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PubMed2026

Integrating clinical and genomic features to predict response to neoadjuvant therapy in microsatellite-stable rectal cancer.

BACKGROUND: Neoadjuvant therapy (NAT) has shifted rectal cancer management toward organ preservation. However, achieving a complete response (CR) for "watch-and-wait" strategies is hindered by high response heterogeneity. Although immunotherapy-combined NAT has expanded the candidate pools, the predictive significance of molecular alterations remains unclear. OBJECTIVES: This study aimed to evaluate clinical and genomic profiles of rectal cancer patients undergoing NAT to identify response predictors and to develop a nomogram for estimating CR probability. DESIGN: Retrospective, single-center cohort study. METHODS: This study included 437 patients with rectal adenocarcinoma at Fudan University Shanghai Cancer Center between December 2019 and March 2023. Patients underwent paired tumor and germline genomic sequencing (887-gene panel) before NAT. Logistic and Cox regression analyses were performed to identify clinical and genetic risk factors associated with tumor response and long-term survival. RESULTS: Of the 437 patients, 96.6% had microsatellite-stable (MSS) tumors. In the MSS locally advanced rectal cancer cohort (N = 307), the CR rate was 35.5%. Multivariate analysis identified immunotherapy-combined NAT (iTNT) (OR 4.41, 95% CI: 2.42-8.27), SYNE1 mutation (OR 2.12, 95% CI: 1.06-4.26), negative mesorectal fascia (MRF) status (OR 0.34, 95% CI: 0.17-0.66), and lower tumor location (OR 0.48, 95% CI: 0.27-0.84) as independent predictors of CR. KRAS mutation was the sole independent predictor of reduced disease-free survival (DFS; HR 1.93, 95% CI: (1.11-3.36), p = 0.020). KRAS G12D subtype was associated with the worst 2-year distant metastasis-free survival (71.3%) and exhibited a distinct predilection for lung metastasis. The clinical-genomic nomogram yielded strong discrimination (AUC = 0.705) and calibration, with favorable DCA net benefit. CONCLUSION: Clinical and genomic features jointly determine outcomes in MSS rectal cancer. SYNE1 mutation serves as a novel biomarker for CR, while KRAS mutations, especially the G12D subtype, identify patients at high risk for systemic relapse. The clinical-genomic nomogram facilitates individualized selection for organ-preservation strategies.

biomarker↗

PubMed2026

A Functionally Constrained Immune Ecosystem in Microsatellite-stable Colorectal Cancer Resolved by Single-cell and Exome Profiling.

BACKGROUND/AIM: Microsatellite-stable (MSS) colorectal cancer (CRC) generally responds poorly to immune checkpoint blockade, but some MSS tumors are T-cell rich. We examined whether such infiltration reflected effective immunity or functional immune constraint. CASE REPORT: A 77-year-old woman underwent resection of a mismatch repair-proficient (pMMR), MSS, low-mutational-burden CRC with a synchronous adenoma. Whole-exome sequencing of tumor, adenoma and adjacent normal tissue detected no shared high-confidence somatic mutations between tumor and adenoma within the sensitivity of this WES analysis and identified tumor-specific APC, KRAS and TP53 alterations. Tumor single-cell RNA sequencing yielded 7,569 cells, with T-lineage populations comprising 83.5%. Cytotoxic T cells showed cytolytic and dysfunction-associated features, regulatory T cells (Tregs) showed suppressive remodeling, and Th17 cells showed inflammatory/profibrotic programs. CellChat nominated stromal MIF/FN1-CD74/CD44 and extracellular-matrix communication with T-cell compartments. CONCLUSION: This molecular case report shows that T-cell abundance and immune effectiveness can be uncoupled in MSS CRC.

Humans↗

PubMed2025

The histone modifier KAT2A presents a selective target in a subset of well-differentiated microsatellite-stable colorectal cancers.

