HOXD13 and lung cancer: The level of sPD-1 in the older subjects (251.0 ± 66.20, N = 10) tended to be higher than those of the young subjects (165.7 ± 20.77, N = 34) and middle-aged group (197.8 ± 29.57, N = 28), but there was no statistical difference; similar results were observed in lung cancer patients (Figure 1C).