MMP9 is upregulated by HOXB9 in ovarian144 and lung cancer,145 and by HOXC6 in gastric cancer,141 while MMP2 is upregulated by HOXB7146 and HOXC1070 in lung cancer, HOXB8 in colorectal cancer51 and HOXC10 in osteosarcoma.71 Here, HOXB9 is linked to lung cancer.