Unlike most SFKs and BRK, which tend to display cell growth-promoting properties and have varying levels of transforming activity [2, 32], FRK has been characterized as a putative tumor suppressor in various cancers including breast cancer and glioma where it has growth inhibitory, rather than transforming activity [1, 10–12, 14, 41]. The gene discussed is PTK6; the disease is glioma.