Dual Transforming Growth Factor-β and Programmed Death-1 Blockade: A Strategy for Immune-Excluded Tumors?

Tumors that elude infiltration by CD8+ T lymphocytes are particularly resistant to multiple forms of treatment, including immune checkpoint blockade. Stromal transforming growth factor (TGF)-β appears to play a key role in this process, potentially constituting a target for novel combinatorial regimens tackling immune-excluded neoplasms.