Abstract C012: Transcriptional profiling of circulating immune cells from patients with early- and late-onset colorectal cancer reveals sex-specific differences

Abstract Early-onset colorectal cancer (EOCRC), CRC diagnosed before age 50, are rising with the global incidence of EOCRC predicted to double by 2030. Notably, this disease is more common in men and women have better survival outcomes. Changes in immunity with age and between sexes are postulated to contribute to these discrepancies, which warrants further investigation. Therefore, we used single-cell RNA sequencing to analyze peripheral blood mononuclear cells (PBMCs) from males and females with CRC. Our analysis revealed reduced proportions of circulating naïve and effector memory CD8+ T-cells in late-onset colorectal cancer (LOCRC) compared to EOCRC. Similarly, genes associated with proliferation were decreased in circulating CD8+ T-cells from LOCRC patients. Hallmark and GO BP pathway analyses revealed that T-cells isolated from patients with LOCRC have decreased transcriptional profiles associated with AKT/MTOR signaling, lymphocyte differentiation, and cell surface/antigen receptor-mediated signaling. Conversely, upregulated pathways were associated with TNF and interferon alpha signaling, apoptosis, DNA damage, oxidative stress, and RNA/protein homeostasis. Regarding NK cells, in LOCRC, the overall frequency of naïve and cytotoxic populations cells was also decreased while interferon-producing NK cells signatures were increased. Notably, pathway analyses revealed almost identical transcriptional immunosuppressive changes in NK and T-cells in LOCRC. Analysis of sex differences in the immune landscape of EOCRC and LOCRC revealed proliferative defects in CD8+ T-cells in males regardless of age. However, NK cells from males with EOCRC appear to be more functional as highlighted by the increased expression of genes associated with cytolysis and more naïve signatures associated with these cells. Conversely, NK cell signatures in females were robust in both the EOCRC and LOCRC, and did not exhibit age-dependent functional declines. Furthermore, in females, NK cells and T-cells in EOCRC had similar decreases in differentiation, intracellular signaling, decreased TNF activation, and apoptosis signatures but signatures associated with metabolism, protein homeostasis, and p53 activation were increased. Compared to females, pathway analyses of NK cells and T-cells from males with EOCRC revealed reduced gene signatures associated with differentiation and intracellular signaling but enhanced signatures associated with inflammation, oxidative stress, RNA processing, MYC activation, G2M checkpoint activation, and apoptosis. In summary, we reveal that circulating lymphocytes from female patients with EOCRC and LOCRC are more functional than those observed in males. Furthermore, T-cells from males with CRC become more dysfunctional with age, potentially due to increased sensing of pro-inflammatory cytokines like TNF and interferon alpha. Therefore, better survival outcomes for women with CRC may potentially be attributed to possessing a more robust immune system that exhibits minimal decline with aging. Citation Format: Timothy J. Kopper, Claire E. Pillsbury, Michael Kaufman, Clara Sánchez-Menéndez, María González-Sanmartin, Montserrat Torres, Mayte Coiras, Jose Perea Garcia, Curtis J. Henry. Transcriptional profiling of circulating immune cells from patients with early- and late-onset colorectal cancer reveals sex-specific differences abstract. In: Proceedings of the AACR Special Conference in Cancer Research: The Rise in Early-Onset Cancers—Knowledge Gaps and Research Opportunities; 2025 Dec 10-13; Montreal, QC, Canada. Philadelphia (PA): AACR; Clin Cancer Res 2025;31 (23Suppl): Abstract nr C012.