GPC1 and breast cancer: Some studies have reported that GPC-1 is highly expressed in multiple human cancer tissues, such as pancreatic cancer (28), breast cancer (29), glioblastoma (30), and ESCC (9), and overexpression of GPC-1 in tumor tissues was found to be associated with shorter OS in patients with PC (10, 28), ESCC (9), breast cancer (29), and glioma (11).