HHLA2 and pancreatic neoplasm: In pancreatic cancer, the positive correlation between HHLA2 expression and improved survival in most studies suggests that it may enhance antitumor immune responses, possibly by facilitating T-cell infiltration and activation, making it a potentially favorable prognostic marker in PC (Byers et al. 2015, Chen et al. 2019, Yan et al. 2019, Boor et al. 2020, Zhang et al. 2021, Aydın & Turhan 2024).