Immune evasion in locally advanced mismatch repair-deficient microsatellite instability-high colorectal cancer: Reduced T-cell infiltration and upregulation of epithelial IDO1 expression

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

Abstract 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.

BRCA1/2-stratified immune profiling of treatment-naive high-grade serous ovarian cancer ascites identifies a Treg-enriched ascitic immune phenotype.

Circulating Immune Profiling Reveals Immune Signatures Associated with Disease Stage and Outcome in Endometrial Cancer

Although the tumor immune microenvironment has been studied in endometrial cancer, the systemic immune alterations associated with disease progression and their potential prognostic significance remain poorly defined. In this study, peripheral blood immune subsets were characterized by multiparametric flow cytometry in 67 patients with EC and 20 healthy controls, including dendritic cells, MDSCs, T-cell subsets, NK cells, and exhaustion and senescence associated markers. Immune profiles were similar between healthy controls and patients with early-stage disease, whereas advanced tumors showed marked changes, including dendritic cell expansion, reduced CD4+ T-cell proportions, and increased frequencies of CD8+CD27-CD28- and CD8+CD57+ populations. Among clinicopathologic features, MDSC levels were associated with tumor grade and myometrial infiltration, while regulatory T cells were increased in TP53-mutated and microsatellite-stable tumors. In the advanced cohort (n=31), non-responders frequently displayed elevated CD8+, CD8+CD27-CD28-, and CD8+CD57+ levels alongside decreased CD27+CD28+ proportions. In multivariable Cox models, higher baseline CD8+ (HR 1.13), CD8+ CD27-CD28- (HR 1.04), and CD8+CD57+ proportions (HR 1.07; all p<0.05) were independently associated with shorter PFS, whereas higher CD27+CD28+ levels were associated with improved PFS. CD27-CD28- proportions were also linked to worse PFS by Kaplan-Meier analysis (HR 5.1, log-rank p=0.005). Longitudinal analysis (n=28) showed that senescent-like lymphocyte levels remained associated with progression across timepoints (OR 18.80), whereas total CD8+ proportions diverged progressively, reaching significance only from 6 months onward. Together, these findings identify systemic immune remodeling as a characteristic of advanced endometrial cancer and support the potential of circulating immune profiling for patient stratification and prognostic assessment, pending validation in larger prospective cohorts.

8 Single Cell Transcriptomic Investigation of Renal Cell Carcinoma (RCC) Reveals Tissue Resident Memory Exhausted CD8+ T Cell Signature Associated with Resistance to Immune Checkpoint Inhibition (ICI)

Abstract Background The current standard of care for advanced RCC is ICI-based combination therapies. However, most patients with advanced RCC develop disease progression despite ICI treatment, suggesting a lack of durable immune response. Although a lack of T cell infiltration or the presence of non-tumor-reactive “bystander” T cells are hypothesized mechanisms of ICI resistance across tumor types, therapeutic resistance in RCC may still occur in the presence of abundant infiltration of tumor-specific CD8+ T cells. We therefore investigated whether CD8+ T cell phenotype in the RCC tumor microenvironment (TME) impacts ICI response or resistance. Methods 70 tumor samples from 63 RCC patients were collected before (n = 48) or after (n = 22) therapies (VEGFi, n = 9; ICI monotherapy, n = 20; ICI combination, n = 26; others, n = 15). 11 samples were collected from patients without tumors. RCC variants included 59 clear cell and 11 non-clear cell samples. 18 were labeled as clinical benefit and 11 as no-clinical benefit. Single-cell RNA sequencing (10x Genomics) was performed on these samples to generate a transcriptome of the RCC TME. Graph-based clustering identified cell type populations, which were annotated with known lineage genes. Non-negative matrix factorization (NMF) identified gene programs within exhausted CD8+ T cells (Tex). Differential gene expression analysis determined the most differentially expressed genes between resident memory Tex and other cell populations. Results Within CD8+ T cells, Tex cells were identified through expression of TOX, PDCD1 (PD-1), and HAVCR2 (TIM-3). NMF generated 4 gene programs within Tex cells, expressing markers for immediate early genes (JUNB, FOS), exhaustion/activation (GZMK, CD74, LAG3), tissue residency (GZMH, ITGAE, IL7R), and stress response (HSPA1A, HSPA6). The tissue residency program was associated with resistance to ICI therapy (p = 0.05); this association was only found in samples with abundant tumor-specific CD8+ T cells. Differential expression between resident memory Tex (Tex-RM) and other cell types generated a signature of 10 markers that were most highly expressed in Tex-RM. Response and survival data of external bulk RNA-seq cohorts were analyzed. A signature score subtracting for Tex-RM signature was calculated (normalized to overall abundance of Tex cells by signature analysis), which was significantly higher in patients with progressive disease than those with complete/partial response (p = 0.0046), specifically for patients receiving ICI-based therapies. Additionally, survival analysis revealed that ICI-based patients with a higher (top 25%) signature score had significantly worse progression free survival (PFS; p = 0.0048) as well as overall survival (p = 0.0069) with ICI. For ICI-treated patients, the Tex-RM signature score was associated with worse PFS, with a hazard ratio of 2.1 (90% CI [1.3, 3.25]). There was no significant impact on patients receiving TKI monotherapy. Conclusions Through scRNA-seq analysis, we identify a tissue residency gene program in Tex cells associated with non-response to immunotherapy. A signature derived from this program was additionally shown to predict significantly worse response and outcomes for patients receiving ICI-based therapies within a group of bulk RNA-seq clinical trial cohorts. This study provides a framework for using scRNA-seq to identify mechanisms of ICI resistance in RCC and nominates resident memory exhausted CD8+ T cells as a targetable subset of cells to improve CD8+ T cell-mediated anti-tumor immunity. DOD CDMRP Funding yes

