61. R-loops in colorectal cancer: mechanisms, mapping strategies, and therapeutic opportunities.
R-loops are three-stranded nucleic acid structures comprising a DNA: RNA hybrid and a displaced single-stranded DNA strand. Their abnormal persistence can trigger transcription-replication conflicts, replication-fork stalling, DNA damage, chromosomal instability, inflammatory signalling, and epigenetic reprogramming. These effects are particularly relevant to colorectal cancer (CRC), which is frequently characterised by replication stress, defective DNA repair, genomic instability, and treatment resistance. This review summarises current evidence linking altered R-loop homeostasis to CRC initiation, progression, metastasis, molecular heterogeneity, and therapeutic response. We discuss key regulators with evidence in CRC or intestinal models, including RNASEH1/2, DDX21, DHX9, TOP1, POLD1/POLD3, and ATR, while distinguishing them from emerging mechanisms requiring CRC-specific validation. We also evaluate major R-loop detection strategies and their limitations. R-loop-associated vulnerabilities may influence responses to irinotecan, ATR/CHK1 and WEE1 inhibitors, PARP-related strategies, and immunotherapy. However, most evidence remains preclinical, highlighting the need for orthogonal detection methods, patient-derived models, and clinically annotated cohorts.
62. SMS1 and SMS2 differentially regulate platinum chemotherapy sensitivity in ovarian cancer cells.
Altered platinum chemotherapy sensitivity is a major determinant of treatment outcome in ovarian cancer; however, the molecular mechanisms underlying adaptive chemotherapy responses remain incompletely understood. Sphingomyelin synthase 1 (SMS1) and sphingomyelin synthase 2 (SMS2), key enzymes involved in sphingomyelin biosynthesis, have been implicated in cancer biology, but their roles in platinum chemotherapy response remain unclear.
63. DBF4B promotes hepatocellular carcinoma progression by regulating CCNA2 and PSMD11 expression.
作者: Bing Dong.;Pengju Xi.;Guangxin Yang.;Zhiqi Jiao.;Shijie Xu.;Lin Han.;Zhenming Gao.
来源: Mol Biol Rep. 2026年53卷1期
Hepatocellular carcinoma (HCC) is a highly aggressive malignancy characterized by unfavorable clinical outcomes. Identifying novel biomarkers and therapeutic targets is essential for advancing HCC management. Although DBF4 zinc finger B (DBF4B) has been associated with the progression of various cancers, its specific role in HCC remains poorly understood.
64. Therapeutic Advances in Adult B-cell Acute Lymphoblastic Leukemia with KMT2A Rearrangements.
作者: Shen-Hao Liu.;Ai-Ni Deng.;Hui-Ying Li.;Kai-Wen Tan.;Sheng-Li Xue.;Hai-Ping Dai.
来源: Ann Hematol. 2026年105卷9期
B-cell acute lymphoblastic leukemia (ALL) with KMT2A rearrangements (KMT2Ar B-ALL) represents a distinct, high-risk subtype in adults, characterized by aggressive disease biology, high relapse rates, and inferior long-term survival. Conventional intensive chemotherapy, even when consolidated with allogeneic hematopoietic stem cell transplantation (allo-HSCT), yields suboptimal outcomes, underscoring the need for novel therapeutic approaches. In recent years, substantial progress has been made with the introduction of antibody-based immunotherapies, cellular immunotherapies, and small molecular inhibitors, reshaping the treatment landscape for this challenging subgroup. This review provides a comprehensive overview of current and emerging therapeutic strategies for adult patients with KMT2Ar B-ALL. We summarize outcomes associated with pediatric-inspired chemotherapy and allo-HSCT, focus on clinical evidence for antibody-based immunotherapy including blinatumomab and inotuzumab ozogamicin, across frontline, consolidation, and relapsed or refractory settings. Advances in cellular immunotherapy, particularly CD19-directed chimeric antigen receptor T-cell therapy, are discussed, with a focus on unique resistance mechanisms such as antigen loss and lineage switch. In addition, we review the biological rationale, efficacy and emerging resistance mechanisms of menin inhibitors, a promising class of agents specifically targeting the epigenetic dependency of KMT2A-rearranged leukemia. Finally, other molecular approaches, including epigenetic modifiers, apoptosis pathway inhibitors, and signaling pathway inhibitors are discussed. Despite these advances, treatment resistance and disease relapse remain major obstacles. These ongoing challenges highlight the urgent need for multi-center, prospective trials to investigate rational combination strategies to improve outcomes for adults with KMT2Ar B-ALL.
