A new Nature study, which sheds light on the varied clinical success of a particular class of cancer drug, known as tyrosine kinase inhibitors, may aid the design of more effective cancer therapies.
Tyrosine kinases are enzymes that modify other proteins by adding phosphate groups to them. Specific tyrosine kinases are overactive in many cancers, and drugs that inhibit them, such as the chronic myeloid leukaemia treatment imatinib, can be successful. But they don't work for all tyrosine-kinase-driven cancers. Researchers think they know why.
One particular kinase, called HER2, is frequently overactive in breast cancers and signals through another family member, HER3. Mark M. Moasser and colleagues now show that when HER2 is inhibited by kinase inhibitors, a feedback mechanism causes an increase of active HER3 at the plasma membrane where it continues to signal cancer cell proliferation (as long as HER2 activity is not completely blocked).
More effective inhibitors are needed to block HER2 completely and reign in HER3. Tests that assess HER3 transphosphorylation could also help to predict any such treatment's success.
Mark M. Moasser (University of California, San Francisco, CA, USA)
(C) Nature press release.
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