Recent studies suggest the possibility of using some olfactory receptors as biomarkers of some types of cancer, such as OR51E1 and OR51E2 [107–111], which were found to be slightly over-expressed in Rb (LFC = 1.36 and 1.45 respectively, adjusted p-value < 0.001) and present in the HOXA2 and ELF5 regulons, respectively. The gene discussed is HOXA2; the disease is cancer.