65. Programmable two-dimensional CoOOH nanosheets with a hybridization chain reaction amplification system for label-free fluorescent detection of miRNA-205 in colorectal cancer.
作者: Wenpei Dong.;Xingda Huang.;Feng Zhang.;Tongshan Zuo.;Xinyi Xia.;Ping Yu.;Dongchao Yang.;Zhicheng Song.;Xia Cheng.;Jing Zhang.;Jianjun Yang.;Yan Gu.
来源: Mikrochim Acta. 2026年193卷9期
MicroRNA-205 (miRNA-205) has been identified as a promising biomarker, yet its clinical application is hindered by the lack of detection strategies that combine simplicity, ultrahigh sensitivity, and high specificity. To address these obstacles, we introduced an innovative biosensor integrating hybridization chain reaction (HCR) with two-dimensional CoOOH nanosheets for precisely detecting the colorectal cancer biomarker miRNA-205 (HCR-CoOOH system). This system took advantage of the preferential binding of CoOOH nanosheets for single-stranded DNA over double-stranded DNA, along with HCR for signal amplification. Without the target miRNA-205, hairpin probes H1 and H2 were adsorbed onto CoOOH nanosheets, resulting in effective FRET-based quenching of the intercalated SYBR Green I fluorescence. In contrast, introduction of the target triggered the HCR cascade, producing numerous long double-stranded DNA polymers. Low affinity between these duplexes and the nanosheets allowed substantial fluorescence recovery under isothermal conditions. A strong linear relationship was observed between fluorescence recovery and miRNA-205 concentration over 0.1-500 nM, with a detection limit of 0.062 nM. Furthermore, the system demonstrated excellent specificity and robust performance in serum samples. Notably, this work circumvented the issues of tedious handling and strong background interference by enabling a swift switch from the "signal-off" to the "signal-on" detection mode, while also simplifying the workflow and reducing non-specific signals. Furthermore, the use of SYBR Green I eliminated the need for covalent fluorophore labeling, markedly reducing assay cost. This versatile strategy provides a valuable new tool for colorectal cancer research and clinical diagnostics.
66. GATA1 knockdown enhances CD8+ T cell responses and protects against immune escape in cervical squamous cell carcinoma through FGL1 downregulation.
Immune escape is a hallmark of cancers, which affects the efficacy of immunotherapy. Herein, this study analyzed the significance of GATA1/FGL1 in the immune escape of cervical squamous cell carcinoma (CESC) to deepen the understanding of immune escape-associated molecular mechanisms. In silico analysis predicted the correlations of FGL1 with CESC prognosis and CD8+ T cell infiltration as well as the relation between FGL1 and GATA1. After FGL1 and/or GATA1 gain- and loss-of-function, CC cells were co-cultured with CD8+ T cells. The sensitivity of CC cells to CD8+ T cells was assessed, as well as the secretion of perforin, GzmB, IFN-γ, and TNF-α. Also, CD8+ T cell proliferation and apoptosis were measured. The binding of GATA1 to the FGL1 promoter was validated through luciferase and ChIP assays. GATA1-knockdown U14 cells were transplanted into immunocompetent C57BL/6 mice in combination with or without CD8α mAb to ascertain the impacts of GATA1 on tumor growth and immune escape in CESC in vivo. Knockdown of either FGL1 or GATA1 markedly enhanced the sensitivity of CC cells to CD8+ T cell‑mediated cytotoxicity and increased the secretion of perforin, GzmB, IFN‑γ, and TNF‑α. It also promoted CD8+ T cell proliferation while reducing their apoptosis. These effects of GATA1 knockdown were partially negated by FGL1. In vivo, GATA1 knockdown prominently diminished the tumor growth and increased the infiltration and cytotoxic effects of CD8+ T cells. Collectively, GATA1 knockdown facilitates CD8+ T cell responses and suppresses immune escape in CESC by downregulating FGL1.
