In the continuously evolving landscape of cancer research, the tumor microenvironment (TME) has emerged as a pivotal frontier, revolutionizing our understanding of tumor biology and immunotherapy. A landmark review recently published in the journal Immunity & Inflammation by Associate Researcher Linnan Zhu and Academician Zemin Zhang from Peking University and Chongqing Medical University, China, offers an unprecedented synthesis of advances in single-cell and spatial transcriptomics technologies applied to the TME. This comprehensive analysis elucidates the intricate cellular heterogeneity and dynamic networks within the TME, setting the stage for pioneering AI-driven precision oncology.
At the core of tumor biology, the TME represents a complex, multicellular ecosystem comprising not only malignant cells but also diverse immune cells, stromal components, blood vessels, and a surprising influence of neural elements. These components are not static entities; instead, they co-evolve and interact in a highly coordinated manner that influences tumor initiation, progression, immune evasion, and, critically, therapeutic outcomes. Harnessing the power of single-cell sequencing and spatial omics, researchers have transcended traditional bulk analyses, enabling a high-dimensional, panoramic view that captures cellular diversity and spatial relationships at an unprecedented resolution.
Among the immune effectors, lymphocytes stand out as the frontline warriors in anti-tumor immunity, with CD8+ cytotoxic T lymphocytes (CTLs) playing a quintessential role by recognizing tumor-specific antigens presented via major histocompatibility complex class I (MHC-I) molecules and mediating tumor cell lysis through cytotoxic molecules such as perforin and granzymes. However, the suppressive nature of the TME frequently drives these CTLs into an exhausted functional state, marked by reduced cytotoxicity and proliferative capacity. Intriguingly, a subset of CD8+ T cells expressing the chemokine CXCL13 has been identified as pre-exhausted but functionally significant, correlating with favorable responses to immune checkpoint blockade (ICB), signaling a nuanced balance within T cell states that could be exploited for therapeutic benefit.
Beyond classical T cells, B cells and natural killer (NK) cells constitute essential, though often underappreciated, components of the tumor immune milieu. Tumor-associated B cells, characterized by high expression of FCRL4 and MHC-II molecules, demonstrate a potent antigen-presenting capacity that is linked to enhanced patient prognosis and improved ICB responses. Conversely, NK cells within the TME frequently adopt a dysfunctional phenotype marked by downregulated cytotoxic pathways, as observed by DNAJB1 expression, contributing to poor clinical outcomes and resistance to PD-1-directed therapies. These observations underscore the complexity of immune cell states within solid tumors and their critical role in shaping therapeutic responses.
The myeloid compartment within the tumor also presents a diverse cellular repertoire, with macrophages, dendritic cells (DCs), neutrophils, and mast cells exhibiting distinct polarization states and functional repertoires. The traditionally simplistic M1/M2 macrophage paradigm is being supplanted by more sophisticated models, such as one centered on mutually exclusive CXCL9 and SPP1 expression. Notably, SPP1+ tumor-associated macrophages have emerged as key pro-tumorigenic players, fostering tumor angiogenesis, extracellular matrix remodeling, and hypoxic adaptations, all hallmarks of aggressive disease and poor prognosis. Likewise, LAMP3+ dendritic cells, particularly subsets derived from conventional type 1 DCs (cDC1) producing CXCL9 and interleukin-15, are instrumental in recruiting and sustaining CD8+ T cell effector responses and mediating responsiveness to immunotherapies.
The stromal compartment adds another layer of complexity; cancer-associated fibroblasts (CAFs), especially those expressing LRRC15, exemplify terminal differentiation states associated with immune exclusion and resistance mediated through transforming growth factor-beta (TGF-β) signaling pathways. Endothelial tip cells marked by CXCR4 expression catalyze aberrant angiogenesis, frequently correlating with adverse outcomes. On the other hand, tumor-associated high endothelial venules and ACKR1+ endothelial cells facilitate immune infiltration, highlighting a dualistic role of vasculature in tumor immunity. More recently, the intersection of neural biology and oncology has revealed TGFBI+ Schwann cells within tumors, which are induced by TGF-β and potentiate tumor cell migration, underscoring a complex neuro-immune-tumor crosstalk that was previously unappreciated.
