Update: Hemangiosarcoma (HSA) remains one of the deadliest canine cancers, with dogs rarely living more than six months after diagnosis. New approaches are needed to improve the survival time of dogs afflicted with this devastating disease. Researchers from Oregon State University are expanding on prior Morris Animal Foundation– funded research into a novel class of drugs called tyrosine kinase inhibitors, which have the potential to control the growth of HSA cells. Tyrosine kinases are enzymes that function as cell-signaling messengers that when overactive are associated with uncontrolled HSA cell growth. To date, researchers have identified a tyrosine kinase– signaling protein that they believe is functioning abnormally. Low concentrations of a candidate tyrosine kinase inhibitor drug seem highly effective in reversing the abnormal activation status of this signaling molecule, alone or in combination with a second anticancer agent. Researchers continue to screen for additional tyrosine kinases that behave abnormally in HSA cell lines. Using a protein-screening strategy, researchers have also identified 25 tyrosine kinase–activated proteins in canine HSA cells that could be associated with cell growth. Researchers have begun to investigate these target proteins with several novel tyrosine kinase inhibitors to determine their contribution to uncontrolled HSA cell growth. Data from this study are encouraging and will provide the basis to continue the investigation of tyrosine kinase inhibitors as a drug therapy to improve care of dogs with HSA.