Breast Cancer Mutations HER2 V777L and PIK3CA H1047R Activate the p21-CDK4/6 –Cyclin D1 Axis Driving Tumorigenesis and Drug Resistance

To study the effects of co-occurring HER2 and PIK3CA mutations, investigators bred genetically engineered mice with the HER2V777L; PIK3CAH1047R transgenes and studied the resulting breast cancers both in vivo as well as ex vivo using cancer organoids.