PDCD1 and neoplasm: For example, Treg infiltration in HCC abrogates the immune system of the tumor, such that the presence of abundant Treg infiltration constitutes an untoward prognosis for the tumor.[4] As immune checkpoints have been associated with tumor cell growth and escape from the immune system,[5] immune checkpoint inhibitors such as PD-1/PDL-1 have been authorized for cancer treatment to increase immune control over malignant cells.