Vitamin D Receptor Antagonist MeTC7 Inhibits PD-L1.

Area of Science:

• Immunology
• Molecular Biology
• Oncology

Background:

• Antibodies targeting the PD-L1/PD-1 axis control tumor immune evasion.
• Small-molecule inhibitors require identification of targetable PD-L1 inducers.
• Vitamin D receptor (VDR) role in PD-L1 regulation in hematologic malignancies is unclear.

Purpose of the Study:

• To investigate VDR's role in regulating PD-L1 expression in acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS).
• To evaluate MeTC7, a VDR antagonist, as a potential small-molecule inhibitor of PD-L1.
• To assess MeTC7's efficacy and specificity in preclinical cancer models.

Main Methods:

• Chromatin immunoprecipitation (ChIP) assay and siRNA to study VDR-PD-L1 regulation.
• Mammalian 2-hybrid (M2H) assay to confirm MeTC7's selective VDR inhibition.
• In vitro assays for cell viability, clonogenicity, and adhesion.
• In vivo studies using AML xenograft and a colorectal cancer radiation therapy model.

Main Results:

• VDR regulates PD-L1 expression in AML and MDS cells.
• MeTC7 selectively inhibits VDR, suppresses PD-L1 (but not PD-L2), and reduces AML cell viability, clonogenicity, and xenograft growth.
• MeTC7 inhibits AML/mesenchymal stem cell adhesion and enhances cancer cell efferocytosis.
• In a colorectal cancer model, MeTC7 inhibited PD-L1 and increased intra-tumoral CD8+ T cells.

Conclusions:

• MeTC7 is a selective VDR inhibitor with potent anti-cancer activity.
• MeTC7 demonstrates potential as a novel small-molecule inhibitor of PD-L1.
• MeTC7 warrants further clinical investigation for cancer therapy.