67. CD1d remodels the tumor-infiltrating myeloid populations controlling antitumor immunity.
作者: Lauren Evans.;Maria Conde Poole.;Cenk Celik.;Harshita Mishra.;Michael J Pitcher.;Anita Grigoriadis.;Maria Secrier.;Patricia Barral.
来源: J Exp Med. 2026年223卷9期
Myeloid cells play crucial roles in cancer progression, influencing tumor growth, metastasis, and response to immunotherapy. The mechanisms shaping their diverse functions in the tumors remain poorly understood and may offer therapeutic opportunities. Here, we identify the lipid-presenting molecule CD1d as a regulator of tumor progression and myeloid heterogeneity in the tumor microenvironment. Using several mouse models of breast cancer, we demonstrate that genetic deletion or antibody-mediated targeting of CD1d leads to reduced tumor growth, altered immune infiltration, and improved efficacy of anti-PD-1 immunotherapy. Specifically, CD1d targeting reshapes the intratumoral myeloid compartment, enhancing proinflammatory programs and resulting in accumulation of inflammatory monocytes. The CD1d-dependent control of myeloid cell functional differentiation is cell-intrinsic and conserved in human and mouse. Through single-cell RNA sequencing, we define the transcriptional landscape associated with CD1d deficiency and derive a gene signature that correlates with clinical outcomes and response to immunotherapy in breast cancer patients. Thus, CD1d could provide a potential target to alter tumor-infiltrating myeloid populations and enhance immunotherapy responses.
68. miR-200a-3p Targets and Downregulates CDC25B Expression to Inhibit the Progression of Hepatocellular Carcinoma.
Cancer originates from the uncontrolled proliferation of normal cells. Previous studies have demonstrated that CDC25B, a cell cycle-regulating phosphatase, is overexpressed in various tumors, including hepatocellular carcinoma, and its expression level may serve as a prognostic biomarker. The present study investigated the upstream miRNA regulators of CDC25B and demonstrated that their interactions can inhibit hepatocellular carcinoma progression. Here, stable hepatocellular carcinoma cell lines overexpressing or knocking down CDC25B were established using lentiviral vectors. The effects of CDC25B expression on the invasive phenotype of hepatocellular carcinoma cells were analyzed using plate cloning, scratch assays, and Transwell assays, and a subcutaneous tumor xenograft model in mice was established to evaluate the impact of CDC25B on tumor growth in vivo. Furthermore, dual-luciferase reporter assays were used to validate the targeted regulatory relationship between miR-200a-3p and CDC25B, while miR-200a-3p mimics and inhibitors were employed to elucidate the specific downstream mechanisms. We found that high expression of CDC25B significantly enhanced the epithelial-mesenchymal transition process, thereby accelerating the proliferation, invasion, and migration of hepatocellular carcinoma cells, whereas CDC25B knockdown exerted the opposite effects. In vivo tumorigenicity experiments in nude mice confirmed that overexpression of CDC25B promoted tumor growth. In addition, the dual-luciferase reporter assay confirmed that miR-200a-3p specifically targets and downregulates CDC25B expression, thereby inhibiting hepatocellular carcinoma progression.
