Citations

Abstract Therapeutic resistance to chemotherapy is frequently the proximate cause of increased tumor burden, cancer treatment failure, and ultimately, patient mortality. The most successful therapy strategy derived from evolutionary practices to date, Adaptive Therapy (AT), leverages the fitness cost of developing therapeutic resistance. AT avoids treating cancer cells with the Maximum Tolerated Dose (MTD) of therapeutic drugs and instead incorporates a series of adaptive dosing schedules. Treatment-sensitive cells are bolstered by modulating or pausing treatment to out-compete and suppress treatment-resistant cell growth. We are evaluating AT for the first time in colorectal cancer, using a syngeneic orthotopic xenograft model. This work represents several key advances: it is the first to longitudinally and non-invasively track sensitive and resistant clones in vivo, to evaluate adaptive therapy in an immunocompetent mouse model, to incorporate multi-drug treatment regimens, and to integrate a targeted therapeutic agent. The dual-bioluminescent sensitive and resistant CT26 cell lines developed for this study allow real-time visualization and quantification of each population throughout tumor progression and treatment. Together, these advances establish a robust and clinically relevant platform for characterizing resistance dynamics and refining adaptive therapy strategies aimed at improving treatment outcomes in colorectal cancer. Citation Format: Harley I. Richker, Bailey Sierra Kane, Gissel Marquez Alcaraz, Ellie Pahl, Ryan Carr, Nagarajan Kannan, Carlo C. Maley. Harnessing clonal dynamics to overcome resistance: An adaptive therapy framework in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 702.

Abstract Introduction: Ewing sarcoma (EwS) is a FET::ETS family member-driven primary bone cancer demonstrating vast heterogeneity. Between a patient’s primary diagnosis and disease progression, tumor cell state adaptation, microenvironment changes, and the landscape of evolving therapeutic vulnerabilities remain poorly understood. To address these gaps, the Sean Karl Cohort was established in 2025 to conduct the largest single-cell transcriptomic analysis of retrospective paired tumor samples from patients with EwS. Here, we present data from the five analytic teams, and through shared SOPs now expand this cohort to Europe. Methods: Common sample processing SOPs were established to isolate cells from FFPE material from paired patient EwS samples. Single-cell (sc) RNAseq was generated using the GEM-X Flex Gene Expression protocol (10x Genomics). Alex’s Lemonade Stand Foundation (ALSF) Data Lab established a common data processing and integration pipeline with an EwS-specific cell annotation workflow to create a harmonized dataset for downstream analyses. Analytic teams were created to define tumor cell subpopulations and their therapeutic vulnerabilities and to characterize the tumor microenvironment. Data: We demonstrate the feasibility of generating high-quality scRNAseq profiles from retrospective FFPE-preserved EwS tumors. To date, 116 samples have yielded ∼800,000 cells. Integrated analysis reveals reproducible EwS tumor cell states shared across patients with regulatory network analyses nominating candidate therapeutic vulnerabilities. The scale of this international cohort enables saturation analysis for rare cell populations. Paired and longitudinal samples further allow correlation of emergent cell states with therapy resistance and metastatic progression. For example, immune-focused analyses show increases in T cell and macrophage populations in post-therapy samples. A novel, standardized EwS-specific cell annotation workflow has been developed to harmonize analyses and findings. These data will be openly shared with the community through the ALSF Single-cell Pediatric Cancer Atlas Portal. Conclusion: Large-scale international collaborative sample sharing, standardized processing pipelines, and harmonized EwS-specific annotations now enable deep single-cell analyses to characterize tumor heterogeneity in this rare pediatric and adolescent cancer. An in vivo expansion of the Sean Karl Cohort is underway to assess conservation of EwS tumor cell states and regulatory vulnerabilities identified in human tumors pre- and post-therapy in preclinical models, further supporting translation of these findings toward therapeutic strategies. Citation Format: Abbe Pannucci, Elina Mukherjee, Jessica D. Daley, Shireen Sita Ganapathi, Elissa Boguslawski, Lea Surrey, Lauren Gutstein, Patrick Azar, Emily Stockfisch, Azfar Neyaz, Ivy John, Jennifer Picarsic, Yutaro Tanaka, Byron Butaney, Riaz Gillani, Brian D. Crompton, Katherine A. Janeway, Jaclyln Taroni, Jessica Davis, Damon Reed, Adam Shlien, Theodore W. Laetsch, Rajen Mody, Clémence Henon, Thomas G. Grünewald, Elizabeth R. Lawlor, Filemon Dela Cruz, Patrick J. Grohar, Jovana Pavisic, Ally Hawkins, Anthony R. Cillo, Kelly M. Bailey. The Sean Karl Cohort: An international single-cell RNAseq study of paired patient Ewing sarcoma specimens [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 643.

