Sarkar, Gobinda

Abstract Background: Aberrations in telomere length have important implications in cancer development and progression. This study aimed to determine whether leukocyte telomere length (LTL) in patients with colorectal cancer (CRC) is associated with survival outcomes. We also investigated whether genetic variants in telomere maintenance genes are associated with survival in these patients. Methods: Blood specimens were collected from 1,007 patients prior to receiving chemotherapy or radiation. Genomic DNA was extracted using the Promega Maxwell RSC instrument. LTL was measured in triplicate using monochrome multiplex PCR, where the average amplification value of telomeric repeats was termed T. Similarly, PCR amplification of a single-copy reference gene was performed, and its average amplification value was termed S. The telomere length for each sample was expressed as the T/S ratio. Genotyping of single-nucleotide polymorphisms (SNPs) in TERC, TERT, and OBFC1 genes was conducted at the institutional Genome Analysis Core facility. Kaplan-Meier survival curves were generated to evaluate patient survival outcomes. Results: Younger individuals (∼25 years) exhibited nearly a twofold longer LTL compared with older individuals (∼75 years). No significant difference in LTL was observed between stage II and stage III CRC patients. A strong inverse correlation was observed between patient age and LTL (Spearman’s r = -0.48; p = 1.13 × 10-58). Females had significantly longer LTL than males (p = 3.97 × 10-5). The TERC SNP rs1317082 was significantly associated with both overall survival (OS) and disease-free survival (DFS) in the combined stage II and stage III patient cohort (p = 0.017 and p = 0.023, respectively). Similarly, the OBFC1 SNP rs9419958 was significantly associated with OS (p = 0.016). Importantly, LTL itself was significantly associated with both OS and DFS (p = 0.008 and p = 0.044, respectively) among the combined stage II and stage III patients. Kaplan-Meier survival analyses demonstrated that age- and sex-adjusted LTL was predictive of long-term survival outcomes. Conclusions: Survival among patients with stage II and III colorectal cancer is significantly influenced by LTL. Additionally, specific allelic variants of telomere maintenance genes, including TERC and OBFC1, are independently associated with improved survival, irrespective of LTL. These findings suggest that peripheral blood LTL measurement, along with telomere-related genotyping, may serve as a valuable prognostic marker for colorectal cancer outcomes. 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: Estela M. Cruz Garcia, Gobinda Sarkar, Jun Chen, Shubham Sood, Kim Kossick, Daniel Schupack, Rondell Graham, Brooke Druliner, Zahra Heydari, Lauren Helgeson, Richard G. Cawthon, Lisa A. Boardman. Longer leukocyte telomeres and specific alleles of telomere maintenance genes are independently associated with improved survival of colon cancer patients [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 1919.

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.

Background and aims: Aberrations in telomere length can have important implications in cancer. Using a cohort of 1007 patients, we investigated whether leukocyte telomere length (LTL) in patients with colorectal cancer (CRC) is associated with survival. We also investigated whether some telomere maintenance genes are associated with survival in these patients. Methods: The Biobank for Gastrointestinal Health Research (BGHR), an ongoing project involving collection of biospecimens at the Mayo Clinic, was utilized to obtain data from patients diagnosed with stage II or III CRC. Blood samples were collected prior to chemotherapy/radiation and DNA was extracted for measuring median LTL. The main outcome measures were overall survival (OS) and disease-free survival (DFS) by disease stage. Results: A significant inverse relationship was observed with patient age and LTL (spearman correlation coefficient (r) = −0.48, 95%; p = 1.13 × 10−58). Females had significantly longer LTL than males (p = 3.97 × 10−5). The rs1317082 SNP in the TERC gene was significantly associated with both OS and DFS in combined stage II and stage III patients (p = 0.017 and p = 0.023, respectively). A statistically significant association of the OBFC1 SNP (rs9419958) was observed for OS for the combined stage II and stage III patients (p = 0.016). Importantly, LTL was significantly associated with both OS and DFS (p = 0.008 and 0.044 respectively) in combined stage II and stage III patients. Conclusions: Our results show that LTL is predictive of OS and DFS for stage II and III CRC patients, particularly over a longer follow-up, extending beyond five years after a diagnosis of CRC, and certain SNPs in genes involved in telomere maintenance are significantly associated with patient outcomes, independent of telomere length.

Early-onset colorectal cancer (EOCRC) in people < 50 years of age has been rising globally, yet its causes remain unknown. Emerging evidence suggests that environmental factors, including exposure to micro-and nanoplastics (MNPs), may contribute to colorectal carcinogenesis. MNPs can enter the gastrointestinal tract through ingestion, translocate across the epithelial barrier via endocytosis or paracellular pathways, and interact directly with epithelial and immune cells. Once internalized, they may generate events associated with tumor initiation including oxidative stress, disruption of membrane integrity, pro-inflammatory signaling, and disruption of genomic and epigenomic stability. Patient-derived colorectal organoids offer a physiologically relevant and scalable 3D model that closely mimics the cellular architecture and genetic landscape of primary tumors. We highlight how organoid models can be leveraged to study the impact of MNPs on the key processes of inflammation, DNA damage, senescence, and epigenetic modifications. Furthermore, we discuss the application of organoid-based systems to model EOCRC driven by environmental exposures, including the integration of organoid platforms with high-throughput assays, omics profiling, and microfluidics to better capture MNP-induced pathogenic mechanisms. Altogether, colorectal organoids provide a powerful bridge between environmental plastic exposure and EOCRC etiology, offering a tractable platform to identify mechanistic pathways and potential biomarkers of early disease.

