PTK2 and central nervous system cancer: However, our previous studies, performed on primary human GBM cell cultures developed from tumor specimens and on mouse glioma implantation models, demonstrated that both Pyk2 and FAK are involved in cell-cycle and invasion regulation, and that the extent of this involvement depends on the distinct levels of Pyk2 or FAK expression within each tumor [31,32]—greater expression and activation of either of these kinases results in a more prominent role for that kinase, relative to the other, in governing cell-cycle progression and invasion.