PDCD1 and hepatocellular carcinoma: This translates to a reduced likelihood of distant tumor spread.[39] An in vitro study has also shown that proton irradiation mediates calreticulin translocation to the cell surface, which increases cross-priming and sensitivity to cytotoxic T lymphocytes.[40] Clinically, Su et al reviewed 29 patients with advanced hepatocellular carcinoma who received PBT and PD-1/PD-L1 (programmed cell death protein 1/programmed cell death 1 ligand 1) inhibitors during 2016 and 2019.