Lysine acetyltransferase 2 A (KAT2A) plays a pivotal role in epigenetic gene regulation across various types of cancer. In colorectal cancer (CRC), increased KAT2A expression is associated with a more aggressive phenotype. Our study aims to elucidate the molecular underpinnings of KAT2A dependency in CRC and assess the consequences of KAT2A depletion. We conducted a comprehensive analysis by integrating CRISPR-Cas9 screening data with genomics, transcriptomics, and global acetylation patterns in CRC cell lines to pinpoint molecular markers indicative of KAT2A dependency. Additionally, we characterized the phenotypic effect of a CRISPR-interference-mediated KAT2A knockdown in CRC cell lines and patient-derived 3D spheroid cultures. Moreover, we assessed the effect of KAT2A depletion within a patient-derived xenograft mouse model in vivo. Our findings reveal that KAT2A dependency is closely associated with microsatellite stability, lower mutational burden, and increased molecular differentiation signatures in CRC, independent of the KAT2A expression levels. KAT2A-dependent CRC cells display higher gene expression levels and enriched H3K27ac marks at gene loci linked to enterocytic differentiation. Furthermore, loss of KAT2A leads to decreased cell growth and viability in vitro and in vivo, downregulation of proliferation- and stem cell-associated genes, and induction of differentiation markers. Altogether, our data show that a specific subset of CRCs with a more differentiated phenotype relies on KAT2A. For these CRC cases, KAT2A might represent a promising novel therapeutic target.

Humans↗

PubMed2025

Identification and Validation of a Previously Missed Mutational Signature in Colorectal Cancer.

Mutational signature analysis has greatly enhanced our understanding of the mutagenic processes found in cancer and normal tissues. As part of a recent study, we analyzed 802 treatment-naïve, microsatellite-stable colorectal cancers (CRC) and identified a de novo signature, SBS_D, which was conservatively decomposed into SBS18, a signature associated with reactive oxygen species. Here, we re-evaluate this decomposition and provide evidence that SBS_D represents a distinct mutational process from that of SBS18. Through an independent analysis of 2,616 whole-genome sequenced microsatellite-stable CRCs across three distinct cohorts, we demonstrate that SBS_D is consistently present at a similar prevalence, suggesting that this signature may have been previously overlooked. Using a naïve decomposition approach, we demonstrate that the pattern of SBS_D better aligns with signatures previously associated with deficiencies in DNA polymerase delta (POLD1) proofreading and mismatch repair. However, multiple lines of evidence, including the absence of pathogenic mutations in the exonuclease domain of POLD1 or in mismatch repair-associated genes, indicate that SBS_D is not driven by canonical defects in these DNA repair pathways. Overall, this study identifies a previously unrecognized mutational signature in microsatellite-stable CRC and proposes that its etiology may be linked to DNA repair infidelity emerging late in tumor development in samples without canonical defects in DNA repair pathways.

Journal Article↗

PubMed2026

Copy Number-low/TP53-mutated Endometrial Cancer With Wild-type p53 Immunoexpression: Implications for Risk Stratification and Management When Using Next-generation Sequencing for Molecular Classification.

Endometrial cancers with the Cancer Genome Atlas (TCGA) molecular profile of TP53-mutated, POLE-wild-type, and microsatellite-stable generally exhibit a high burden of copy number (CN) alterations and carry an increased risk for adverse outcomes, meriting maximal adjuvant therapy. In contrast, the prognosis associated with a TP53 mutation that coexists with a POLE mutation or microsatellite instability aligns with that of ultramutated or hypermutated cancers, respectively. In this study, we characterized a rare molecular subclass of endometrial cancers defined by TP53 mutation but low burden of CN alterations, wild-type p53 immunoexpression (immunohistochemistry [IHC]), and low TP53 variant allele frequency (median 13% and maximum 47%). Among 723 consecutive endometrial cancers prospectively classified using next-generation sequencing, 16 (2.2%) were CN-low/TP53-mutated/p53 wild-type IHC. Two additional cases were identified in a separate retrospective cohort of 32 recurrent low-grade early-stage endometrial cancers, bringing the total to 18 cases. They affected postmenopausal patients, exhibited low-grade endometrioid histotype, and were mostly confined to the uterus without lymphovascular space invasion. The recurrence rate was 6.25% (1/16) in the prospective cohort, and none died, placing their prognosis closer to that of CN-low than CN-high cancers. We conclude that next-generation sequencing-based TCGA classification of TP53-mutated, POLE-wild-type, microsatellite-stable endometrial cancers with TP53 variant allele frequency < 50% requires further evaluation using CN analysis and/or p53 IHC to detect this rare molecular category. IHC-based TCGA classification, such as the ProMisE protocol, will not be able to detect these cases because the p53 IHC pattern is wild-type and there are no distinguishing morphological features; this may be of relevance for analyzing ProMisE protocol-based clinical trials and outcomes studies. Long-term outcome studies are needed to refine risk stratification and treatment decisions for this unique molecular class of endometrial cancers that further contributes to the evolving understanding that the clinical significance of TP53 mutation in endometrial cancer is complex and depends on coexisting molecular alterations.