Crucially, these individual cellular players do not exist in isolation but form spatially organized, functionally integrated multicellular networks within the TME. The identification of ‘immunity hubs’—cellular modules comprised of LAMP3+ dendritic cells, TCF7+ T cells, and CCL19+ fibroblasts—illustrates how coordinated cellular consortia establish niches critical for effective immune surveillance and response. The integrity and spatial arrangement of these hubs strongly predict immunotherapy outcomes. However, tumor progression drives the degradation of healthy multicellular networks and the emergence of aberrant, conserved oncogenic modules, providing insights into shared TME remodeling trajectories that transcend tumor types and offer targets for broad-spectrum therapies.
Looking toward the future, the review highlights a visionary framework termed the “AI virtual tumor”—a computational ecosystem that integrates cellular composition, spatial tissue architecture, intercellular communication, and response to perturbations to model tumor-scale dynamics in silico. This AI-driven paradigm could revolutionize patient stratification, enable in silico hypothesis testing, optimize combination therapy design, and predict treatment efficacy with unprecedented accuracy. Such digital twin models combine high-dimensional biological data with advanced computational algorithms, driving precision oncology toward a new horizon.
In the domain of immunotherapy, the review delineates three promising frontiers. Immune checkpoint blockade (ICB) therapies benefit from biomarkers such as CXCL13+ T cells that predict favorable clinical responses, whereas cell types like CCR8+ regulatory T cells, SPP1+ macrophages, and LRRC15+ CAFs are associated with resistance mechanisms. Remarkably, novel dual checkpoint inhibitors, such as the combination of LAG-3 and PD-1 blockade, have demonstrated encouraging clinical success. Meanwhile, adoptive cell therapies progress with CAR-T cells revolutionizing hematological malignancy treatment and emerging CAR-macrophage (CAR-M) therapies showing potential in solid tumors due to superior tumor infiltration, currently undergoing early-phase clinical trials.
Further, personalized cancer vaccines are gaining traction, with cDC1-targeted vaccines offering strategies to circumvent ICB resistance, exemplified in pancreatic cancer models. mRNA neoantigen vaccines evaluated in high-risk renal cell carcinoma patients have demonstrated safety and immunogenicity, heralding a new era of patient-specific immunotherapy that synergizes with insights from spatial and single-cell analyses. Collectively, these advances exemplify an integrated pathway from fundamental tumor biology investigation to innovative, AI-supported immunotherapy modalities.
The synthesis provided by this review offers an indispensable roadmap linking cell biology, spatial organization, and computational modeling with clinical applications in cancer immunotherapy. By illuminating specialized cellular subtypes and their coordinated networks within the TME, this research advances our understanding of tumor heterogeneity and therapeutic resistance. Moreover, the AI virtual tumor concept promises to catalyze a paradigm shift, enabling in silico experimentation and rational design of next-generation, mechanism-based precision immunotherapies that could significantly improve patient outcomes.
As the realm of cancer treatment moves toward increasingly personalized approaches, the interweaving of single-cell genomics, spatial biology, and computational intelligence foretells a future where detailed biological knowledge is harnessed alongside artificial intelligence to confront the multifaceted challenges posed by tumors. This work by Zhu, Zhang, and colleagues exemplifies how multidisciplinary integration can transform cancer research, inspiring new strategies that transcend existing therapeutic limitations and usher in a new era of immuno-oncology.
Subject of Research: Not applicable
Article Title: The cellular actors of the tumor microenvironment: a single‑cell atlas perspective on specialized subtypes, coordinated networks, and immunotherapy
News Publication Date: 5-Jun-2026
References: DOI 10.1007/s44466-026-00043-3
Image Credits: Professor Zemin Zhang and Dr. Linnan Zhu from Peking University, China, and Chongqing Medical University, China
