What Is the Tumor Immune Atlas?
July 23, 20261 Min Read What Is Immune Microenvironment Engineering?
July 23, 2026An impenetrable fortress can't be overcome only by stronger soldiers — the fortress itself needs to be transformed
—— Immune Microenvironment Engineering: transforming the tumor's 'forbidden zone' into a battlefield for immune cells.
I. Why 'giving stronger soldiers' isn't enough
This question is one of the most important clinical lessons in solid tumor immunotherapy over the past decade. CAR-T achieved stunning success in blood tumors, but had minimal effect in solid tumors. Not because CAR-T design is flawed, but because the battlefield conditions it faces after entering solid tumors are too poor: physical barriers (CAF-formed dense matrix) prevent CAR-T from penetrating the tumor core; low-glucose, high-lactate, low-pH metabolic environment sharply reduces CAR-T's glycolytic efficiency, impairing proliferation and effector function; TGF-β, adenosine and other suppressive signals quickly inactivate CAR-T that enters the tumor; and Treg and M2-type macrophages actively suppress CAR-T activity.
A perfect analogy: sending CAR-T into solid tumors is like air-dropping special forces into a mine-covered, communication-jammed, supply-cut area — even if they're highly capable, they'll struggle to perform in those conditions. Immune microenvironment engineering, in this situation, systematically 'clears mines, restores communications, establishes logistics' — allowing immune cells to get in, survive, and kill.
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CAR-T or checkpoint inhibitors give soldiers better weapons or remove weapon safeties. Immune microenvironment engineering clears mines from the battlefield, repairs roads, establishes supply logistics — letting all weapons work better. These are complementary, not competing strategies. |
2. Vessel normalization: letting immune cells 'enter the door'
Anti-VEGF treatment (like bevacizumab) was originally designed to 'cut off tumor blood supply, starve the tumor.' But researchers discovered an unexpected effect: moderate anti-VEGF treatment doesn't eliminate tumor vessels but 'normalizes' them — making them more regular in structure, less permeable, with improved oxygen supply. This vessel normalization has dual benefits for immune cells: improved oxygen supply inside tumors (even mild hypoxia can significantly inhibit NK cell and T cell cytotoxicity); and improved immune cell passage into tumors (normalized vessels allow more efficient immune cell extravasation). This recognition supports the rationale for 'anti-angiogenesis + immune checkpoint inhibitor' combination strategies — anti-vascular treatment improves the microenvironment for immunotherapy rather than just two therapies stacking. This combination has already achieved clinical success in liver cancer (atezolizumab + bevacizumab, FDA approved 2020) and multiple other cancer types.
3. STING agonists: igniting innate immunity to warm cold tumors
STING (Stimulator of Interferon Genes) is the key element of the cGAS-STING pathway introduced in earlier articles — when abnormal DNA appears in the cytoplasm, cGAS senses and activates STING, triggering massive production of type I interferons, initiating a strong innate immune response. In tumor immune microenvironment engineering, STING agonists (artificially synthesized STING-activating molecules, like ADU-S100) are directly injected into tumor interiors to: trigger strong local innate immune responses — large amounts of type I interferon promote dendritic cell maturation, activating tumor-specific T cells; induce tumor cells' immunogenic death — STING activation can promote tumor cells releasing more tumor antigens, captured by dendritic cells; and change tumor microenvironment from 'immunosuppressive' to 'immune-activating' — precisely the core mechanism of converting 'cold tumors' to hot.
STING agonists' clinical trials mainly use intratumoral injection (IT) route, because systemic administration's toxic effects are too great (systemic immune activation produces severe cytokine storm-like toxicity). IT-STING agonists combined with PD-1 inhibitors are advancing in multiple clinical trials showing early signals of the synergistic strategy of 'warming cold tumors, then releasing them with checkpoint inhibitors.'
4. CAF targeting: clearing the physical barrier
Cancer-associated fibroblasts (CAFs) are the main cells forming tumors' physical barriers — by secreting large amounts of extracellular matrix proteins like collagen fibers, building a dense 'wall' around tumors that physically blocks immune cells outside. CAF targeting strategies include: eliminating CAFs — targeting FAP (fibroblast activation protein, CAF's specific surface marker), using CAR-T or bispecific antibodies to eliminate CAFs (but completely eliminating CAFs risks reverse fibrotic reactions); reprogramming CAFs — not eliminating but using signal interventions to convert 'tumor-promoting type' CAFs to 'tumor-combating type' CAFs; and softening CAF matrix output — targeting hyaluronic acid (using PEGPH20, a hyaluronidase) or targeting collagen fiber cross-linking (using LOX inhibitors), softening extracellular matrix, improving immune cell physical permeability.
In pancreatic cancer (famous for extremely dense stroma, one of the 'coldest' solid tumors), targeting stroma/CAFs is one of the most hoped-for directions for breaking through immunotherapy ineffectiveness. These strategies are rapidly advancing in combination with CAR-NK cells and checkpoint inhibitors.
5. Oncolytic viruses: immune activators that 'ignite' from inside
Oncolytic viruses (OV) are modified viruses that can selectively infect and lyse cancer cells while triggering local inflammatory responses in tumors, 'igniting' the tumor from inside. Oncolytic viruses' working logic is currently one of the most comprehensive strategies for remodeling tumor microenvironment: directly lyse cancer cells, releasing tumor antigens (exposing hidden 'evidence' to the immune system); trigger local innate immune responses (type I interferons, NK cell activation), warming 'cold tumors'; trigger dendritic cell maturation, promoting tumor-specific T cell activation; and physically disrupt tumor structure, improving immune cell penetration channels.
The first FDA-approved oncolytic virus product is T-VEC (Talimogene Laherparepvec, brand name Imlygic, approved 2015), used for unresectable melanoma. T-VEC is a modified herpes simplex virus type 1 (HSV-1), not only lysing tumor cells but also engineered to secrete GM-CSF (a cytokine promoting dendritic cell maturation) inside tumor cells, further amplifying immune activation effects. Oncolytic viruses combined with immune checkpoint inhibitors (OV + PD-1 inhibitors) is currently the 'warming cold tumors' combination strategy receiving the most clinical attention, with multiple large clinical trials underway.
6. Local delivery: precisely delivering battlefield transformation tools
A core challenge of immune microenvironment engineering is precisely delivering various transformation tools (cytokines, STING agonists, oncolytic viruses, etc.) to the tumor microenvironment while avoiding systemic toxic side effects. Local delivery (Locoregional Delivery) strategies: intratumoral injection (IT) — directly injecting immune-activating drugs into tumors, high concentration with small side effects, suitable for accessible or imaging-guided tumors; hydrogel-based sustained-release systems — embedding immune-activating drugs in degradable hydrogel, placed at tumor resection surgical sites to continuously release drugs locally, activating post-surgical immune surveillance and reducing relapse risk; nanoparticle targeted delivery (closely related to the next Article 136) — designing nanoparticles targeting specific TME cells (like FAP+ CAFs), precisely delivering transformation tools. Local delivery transforms 'systemic immune activation' toxicity risks into 'local precision transformation' high-efficiency low-toxicity strategies.
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