Anti-TOP1 monoclonal antibody, clone 2302DU986.253.277

Type IB DNA topoisomerases can eliminate torsional stresses produced during replication and transcription. These enzymes are found in all eukaryotes and a short version is present in some bacteria and viruses. Among prokaryotes, the long eukaryotic version is only observed in archaea of the phylum Thaumarchaeota. However, the activities and the roles of these topoisomerases have remained an open question. Here, we demonstrate that all available thaumarchaeal genomes contain a topoisomerase IB gene that defines a monophyletic group closely related to the eukaryotic enzymes. We show that the topIB gene is expressed in the model thaumarchaeon Nitrososphaera viennensis and we purified the recombinant enzyme from the uncultivated thaumarchaeon Candidatus Caldiarchaeum subterraneum. This enzyme is active in vitro at high temperature, making it the first thermophilic topoisomerase IB characterized so far. We have compared this archaeal type IB enzyme to its human mitochondrial and nuclear counterparts. The archaeal enzyme relaxes both negatively and positively supercoiled DNA like the eukaryotic enzymes. However, its pattern of DNA cleavage specificity is different and it is resistant to camptothecins (CPTs) and non-CPT Top1 inhibitors, LMP744 and lamellarin D. This newly described thermostable topoisomerases IB should be a promising new model for evolutionary, mechanistic and structural studies.

Tumor heterogeneity has been shown for several cancers including breast cancer (BC). Despite the fact that expression of tumor markers may change throughout the metastatic process, rebiopsies at the time of recurrence are still not performed routinely at all institutions. The aims of the study were to evaluate changes in biomarker profiles during the metastatic process and to investigate whether previous anthracycline or endocrine therapy given in the adjuvant setting could affect the biomarker profile in metastatic lesions. We investigated the expression pattern of ER, HER2, TOP2a, TOP1, p53, Bcl-2, and Ki-67 in 110 paired samples of primary BC and corresponding asynchronous metastases. We found discordant expressions in primary tumor and metastasis for all biomarkers, although only significant for Ki-67. Changes in the expression profile of the metastatic lesions would have altered treatment decisions in 14% of patients. We found no effect of previous anthracycline or endocrine therapy on the expression profiles. Our data confirm that discordant expressions of biomarkers are common in BC and often carry therapeutic consequences. This emphasizes the need for biopsies from metastatic lesions, even in cases where the localization of the metastatic process is not easily accessible.