69. Activation of a TFAM-Dependent Mitochondrial Translational Axis Drives Oxidative Metabolism in Grade 2 Meningiomas.
作者: Stella G Cavalcante.;Benedito Jamilson Araújo Pereira.;Antonio M Lerario.;Paula R Sola.;Sueli M Oba-Shinjo.;Suely K N Marie.
来源: Cell Biochem Funct. 2026年44卷8期e70277页
Meningiomas exhibit marked biological heterogeneity that is not fully captured by current histopathological grading. Increasing evidence suggests that mitochondrial metabolism contributes to tumor aggressiveness; however, the molecular mechanisms regulating mitochondrial function in meningiomas remain poorly defined. Here, we investigated the role of mitochondrial transcription factor A (TFAM)-driven mitochondrial biogenesis and translation in meningioma progression. We performed integrative transcriptomic, immunohistochemical, and mitochondrial DNA analyses in a well-characterized cohort of 91 meningiomas, comprising World Health Organization grade 1 (G1) and grade 2 (G2) tumors with long-term clinical follow-up. RNA sequencing identified enrichment for mitochondrial metabolic pathways, including oxidative phosphorylation and ATP metabolism, that was preferentially activated in G2 meningiomas. TFAM and its upstream regulator PGC1α were significantly upregulated at both mRNA and protein levels in G2 tumors and exhibited a positive correlation, consistent with enhanced mitochondrial biogenesis. Although mitochondrial DNA copy number did not differ significantly between grades, G2 meningiomas showed a trend toward increased mitochondrial mass. Notably, G2 meningiomas demonstrated marked enrichment of mitoribosomal genes, including MRPL15, MRPL35, MRPL42 and MRPS22, whose expression correlated positively with TFAM and PGC1α expression levels. Network analysis identified TFAM as a central hub linking mitochondrial biogenesis, translation, and metabolic pathway activation. These findings were independently validated using a publicly available meningioma transcriptomic dataset. Together, our results reveal a TFAM-centered mitochondrial regulatory program that integrates mitochondrial biogenesis, translational capacity, and oxidative metabolism in higher-grade meningiomas. This mitochondrial translational axis represents a previously unrecognized mechanism underlying meningioma progression and highlights potential metabolic vulnerabilities for therapeutic intervention.
70. Cigarette Smoke Extract Promotes Epithelial-Mesenchymal Transition in Non-Small Cell Lung Cancer by Upregulating PRMT6.
作者: Yanwen Zhang.;Xiaojing Chang.;Jie Cao.;Jing Zhang.;Haiyan Zhao.
来源: Thorac Cancer. 2026年17卷16期e70357页
Non-small cell lung cancer (NSCLC) is a leading cause of cancer-related mortality worldwide. Cigarette smoke extract (CSE) is a major environmental factor driving NSCLC progression, yet the underlying molecular mechanisms remain incompletely understood. Protein arginine methyltransferase 6 (PRMT6) is implicated in various malignancies, including NSCLC, and epithelial-mesenchymal transition (EMT) contributes to metastasis and poor prognosis in this disease. However, the role of PRMT6 in CSE-induced NSCLC progression has not been elucidated.
71. In vivo CRISPR editing for cancer immunotherapy.
Cancer immunotherapy has shown significant promise in certain patient populations, but further advancements are needed to extend its benefits to a wider range of patients. Clustered regularly interspaced short palindromic repeats (CRISPR)-based editing has rapidly evolved in recent years, enabling its transition into direct therapeutic applications. This review summarizes recent progress in applying CRISPR systems in vivo for cancer immunotherapy, focusing on approaches that target cancer cells and the tumor microenvironment, as well as those that directly engineer immune cell populations themselves. Novel CRISPR editing platforms and strategies enabling multiplexed editing have also recently demonstrated promising impacts on driving antitumor immunity, however, the platforms investigated are still in the early stages and further investigation will be needed to robustly assess the potential for clinical translation. Future work can expand the array of therapeutic targets by incorporating data from functional genomics and must also carefully evaluate both editing modalities and delivery systems to optimize efficacy, safety, and scalability.
