Programmed death-ligand 1 and DNA methyltransferases (PD-L1 + DNMTs)

The PD-L1 and DNA methyltransferase (DNMT) axis represents a synergistic therapeutic target strategy in oncology that combines immune checkpoint blockade with epigenetic modulation. DNA methyltransferases, particularly DNMT1, often mediate the silencing of tumor-associated antigens, MHC molecules, and immune checkpoints like PD-L1, allowing cancer cells to evade immune detection. Treatment with DNMT inhibitors (DNMTi) such as azacitidine or decitabine reverses this hypermethylation, leading to the re-expression of these genes and the induction of a 'viral mimicry' state by activating endogenous retroviral elements. This process triggers a type I interferon response and recruits T-cells into the tumor microenvironment, effectively turning 'cold' tumors 'hot.' While DNMTi treatment can upregulate PD-L1 expression, this effect is leveraged by co-administering PD-L1 or PD-1 inhibitors to prevent the newly visible tumor cells from suppressing the activated T-cell response. This combination approach is currently being extensively studied in clinical trials to overcome resistance to standard immunotherapy in various solid and hematological malignancies.

Other names

PD-L1/DNMT1 axisCD274 and DNA methyltransferasesB7-H1 and DNMTsImmune checkpoint and epigenetic modifiers

DNMT inhibitors (DNMTi) reverse the epigenetic silencing of immune-related genes, including the upregulation of PD-L1 expression via promoter demethylation and the induction of 'viral mimicry' through the activation of endogenous retroviruses (ERVs). This triggers a type I interferon response and increases tumor immunogenicity (e.g., MHC expression and T-cell chemokines), which sensitizes the tumor to PD-L1/PD-1 blockade therapy that prevents T-cell exhaustion and restores anti-tumor immunity.