[IF 16.6] PRMT3 Regulates IDO1 Metabolic Axis: Novel Mechanism of Radioresistance in Non-Small Cell Lung Cancer

Recently, a study on radioresistance mechanisms in non-small cell lung cancer (NSCLC) published in Cancer Research not only revealed the central role of the PRMT3-TFAP2A-IDO1-Kyn axis in radioresistance and immunosuppression in lung cancer, but also provided novel therapeutic targets for clinical treatment. Notably, the mIHC experiments in this study relied on the absin mIHC kit for precise protein localization and expression analysis, fully demonstrating the supporting value of absin tools for high-quality scientific research.

I. Research Strategy: Decoding the "Metabolism-Immunity" Dual Mechanisms of Lung Cancer Radioresistance

Radioresistance in NSCLC is one of the primary causes of clinical treatment failure, with metabolic reprogramming and immune microenvironment dysregulation being two core drivers of tumor resistance. The research team initiated with "identifying key regulators of radioresistance" and explored through the following logical framework:

1. Screening Key Regulatory Factors: By comparing PRMT family gene expression between NSCLC patients with radioresponsive and non-responsive tumors, PRMT3 was found to be significantly overexpressed in the non-responsive group and associated with poor patient prognosis, initially identifying PRMT3 as the core research target.
2. Investigating Metabolic Regulatory Pathways: Through 4D-Fast DIA proteomics and untargeted metabolomics analysis, PRMT3 overexpression was found to significantly activate the tryptophan-kynurenine (Kyn) metabolic pathway, with Kyn being the most significantly upregulated metabolite, suggesting that PRMT3 may influence radiosensitivity through regulation of Kyn metabolism.
3. Elucidating Molecular Mechanisms: Further through transcription factor prediction, Co-IP, and dual-luciferase reporter assays, the study confirmed that PRMT3 methylates transcription factor TFAP2A, prolonging its half-life, promoting nuclear localization and dimerization, thereby enhancing the transcriptional activity of IDO1 (the key enzyme in Kyn metabolism), forming the "PRMT3-TFAP2A-IDO1-Kyn" regulatory axis.
4. Correlating with Immune Microenvironment: Combining animal models and clinical sample analysis, PRMT3-mediated Kyn accumulation was found to activate the aryl hydrocarbon receptor (AhR) in CD8+ T cells, leading to T cell exhaustion (high PD-1 expression) and functional suppression, forming a "metabolic dysregulation-immunosuppression" vicious cycle that exacerbates radioresistance.
5. Validating Therapeutic Strategies: In PDX models and patient-derived organoids (PDO), combined inhibition of PRMT3 (SGC707) and IDO1 (1-MT) was confirmed to effectively block the above regulatory axis, reverse radioresistance and activate anti-tumor immunity, providing evidence for clinical combination therapy.

II. Research Findings: Three Core Discoveries Providing New Directions for Lung Cancer Treatment

Through rigorous cellular experiments, animal models, and clinical sample validation, this study achieved three key outcomes:

1. PRMT3 is the "Culprit" of NSCLC Radioresistance: PRMT3 overexpression significantly enhanced clonogenic capacity, migration, and proliferation of NSCLC cells, reduced radiation-induced ROS production and apoptosis rates (Fig. 1I), and decreased accumulation of DNA damage marker γH2AX (Fig. 1J, K); conversely, PRMT3 knockdown or inhibitor SGC707 significantly enhanced radiosensitivity, significantly reducing tumor volume in PDX models (Fig. 1M).

2. The "PRMT3-TFAP2A-IDO1-Kyn" Axis is the Core of Metabolic Regulation: PRMT3 enhances TFAP2A binding to the IDO1 promoter through methylation of R363 (Fig. 5G, H); IDO1, as the rate-limiting enzyme in Kyn synthesis, has activity dependent on PRMT3 regulation—IDO1 knockdown completely reversed PRMT3-mediated radioresistance (Fig. 3I, J), confirming IDO1 as the key downstream effector molecule in the PRMT3-regulated metabolic pathway.

3. Kyn-AhR Pathway Mediates Immunosuppression, Combined Targeted Therapy Shows Efficacy: PRMT3-mediated Kyn accumulation significantly reduced CD8+ T cell infiltration (Fig. 4C, D) and inhibited their cytotoxic function (reduced granzyme B expression, Fig. 4J); combined use of PRMT3 inhibitor, IDO1 inhibitor, and radiotherapy significantly enhanced CD8+ T cell activity in mouse models (Fig. 4M), and this effect disappeared after CD8+ T cell depletion, confirming immune activation as the key mechanism of combined therapy efficacy. Furthermore, clinical sample analysis showed that PRMT3(high)/IDO1(high) patients had significantly lower radiotherapy response rates than PRMT3(low)/IDO1(low) patients (Fig. 8F, G), suggesting this axis as a biomarker for predicting radiotherapy efficacy.

III. Absin Product Applications: "Precision Localization Tools" for Immunofluorescence Experiments

In elucidating the interaction and protein localization of PRMT3 and TFAP2A, immunofluorescence (IF) experiments were key technical approaches. This study utilized absin's Four-Color Multiplex Immunofluorescence IHC Kit (abs50028) to complete the following core experiments, providing direct visual evidence for mechanism validation:

1. Colocalization Validation of PRMT3 and TFAP2A: Through staining of H1299 and H1993 cells with this kit, clear colocalization signals of PRMT3 and TFAP2A in the nucleus were observed (Fig. 5D), directly confirming their intracellular interaction and providing prerequisite evidence for subsequent Co-IP experiments.

2. Analysis of TFAP2A Nuclear Localization Regulation: In PRMT3 knockdown or overexpression cells, this kit was used to detect TFAP2A subcellular localization, finding that PRMT3 overexpression significantly promoted TFAP2A nuclear entry (Fig. 6C), while PRMT3 knockdown or inhibitor SGC707 significantly inhibited its nuclear localization (Fig. 6B, H), confirming that PRMT3 regulates TFAP2A transcriptional activity through modulation of its nuclear transport.

3. CD8+ T Cell Infiltration Analysis in Mouse Tumor Tissues: In mouse subcutaneous xenograft models, tumor sections were stained with this kit for quantitative analysis of CD8+ T cell infiltration, finding that CD8+ T cell infiltration was significantly reduced in the PRMT3 overexpression group (Fig. 4D), while combined inhibition of PRMT3 and IDO1 significantly restored CD8+ T cell infiltration (Fig. 4M), providing tissue-level evidence for the "metabolism-immunity" regulatory mechanism.

IV. Summary and Outlook: From Basic Research to Clinical Translation, Absin Provides Comprehensive Support

This study not only revealed novel mechanisms of NSCLC radioresistance but also proposed a "targeting metabolism-immunity axis" combination therapy strategy, providing new directions for clinical precision treatment. As a "partner" in life science research, absin consistently supports scientific innovation with high-quality reagent products—from immunofluorescence, Western blot to flow cytometry analysis, absin's product portfolio can meet research needs in tumor metabolism, immune microenvironment, signal transduction, and other fields.

Catalog Number	Product Name	Specification
abs50028	Absin 4-Color IHC Kit(Anti-Rabbit Secondary Antibody)	20T/50T/100T
abs955	Immunoprecipitation (IP/CoIP) kit	50T

Contact Absin

Absin provides antibodies, proteins, ELISA kits, cell culture, detection kits, and other research reagents. If you have any product needs, please contact us.

Absin Bioscience Inc. worldwide@absin.cn

Follow us on Facebook: Absin Bio