The crossroads of cancer epigenetics and immune checkpoint therapy.

Immune checkpoint inhibitors (ICI) have significantly improved treatment outcomes for several types of cancer over the past decade, but significant challenges that limit wider effectiveness of current immunotherapies remain to be addressed. Certain 'cold' tumor types, such as pancreatic cancer, exhibit very low response rates to ICI due to intrinsically low immunogenicity. Additionally, many patients who initially respond to ICI lack a sustained response due to T-cell exhaustion. Several recent studies show that epigenetic modifiers, such as SETDB1 and LSD1, can play critical roles in regulating both tumor cell-intrinsic immunity and T-cell exhaustion. Here, we review the evidence showing that multiple epigenetic regulators silence the expression of endogenous antigens, and their loss induces viral mimicry responses bolstering the response of 'cold' tumors to ICI in pre-clinical models. Similarly, a previously unappreciated role for epigenetic enzymes is emerging in the establishment and maintenance of stem-like T-cell populations that are critical mediators of response to ICI. Targeting the crossroads of epigenetics and immune checkpoint therapy has tremendous potential to improve anti-tumor immune responses and herald the next generation of sustained responses in immuno-oncology.