Abstract Breast cancer is the most common female malignancy in the U.S. and the leading cause of cancer-related deaths in women worldwide. Nearly 80% of breast tumors express estrogen receptor alpha (ERα) which drives tumor progression. While endocrine therapies and CDK4/6 inhibitors have increased overall survival, many patients experience recurrence of metastatic disease that is largely refractory to additional lines of endocrine therapy. Metastatic disease remains incurable, highlighting the need for alternative treatment approaches. Through a genome-wide CRISPR knockout screen, we identified Lemur Tail Kinase 2 (LMTK2) as the top hit exhibiting synthetic lethality in the presence of the endocrine therapy, endoxifen, in both endocrine-sensitive and -resistant cell line models. Using publicly available patient tumor databases we identified LMTK2 copy number gain/amplification in 67% of ERα+ human metastatic breast tumors, while only 1% of primary tumors harbored these genomic alterations. Elevated LMTK2 expression in early-stage primary breast tumors was associated with worse recurrence-free survival and overall survival. We discovered that LMTK2 mRNA and protein levels were substantially elevated in nearly all cell-line and patient-derived models of endocrine and CDK4/6i resistance. Utilizing siRNAs and dox-inducible shRNA expressing cell lines, we found that knockdown of LMTK2 enhanced the efficacy of multiple endocrine therapies in treatment naïve models and resensitized resistant models to their respective treatment. LMTK2 overexpression was found to be sufficient for conferring resistance to all standard of care therapies tested including endocrine agents, CDK4/6i, and PI3K inhibitors. RNAseq and global proteomics of LMTK2 overexpressing and knockout models revealed the PI3K/AKT pathway and estrogen signaling as highly regulated pathways by LMTK2. Confirmatory western blot studies demonstrated that LMTK2 overexpression results in dramatic increases in AKT and ERα phosphorylation and activity, while knockout of LMTK2 diminishes these effects. Attempts to completely ablate LMTK2 in endocrine/CDK4/6i-resistant models via CRISPR were not successful, and continuous siRNA or shRNA-mediated knockdown was lethal in resistant cell lines, confirming its essentiality in this setting. In summary we have uncovered LMTK2 as a novel mediator of endocrine/CDK4/6i resistance that is mechanistically linked to the PI3K/AKT pathway among others. Genetic manipulation of LMTK2 has validated it as an ideal therapeutic target for both advanced and newly diagnosed forms of ERα+ breast cancer. Citation Format: Anna Detry, Sofia Marigliano, Jenna Heinen, Adam Bass, Calley Jones, Rajeev Muthyala, Matthew Goetz, John Hawse. LMTK2: A novel driver of endocrine resistance in ERα+ breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 443.

Abstract Background: Small cell lung cancer (SCLC) remains an aggressive malignancy with limited treatment options and a 5-year survival rate under 10%. Delta-like ligand 3 (DLL3), expressed in >85% of SCLC but absent from normal tissue, represents an attractive therapeutic target. Existing DLL3-directed antibody-drug conjugates suffer from poor payload stability and limited tumor penetration. To overcome these limitations, we engineered a DLL3-targeted nano-immunoconjugate (NIC) of SN38, the active metabolite of irinotecan, using an albumin-based nanoscaffold. Methods: SN38 was encapsulated in a human serum albumin (HSA) matrix and non-covalently coated with a recombinant anti-DLL3 monoclonal antibody to yield DLL3-SN38-NIC. Stable conjugation was confirmed by HSA-IgG interactions and zeta-potential shift. Binding kinetics were evaluated using Biacore surface plasmon resonance (SPR) and Octet bio-layer interferometry (BLI) employing AHC biosensors to determine DLL3-antibody affinity and specificity. Cytotoxicity was assessed using IncuCyte live-cell imaging across five SCLC cell lines (DMS454, SHP77, NCI-H82, NCI-H889, and NCI-H211) with varying DLL3 expression. Results: DLL3-SN38-NIC retained high-affinity DLL3 binding (KD ≈ 3 × 10-10 M) and demonstrated potent cytotoxicity in SCLC cell lines. NIC formation did not reduce cytotoxic activity compared with free SN38, confirming preserved potency. Cytotoxicity trends were consistent across lines with variable DLL3 expression, and DLL3 antibody alone exhibited negligible cytotoxicity. These findings confirm that nano-immunoconjugate formation maintains drug activity and DLL3 binding; additional in-vivo studies are underway to evaluate pharmacokinetics and tumor selectivity. Conclusions: Albumin-based DLL3-SN38-NICs represent a novel nano-oncologic platform that preserves SN38 potency and achieves high-affinity DLL3 engagement. Ongoing studies will assess in-vivo selectivity, biodistribution, and therapeutic potential in DLL3-positive SCLC and other neuroendocrine malignancies. Citation Format: Mohamed Shanshal, Lin Yang, Liyi Geng, Wendy Nevala, Aaron S. Mansfield, Bharath Wootla, Konstantinos Leventakos, Kyle Korshavn, Svetomir N. Markovic. Albumin-based DLL3-targeted nano-immunoconjugates of SN38 preserve potency and demonstrate high-affinity DLL3 binding in small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 449.

