Study summary · research use only
NAD(+) metabolism enzyme NNMT in cancer-associated fibroblasts drives tumor progression and resistance to immunotherapy by modulating macrophages in urothelial bladder cancer
Plain-language summary
Paraphrased from the published abstract below — not a verdict on whether anything works.
This study examined the role of nicotinamide N-methyltransferase (NNMT) in cancer-associated fibroblasts (CAFs) in urothelial bladder cancer (UBC), using single-cell transcriptomics, immunohistochemistry, and immunofluorescence on human bladder cancer samples, plus in vivo UBC mouse models. Elevated NNMT expression in CAFs (NNMT+ CAFs) was associated with non-response to PD-L1 blockade immunotherapy and unfavorable prognosis in two independent patient cohorts. Targeting NNMT with the inhibitor 5-Amino-1-methylquinolinium iodide reduced tumor growth and increased apoptotic effects of an anti-PD-L1 antibody in UBC mouse models. The authors report that NNMT+ CAFs recruit tumor-associated macrophages via epigenetic reprogramming of serum amyloid A (SAA), which was associated with tumor cell proliferation and resistance to PD-1/PD-L1 blockade immunotherapy in bladder cancer.
Abstract
This study comprehensively investigates the association between the expression of nicotinamide N-methyltransferase (NNMT) and clinical outcomes of urothelial bladder cancer (UBC), as well as the molecular mechanisms by which NNMT in cancer-associated fibroblast (CAF) modulates tumor progression and immunotherapy resistance in UBC. Single-cell transcriptomic analyses, immunohistochemical and immunofluorescence assays were performed on bladder cancer samples to validate the relationship between NNMT expression and clinical outcomes. A series of experiments, including chromatin immunoprecipitation assay, liquid chromatography tandem mass spectrometry assay, and CRISPR‒Cas9 (Clustered Regularly Interspaced Short Palindromic Repeats and CRISPR-associated protein 9) knockout, together with in vivo models, have been established to determine the molecular functions of NNMT in CAFs in UBC. We demonstrated that elevated expression of the nicotinamide adenine dinucleotide (NAD+) metabolism enzyme NNMT in CAFs (NNMT+ CAFs) was significantly associated with non-response to programmed death-ligand 1 (PD-L1) blockade immunotherapy in patients with UBC and predicted the unfavorable prognosis of UBC in two independent large cohorts. Targeting NNMT using the inhibitor 5-Amino-1-methylquinolinium iodide significantly reduced tumor growth and enhanced the apoptotic effects of the anti-PD-L1 antibody in UBC mouse models. Mechanistically, NNMT+ CAFs recruit tumor-associated macrophages via epigenetic reprogramming of serum amyloid A (SAA) to drive tumor cell proliferation and confer resistance to programmed death-1/PD-L1 blockade immunotherapy. NNMT+ CAFs were significantly associated with non-response to PD-L1 blockade immunotherapy in patients with UBC. Elevated NNMT, specifically in CAFs, upregulates SAA expression and enhances the recruitment and differentiation of macrophages in the tumor microenvironment, thereby directly or indirectly promoting tumor progression and conferring resistance to immunotherapies in bladder cancer.
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