Tony Hunter discovered that tyrosine phosphorylation is a fundamental mechanism for transmembrane-signal transduction in response to growth factor stimulation, and that disregulation of such tyrosine phosphorylation, by activated oncogenic protein tyrosine kinases, is a pivotal mechanism utilized in the malignant transformation of cells. This cell-signaling mechanism revolutionized basic research on cancer. Digital facsimile from PubMedCentral at this link.