Abstract Background: Spatial cellular ecosystems in the tumor microenvironment (TME) form dynamic signaling hubs that critically influence cancer disease progression and response to therapy, including response to immune checkpoint inhibitors (ICIs). However, tumor sampling bias and the impracticality of acquiring serial tumor biopsies have made it challenging to profile the TME clinically. To address this challenge, we developed Liquid EcoTyper, a multi-analyte AI framework to quantify TME spatial cellular ecosystems—termed spatial ecotypes (SEs)—noninvasively from cell-free DNA (cfDNA) methylation data. Methods: In previous work, we discovered nine spatial ecotypes, including SEs associated with ICI response (e.g., SE7 with benefit, SE4 with resistance), and quantified them from 1,249 bulk tumor RNA-seq profiles of melanoma, non-small cell lung cancer (NSCLC), and bladder cancer (BC) patients (Cancer Res (2025) 85 (8_Supplement_1): 153). Here we trained Liquid EcoTyper, an interpretable deep learning model, to transfer SE profiling to cell-free DNA using CpG methylation profiles. Performance was quantified using simulated and real data, including methylation profiles (EM-seq) of plasma cfDNA paired with tumor biopsy-derived SE levels determined by EM-seq (n=20 pairs) or 10x Visium (n=15 pairs). Clinical outcome prediction was evaluated using pretreatment plasma from patients treated with ICI alone (n=78 melanoma pts), chemotherapy and ICI (n=25 NSCLC pts), and enfortumab vedotin and ICI (n=10 localized muscle-invasive BC (MIBC) pts). Tumor mutational burden (TMB), tumor PD-L1, or circulating tumor DNA (ctDNA) were profiled as a comparator where possible. Results: We observed striking concordance between plasma-derived SE levels and tumor biopsy-confirmed SE levels from the same patients, demonstrating that liquid biopsy analysis of cfDNA methylomes can recapitulate TME spatial biology. Underscoring specificity, no reliable SE signal was detectable from peripheral blood mononuclear cells. In pre-ICI plasma, liquid SE levels were significantly associated with ICI-based response (SE7) versus resistance (SE4) in patients with melanoma, NSCLC, and MIBC, with a mean cross-cancer area under the curve (AUC) of 0.87 for SE7 (range 0.8-0.97) and 0.81 for SE4 (range 0.76-0.85)—far surpassing TMB, tumor PD-L1, and ctDNA in evaluable patients, both in binary analyses of response and multivariable models of survival. Our results also showed potential to predict pathologic complete response in the neoadjuvant setting. Conclusion: Liquid EcoTyper is a scalable noninvasive AI-based framework for spatiotemporal assessment of the TME. By enabling TME-informed risk stratification without surgical biopsies, Liquid EcoTyper has potential to enable more precise and actionable decision making in patients with solid tumors. Citation Format: Erin L. Brown, Wubing Zhang, Abul Usmani, Noah Earland, Ayesha Hashmi, Chibuzor Olelewe, Anushka Viswanathan, Pradeep S. Chauhan, Minji Kang, Chloé B. Steen, Hyun Soo Jeon, Susanna Avagyan, Irfan Alahi, Nicholas P. Semenkovich, Matteo Bergsagel, Janella C. Schwab, Chloe M. Sachs, Faridi Qaium, Peter K. Harris, Antonella Bacchiocchi, Qingyuan Cai, Andrew J. Gentles, Rondell P. Graham, Peter C. Lucas, Ryan C. Fields, Jacob J. Orme, Aaron S. Mansfield, Mario Sznol, Ruth Halaban, David Y. Chen, Aaron M. Newman, Aadel A. Chaudhuri. Liquid biopsy profiling of the tumor microenvironment to determine response to immunotherapy regimens across solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 94.

