Description
PD-1/PD-L1: An immune checkpoint and tumor-associated target for therapeutic intervention
- Gene Information: PD-1 (PDCD1/CD279) is an inhibitory immune checkpoint receptor. PD-L1 (CD274/B7-H1) is a key PD-1 ligand that mediates immune suppression in tumors and antigen-presenting cell contexts.
- Protein Expression: PD-1 is induced after antigen-specific T-cell stimulation and is often sustained during chronic activation. PD-L1 can be constitutively expressed by tumor cells or induced by IFN-γ and other inflammatory cues.
- Signaling Pathway: PD-L1/PD-1 interaction initiates inhibitory signaling, including dephosphorylation events that suppress TCR downstream signaling. This reduces T-cell activation, cytotoxicity, and tumor cell killing.
- Therapeutic Inhibition: Anti-PD-1 or anti-PD-L1 monoclonal antibodies block the inhibitory interaction and restore cytotoxic T-cell activity. B-hPD-1 plus/hPD-L1/hGDF15 mice provide an in vivo platform for evaluating PD-1/PD-L1 checkpoint blockade and combination therapies.
GDF15: A stress-responsive cytokine and key regulator of energy homeostasis
- Gene Information: GDF15 is a protein-coding gene located on chromosome 19p13.11 and encodes a stress-responsive member of the TGF-β superfamily.
- Protein Expression: GDF15 is broadly expressed at low basal levels and is strongly induced by cellular stress, inflammation, tissue injury, and cancer. It is synthesized as a precursor and secreted as a mature homodimer. Circulating GDF15 levels are elevated in several pathological conditions and are closely associated with anorexia, body weight loss, and cancer cachexia.
- Signaling Pathway: GDF15 binds to GFRAL, which recruits the co-receptor RET to activate downstream ERK, AKT, and PLCγ signaling. The GDF15/GFRAL/RET axis plays a central role in regulating appetite, energy expenditure, and body weight.
- Therapeutic Inhibition: Targeting the GDF15/GFRAL/RET axis represents a potential therapeutic strategy for cancer cachexia, anorexia, and metabolic disorders. Blocking GDF15 or GFRAL signaling has demonstrated potential to alleviate anorexia and weight loss in preclinical models, while GDF15/GFRAL agonism is being investigated for metabolic disease applications.
Targeting Strategy
PD-1
- A chimeric CDS including the human PD-1 gene sequence encoding the signal peptide and extracellular region, and the mouse Pd-1 gene sequence encoding the transmembrane and cytoplasmic regions, followed by a stop sequence and WPRE, was inserted after the initiation codon (ATG) of the mouse Pd-1 gene in B-hPD-1 plus/hPD-L1/hGDF15 mice.
- The endogenous mouse promoter and 5' UTR were retained. Chimeric PD-1 expression is driven by the endogenous mouse Pd-1 promoter, while endogenous mouse Pd-1 transcription and translation are disrupted.
PD-L1
- Exon 3 of the mouse Pd-l1 gene, which encodes the IgV domain, was replaced with human PD-L1 exon 3 in B-hPD-1 plus/hPD-L1/hGDF15 mice.
- The endogenous mouse promoter, 5' UTR, 3' UTR, and genomic regions encoding the signal peptide, the non-IgV domain of the extracellular region, and the transmembrane and cytoplasmic domains were retained. Chimeric PD-L1 expression is driven by the endogenous mouse Pd-l1 promoter, while endogenous mouse Pd-l1 transcription and translation are disrupted.
GDF15
- Exons 1-2 of the mouse Gdf15 gene that encode the full-length protein were replaced by human GDF15 exons 1-2 in B-hPD-1 plus/hPD-L1/hGDF15 mice.
- The promoter, 5' UTR, and 3' UTR regions of the endogenous mouse gene were retained, while endogenous mouse Gdf15 transcription and translation are disrupted.
PD-1 Protein Expression in Spleen
Mouse and human PD-1 expression analysis in wild-type C57BL/6 mice and homozygous B-hPD-1 plus/hPD-L1/hGDF15 mice by flow cytometry. Splenocytes were collected from wild-type C57BL/6 mice (+/+) and homozygous B-hPD-1 plus/hPD-L1/hGDF15 mice (H/H) (female, 6-week-old, n = 1/group) either left unstimulated or stimulated with an anti-mouse CD3ε antibody (7.5 μg, i.p.) in vivo for 24 hours. Protein expression was analyzed by flow cytometry using an anti-human PD-1 antibody (BioLegend, 329908) and an anti-mouse PD-1 antibody (BioLegend, 109104).
PD-L1 Protein Expression in Spleen
Mouse and human PD-L1 expression analysis in wild-type C57BL/6 mice and homozygous B-hPD-1 plus/hPD-L1/hGDF15 mice by flow cytometry. Splenocytes were collected from wild-type C57BL/6 mice (+/+) and homozygous B-hPD-1 plus/hPD-L1/hGDF15 mice (H/H) (female, 6-week-old, n = 1/group) either left unstimulated or stimulated with an anti-mouse CD3ε antibody (7.5 μg, i.p.) in vivo for 24 hours. Protein expression was analyzed by flow cytometry using an anti-human PD-L1 antibody (BioLegend, 329706) and an anti-mouse PD-L1 antibody (BioLegend, 124312).
GDF15 Protein Expression Analysis
Strain specific GDF15 expression analysis in wild-type C57BL/6 mice and homozygous humanized B-hPD-1 plus/hPD-L1/hGDF15 mice by ELISA. Serum wascollected from C57BL/6 mice (+/+) (Female, n=3, 6-week-old) and homozygous B-hPD-1 plus/hPD-L1/hGDF15 mice (H/H) (Female, n=3, 6-week-old). Expression levelof mouse and human GDF15 were analyzed by ELISA (Mouse/Rat GDF-15 Quantikine ELISA Kit: RD, MGD150; Human GDF-15 Quantikine ELISA Kit: RD, DGD150).
* When publishing results obtained using this animal model, please acknowledge the source as follows: The animal model [B-hPD-1 plus/hPD-L1/hGDF15 mice] (Cat# 114947) was purchased from Biocytogen.
