Most studies have found sPD-1 to be elevated in cancer patients compared to healthy donors, with elevated levels reported in patients with NSCLC [47, 104], esophageal cancer [63], differentiated thyroid carcinoma [56], hepatocellular carcinoma [105], nasopharyngeal carcinoma [55], basal cell carcinoma [57], triple-negative breast cancer [64], prostate cancer [59], and ovarian cancer [23]. This evidence concerns the gene HOXD13 and cancer.