Patient-derived organoids, or PDOs, are three-dimensional cultures grown directly from a patient’s own tumor tissue, often obtained through surgery, biopsy, or fine-needle aspiration. Embedded in basement membrane extract and nourished with tailored media, dissociated tumor cells reorganize themselves into miniature structures that recapitulate key genetic, histological, and functional features of the original cancer. Unlike conventional two-dimensional cell lines, which accumulate adaptations over years of laboratory passage, PDOs retain the copy-number variations, mutations, and gene-expression programs of the tumor from which they came. Unlike patient-derived xenografts implanted in mice, they can be established and drug-tested within weeks, at a scale that permits longitudinal study of the very same tumor over many treatment cycles. That combination of fidelity and throughput is precisely what makes them attractive for studying the dynamics of treatment failure.

The review’s most distinctive contribution is a dynamic conceptual map that integrates four determinants of drug response — genetic background, cell-state plasticity, cell-cycle state, and microenvironmental context — along three experimentally measurable dimensions: drug sensitivity, proliferative activity, and temporal reversibility. The authors emphasize that clonal evolution, drug-tolerant persister states, cancer stem cell plasticity, cell-cycle heterogeneity, and microenvironment-mediated protection have traditionally been discussed as separate mechanisms of resistance. In reality, they intersect and reinforce one another. A tumor cell may tolerate a targeted drug by entering a reversible, slow-cycling persister state; over months, those persister populations can provide the raw material for stable, genetically fixed resistance. Organoids, because they allow repeated drug exposure, clonal tracking, and single-cell profiling over time, make it possible to watch that transition happen rather than merely infer it from end-stage samples.

The distinction between tolerance, persistence, and frank resistance carries real clinical weight. Tolerance describes a reversible, non-genetic state in which cells survive drug exposure without dividing — the hallmark of drug-tolerant persisters, a subpopulation first characterized in melanoma and lung cancer models treated with targeted agents. Persistence describes the survival of such cells over longer periods and their eventual re-expansion. Resistance, by contrast, typically involves durable changes, such as secondary mutations in drug targets, activation of bypass signaling pathways, or selection of pre-existing resistant clones. The authors caution against conflating these categories, because interventions that work for one may fail for another. A reversible persister state might be dismantled by epigenetic inhibitors given alongside the primary therapy, whereas a genetically resistant clone demands a fundamentally different strategy. Organoids, which preserve both the genetic and the epigenetic heterogeneity of the source tumor, are uniquely suited to distinguishing the two in an individual patient’s cancer.

Technically, the toolkit available to organoid researchers has matured dramatically. Longitudinal drug exposure protocols now allow researchers to mimic the pulsed, cyclical nature of clinical chemotherapy regimens rather than applying constant drug concentrations. Clonal tracking with fluorescent barcoding reveals which lineages survive treatment and repopulate the culture. Single-cell RNA sequencing and single-cell ATAC sequencing resolve the transcriptional and chromatin states of surviving cells, exposing the epithelial-mesenchymal plasticity and stem-like programs that often accompany drug tolerance. Fluorescence ubiquitination cell cycle indicator, or FUCCI, imaging makes cell-cycle heterogeneity visible in real time, linking quiescent subpopulations to survival under cytotoxic pressure. Growth-rate-corrected pharmacological metrics, such as the GR50 and growth-rate-corrected area under the curve, correct for the confounding effects of differing proliferation rates, yielding more comparable drug sensitivity measurements across cultures. Together, these methods turn a static drug-screening assay into a dynamic record of evolutionary response.

