Mus musculus breed:FVB Transcriptome or Gene expression. Mus musculus breed:FVB

Activating mutations in PIK3CA, the gene encoding the p110α subunit of PI3K, are associated with resistance to HER2-targeted therapies in HER2+ breast cancer. We previously showed that transgenic HER2+/PIK3CAH1047R mammary tumor growth was inhibited by treatment with the HER2 antibodies trastuzumab and pertuzumab in combination with the pan-PI3K inhibitor buparlisib (TPB). In order to discover mechanisms of resistance to combined inhibition of HER2 and PI3K, we generated TPB-resistant tumors by treating HER2+/PIK3CAH1047R mice long term with the drug combination. Exome sequencing was performed to determine if resistance was associated with additional mutations.