To investigate if adrenal tumour growth is dependent on HOX genes, we performed siRNA knockdown studies of HOX genes expressed in H295R cells.13 Knockdown of HOXA11, but not HOXA10 or HOXA13, led to reduced growth of H295R cells, supporting a role of HOX genes in promoting adrenal tumour cell proliferation (Fig. 6a, b). This evidence concerns the gene HOXA11 and adrenal gland neoplasm.