Crucially, the review resists the temptation to treat chemotherapy, targeted therapy, and immunotherapy as interchangeable contexts. Evidence from cytotoxic chemotherapy, the authors note, reflects selection among genotypically diverse clones and the protection of quiescent cells, whereas targeted therapy failures frequently involve adaptive rewiring of signaling networks such as EGFR or downstream bypass pathways in a defined genetic background. Immunotherapy and cellular therapy, including CAR-T and CAR-NK approaches, introduce an entirely different dimension: the interplay between malignant cells and immune effectors. Organoid systems are only beginning to capture that dimension through co-culture with tumor-infiltrating lymphocytes, peripheral blood mononuclear cells, natural killer cells, and myeloid populations. Air-liquid interface cultures, which preserve tumor epithelium alongside native immune and stromal cells, have enabled testing of immune checkpoint blockade responses in vitro — a capability that classical immersed organoid cultures, which strip away most immune components, simply lack.

The tumor microenvironment receives particularly careful treatment. Cancer-associated fibroblasts secrete growth factors such as hepatocyte growth factor and heparin-binding EGF-like growth factor that can shield tumor cells from targeted drugs; tumor-associated macrophages and myeloid-derived suppressor cells blunt immune attack; and stromal cells transformed by oncogenic signaling — for example, pancreatic stellate cells in pancreatic ductal adenocarcinoma — can turn chemotherapy into an unintended pro-survival signal. Organoid co-cultures now allow researchers to reconstruct these interactions deliberately, adding defined stromal or immune populations and measuring how sensitivity shifts. Organ-on-chip platforms go further, introducing controlled fluid flow, drug gradients, and spatial organization that better approximate the physiological conditions of a tumor. Spatial transcriptomics and multiplexed imaging then map where resistant niches form within the culture, connecting cell state to physical location. The result, the authors suggest, is the ability to define resistance niches — specific microenvironments in which tumor cells are actively protected from therapy.

The translational ambition of the framework is equally clear. Patient-derived organoid-based drug sensitivity testing has already been explored prospectively across gastrointestinal cancers and other tumor types, with studies reporting meaningful concordance between organoid responses and patient outcomes in progression-free survival and overall survival. Negative predictive value — the ability to identify therapies that will not work — appears particularly strong, an attribute that could spare patients futile and toxic regimens. The authors argue that standardized functional testing, pathology-based interpretation, and careful pharmacometric normalization will be essential if organoid testing is to move from exploratory studies into routine clinical decision-making, potentially supporting adaptive clinical trial designs in which treatment is matched to live drug-response data. They are equally candid about limitations: organoid establishment rates vary by tumor type, culture conditions select for certain subclones, and immune and stromal components remain incompletely reconstructed in many systems.

What emerges from the review is a deliberate repositioning of the organoid itself. The authors insist that the value of their framework lies not in replacing existing models of resistance — clonal evolution, persister biology, stem cell plasticity — but in integrating them along measurable dimensions within a clinically relevant system. PDOs, in this vision, are not merely drug screening tools but living systems for mapping the dynamic architecture of therapy resistance: an experimental arena in which genetics, cell state, cell cycle, and microenvironment can be observed interacting under longitudinal drug pressure. As co-culture methods, organ-on-chip engineering, spatial transcriptomics, and artificial intelligence-assisted image analysis continue to converge, the prospect of predicting, monitoring, and ultimately preempting the evolution of resistance in an individual patient’s tumor moves from aspiration toward feasible clinical practice. The resistance problem in cancer may not have a single answer, but it may finally have a laboratory in which all of its faces can be studied at once.

Subject of Research: Patient-derived organoids for modeling therapy tolerance, persistence, and resistance in cancer

Article Title: Patient-derived organoids for modeling therapy tolerance, persistence, and resistance in cancer

Article References: Harada, K., Sakamoto, N., Ukai, S., & Ishikawa, S. (2026). Patient-derived organoids for modeling therapy tolerance, persistence, and resistance in cancer. Molecular Cancer. https://doi.org/10.1186/s12943-026-02800-9

Image Credits: AI Generated

DOI: 10.1186/s12943-026-02800-9

Keywords: patient-derived organoids, therapy resistance, drug-tolerant persisters, cancer models, tumor microenvironment, personalized medicine, drug sensitivity testing, cancer stem cells, targeted therapy, immunotherapy, single-cell analysis, Molecular Cancer