As such, CXCR4-directed PET agents that can noninvasive in vivo quantification of CXCR4 expression display significant clinical value not only for guiding precise diagnosis and prognosis of several cancers but also for the patient selection suitable for CXCR4-targeted therapy 5,6, such as pharmacologic or endoradiotherapeutic interventions 7,8. The gene discussed is CXCR4; the disease is cancer.