72. Integrated Mutation Profiling and Prognostic Genomic Signature in Pediatric Testicular and Ovarian Germ Cell Tumors.
作者: Xiaoqi Xuan.;Yue Yang.;Yongle Li.;Jinlong Yang.;Hang Wu.;Yulong Gong.;Guogen Li.;Xiao Pu.
来源: Hum Mutat. 2026年2026卷3009537页
Pediatric testicular and ovarian germ cell tumors generally have favorable outcomes, but a subset of patients experience relapse, progression, or persistent disease. Conventional risk assessment is based primarily on stage, histology, primary site, serum tumor markers, and treatment response; the incremental prognostic value of genomic profiling remains uncertain.
73. A TMED3-governed disulfidptosis-related diagnostic signature reveals tumor microenvironment remodeling in intrahepatic cholangiocarcinoma.
作者: Wanjia Qiao.;Yixiang He.;Jing Li.;Xiaohan Liu.;Lingfang Zhang.;Xin Bai.;Yeying Wang.;Jianming Tang.
来源: Front Immunol. 2026年17卷1858117页
Intrahepatic cholangiocarcinoma (ICC) is an aggressive malignancy with poor prognosis and limited treatment options. Disulfidptosis, a novel cell death pathway driven by disulfide bond accumulation, has emerged as a potential mechanism in cancer biology; however, its role in ICC remains unclear.
74. FGFR1 copy number gain is independently associated with shorter progression-free survival in advanced lung squamous cell carcinoma treated with first-line immune checkpoint inhibitor-based therapy.
Lung squamous cell carcinoma (LUSC) represents a predominant subtype of non-small cell lung cancer (NSCLC) with scarce effective targeted therapeutic options, rendering immune checkpoint inhibitor (ICI)-based regimens the standard first-line treatment for advanced-stage disease. Fibroblast growth factor receptor 1 (FGFR1) copy number (CN) gain is a prevalent genomic aberration in LUSC; nevertheless, the correlation between FGFR1 CN gain and ICI therapeutic efficacy has not yet been clarified. This retrospective single-center study aimed to explore the predictive value of FGFR1 CN gain in advanced LUSC patients receiving first-line ICI monotherapy or combination regimens.
75. Beyond the canonical view: steroid receptor network plasticity and mechanosensitive chromatin integration in breast cancer.
作者: Judith García-García.;Rosario Sanz Pérez.;A Silvina Nacht.;Diego M Presman.;Adali Pecci.;Guillermo P Vicent.
来源: NAR Cancer. 2026年8卷3期zcag016页
Steroid hormone receptors are traditionally described through models derived from simplified experimental conditions that do not fully recapitulate the physiological environment. In this review, we propose an integrated physiological framework for understanding steroid receptor function, in which chromatin organization, mechanotransduction, receptor network plasticity, and dynamic nuclear organization are recognized as fundamental components of hormone signaling rather than secondary regulatory layers. We highlight how steroid receptor signaling in breast cancer emerges from the coordinated integration of hormonal, chromatin, and mechanical cues, rather than from isolated ligand-driven events. In vivo, hormone responses occur within a complex endocrine milieu characterized by fluctuating hormone concentrations, multiple receptor interactions, and continuous communication with the chromatin landscape. Emerging evidence further indicates that biomolecular condensates and dynamic receptor assemblies contribute to the spatial and temporal coordination of transcriptional programs. By integrating advances in nuclear receptor biology, chromatin regulation, and mechanobiology, we argue that many mechanisms historically classified as "noncanonical" are more appropriately viewed as integral components of physiological steroid receptor function. This integrated perspective provides a broader framework for understanding breast cancer biology, disease progression, and therapeutic response.
76. Distinguishing chronic myeloid leukemia in megakaryocytic blast crisis from de novo Ph+ acute megakaryoblastic leukemia: a case report and systematic review.