Humans↗

PubMed2026

Noncanonical Transcription and Splicing Shape the Colorectal Cancer Immunopeptidome in MSI and MSS Tumors.

Treatment with immune checkpoint inhibitors in colorectal cancer (CRC) has largely benefited patients with microsatellite instability-high (MSI-H) and not the larger proportion of patient with microsatellite-stable (MSS) tumors. This clinical dichotomy has fueled the view that high mutational burden is the dominant driver of tumor immunogenicity and that MSS CRC fails to respond because it is "antigen poor". To directly test this premise and define the origins of presented tumor antigens, we integrated HLA class I immunopeptidomics and matched RNA-seq from 26 primary CRC tumors spanning MSI-H and MSS subtypes. Using patient-specific canonical and cancer-specific proteogenomic databases, we identified 115,292 unique major histocompatibility complex (MHC)-associated peptides (MAPs) across 61 HLA alleles, with a mean of 9292 MAPs per tumor and no significant difference in MAP counts between MSI-H and MSS tumors. In toto, we identified 266 tumor antigens, all coded by unmutated genomic sequences, comprising 70 aberrantly expressed tumor-specific antigens (aeTSAs) and 196 tumor-associated antigens (TAAs). In our cohort, MSS tumors presented more TAAs and a comparable number of aeTSAs per tumor relative to MSI-H tumors. In TCGA-COAD stratified analyses (483 tumors), MSS tumors yielded more presentable aeTSAs and TAAs per patient than MSI-H tumors. Across both subtypes, aeTSAs arose predominantly from intronic translation, UTR usage, retroelement activation, and germline-like transcription, including recurrent aeTSAs from PIWIL1, L1TD1, and endogenous retroviral loci. Together, these data demonstrate that MSS CRC is not antigen poor and highlight noncanonical translation as a major, previously underappreciated contributor to the CRC immunopeptidome.

Humans↗

PubMed2026

Identification and validation of a previously missed mutational signature in colorectal cancer.

Mutational signature analysis has enhanced our understanding of mutagenic processes. In a recent study, we analyzed 802 microsatellite-stable colorectal cancers (CRC) and identified a de novo signature, SBS_D, which was decomposed into SBS18. Here, we re-evaluate this decomposition and provide evidence that SBS_D represents a distinct mutational process from SBS18. Through an analysis of 2,616 CRCs across three independent cohorts, we demonstrate that SBS_D is consistently present, suggesting this signature may have been previously overlooked. We illustrate that the pattern of SBS_D better aligns with signatures associated with deficiencies in DNA repair, despite evidence that SBS_D is not driven by canonical defects in these DNA repair pathways. Overall, this study identifies a previously unrecognized mutational signature in DNA repair-proficient CRC and proposes that its etiology may be linked to DNA repair infidelity emerging late in tumor development. SBS_D has been submitted to the COSMIC database and provisionally designated as SBS111.

Colorectal Neoplasms↗

PubMed2026

Conserved miRNA regulators of PD-1/PD-L1 in glioblastoma and colorectal cancer.

Immune checkpoint inhibitors (ICIs) targeting the PD-1/PD-L1 axis have transformed cancer therapy, but their efficacy remains limited in glioblastoma (GBM) and heterogeneous in colorectal cancer (CRC). MicroRNAs (miRNAs) regulate gene expression at the post-transcriptional level, including immune checkpoint molecules, yet conserved regulatory miRNA networks across distinct cancers remain poorly defined. Five conserved miRNAs (miR-106a-5p, miR-106b-5p, miR-20a-5p, miR-20b-5p, miR-138-5p) fulfilled the selection criteria and were consistently dysregulated in GBM and CRC. MiR-106a-5p and miR-106b-5p were upregulated in both cancers and showed favourable prognostic associations, with higher expression correlating with improved survival. miR-20a-5p and miR-20b-5p were preferentially expressed in microsatellite-stable (MSS) CRC and correlated with favourable outcomes in both cancers, whereas miR-138-5p was downregulated in both tumours compared to normal tissue, but showed opposite survival associations, with higher levels linked to worse prognosis. Correlation analysis revealed significant inverse associations between several miRNAs and checkpoint gene expression, including moderate inverse correlations for CD274-miR-106a-5p in GBM, CD274-miR-20a-5p in CRC and PDCD1LG2-miR-20a-5p in both cancers. Pan-cancer profiling demonstrated broad and heterogeneous dysregulation, with expression absent in ovarian cancer for four of the five miRNAs. Pathway enrichment implicated the TGF-β, Hippo, FoxO, and cell cycle pathways, consistent with their known roles in tumour immune evasion. We identified a conserved set of miRNAs that are dysregulated in both GBM and CRC, correlate with survival, and display inverse relationships with PD-1/PD-L1/PD-L2 expression. These miRNAs represent candidate regulators of the PD-1/PD-L1/PD-L2 axis and potential biomarkers of tumour biology that may influence immune checkpoint signalling.

