Notably, a number of genes in the HOXA group are strongly expressed in normal tissue, but are downregulated in both primary tumours and A549, including HOXA3 and HOXA5. Conversely, many members of the HOXC and HOXD groups are strongly upregulated in the primary tumours and A549, including HOXC4, HOXC8, HOXC9, HOXC13, HOXD8 and HOXD10. H23 cells also express HOX genes but to a considerably lesser degree than the other cell types studied. This evidence concerns the gene HOXC4 and neoplasm.