Background/Objectives: Interactions between colorectal tumours and their immune microenvironment critically influence disease progression and response to immunotherapy. However, most organoid systems fail to preserve the complex architecture and immune composition of the original tissue. Here, we applied the air–liquid interface (ALI) organoid model to paired tumour and perilesional colon tissues from colorectal cancer patients to evaluate its ability to retain immune and genetic features and to reproduce responses to chemotherapy and immune checkpoint blockade. Methods: Fresh human tumour and matched healthy colon tissues were processed to generate ALI organoids. Their histological organization, immune cell composition (including CD45⁺ subsets), and genomic profiles were compared with those of the parental tissues and with conventional Matrigel organoids, either alone or co-cultured with peripheral blood mononuclear cells (PBMCs). Organoids were exposed to 5-FU and nivolumab (anti–PD-1) to assess local immune modulation. Results: ALI organoids faithfully preserved the three-dimensional architecture, native immune infiltrates, and somatic mutational landscape of the source tissues. Importantly, upon PD-1 blockade with nivolumab, ALI organoids consistently exhibited a local expansion of regulatory T cells (Tregs), a phenomenon that could contribute to adaptive immune resistance. This response was not reproduced in PBMC–Matrigel co-culture systems, highlighting the importance of preserving endogenous tumour–immune interactions. Conclusions: Patient-derived ALI organoids represent a physiologically relevant platform that conserves key structural, immunological, and genomic hallmarks of colorectal cancer. By capturing clinically relevant immune remodeling events, such as Treg expansion following PD-1 blockade, this model provides a powerful tool for dissecting tumour–immune interactions.

Human-adipose-derived mesenchymal stem cells (hADMSCs) are multipotent stem cells which have become of great interest in stem-cell therapy due to their less invasive isolation. However, they have limited migration and short lifespans. Therefore, understanding the mechanisms by which these cells could migrate is of critical importance for regenerative medicine. Methods: Looking for novel alternatives, herein, hADMSCs were isolated from adipose tissue and co-cultured with human monocytes ex vivo. Results: A new fused hybrid entity, a foam hybrid cell (FHC), which was CD90⁺CD14⁺, resulted from this co-culture and was observed to have enhanced motility, proliferation, immunomodulation properties, and maintained stemness features. Conclusions: Our study demonstrates the generation of a new hybrid cellular population that could provide migration advantages to MSCs, while at the same time maintaining stemness properties.

Lung cancer remains the leading cause of cancer-related mortality worldwide and is frequently diagnosed at advanced stages, when metastatic dissemination is already present. Tumour hybrid cells (THCs) are rare circulating cells formed through fusion between cancer stem cells with leukocytes, predominantly monocytes. These cells combine traits from both lineages, conferring enhanced migratory, invasive and immune-evasive capacities that could promote metastasis. In parallel, soluble immune checkpoints (sICs) have emerged as minimally invasive biomarkers and indicators of systemic immune dysregulation and tumour-driven immune escape. In this study, 31 patients with lung cancer were prospectively enrolled at La Paz University Hospital (Madrid, Spain). Circulating THCs were quantified by spectral flow cytometry, and plasma sICs concentrations were determined using multiplex immunoassays. Patients were stratified by metastatic status and survival. Variables showing the strongest discriminative capacity were integrated into multivariable logistic regression models. Number of THCs, and levels of sCTLA-4, s-41BB, sLAG-3, and sTIM-3 exhibited the strongest discrimination for metastasis, while THCs, sLAG-3, and sTIM-3 distinguished deceased from surviving patients. Integrating predictive models demonstrated high accuracy, and survival analyses supported their prognostic significance. These findings indicate circulating THCs and selected sICs represent promising liquid biomarkers for monitoring lung cancer progression and patient outcomes.