Chronic myeloid leukemia (CML) with megakaryoblastic blast crisis (MKBC) as the initial manifestation is extremely rare, accounting for less than 3% of all CML cases. Philadelphia chromosome-positive acute myeloid leukemia, FAB M7 subtype (Ph+ AML-M7), is also known as Philadelphia chromosome-positive acute megakaryoblastic leukemia (Ph+ AMKL), representing a distinct and prognostically unfavorable category of AML. Morphologically and immunophenotypically, these two entities are nearly identical, posing significant diagnostic challenges. We describe a novel case of Ph+ leukemia with MKBC differentiation that appears most consistent with CML in blast phase (BP). Following treatment with a tyrosine kinase inhibitor (TKI) combined with induction and consolidation chemotherapy, the patient achieved complete remission (CR). Although hematopoietic stem cell transplantation (HSCT) was declined due to economic constraints, the patient has maintained deep molecular remission(MR5, BCR::ABL1IS ≤ 0.001%)for 35 months to date. Through a systematic review of existing literature, this article elucidates key discriminative features between the two conditions and proposes a practical diagnostic and therapeutic framework to guide clinical decision-making.
77. Case Report: Immune-driven clonal selection underlying lineage switch from B-Precursor acute lymphoblastic leukemia to acute myeloid leukemia following inotuzumab ozogamicin.
作者: Kaori Kondo.;Daichi Sadato.;Yuho Najima.;Toshikazu Itabashi.;Takahiro Ueda.;Chizuko Hirama.;Masashi Shimabukuro.;Atushi Jinguji.;Naoki Shingai.;Takashi Toya.;Hiroaki Shimizu.;Tomomi Toubai.;Hironori Harada.;Yuka Harada.;Noriko Doki.
来源: Front Immunol. 2026年17卷1828617页
Lineage switch (LS), defined as a change in leukemic lineage during the disease course, is a rare but clinically significant event in acute leukemia and is typically associated with poor prognosis. Although LS has been increasingly reported following targeted immunotherapies, the clonal mechanisms underlying this phenomenon remain incompletely understood, particularly in cases without KMT2A rearrangement. We report a case of LS from B-precursor acute lymphoblastic leukemia (BCP-ALL) to acute myeloid leukemia (AML) following treatment with the CD22-targeted antibody-drug conjugate inotuzumab ozogamicin. To elucidate the clonal architecture underlying LS, targeted next-generation sequencing was performed on bone marrow samples obtained at multiple time points throughout the disease course. Genomic analysis demonstrated that the lymphoid and myeloid disease phases shared ancestral genetic alterations but displayed distinct mutational profiles. At the time of LS, TP53 and SMC1A mutations newly emerged, whereas only a subset of mutations detected at ALL relapse was retained. These findings suggest that the AML phase most likely resulted from the selective expansion of a genetically distinct subclone derived from a common progenitor, rather than the direct transdifferentiation of the dominant ALL clone, consistent with immunotherapy-driven clonal selection. Longitudinal genomic profiling revealed stepwise clonal evolution during disease progression, supporting a model of immunotherapy-driven clonal selection leading to LS. This case provides molecular evidence suggesting that immune-targeted therapy can promote expansion of minor pre-existing subclones with alternative lineage potential within a common progenitor even in non-KMT2A-rearranged leukemia. Our findings highlight the importance of comprehensive genomic monitoring during immunotherapy to identify therapy-resistant subclones and better understand mechanisms of lineage plasticity in acute leukemia.
78. Clinical outcomes associated with NPM1 mutations in newly diagnosed acute myeloid leukemia.
作者: Aziz Farhat.;Georgina El Hajjar.;Hagop Kantarjian.;Koji Sasaki.;Nicholas J Short.;Branko Cuglievan.;Sanam Loghavi.;Keyur Patel.;Alex Bataller.;Wei Ying Jen.;Musa Yilmaz.;Guillermo Montalban-Bravo.;Danielle Hammond.;Naveen Pemmaraju.;Naval Daver.;Farhad Ravandi.;Elias Jabbour.;Tapan Kadia.;Gautam Borthakur.;Guillermo Garcia-Manero.;Courtney D DiNardo.;Ghayas C Issa.