Abstract Background: Despite the decline in overall mortality and incidence of cancer in the US population, the burden of cancer is still high, especially in underserved and under-researched populations. A major contributor to poor cancer outcomes is the absence of dedicated efforts utilizing scientifically rigorous approaches and implementation strategies to optimize participant enrollment and accrual in clinical trials. The Connecting Patient Populations to Clinical Trials (CP2CT) program implements innovative multilevel interventions to enhance clinical trial awareness and optimize referral pathways that facilitate patient enrollment. The CP2CT Data, Evaluation, and Coordinating Center (DECC) supports its data and evaluation activities, and coordinates a learning collaborative towards mitigating the key barriers of cancer burden in all populations. Methods: Using an implementation science-informed approach, the DECC deployed coordinated strategies over three years: (1) administrative structuring through streamlined governance, centralized reporting, and stakeholder integration; (2) data standardization via Common Data Elements (CDEs), a cross-network REDCap system, and a multi-institution Data Transfer Agreement (DTA); (3) evaluation infrastructure through a Network Logic Model, evaluation plan, standardized constructs, and a Process Evaluation Plan with tools; (4) learning supports through an internal website and expanded Speaker Series; and (5) site-level implementation facilitation through structured visits. Results: In collaboration with the CP2CT Network and NCI, the DECC’s achievements span four domains: (1) Administrative: built infrastructure, deployed centralized reporting platforms, coordinated key meetings, and strengthened community integration. (2) Data: standardized collection, secured network-wide data sharing through the DTA, enabled harmonized multi-site reporting, and advanced groundwork for interoperability and scientific value. (3) Program Evaluation: linked CP2CT activities to measurable outcomes through a Network-wide Logic Model, guided evaluation, established shared evaluation language, and launched a transferable Process Evaluation framework. (4) Learning Collaborative: developed a centralized resource hub, expanded the Speaker Series, and advanced authorship transparency with the CP2CT Publication Policy. < Conclusion: The CP2CT DECC has established a sustainable, scalable infrastructure that integrates administrative coordination, standardized data collection, robust program evaluation, and a collaborative learning environment. These efforts enhance clinical trial awareness, optimize referral pathways, and provide a transferable model for improving participant enrollment and scientific rigor across national research networks, ultimately addressing disparities in cancer outcomes. Citation Format: Laura E. Lectora, Cristina J. Orozco, Holly A. Thorson, Timethia Bonner, Robert R. Freimuth, Jennifer G. Le-Rademacher, Folakemi T. Odedina. Building a national network coordination center for clinical trials: Early implementation outcomes from the CP2CT DECC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 899.

Abstract Introduction: The prostate cancer (PCa) tumor microenvironment (TME) is immunosuppressive and resistant to immune checkpoint blockade (ICB). Based on multi-omic single cell correlatives of response to neoadjuvant Fc-enhanced (FcE) αCTLA-4 in high-risk localized PCa (NCT04301414), we explored how modulating the balance between regulatory T cells (Tregs) and dendritic cells (DCs) in the PCa TME affects sensitivity to ICB. Methods: We leveraged three single cell transcriptomic atlases of PCa to assess how Tregs and DC frequencies are dynamically regulated during PCa progression. To investigate responses to Treg depletion (via FcE-αCTLA-4) alongside DC expansion (via Flt3L-Ig) and stimulation (via STING agonist ADU-S100) in PCa, we employed the castration-sensitive MycCaP PCa model and 45-parameter spectral flow cytometry. To investigate novel direct mechanisms of DC stimulation by FcE-αCTLA-4 via Fcγ receptor (FcγR) engagement, we optimized reductionist in vitro assays involving bone marrow-derived DCs (BMDCs) from wild-type (WT) mice or mice deficient in activating FcγRs (Fcer1g-/-) or inhibitory FcγRIIb (Fcgr2b-/-). To validate this effect in vivo we established a tumor antigen-specific T cell priming assay with both flow cytometry and ex vivo 2-photon live cell imaging readouts. Results: In three independent single cell transcriptomic PCa atlases, we find cDC2 frequencies are significantly decreased in