. Recent research suggests one reason may be that some tumors lack important immune cells needed to start a strong anti-cancer response. When these key cells are missing from the tumor environment, the immune system may fail to recognize cancer cells—even when advanced immunotherapy drugs are used. Scientists have identified a group of immune cells called dendritic cells as crucial players. These cells function like watchtowers of the immune system. Normally, dendritic cells collect pieces of tumor cells and present them to T cells, which then activate, multiply, and attack the cancer. However, if dendritic cells are scarce or absent within a tumor, T cells are not properly activated, allowing the cancer to continue growing unchecked. Studies show that tumors from patients who did not respond to immunotherapy often had very low levels of these cells. This insight also helps explain the concept of “cold tumors.” Cold tumors are cancers that do not trigger a strong immune reaction. Without sufficient dendritic cells to alert the immune system, these tumors remain largely invisible to immune defenses. The discovery is encouraging because it points to new treatment strategies. Researchers are exploring ways to convert cold tumors into “hot tumors,” which are more responsive to immunotherapy. Possible approaches include treatments that draw dendritic cells into tumors or therapies that activate dendritic cells in the laboratory and then return them to the patient’s body. While immunotherapy can still work in some cases without these cells, the research highlights how important dendritic cells are in determining treatment success. By filling this missing link in the immune response, scientists hope to design combination therapies that allow more patients to benefit from cancer immunotherapy in the future. Submit your related work online here : https://lnkd.in/eeS-X_yV #CancerResearch #Immunotherapy #DendriticCells #TumorMicroenvironment #CancerImmunity #TCells #ColdTumors #HotTumors #CancerTreatment #MedicalResearch #Oncology #Immunology #FutureMedicine

Batf3+ DCs and the 4-1BB/4-1BBL axis are required at the effector phase in the tumor microenvironment for PD-1/PD-L1 blockade efficacy The cellular source of positive signals that reinvigorate T cells within the tumor microenvironment (TME) for the therapeutic efficacy of programmed death-1 (PD-1)/programmed death-ligand 1 (PD-L1) blockade has not been clearly defined. We now show that Batf3-lineage dendritic cells (DCs) are essential in this process. Flow cytometric analysis, gene-targeted mice, and blocking antibody studies revealed that 4-1BBL is a major positive co-stimulatory signal provided by these DCs within the TME that translates to CD8+ T cell functional reinvigoration and tumor regression. Immunofluorescence and spatial transcriptomics on human tumor samples revealed clustering of Batf3+ DCs and CD8+ T cells, which correlates with anti-PD-1 efficacy. In addition, proximity to Batf3+ DCs within the TME is associated with CD8+ T cell transcriptional states linked to anti-PD-1 response. Our results demonstrate that Batf3+ DCs within the TME are critical for PD-1/PD-L1 blockade efficacy and indicate a major role for the 4-1BB/4-1BB ligand (4-1BBL) axis during this process. https://lnkd.in/eeFUD98q

Tumors don't just outgrow your immune system. They starve it into silence. A paper just published in Science (You et al., 2026) from St. Jude Children's Research Hospital reveals something that should fundamentally change how we think about cancer immunotherapy failure — and it comes down to mitochondria. The researchers found that within the nutrient-sparse tumor microenvironment, dendritic cells progressively lose their mitochondrial activity. That loss drives dysfunction and weakens the body's immune defenses against cancer. MedicalXpress Not T cell exhaustion. Not checkpoint upregulation. The problem starts earlier — at the energy level of the cell that should be sounding the alarm. Here's the mechanism: Intratumoral cDC1s exhibit discrete mitochondrial states. OPA1-mediated mitochondrial energy and redox metabolism dictate their antitumor responses. Mechanistically, OPA1 orchestrates antigen presentation and CD8+ T cell priming by promoting NRF1 expression and electron transport chain integrity, thereby supporting bioenergetics and NAD⁺/NADH balance. Science In other words:  no ETC integrity → no redox balance → no MHC-I surface expression → no CD8+ T cell activation → immunotherapy fails. The OPA1-NRF1 circuit's downregulation acts as a metabolic switch, in effect telling the cell that it is in an energy crisis, leading dendritic cells to shut down their nonessential functions — including immunogenic activity.  St. Jude Children's Research Hospital And here's the therapeutic proof-of-concept: Enhancing mitochondrial fitness in dendritic cells restores their immunogenic activity, improves tumor control, and synergizes with immune checkpoint blockade to slow tumor growth and establish durable immune memory. MedicalXpress This is immunometabolism meeting clinical reality. We've spent years optimizing checkpoint inhibitors without asking: what if the cell that's supposed to present the antigen has already given up metabolically? From a thermodynamic perspective, this is not surprising. A dissipative system deprived of free energy flux cannot maintain its functional organization. The tumor microenvironment is a masterclass in entropy weaponization — reduce the energy available to immune sentinels, and the entire downstream cascade collapses without firing a single bullet. The question now is not whether mitochondrial fitness matters for immunity. It does. Profoundly. The question is: how do we measure and restore it in patients, not just mice? Mitochondrial membrane potential as a predictive biomarker for immunotherapy response? OPA1 agonism as an adjuvant strategy? These are the translational questions worth asking. 💬 Are you thinking about immunometabolic fitness in your clinical or research practice? You Z. et al. Mitochondrial metabolism and signaling direct dendritic cell function in antitumor immunity. Science 392, eadv6582 (2026) DOI: 10.1126/science.adv6582 #Immunology #Mitochondria #CancerImmunotherapy #Immunometabolism