SMO and cancer: Depleted RARA may be targeted using oral retinoids, such as acitretin; depleted SRC using Src-tyrosine kinase inhibitors, such as bosutinib; SMO with smoothened inhibitors or hedgehog pathway antagonists, such as vismodegib RARA, SRC and SMO, can also be used as diagnostic, prognostic and/or therapy-response biomarkers in cancer.