Minimal functional driver gene heterogeneity among untreated metastases.

Metastases are responsible for the majority of cancer-related deaths. Although genomic heterogeneity within primary tumors is associated with relapse, heterogeneity among treatment-naïve metastases has not been comprehensively assessed. We analyzed sequencing data for 76 untreated metastases from 20 patients and inferred cancer phylogenies for breast, colorectal, endometrial, gastric, lung, melanoma, pancreatic, and prostate cancers. We found that within individual patients, a large majority of driver gene mutations are common to all metastases. Further analysis revealed that the driver gene mutations that were not shared by all metastases are unlikely to have functional consequences. A mathematical model of tumor evolution and metastasis formation provides an explanation for the observed driver gene homogeneity. Thus, single biopsies capture most of the functionally important mutations in metastases and therefore provide essential information for therapeutic decision-making.

Enhanced sensitivity to hydrogen peroxide-induced apoptosis in Evi1 transformed Rat1 fibroblasts due to repression of carbonic anhydrase III.

EVI1 is a nuclear zinc finger protein essential to normal development, which participates in acute myeloid leukaemia progression and transforms Rat1 fibroblasts. In this study we show that enforced expression of Evi1 in Rat1 fibroblasts protects from paclitaxel-induced apoptosis, consistent with previously published studies. Surprisingly, however, these cells show increased sensitivity to hydrogen peroxide (H(2)O(2))-induced apoptosis, demonstrated by elevated caspase 3 catalytic activity. This effect is caused by a reduction in carbonic anhydrase III (caIII) production. caIII transcripts are repressed by 92-97% by Evi1 expression, accompanied by a similar reduction in caIII protein. Reporter assays with the rat caIII gene promoter show repressed activity, demonstrating that Evi1 either directly or indirectly modulates transcription of this gene in Rat1 cells. Targeted knockdown of caIII alone, with Dicer-substrate short inhibitory RNAs, also increases the sensitivity of Rat1 fibroblasts to H(2)O(2), which occurs in the absence of any other changes mediated by Evi1 expression. Enforced expression of caIII in Evi1-expressing Rat1 cells reverts the phenotype, restoring H(2)O(2) resistance. Together these data show that Evi1 represses transcription of caIII gene expression, leading to increased sensitivity to H(2)O(2)-induced apoptosis in Rat1 cells and might suggest the basis for the development of a novel therapeutic strategy for the treatment of leukaemias and solid tumours where EVI1 is overexpressed.