show Abstracthide Abstract"We have developed orthotopic patient-derived xenograft models of HER2 positive breast cancer metastasized into the brain of patients to test novel therapeutic strategies. In this study, we identified a novel combinatorial therapeutic strategy that has resulted in a durable remission and markedly increased overall survival in majority of patient-derived xenograft (PDX) models tested. We performed whole exome sequencing analysis of these PDX tumors and their matched blood and patient samples to investigate drug sensitive and resistance mechanisms. Our sequencing data revealed an interesting association of genotyping and phenotyping with tumors responses to drug treatment."