Androgen-induced gene 1 correlates with extracellular vesicle-associated cholesterol metabolism and hepatic metastasis of pancreatic cancer

Abstract

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) liver metastasis is a major cause of cancer-related mortality and is associated with profound metabolic and immune disorders. However, the tumor-intrinsic mechanisms that drive metabolic reprogramming and shape the immunosuppressive hepatic niche remain poorly understood.

AIM

To examine the potential role of androgen-induced gene 1 (AIG1) as a candidate regulator linking cholesterol metabolism to immune remodeling during PDAC liver metastasis.

METHODS

We integrated single-cell RNA sequencing data from 199 human samples across 12 cohorts to identify metastasis-associated PDAC tumor cell-intrinsic gene, whose expression was subsequently validated by immunohistochemistry. With AIG1 pinpointed as a candidate gene, functional studies were performed using a clustered regularly interspaced short palindromic repeats/Cas9-engineered AIG1-knockdown mouse pancreatic cancer cell line in a portal vein injection liver metastasis model. Immune landscape alterations were revealed by flow cytometry and immunofluorescence staining. Tumor cell metabolic changes were evaluated by bulk RNA sequencing and cholesterol measurement. We performed isolation, characterization and cholesterol content detection of small extracellular vesicles (sEVs) derived from tumor cells. We co-cultured bone marrow-derived macrophages with tumor cell-conditioned media to assess macrophage polarization by quantitative real-time polymerase chain reaction.

RESULTS

AIG1 was enriched in basal-like tumor cells and further amplified during PDAC liver metastasis. This metastasis-associated upregulation was more pronounced in male patients, as validated by paired clinical specimens. AIG1 knockdown suppressed metastatic growth in vivo and reshaped the immune microenvironment, characterized by reduced monocyte-derived macrophage infiltration (with decreased programmed death-ligand 1 expression), decreased regulatory T cells and exhausted CD8⁺ T cells, and increased Kupffer cell proportions. Bulk RNA sequencing revealed that cholesterol metabolism was the only significantly downregulated pathway upon AIG1 loss, accompanied by elevated intracellular cholesterol and upregulation of inflammatory cytokines. Furthermore, we observed that AIG1 knockdown led to reduced sEV particle number and decreased cholesterol content within sEVs. Conditioned medium from AIG1-deficient cells polarized bone marrow-derived macrophages toward a more inflammatory phenotype.

CONCLUSION

Our findings suggest that AIG1 is related to sEV-associated cholesterol metabolic reprogramming and immunosuppressive niche formation in PDAC liver metastasis, and may represent a candidate for further therapeutic exploration.

Keywords: Androgen-induced gene 1; Pancreatic ductal adenocarcinoma; Liver metastasis; Small extracellular vesicle; Cholesterol metabolism; Immune remodeling

Core Tip: Active cholesterol metabolism is a hallmark of pancreatic cancer malignancy. Here, we show that tumor-intrinsic androgen-induced gene 1 knockdown disrupts this metabolic program, remodels the hepatic niche away from immunosuppression, and inhibits metastatic growth. Our findings position androgen-induced gene 1 at the intersection of metabolic and immune regulation, warranting further investigation.