Patient-derived organoids (PDOs) have emerged as powerful tools in personalized medicine applicable to both non-malignant conditions and to cancer, where they are increasingly used for personalized drug screening and precision treatment strategies in part due to their ability to replicate tumor heterogeneity. They also serve as study model systems to understand disease mechanisms, pathways, and the impact of ex vivo exposures. We present a detailed step-by-step protocol for generating organoids from normal crypts, polyps, and tumors, including methods for tissue processing, crypt isolation, culture establishment, and the transition from basolateral to apical-out polarity for co-culture and exposure-based studies. The protocol also includes immunofluorescence staining procedures for cellular characterization and quality control measures. Our standardized approach successfully generates organoids from diverse colorectal tissues with high efficiency and reproducibility. This comprehensive guide addresses common technical challenges and provides troubleshooting strategies to improve success rates across different sample types. We believe that this resource will enhance reproducibility in organoid research and expand their utility in translational applications, particularly for personalized medicine approaches in colorectal cancer.

Organoids are three-dimensional (3D) structures that mimic the architecture and functionality of human organs, providing a novel approach to study diseases such as colorectal cancer (CRC). This review aims to explore the impact of organoids on understanding CRC and their potential use in exploring therapeutic outcomes. Colorectal cancer, characterized by the transformation of colonic epithelial cells into adenomas and carcinomas, remains one of the top causes of cancer-related morbidity and mortality worldwide. Traditional two-dimensional (2D) cell cultures fail to replicate the tumor microenvironment in an effective manner, which highlights the need for advanced 3D models. Organoids preserve the genetic and phenotypic properties of the original tumors, allowing for improved disease modeling, drug screening, and personalized medicine applications. When using patient-derived organoids (PDOs), researchers can gain insights into CRC initiation, progression, and treatment outcome. Ultimately, organoids represent an encouraging platform for improving therapeutic strategies for CRC, potentially leading to better patient outcomes through tailored treatment approaches.

Abstract Histologic features, presence of CDKN2A/B homozygous deletion and methylation subtype are strong determinants of outcome and of therapy in IDH-mutant gliomas. We were interested in learning if there are additional markers of outcome in these tumors. To address this question, we assembled a cohort of 963 IDH-mutant gliomas with overall survival data (median follow-up alive 2.7 years, median follow-up deceased 3.9 years). Array-based copy number data, targeted NGS, germline genotyping data and Illumina EPIC array methylation data were available on 872, 226, 542, and 401 patients, respectively. Morphologic type (oligodendroglioma versus astrocytoma, grade (2/3 vs 4) and methylation subtype (A_IDH_LG vs A_IDH_HG) were all significantly associated with survival (p &lt;0.001). There was no significant difference in survival between grade 2 vs 3 IDH-mutant astrocytomas (p=0.53 adjusting for age and sex). However, subjects with the risk allele (G) for rs55705857 had a better overall survival than subjects with the non-risk allele (A) in IDH-mutant oligodendroglioma (AG/GG vs AA, median overall survival 21.6 vs 15.7 years, p=0.048 after adjusting for grade, age, and sex). Conversely, rs55705857 was associated with a markedly worse survival in grade 2 IDH-mutant astrocytomas (AG/GG vs AA, median overall survival 8.6 vs 19.6 years, p=0.007 after adjusting for age and sex). Despite similar sample sizes and number of deaths, there was no significant difference in overall survival by rs55705857 genotype in grade 3 or 4 IDH-mutant astrocytomas. Upon further functional analyses, TLX1 and GALNT17 were found to be differentially methylated in IDH1-mutant astrocytomas and oligodendrogliomas, respectively, when stratified by rs55705857 risk allele. This is the first observation of a germline characteristic (e.g. rs55705857) predicting survival in low-grade IDH-mutant astrocytoma. While this observation requires validation, it suggests that germline genotype may be practice changing and inform results of trials such as CATNON and CODEL.

The CRISPR-Cas9 system has enabled researchers to precisely modify/edit the sequence of a genome. A typical editing experiment consists of two steps: (1) editing cultured cells; (2) cell cloning and selection of clones with and without intended edit, presumed to be isogenic. The application of CRISPR-Cas9 system may result in off-target edits, whereas cloning will reveal culture-acquired mutations. We analyzed the extent of the former and the latter by whole genome sequencing in three experiments involving separate genomic loci and conducted by three independent laboratories. In all experiments we hardly found any off-target edits, whereas detecting hundreds to thousands of single nucleotide mutations unique to each clone after relatively short culture of 10–20 passages. Notably, clones also differed in copy number alterations (CNAs) that were several kb to several mb in size and represented the largest source of genomic divergence among clones. We suggest that screening of clones for mutations and CNAs acquired in culture is a necessary step to allow correct interpretation of DNA editing experiments. Furthermore, since culture associated mutations are inevitable, we propose that experiments involving derivation of clonal lines should compare a mix of multiple unedited lines and a mix of multiple edited lines.