PDCD1LG2 and neoplasm: We linked the chemoresistance of these cells to a reduced proliferative state, a highly fibrotic and vascularized tumor ecosystem, and expression of the chemoresistance gene ALDH1A1. However, these cells also express high levels of ligands for CD49a as well as PD-L1 and PD-L2, which combine to promote a microenvironment enriched for exhausted T-cells that likely become unleashed and benefit from immune checkpoint blockade.