Integrated Systems and Technologies: Mathematical Oncology Genetic and Phenotypic Diversity in Breast Tumor

Metastatic disease is themain cause of cancer-relatedmortality due to almost universal therapeutic resistance. Despite its high clinical relevance, our knowledge of how cancer cell populations change during metastatic progression is limited. Here, we investigated intratumor genetic and phenotypic heterogeneity during metastatic progression of breast cancer.We analyzed cellular genotypes and phenotypes at the single cell level by performing immunoFISH in intact tissue sections of distant metastatic tumors from rapid autopsy cases and from primary tumors andmatched lymph nodemetastases collected before systemic therapy.We calculated the Shannon index of intratumor diversity in all cancer cells and within phenotypically distinct cell populations. We found that the extent of intratumor genetic diversity was similar regardless of the chromosomal region analyzed, implying that it may reflect an inherent property of the tumors. We observed that genetic diversity was highest in distant metastases and was generally concordant across lesions within the same patient, whereas treatment-na€ve primary tumors and matched lymph node metastases were frequently genetically more divergent. In contrast, cellular phenotypes weremore discordant between distant metastases than primary tumors andmatched lymph nodemetastases. Diversity for 8q24 was consistently higher in HER2þ tumors compared with other subtypes and in metastases of triple-negative tumors relative to primary sites. We conclude that our integrative method that couples ecologic models with experimental data in human tissue samples could be used for the improved prognostication of patients with cancer and for the design of more effective therapies for progressive disease. Cancer Res; 74(5); 1338–48. 2014 AACR