METTL3 suppresses pancreatic ductal denocarcinoma progression through activating endogenous dsRNA-induced anti-tumor immunity

Lili Zhu1,2 · Botai Li1  · Rongkun Li3  · Lipeng Hu2  · Yanli Zhang2  · Zhigang Zhang2  · Shuheng Jiang2  · Xueli Zhang2

Abstract

Purpose Although immunotherapy improves clinical outcomes in several types of alignancies, as an immunologically ‘cold’ tumor, pancreatic ductal adenocarcinoma (PDAC) is arrantly resistant to immunotherapy. However, the role of N6-methyladenosine (m6 A) modifcation in the immune microenvironment of PDAC is still poorly understood.

Methods The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) datasets were used to identify diferentially expressed m6 A related enzymes. The biological role and mechanism of METTL3 in PDAC growth and metastasis were determined in vitro and in vivo. RNA-sequencing and bioinformatics analysis were used to identify signaling pathways involved in METTL3. Western blot, m6 A dot blot assays, co-immunoprecipitation, immunofuorescence, and fow cytometry were used to explore the molecular mechanism.

Results Here, we demonstrate that METTL3, the key regulator of m6 A modifcation, is downregulated in PDAC, and negatively correlates with PDAC malignant features. Elevated METTL3 suppresses PDAC growth and overcomes resistance to immune checkpoint blockade. Mechanistically, METTL3 promotes the accumulation of endogenous double-stranded RNA (dsRNA) through protecting m6 A-transcripts from further Adenosine-to-inosine (A-to-I) editing. The dsRNA stress activates RIG-I-like receptors (RLRs) to enhance anti-tumor immunity, fnally suppressing PDAC progression.

Conclusion Our fndings indicate that tumor cell-intrinsic m6 A modifcation participates in the regulation of tumor immune landscape. Adjusting the m6 A level may be an efective strategy to overcome the resistance to immunotherapy and increase responsiveness to immunotherapy in PDAC.

详情请见：https://doi.org/10.1007/s13402-023-00829-2

在该研究中，圣尔生物CCK8细胞增殖检测试剂盒应用于“体外细胞行为检测技术”

In vitro cell behavior assays

For the cell proliferation assay, 1000 cells were plated and counted 5 days after seeding in complete culture media, Cell Counting Kit-8 assay (SB-CCK8S, Share-Bio, China) was performed to measure cell viability according to manufacturer’s instructions.