HOXD9 and cancer: We examined the overall expression of HOX genes in 33 cancer types from UCSC Xena database (Figure 2A) and discovered that there were obvious differences in the expression of each HOX gene in tumor samples, with the average expression levels of HOXA5, HOXA10, HOXB2, HOXB3, HOXB7, HOXC4, HOXD8, and HOXD9 being higher in pan-cancer samples, indicating that they might play an indispensable role.