advanced PCa while effector Tregs (TNFRSF9+) increase in proportion. Hypothesizing that excessive Treg function and DC insufficiency drive ICB resistance in PCa, we find in vivo DC expansion (Flt3L-Ig) prior to hormonal therapy, Treg depletion (FcE-αCTLA-4), and in situ DC stimulation (ADU-S100) drives robust control of established MycCaP tumors, with 87% of animals tumor-free 40-days post-treatment (27/31). Using 45-parameter spectral flow cytometry we find FcE-αCTLA-4 drives DC activation prior to Treg depletion in the TME, supporting a novel direct mechanism of DC modulation by FcE-αCTLA-4. In vitro, we find cell-associated FcE-αCTLA-4 is sufficient to drive BMDC maturation in an FcγR-dependent manner. In vivo, FcE-αCTLA-4 augments DC-mediated T cell priming in an FcγR-dependent manner. Ongoing experiments are investigating how FcE-αCTLA-4 shapes DC-T cell interactions via FcγR engagement and how DC/Treg axis modulation can be optimized to improve long-term curative response rates in the MycCaP model. Conclusions: DC insufficiency and effector Treg differentiation are hallmarks of advanced PCa. Enhancing DC number and function concomitant with Treg depletion can drive effective antitumor immunity in a pre-clinical PCa model. Direct DC modulation via FcγR engagement represents a novel mechanism of response to CTLA-4-targeted ICB. These findings will inform ongoing translation of FcE-αCTLA-4 agents and development of novel immunotherapy strategies for PCa. Citation Format: Jessica C. Hill, Kade R. Copple, Collin Jugler, Phuong Nguyen, Nilika Bhattacharya, Jessica N. Lancaster, Casey R. Ager. Rewiring the dendritic cell: Regulatory T cell axis sensitizes prostate cancer to immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 166.

Abstract Backgroud. Breast cancer (BC) is the most common and deadly cancer in women worldwide. Emerging evidence highlights the role of gut microbiota in modulating breast cancer risk, treatment response, and recurrence through various mechanisms, including the production of biologically active compounds and metabolites. These non-viable microbial products and metabolic byproducts from probiotic fermentation, known as postbiotics, exert beneficial effects on the host without the need for live microorganisms. Postbiotics derived from Lacticaseibacillus species represent a novel class of therapeutics with potential anti-cancer properties. In this study, we investigated the therapeutic effects of an innovative postbiotic product (iPB), developed through sequential fermentation of L.paracasei NPB01 and L.rhamnosus GG, in BC experimental models. Methods. The following cell lines were used to represent main BC subtypes: MCF7 cells (ER+/HER2), MDA-MB-231 (triple negative breast cancer), SKBR3 (HER2+). MCF-10A (normal breast epithelial cells), Caco-2 (enterocytes), and peripheral mononuclear blood cells (PBMC) were used as control. Cell viability was assessed by colony formation assay. Apoptosis was evaluated using Annexin V/7-AAD staining, HLA class I surface expression by flow cytometry, and cancer cells migration by wound healing assay. Results. iPB exposure resulted in >50% colony formation reduction in MCF7, >30% in MDA-MB-231 and >40% in SKBR3 cells starting from 0.5 mg/ml for 72 h (p<0.01). iPB increased early and late apoptotic cell rate in all BC cell lines starting from 0.5 mg/ml for 72 h. On the contrary, iPB exposure up to 5 mg/ml for 120 h did not affect cell viability in control cells (MCF-10A, Caco-2, PBMC). 1.20 to 1.30 fold increase in HLA class I expression was observed in all BC cell lines after the exposure with iPB starting from the dose of 0.5 mg/ml for 72 h. A less intense HLA class I expression increase was observed in control cells after the iPB exposure. Cell migration process and inflammatory cytokines response were inhibited by the iPB exposure in all BC cell models. Conclusions. iPB reduces cell viability and cell migration in all main BC phenotypes. These effects parallel with HLA class I surface expression increase in all BC cell phenotypes, potentially enhancing immunogenicity. These findings suggest that iPB may represent a promising novel agent in BC treatment and prevention. Citation Format: Roberto Berni Canani, Chiara Luongo, Laura Pisapia, Franca Oglio, Roberta Di Santillo, Alessia Gaeta, Chiara Scocco, Marco Michelini, Vittoria Mauriello, Alessia Cadavere, Camilla Messuri, Saranya Chumsri, Dawn Mussallem. Postbiotic based on sequential fermentation of L.paracasei NPB01 and L.rhamnosus GG exerts antitumor activities against breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 312.

