Novel Roles of Splice-Derived Tumor Mirtrons in the Regulation of Macrophage Dichotomy 2310054

Mirtron Overexpression Drives Immune Modulation and Tumor Progression Through Macrophage Polarization and Oncogenic Pathway Regulation 2309835

Mirtrons, a specialized subclass of intron-derived microRNAs (miRNAs), bypass canonical Drosha-dependent processing by undergoing splicing and debranching to form pre-miRNA hairpins directly processed by Dicer. This alternative pathway imparts high structural stability and resistance to exonucleolytic degradation, supporting their persistence in the tumor microenvironment. This study investigates the expression of specific human mirtrons and their influence on macrophage proliferation and polarization within cancer-associated conditions. Human cancer cell lines (T47D, MDA-MB-231, PC-3, and MCF-7) and normal HEK cells were cultured to assess mirtron expression. Quantitative RT-PCR was performed to measure levels of human mirtrons such as miR-5010, miR-1228, miR-1224, miR-6756, miR-7110, and uc002mxv.2. Exosomes isolated from mirtron-overexpressing cancer cells were co-cultured with THP-1 and U937 macrophage models. Cell proliferation assays evaluated macrophage growth following exposure, while qRT-PCR quantified polarization markers to distinguish M1 and M2 phenotypes. All tested mirtrons showed marked overexpression in cancer cell lines relative to normal HEK controls. Exosome-mediated delivery of these mirtrons to macrophages significantly reduced proliferation rates. Expression analysis revealed downregulation of M1-associated markers (TNFα, IL-6, ARG2) and upregulation of M2-associated markers (CD206, IL-10, TGFβ), indicating polarization toward an immunosuppressive phenotype. These results suggest that mirtrons modulate macrophage fate through post-transcriptional regulation of inflammatory pathways, linking RNA processing mechanisms to tumor—immune crosstalk. Their overexpression in cancer cells promotes M2 macrophage polarization and suppresses macrophage proliferation, thereby supporting immune evasion and tumor progression. These findings highlight mirtrons as potential diagnostic biomarkers and RNA-based therapeutic targets in molecular oncology. NIGMS (R16GM153648) Tumor Immunology: Cellular Responses and Tumor Microevironment (TIME)

YBX1-mediated m5C modification of exosomal LGALS3 derived from M2 tumor-associated macrophages drives colorectal cancer cell malignant behaviors.

Exosome-mediated hepatocellular carcinoma progression by modulating macrophage metabolic reprogramming and macrophage M2 polarization via exosome-derived hsa_circ_0057320-miR-28-5p/E2F6 axis.

BACKGROUND Hepatocellular carcinoma is an aggressive malignancy with poor outcomes. Emerging studies highlight the importance of the tumor microenvironment in HCC progression, where exosomes serve as critical messengers linking tumor cells with surrounding stromal components. Although circRNAs are abundantly present in tumor-derived exosomes, their precise roles and mechanisms in HCC remain poorly defined. METHODS Exosomes were characterized using transmission electron microscopy and flow cytometry. Differentially expressed circRNAs were identified by RNA sequencing. Macrophage polarization and metabolic reprogramming were evaluated by western blotting, immunofluorescence and metabolomics. The role of hsa_circ_0057320, miR-28-5p, and E2F6 in HCC progression was examined through transwell, tube formation, and spheroid-sprouting assays. Xenograft mouse models were constructed to verify the role of them in metastasis and angiogenesis, exosomes in progression of HCC. Interactions among hsa_circ_0057320, miR-28-5p, and E2F6 were explored using RIP and dual-luciferase reporter assays. RESULTS In this study, we found that exosomes derived from HOXD3-treated HCCs induced macrophage polarization toward the M2 phenotype via metabolic reprogramming. In addition, HOXD3-stimulated HCC cells secreted exosomes enriched in hsa_circ_0057320, which induce the alternatively activated (M2) macrophage phenotype and enhanced angiogenesis and metastatic capability in vivo and vitro. The role of hsa_circ_0057320 in the metastasis and invasion of HCC was reversed after the enhance of miR-28-5p. E2F6, a target of miR-28-5p, was markedly upregulated in HCC tissues and cells. Additionally, a positive relationship was established between hsa_circ_0057320 and E2F6, contrasting with a negative association with miR-28-5p. CONCLUSIONS Exosomes derived from HOXD3-induced HCC cells promotes M2 macrophage polarization via metabolic reprogramming. In addition, HOXD3-induced exosomal hsa_circ_0057320 promotes macrophage M2 polarization via the miR-28-5p/E2F6 axis, thereby accelerating HCC malignancy. These findings reveal the interactive communication mechanism between HCCs and TME, and highlight hsa_circ_0057320 as a potential exosomal indicator and therapeutic target for metastatic HCC.

