IGFBP6 and kidney cancer: Among them, IGFBP2, IGFBP3, IGFBP4, IGFBP6 and IGFBP7 showed higher expression levels, especially in gastric, liver and lung cancer cell lines; conversely, IGFBP1, IGFBP5 and IGFBPL1 showed relatively lower expression, particularly in colorectal, gastric and kidney cancer cell lines (Fig. 2B).