来源: Cancer. 2026年132卷16期e70568页
Nucleophosmin 1-mutated (NPM1mt) acute myeloid leukemia (AML) is associated with a relatively favorable prognosis though long-term outcomes remain suboptimal without clear predictors identified by therapy.
79. Mechanisms of PARP Inhibitor Resistance: From Replication Gap Biology and Transcription-Replication Conflicts to PROTAC-Based Next-Generation Strategies.
Poly(ADP-ribose) polymerase (PARP) inhibitors (PARPi) have transformed precision oncology by exploiting synthetic lethality in homologous recombination (HR)-deficient cancers, with multiple FDA-approved agents targeting BRCA1/2-mutant tumors. Despite initial efficacy, resistance inevitably emerges, limiting long-term clinical benefit. This review synthesizes emerging mechanistic insights into PARPi response and resistance. Recent evidence reframes PARP inhibition cytotoxicity through a transcription-replication conflict model and identifies single-stranded DNA gaps as the primary lethal lesion in HR-deficient cells, rather than double-strand breaks. These findings suggest that resistance reflects restoration of replication gap suppression or resolution of transcription-replication stress. We further highlight DNA ligase III as a collateral vulnerability in 53BP1-deficient resistant tumors, and discuss proteolysis-targeting chimera (PROTAC)-based PARP1 degraders as a strategy to overcome resistance and induce alternative cell death pathways. Established resistance mechanisms-including BRCA1/2 reversion mutations, shieldin complex loss, RAD51 hyperactivation, and pharmacokinetic alterations-are reconsidered within this updated framework. Combination strategies with ATR inhibitors show promising clinical activity in PARPi-resistant HR-deficient ovarian cancer. Finally, we propose an integrated biomarker framework combining HRD scar assays, functional RAD51 foci analysis, replication gap profiling, and circulating tumor DNA (ctDNA) monitoring to enable dynamic resistance tracking.
80. Immunotherapy Resistance in dMMR/MSI-H Colorectal Cancer: Unraveling Mechanisms and Exploring Overcoming Strategies.
Colorectal cancer (CRC) remains a leading cause of cancer-related mortality worldwide. Approximately 15% of localized and 5% of metastatic cases exhibit mismatch repair deficiency (dMMR) or high microsatellite instability (MSI-H). While immune checkpoint inhibitors (ICIs) have revolutionized the first-line treatment for this subgroup, 15%-46% of patients experience primary resistance, and a subset of responders eventually acquires resistance. This review synthesizes the multifaceted mechanisms underlying ICI resistance in dMMR/MSI-H CRC. We delineate tumor-intrinsic alterations, including defects in the antigen presentation machinery (specifically transporter associated with antigen processing [TAP]1/TAP2 and β2-microglobulin [β2m]), oncogenic signaling via the Wnt/β-catenin and JAK/STAT pathways, and epigenetic remodeling involving ARID1A. Furthermore, we explore the role of the immunosuppressive tumor microenvironment (TME), characterized by T-cell exclusion and myeloid-derived suppressor cell (MDSC) accumulation. To address these barriers, we evaluate the clinical potential of third-generation ICIs targeting lymphocyte activation gene 3 (LAG-3), T-cell immunoglobulin and mucin-domain-containing-3 (TIM-3), and TIGIT, as well as emerging biomarker strategies such as gut microbiome modulation and circulating tumor DNA (ctDNA) dynamics. By integrating these mechanistic insights with novel therapeutic approaches, including bispecific antibodies (BsAbs) and adoptive cell transfer, this review aims to provide a roadmap for overcoming resistance and advancing precision immunotherapy in dMMR/MSI-H CRC.
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