M2-TAM-derived exosomal miR-491-3p modulates UBE2D3 and promotes the proliferation, migration and invasion of lung cancer cells

M2 tumor-associated macrophages (M2-TAMs) have been reported to promote tumor growth through exosome-dependent mechanisms. However, the exact role of exosomes derived from M2-TAMs (M2-TAM-Exos) in lung cancer progression remains unclear. In The present study, M2-like macrophages (IL-4/IL-13-polarized THP-1-derived macrophages) were shown to release exosomes that lung cancer cells effectively internalized. These exosomes markedly enhanced the proliferation, migration, and invasion of lung cancer cells, thereby promoting malignancy. Further analyses revealed that M2-like macrophage-derived exosomes contain high levels of microRNA (miR)-491-3p. In vitro and in vivo experiments confirmed miR-491-3p as an oncogenic miR, while its inhibition markedly reduced cancer cell aggressiveness. Additional experiments demonstrated that miR-491-3p suppressed UBE2D3 expression after entering lung cancer cells. Collectively, these findings suggest a model in which M2-like macrophages deliver miR-491-3p via exosomes to downregulate UBE2D3, facilitating lung cancer progression.

Potential Roles of Mirtron-5010 in Tumor Stemness and Immune Regulation 2308336

Despite advances in treatment, invasive breast cancer remains among the deadliest cancers in women, driven by limited therapeutic options that precisely target their molecular drivers. Mirtrons, an emerging class of intron-derived microRNAs, may represent unrecognized regulators of tumor progression and invasion. This study examines how mirtron-5010 influences cancer stemness and iron accumulation in triple negative MDA-MB-231 breast cancer. MDA-MB-231 bulk and stem cell populations were engineered to upregulate mirtron-5010. Classical stemness markers (SOX2, OCT4, NANOG, and KLF4) as well as the regulatory subunit PPP2R2D, were analyzed using quantitative PCR and immunohistochemistry. Intracellular iron levels were measured using FerroOrange fluorescence quantification. Across bulk cultures, mirtron-5010 upregulation elevated SOX2, OCT4, and NANOG expression, indicating enhanced stem-like characteristics. When looking into tumor stem cell population, mirtron-5010 upregulation further increased SOX2 and NANOG expression. Consistent with this, both bulk and tumor stem cells with mirtron-5010 upregulation showed greater labile iron pool determined by FerroOrange fluorescence, signifying an altered preference in iron metabolic pathways than controls. Interestingly, the subunit PPP2R2D of the PP2A enzyme complex was downregulated in mirtron-5010 upregulated cells. In conclusion, mirtron-5010 enhances stemness and promotes iron accumulation in invasive breast cancer cells, highlighting its potential as a molecular target for therapy-resistant subtypes. Through modulation of the PP2A enzyme complex, mirtron-5010 also dampens IL-2—driven T-cell activation and proliferation, suggesting a role in shaping the tumor immune microenvironment. Future studies will further delineate the functional consequences of mirtron-5010 expression in both cancer and immune cell contexts across diverse breast cancer models. NIGMS (R16GM153648) Tumor Immunology: Cellular Responses and Tumor Microevironment (TIME)

Colorectal cancer-derived exosomal ETS2 promotes macrophage M2 polarization by transcriptionally activating PRPF4