Abstract Background: Early-onset colorectal cancer (EOCRC) is rapidly increasing, with projections that by 2030, one in ten colon cancers will occur in individuals under 50. Unlike hereditary syndromes, most EOCRC cases are sporadic, implicating environmental and aging-related mechanisms. Accelerated biological aging, characterized by telomere attrition, oxidative stress, and senescence-associated inflammation, is a defining feature of EOCRC. Micro- and nanoplastics (MNPs) can accumulate in the gut, induce oxidative stress, and damage DNA. These processes mirror hallmarks of aging, suggesting that chronic MNP exposure may accelerate colonic epithelial aging and promote EOCRC initiation. Methods: To test this hypothesis, we used patient-derived human colon organoids from normal and polyp tissues. Apical-out organoids, which expose the luminal surface to the environment, were treated with defined polyethylene-derived microplastics (1.7-2.2 μm) and nanoplastics (0.04-0.06 μm) at 0, 1 and10 μg/mL for up to 72 hours. We assessed viability, oxidative stress, senescence markers, and inflammatory cytokines. Telomere length will be quantified by qPCR, and cytokine profiling was performed using Olink proteomics. Results: Live/Dead assays revealed minimal cytotoxicity at 1 μg/mL, while nanoplastics induced greater cell death and oxidative stress at 10 μg/mL. Preliminary data suggest that nanoplastic exposure leads to telomere shortening. Moreover, gene expression analyses showed that nanoplastics triggered stronger mitochondrial and redox stress responses than microplastics, consistent with higher reactivity of smaller particles. Additional experimental groups will be included to validate and expand upon these preliminary findings. Conclusions: Although preliminary, these data point to potential links between MNP exposure and early aging-associated stress pathways in the colon epithelium. Continued refinement of this organoid model, together with expanded sample sizes and multiomic analyses, will be essential for determining whether these early signals represent meaningful contributors to EOCRC risk. Funding: Individualizing colorectal cancer patient care using the host and tumor telomere phenotype (RO1 CA204013), Curtiss Fund (92541775), C-SiG Core(s): Epigenomics & Spatial Biology Core, and Clinical Core of the Mayo Clinic Center for Cell Signaling in Gastroenterology (P30DK084567) Citation Format: Zahra Heydari, Gobinda Sarkar, Lisa A. Boardman. Modeling micro- and nanoplastics-induced colon aging in organoids to unravel pathways leading to early-onset colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 746.

Abstract Maternal obesity has been epidemiologically linked to an increased risk of sporadic colorectal cancer (CRC) in offspring, the third most prevalent cancer worldwide. This association underscores the lasting influence of early-life exposures on long-term health and disease susceptibility. Intestinal stem cells (ISCs), the long-lived cells that sustain epithelial renewal and often serve as the origin of intestinal cancers, are thought to play a central role in mediating this elevated cancer risk. However, how maternal obesity shapes the early-life programming and maturation of ISCs in their offspring remains poorly understood. Using mouse models of diet-induced obesity, we show that offspring exposed to a maternal high-fat Western diet (HFD) during pre- and postnatal development exhibit increased colonic proliferation, enhanced stem cell self-renewal, and a hypermetabolic state that persists into adulthood, even after dietary normalization. Alongside changes in stem cell properties, we observe a significant shift in epithelial cell composition, characterized by an increase in cells of secretory lineage at the expense of absorptive enterocytes, and these changes endure into adult life. Additionally, these changes are accompanied by an increased tumor burden in the loss of Apc heterozygosity model. Our data indicate that IL-17a, a pro-inflammatory cytokine, is critical in mediating these changes. Specifically, receptor IL-17RA/C expression is significantly upregulated in ISCs and secretory cells in maternal HFD-exposed offspring. Administration of IL-17a to intestinal organoids demonstrates sufficiency by mimicking the maternal obesogenic phenotype, indicating that immune-epithelial interactions influence ISC function and may be a driver of durable molecular patterning. These findings emphasize the long-term consequences of maternal HFD exposure on intestinal stem cell activity and epithelial composition, and possibly contribute to a higher risk of CRC in offspring later in life. Citation Format: Gourab Lahiri, Karla Mullen, Yesenia B. Millan, Swathi Sankar, Dominic R. Saiz, Thomas H. McDermott, Madeline Blatt, Abhigyan Shukla, Khashayarsha Khazaie, Miyeko D. Mana. Maternal obesity reprograms intestinal stem cells to elevate colorectal cancer risk in offspring [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 841.