Humans↗

PubMed2026

Heterozygous germline mutations in MSH3, and probably MLH3, act as classical tumour suppressors, leading to excess somatic deletion mutations, signature ID4 and increased colorectal cancer risk.

BACKGROUND: MSH3 and MLH3 are non-canonical DNA mismatch repair genes, involved in repairing insertion-deletion mutations. Colorectal cancer (CRC) and adenomas have been reported in patients with bi-allelic germline MSH3 mutations, and in a very few bi-allelic MLH3 mutation carriers. OBJECTIVES: We hypothesised that germline loss-of-function MSH3 and MLH3 mutations were akin to constitutional mismatch repair deficiency (cMMRd) and Lynch syndrome, such that CRC could result from either bi-allelic germline mutations or heterozygous germline mutations after second hits. DESIGN: About 12 000 CRC and multiple polyp cases and 460 000 controls were studied. 2023 patients underwent cancer genome sequencing. RESULTS: One CRC/multiple polyp case had bi-allelic MSH3 mutations and another, bi-allelic MLH3 mutations. MSH3 and MLH3 germline heterozygotes had an increased risk of CRC (2.2-fold, p=6.6×10-5 and 1.6-fold, p=0.028, respectively), owing to somatic 'second hits' that inactivated the wildtype allele. Single second hits sometimes inactivated both MSH3 and the nearby APC gene. All CRCs with MSH3 or MLH3 deficiency were microsatellite-stable but hypermutant. Deletions of ≥2 bp were particularly increased (~12-fold) and signature ID4 was usually present (p<0.0001). CRCs from heterozygotes without 'second hits' showed no hypermutation. CONCLUSION: The phenotypes of bi-allelic MSH3 and MLH3 mutation carriers resemble some patients with cMMRd. Heterozygous germline MSH3 and MLH3 alleles have incomplete penetrance, but increase CRC risk via hypermutation, phenotypically resembling PMS2-mutant Lynch syndrome. A causal association with specific mutations has not previously been reported for ID4 in human tumours. ID4 probably does not have a single aetiology, but can result from MSH3 or MLH3 deficiency.

COLONIC POLYPS↗

PubMed2026

Transcriptomic Association Between Poliovirus Receptor (PVR/CD155) and Claudin Signaling Pathways in Colorectal Cancer.

BACKGROUND/AIM: Enterotoxigenic Bacteroides fragilis promotes colorectal carcinogenesis through toxin-mediated cleavage of E-cadherin, a process facilitated by membrane-associated Claudin-4 (CLDN4). Separately, the poliovirus receptor (PVR/CD155) modulates tumor epithelial and immune dynamics. This study explored potential transcriptomic interactions and co-expression frameworks between PVR and claudin signaling pathways in colorectal cancer. MATERIALS AND METHODS: Transcriptomic and proteomic data from the The Cancer Genome Atlas-colon adenocarcinoma cohort (TCGA-COAD) were evaluated. An exploratory E-cadherin Cleavage Index was modeled to capture transcript-protein discordance. To control for tissue composition heterogeneity without mathematical circularity, a de-circularized, non-parametric partial rank residual model adjusted for independent CLDN4 expression was deployed within the stable microsatellite-stable (MSS) sub-cohort (N=473). RESULTS: Multivariable survival models showed no independent associations between overall survival and continuous PVR (p=0.79) or CLDN3 (p=0.56) expression. Robust linear modeling revealed no significant baseline interaction between PVR and CLDN4 regarding the exploratory Cleavage Index (p=0.82). However, de-circularized partial correlation analysis revealed a highly stable, positive co-expression between PVR and CLDN3 (rho=0.2459, p=3.23×10-7). Both epithelial markers retained modest inverse correlations with the infiltrating lymphocytic axis (TIGIT and CD96). CONCLUSION: Baseline PVR expression is coordinated with CLDN3 tissue programs independent of general epithelial cellularity but does not interact with the CLDN4 axis or impact overall survival in an unexposed cohort. Because TCGA lacks virome or active microbial exposure tracking, these findings serve as baseline benchmarks for future context-dependent mechanistic studies.

Bacteroides fragilis toxin↗