Tumor-Intrinsic DNA Damage Signaling Is Associated with MHC-I Expression and CD8 Cytotoxic T-Cell Engagement in Triple-Negative Breast Cancer

An exploratory, integrative analysis using single-cell RNA sequencing of TNBC patients operationally stratified into Good and Bad Prognosis groups suggests a framework in which tumor-intrinsic DNA damage signaling is associated with MHC-I antigen presentation upregulation and CD8 cytotoxic T-cell engagement, supporting further investigation of this axis.

Prognostic value of CD103+ tumor-infiltrating lymphocytes in bladder cancer: A systematic review and meta-analysis.

CD103+ tissue-resident memory T cells are emerging mediators of antitumor immunity whose prognostic significance in bladder cancer, across muscle-invasive and metastatic urothelial carcinoma, remains undefined at a meta-analytic level. We performed a systematic review and meta-analysis of cohorts with histologically confirmed muscle-invasive bladder cancer or metastatic urothelial carcinoma, comparing high vs. low CD103+ tumor-infiltrating lymphocyte density assessed by immunohistochemistry or ITGAE mRNA expression, with overall survival endpoint. PubMed, Embase, Scopus, and Cochrane CENTRAL were searched from inception through March 2026. Pooled hazard ratios (HR) with 95% confidence intervals (CIs) were estimated using a restricted maximum likelihood random-effects model. Subgroup analyses were performed by treatment context, disease stage, and assessment method. The protocol was registered at OSF (u36xv). Three studies comprising 6 cohorts were included. High CD103⁺ infiltration was significantly associated with prolonged overall survival (HR: 0.50, 95% CI: 0.30-0.83). A significant treatment-context interaction (P = 0.005) favored patients undergoing surgery with adjuvant chemotherapy (HR: 0.20) over those receiving immunotherapy (HR: 0.69). Stage-stratified analysis showed a significant interaction (P = 0.003), with pronounced benefit in muscle-invasive bladder cancer (HR: 0.27) but a non-significant trend in metastatic urothelial carcinoma (HR: 0.79). Immunohistochemistry-based cohorts showed a numerically larger effect than ITGAE mRNA cohorts. High CD103⁺ tumor-infiltrating lymphocyte infiltration may be associated with improved overall survival in bladder cancer, particularly in muscle-invasive bladder cancer patients undergoing surgery with adjuvant chemotherapy. Prospective validation in larger, stage-homogeneous cohorts is warranted to establish CD103 as a prognostic biomarker. These findings are hypothesis-generating and CD103 assessment is not currently ready for clinical use.